Hollow or Solid Sway Bar [Archive]

silver69camaro

06-15-2010, 05:35 AM

The problem being that most hollow bars are .188 wall and on a 1.25" if most of the stiffness comes from the outer most .66" you're not saving much removing the center. There can be little dispute that if you want the stiffer bar, given the same diameter, the solid will be the one to go with.

We are currently making the switch from solid to hollow bars - and we have about 20 different designs. They are consistantly 40%-50% lighter each time. Shaving 6lbs off a bar doesn't seem like much, but remember how far ahead from the COG it is - it reduces PMOI for better stability. These little benefits here and there add up!

79T/Aman, while arm flex is a valid point, it rarely proves to be an issue - hollow or not. There isn't that much force applied to the bar, or at least enough to worry about arm flex. Then again, in beam strength, the center of the bar is doing little of the work...again it's on the outside. The bars are typically made of heat treated 4000-series material, which makes them stiff (bending wise, not torsion).

Guys, remember OEMs have been using hollow bars for years...it's nothing new. If you do the design right, it's a no-brainer.

IBDMANN

06-15-2010, 05:41 PM

will speed-tech be offering a hollow bar any time soon?

onechev

06-15-2010, 09:01 PM

going to a bar that much bigger is going to make the front a lot stiffer if weighs important then i would pay more and get a hollow bar. the hollow bars i have use did not seem to be as stiff as a solid bar same diameter.

JRouche

06-15-2010, 09:42 PM

In most cases, it wont be. Most of the bar's stiffness will come from, say, 1/3" of the outer material. The majority of the inner material is just along for the ride.

Yup!! A solid bar is mostly extra weight with no use. Thats why OEM went with a hollow bar. Its old tech but still needs to be talked about. Solid bars are a thing of the past. JR

ArtosDracon

06-15-2010, 11:24 PM

I still use nascar style gun-drilled straight bars with billet arms on everything but my DD, and it's completely stock. There is something to be said for just using what works.

And really 6-8lbs, most of the guys I've seen that worry about saving 8 lbs on a sway bar look like they could afford to lose 40lbs before they got into the "healthy" weight range. Taking a big dump right before a race can shave a pound or two, that doesn't mean laxatives should start being standard racer equipment.

onechev

06-16-2010, 07:05 PM

i see paying more for a drag car where less weigh results in quicker ets but how much weigh bais change will come from 6 pounds and what different result do you think it can give you on a pro touring
platform? cost vs benefit

Skip Fix

06-17-2010, 07:31 AM

wmhjr

06-17-2010, 07:33 AM

A lot of people are missing the point here. A couple things - and I KNOW there are people on this site that are far more experienced and educated about these things than I.....

1) It makes absolutely zero difference what the maximum stress calculations, etc are concerning solid versus tubular. All that matters is whether or not the device is capable of supporting the maximum amount of stress IT WILL ACTUALLY EXPERIENCE IN A GIVEN APPLICATION. To summarize, you could have a sway bar that is strong and stiff enough to propel the Battleship Missouri through the Panama Canal, but it will be no more effective than one designed to support barely 100% of what the car "needs". Overkill is without value.

2) As it pertains to weight, people are forgetting the differences between weight and weight MOVEMENT and REDUCTION. Some examples:

Taking spring vs unsprung weight into consideration, I'd guess the sway bar is partially both. The center section is sprung, but the outboard areas in vicinity of the end links I suppose are sprung? That muddies the waters a bit. But in any case, reducing the same amount of weight so far outboard and forward in the vehicle will certainly have far greater affects than losing that amount of weight in your beer belly.

Beyond that, it's the weight MOVEMENT. In order to get around corners in a reasonable effective manner, we attempt to get proper weight distribution in terms of COG and balance, right? By reducing mass so far forward, we effectively move weight distribution. It's one reason why when I weighed my car recently, I was not upset that the car is still pretty heavy - roughly 3700lbs. That's because while the total weight was NOT reduced a huge amount during my build, the weight DISTRIBUTION was. Left to right the car is well balanced, and front to rear distribution was 50.6% front, 49.4% rear. Every little bit such as rear battery mounts, aluminum heads, tubular sway bar, helps. The stock 7/8" solid front bar probably weights 3x that of the Hellwig 1 1/4" tubular bar that's on there.

My take is that if your'e replacing the bar, not going tubular makes no sense. If you don't need to replace the bar, it's probably not a game changer.

wmhjr

06-17-2010, 07:36 AM

So how much weight does billet pulleys,hood hinges braided line etc add vs stamped steel factory pieces? And as the other guy said that Big Mac for lunch.

Heck even my mainly drag car ran the same with the solid 22lb front bar back on it!

My billet pulleys and hinges weigh less than the stock OEM steel stuff. JFYI. Good question about braided line, but I suspect very little total weight difference - certainly less than 1lb in an entire car. They are likely offset by aluminum hose ends which are lighter than steel, but who knows.

John Wright

06-17-2010, 08:04 AM

I'm guessing that determining the wall thickness is part of designing for fatigue also? Those bars see alot of back and forth twisting in their lifetime.

Norm Peterson

06-17-2010, 08:22 AM

1) It makes absolutely zero difference what the maximum stress calculations, etc are concerning solid versus tubular. All that matters is whether or not the device is capable of supporting the maximum amount of stress IT WILL ACTUALLY EXPERIENCE IN A GIVEN APPLICATION. To summarize, you could have a sway bar that is strong and stiff enough to propel the Battleship Missouri through the Panama Canal, but it will be no more effective than one designed to support barely 100% of what the car "needs". Overkill is without value.
Actually, what you want is what provides the balance that you seek. It is entirely possible for "overkill" to put you at a clear disadvantage. Using a drag race rear bar anywhere except on the drag strip is one example. At the other end of the car, I'm pretty sure that the bars used in the "big bar soft spring" circle track setups would be way too much for anything you'd drive on the street.

Numbers aren't magic solutions in and of themselves. But they do give you a way to put things in order or to get a feel for what a given change will generally do (without buying everything available and having to try it all).

90% of a solid bar's stiffness lies in the outer 22%, and 95% in the outer 26%. The tubular bars in those cases would weigh about 68% and 78% as much as a solid bar of the same OD. FWIW.

It's better when making a tubular bar to start from larger OD stock than you'd use for a solid bar, as long as you don't let the wall thickness get too thin trying to meet your stiffness target. Just as reference, Ford's OE bar for the S197 Mustang is 34mm OD, and the wall thickness is 15% of the OD (1.34 x 0.20 tube). A 1.375 x 0.25 adjustable bar is aftermarket-available. I think I've heard that 15% wall thickness guideline elsewhere as well.

Norm

wmhjr

06-17-2010, 08:30 AM

Actually, what you want is what provides the balance that you seek.

This may well be the perfect summary. It's all about individual needs and the combination you're putting together. Wrong answer to concentrate on the sway bar and excluding the remainder of the suspension/chassis.

It is entirely possible for "overkill" to put you at a clear disadvantage.

Norm - agreed. I should clarify, I meant that in terms of "Strength" or the "ability to resist deflection/flex" overkill provides no value. In terms of "performance", too much may well be a bad thing.

Skip Fix

06-17-2010, 02:17 PM

wmhjr

06-17-2010, 03:16 PM

I would bet my RARE billets are heavier than my stamped steel sure not dramatically lighter. Point was as one of the other guys said 8 lbs difference of non sprung weight is a little more than a gallon of gas in the tank. Probably more than that of sound deadener or jute in the carpet in most cars.

I know my March non-air system is significantly lighter than steel pulleys and brackets - by a LONG shot. I've installed the RARE pulleys, and can't say for sure about them. They are great quality pieces, but I think there are pretty thick and heavy. Beyond that, I think we're arguing fractions, but frankly the entire gas in the tank argument further shows the value of decreasing the weight of front suspension components for many of us driving 60s/70s PT cars. Without starting a physics lesson, let's just say that the further forward in the car the weight, the more its effect on balance, OK? Because so many of our cars from the factory had heavy front ends and light rear ends, we like to move that balance point back, right? At the same time, as we drive, we LOSE weight (in fuel) in the fuel cell/tank. Meaning, that over every mile you're moving the "balance point" forward in the car due to less fuel (or ballast) in the back. So, at least from my perspective, I'm happy for every pound I can move back behind the drivers seat. MOVING weight (or percentage of mass) is more important to me than LOSING weight.

Skip Fix

06-18-2010, 07:26 AM

I agree moving weight off the front end helps balance most cars better esp since most of our early cars are so nose heavy. I think some of it though is more a theoretical thing though. Even my current pump gas TA car at the drags ran identical times/mph with the 22lb sway bar added back on the front and hooked up. Two things that in theory should slow it down with weight and weight transfer.

Now light weight skinny front tires went faster than just the weight difference I assume form the decreased rolling resistance and being sprung weight.

I would still bet you if you had a close size solid sway bar to a hollow and did an autocross there would be more variables in your lap time than what the bar did weight wise or handling.

wmhjr

06-18-2010, 07:41 AM

First, no relationship whatsoever between 1/4 drag performance and road racing/autox performance. We're not talking about how much drag slicks improve drag performance so they should be applied to autox, right?

Second, the skinny tires and wheels are UNSPRUNG and not sprung weight. But your point is correct in that weight in the tire/wheel will have a greater effect due to the physics of rotational energy.

Most important, like I said - if you're replacing the bar anyway, no reason to NOT get a tubular bar as opposed to a solid bar. If you don't need to replace the bar, then it's probably not going to make a measurable difference.

Keep in mind, though - the really good builds are not the result of one or two really light or better components. They are the result of the COMBINATION of MANY good decisions and improvements. A pound here, an ounce there, right?

silver69camaro

06-18-2010, 07:42 AM

I would still bet you if you had a close size solid sway bar to a hollow and did an autocross there would be more variables in your lap time than what the bar did weight wise or handling.

That's true. But we're just talking about one item here though. If you had that thought for each part you purchased when building a car, you'll be several hundred pounds heavier than what you could be. I understand there is a cost to benefit ratio to consider as well...

zbadone

06-21-2010, 06:51 AM

Well........I got my Hotchkis Sway bar from Summit on Friday and got it installed on Saturday. I didn't drive it much on Saturday, but I drove it into work today and it feels great. I took a hard corner this morning and the car felt very level and had no push in the corner. I didn't push it to the limit since it was the first hard corner that I have taken. My onboard "G-meter" in my kenwood deck said .92 Gs. The previous reading had been .85 Gs. So far I love it. There is one thing though, the clearance between the sway bar and the idler arm are incredibly close. There is a note about this on the installation instructions. I have the Moog Problem solver arm which is bigger then what Hotchkis says will fit. So far it seems fine. No rubbing, but I will keep an eye on it

Skip Fix

06-22-2010, 01:21 PM

"First, no relationship whatsoever between 1/4 drag performance and road racing/autox performance. We're not talking about how much drag slicks improve drag performance so they should be applied to autox, right?"

I'll diasagree-some of the concept is still the same -lighter wheels have less inertia effect to accelerate and stop be they drag or autocross. In drag racing it is much easier to quantitate exact weight vs performance based strictly on weight(done that class racing adding and subtracting weight . I would also bet going wider tires autocrossing/road racing than you need for traction would slow you down also. And I've autocrossed with light weight wheels and autocross compound DOT tires and heavier wheels(cheaper) and road race slicks. No comparison the slicks will kick the DOTs rear(CP vs ESP in SCCA). I've been a few laps around tracks as well as straight line. John Berget has lots of roadrace slicks in all sizes.

Of course in autocross or road race we generally are not looking for small tread to reduce rolling resistance as in drag racing, but going too big even if they fit(usually the limiting factor) will slow you down.

Matt I agree with you in part that every little bit adds up. I would bet though most of the guys here have more street touring cars with thing like stereos/amps, electric windows etc etc that eat up any little savings thing like 8lbs in a sway bar would save. Now a purpose built race car-different thing. Heck while painting my TA years ago while autocrossing it I thought man I'll take the torch to those front bumper supports and cut big holes every where. Spent all day and save a whole 12 lbs on the front and 9 on the rear!

And then I always joke to my bigger friends to put my skinny butt in their car if they need an all time faster time:)

wmhjr

06-22-2010, 04:16 PM

Sorry, but I couldn't disagree more with the previous post. There are SO few similarities between autox and drag performance that you may as well say there are none. Think about CoD, differences in camber, caster, effects on shock performance (ie, in drag racing, a softer front end goes faster - try that in autox once, OK?), the different effects of weight location and center of gravity, and the list goes on.

About the only thing I see is both would benefit from less weight in general, more power, and better traction. But HOW you get each of them is totally and completely different. Find me one single car setup properly for 1/4 mile slips that can go around a corner..... Just one. I mean one optimized for drag. Think of it another way. Take a 'Busa bike setup for drags and try to ride it fast on a road course. Make sure somebody has a camera first, though :)

Bottom line remains the same. Every little bit helps. It probably won't make a measurable difference in terms of weight by itself. If your sway bar is already performing well, probably not cost effective for most people to swap it. If you need a better sway bar anyway, no reason NOT to get tubular. It IS a better quality component. The difference between nice cars and REALLY nice cars is the combined attention to detail on the combination.

MrQuick

06-22-2010, 08:45 PM

Well........I got my Hotchkis Sway bar from Summit on Friday and got it installed on Saturday. I didn't drive it much on Saturday, but I drove it into work today and it feels great. I took a hard corner this morning and the car felt very level and had no push in the corner. I didn't push it to the limit since it was the first hard corner that I have taken. My onboard "G-meter" in my kenwood deck said .92 Gs. The previous reading had been .85 Gs. So far I love it.

There is one thing though, the clearance between the sway bar and the idler arm are incredibly close. There is a note about this on the installation instructions. I have the Moog Problem solver arm which is bigger then what Hotchkis says will fit. So far it seems fine. No rubbing, but I will keep an eye on it

good stuff, glad you went with the hollow bar.

Don't worry about the clearance, its by design. The bar wipes the grease off of the pitman.

Vince

JRouche

06-22-2010, 09:34 PM

Well........I got my Hotchkis Sway bar from Summit on Friday and got it installed on Saturday. I didn't drive it much on Saturday, but I drove it into work today and it feels great.

Sweet!!! And close tolerances are not a problem. Till they are. So many times I have to run very tight tolerances and I think damm, shes gonna hit. But... After running it for abit I raise the car and look for shiny sections, like where metal on metal was a problem.

I dont like ANY shiny parts. Even if its just rubbing the paint off. Paint is thin. If there is ANY bare metal. Metal on metal I wont let that go. Thats too close. Gonna be some hard rubbing. Not good. JR

Norm Peterson

06-23-2010, 03:41 AM

Sorry, but I couldn't disagree more with the previous post. There are SO few similarities between autox and drag performance that you may as well say there are none. Think about CoD, differences in camber, caster, effects on shock performance (ie, in drag racing, a softer front end goes faster - try that in autox once, OK?), the different effects of weight location and center of gravity, and the list goes on.

About the only thing I see is both would benefit from less weight in general, more power, and better traction. But HOW you get each of them is totally and completely different.
The physics is the same for both types of cars (F=ma is still F=ma, etc.), so it's what you do with it that differs. One has to look at a much wider picture than just the nitty-gritty of every little detail that's different. That's how you optimize for one activity - by giving up performance that doesn't matter as much to get more of what does.

I suspect that it is possible to "over-tire" a car for autocross, though this is probably not as likely in PT-size/weight cars as it could be in cars that make Miatas look big and heavy. One problem specifically related to light cars, big tires, and autocross would involve the ability (or lack thereof) to get the tires up to optimum temperature quickly enough.

Norm

Hotchkis

06-23-2010, 07:49 AM

It's good to see such knowledgeable conversation. This forum is full of very smart people.

It looks like zbadone is happy with the Hotchkis bar, and we (of course) are happy to hear that.

Still, this topic comes up a lot, and for future conversations, this is our take on sway bars in general and the hollow vs solid disscussion:

To start, let's think about how a sway bar controls body roll and control. The sway bar is attached to the left and right suspension and chassis. It controls body roll by twisting in torsion. Think torsion bars and you get the idea. The more the body wants to roll in heavy cornering, the more resistance, twist, the sway bar provides.

Since sway bars work off of torsional force (twisting motion), the material in the center of a solid bar plays little role in the resistance of torsional force. With this in mind, we have eliminated some of the center material and also moved some to the outside of the tube, where it is most effective. In turn, this produces a sway bar that is lighter in weight and just as stiff (http://www.hotchkis.net/_uploaded_files/hollow_vs_solidinstructions162file.pdf), if not stiffer than solid. For example, a 1'3/8" hollow bar is equivalent to a 1'1/4" solid. But the 1'3/8" hollow bar is 6% stiffer and 43% lighter than the 1'1/4" solid.

Years ago the feeling was that a car only needed a front sway bar. Back then the best tires were skinny with relatively soft sidewalls. Today people are packin' super sticky tires on the rear of their muscle cars. These tires produce some serious grip and are miles better than yesterday's race tires. Your car will be the quickest and most comfortable around a track or down your favorite twisty road with a neutral handling balance. This is achieved when the car is neither loose nor tight (excessive understeer or oversteer) but balanced with the front and rear tires doing equal work. Providing that the springs are of sufficient rate to keep the car from bottoming out, the handling balance is tuned with the front and rear sway bars. We generally engineer the largest front sway bar possible that doesn't overpower the front suspension and then tune (change roll stiffness) with an adjustable rear sway bar.

Some people recommend running a stiff rear spring combination without a rear sway bar. In this case the heavy spring rate keeps the chassis from rolling thereby eliminating the need for a rear sway bar. This is fine if the passengers wear kidney belts and interior rattles are no problem. For the rest of us we want a comfortable ride with great handling. Adding a rear sway bar solves the ride quality issue and creates an optimum handling balance. The rear spring rate can be softer for better ride quality and corner exit traction because the rear sway bar (not the springs) is controlling the rear body roll.

We have conducted extensive street/track testing over the past 15 years and continue to refine our suspension systems for the optimal balance of on-track handling and comfortable street driving. We find that our latest generation of lightweight strong, hollow sway bar packages with adjustable rear sway bars provides a full range of handling balance tunability for all types of performance driving.

Now you have some tuning options!

79T/Aman

06-23-2010, 10:05 AM

Skip Fix

06-23-2010, 10:23 AM

So lighter wheels and reduced roll resistance only help a drag car??? As Norm said the physics are the same. I guess why the F1 guys use steel wheels and steel bolt no lightweight titanium stuff.

I'll agree there are different optimal chassis settings for strictly straight line vs corners. But again some is theory. As I said general drag theory get rid of the front sway bar for weight and to let the front end lift for weight transfer-my car ran identical times. Open headers/no exhaust system should go faster than adding an 80 lb system-my car ran identical 1/8 mile times.

Yes there are some differences -drag cars generally do better with a taller sidewal to absorb some of the shock and not blow the tires away. Why many of the street/strip LS guys I know hook better with a taller sticky DOT even a 275/60/15 than a 275/50/17.

It is generally a little easier to quantitate strictly weight changes on a drag car. In an autoX or open road course the longer time and course has more variables in driver(take a different line in a turn, brake at a different point etc etc) that can change lap time. vs adding 50 lbs. Most 11-13 second drag cars 100lbs is generally .1 seconds/1mph. I would bet on an autoX car that would be tough to measure.

I still go back to my original contention if you put the majority of folks here on a road or autoX course. Pull 8lbs, shoot I'd bet even 40 lbs, off the nose it would be hard to quantitate back to back run differences. I woud bet though lighter wheels with road race slicks they would go faster than heavy wheels and DOTs.

silver69camaro

06-23-2010, 10:27 AM

as much as proponents of hollow bars want to avoid aswering the point that unless the sway bar is STRAIGHT you cannot use tortion bar equations to prove a point, because the forces applied to the sway bar not only twist but also bend the bar and in the case of a tube VS solid bar the solid bar will flex less than the tube.

That's why we have FEA:
https://static1.pt-content.com/images/noimg.gif

Your statement is true that a bar will exhibit bending stress if it contains bends on different planes, but even then a hollow bar still shows a true advantage. The principle of the outer material "doing the work" still is valid in bending stress.

I think perhaps some people are missing the point here. If you were to compare the stiffness of a 1.125 x 0.156" hollow bar to a 1.125" solid, the solid will be stiffer. BUT, every manufacturer will bump the OD up 1/8" or so to compensate for the lack of inner material. The result is a lighter bar, with equal (usually more) stiffness, and the price is usually comparable. I don't see the benefits for a solid bar except for packaging requirements.

Norm Peterson

06-23-2010, 10:57 AM

as much as proponents of hollow bars want to avoid aswering the point that unless the sway bar is STRAIGHT you cannot use tortion bar equations to prove a point, because the forces applied to the sway bar not only twist but also bend the bar and in the case of a tube VS solid bar the solid bar will flex less than the tube.
You can still use the OD^4 - ID^4 equations as long as the bars being compared have essentially the same bent shape. Bending stiffness also follows the OD^4 - ID^4 rule. Some of the really little terms (you won't find them in Puhn's formula or most anybody else's online tech) follow an OD^2 - ID^2 rule, but they don't make for much difference.

Circle track bars built up from three pieces (two arms splined to a torsional center section) won't follow the OD^4 - ID^4 rule.

Norm

Norm Peterson

06-23-2010, 11:11 AM

It is generally a little easier to quantitate strictly weight changes on a drag car. In an autoX or open road course the longer time and course has more variables in driver(take a different line in a turn, brake at a different point etc etc) that can change lap time. vs adding 50 lbs. Most 11-13 second drag cars 100lbs is generally .1 seconds/1mph. I would bet on an autoX car that would be tough to measure.

I still go back to my original contention if you put the majority of folks here on a road or autoX course. Pull 8lbs, shoot I'd bet even 40 lbs, off the nose it would be hard to quantitate back to back run differences. I woud bet though lighter wheels with road race slicks they would go faster than heavy wheels and DOTs.
If it helps any, lateral grip is about an 0.7 power function of weight. IOW, a 5% weight increase is worth about 3.5% more lateral grip. That's a loss of 1.5% in lateral acceleration when you compare the added grip to the added weight that it has to work against. SOTP you probably wouldn't feel it, but the 0.001 second clocks will find it every time assuming that you're sufficiently consistent.

Wheel weight and rolling resistance is sort of off-topic here, but of course it matters everywhere that it is legal to tinker with, is sufficiently safe, and is productive to do so.

Norm

Skip Fix

06-23-2010, 02:07 PM

Norm Peterson

06-23-2010, 03:25 PM

but the 0.001 second clocks will find it every time assuming that you're sufficiently consistent.

8 lbs on a 3600lbs car(so it has been on a diet and not 3800lbs anymore from all those 8 lbs adding up) I would bet the 0.001 clock would pick up more driver inconsistency than the weight reduction from that hollow vs solid bar.
Probably true. But on balance, the average time could reasonably be expected to drop. 50.040 seconds ± 0.200 is still going to lose to 50.000 ± 0.200 more often than not. I think most years a couple to maybe a few National jackets are won by less than 0.040.

"BUT, every manufacturer will bump the OD up 1/8" or so to compensate for the lack of inner material." I would bet though most folks brains are assuming that the hollow since it is "bigger" by 1/8 would act like a bigger solid bar. So they buy a bar that is bigger but get comparible stiffness to the smaller solid bar. So did the car handle better or they get the placebo effect from "bigger is better"?
If the stiffnesses are identical, the car with the tubular bar will still get the benefit of reduced weight at that end of the car with its potentially increased lateral-g capability, along with an equally small but beneficial effect on unsprung mass. True, in this example the weight effect is only on the order of an 0.3% increase in lat-g, but if you're serious about the competition you'd chase those kinds of things.

If the stiffness aren't quite equal and the tubular bar ends up giving a slightly inferior balance, the picture gets a bit cloudy even from a purely theoretical point of view.

Most of us probably wouldn't notice, and haven't picked all the low-hanging fruit anyway.

Norm

JRouche

06-23-2010, 11:01 PM

I use a hollow bar up front and at the rear. Straight bar with splined ends, and solid arms.

These.... http://www.1speedway.com/standard_swaybars.htm

A few benefits and some drawbacks.

The benefits.....

One being able to tune it without much extra cost. Changing the rate can be done to a small degree by changing the location of the mounting holes on the arms. Same with some solid or hollow aftermarket bars but maybe with a lil more control.

The arms come undrilled. So you can place the holes anywhere on the arm as long as you take into concerderation the links and their angles. You dont want a sever angle on the links. Longer links will afford more fore and aft locations on the arm while still keeping the links closer to 90* of the arms. If the packaging of the suspension only allows you to have very short links then the placement of the mounting holes on the arms becomes very limited.

But the low cost of tuning with a straight bar really comes from the low cost of the torsion bars. They are 90 bucks. And really, they are the standard if bought from speedway. You will see their bars relabeled under other dealers names. They make some good bars.

So to change rates its just a matter of determining if you need more or less. And thats a crap shoot for the most part, until you drive the car. With any ones bars. Unless you are building an exact car that the testers used to show performance most of us are just shooting in the wind.

But I imagine many guys are just looking for a bar that they can buy and it will fit. As busy as most suspensions are there really isn't alot of room to put a sway bar in, specially if one wasnt there to begin with.

And that leads me to the downfalls of the straight torsion bar sway bar. Packaging.

I thought I had a bear of a time finding room and making the mounts for my rear bar. But it fit and I didnt have any clearance issues in the end.

But hang on now. To put a straight bar in the front was almost not doable. Now I know why stock or aftermarket bars look like limp spaghetti, all bent around in many variations. You have to wind around ALOT of other components. It was a nightmare. But I got her in with a decent 3/8", oh, ok, more like a 1/4" clearance from ALL of the other cars structures. Full travel and Im not hitting. Took some and work. But the straight hollow 1-1/4" bar fits.

But anyway. Back to zbadone (https://www.pro-touring.com/forum/member.php?u=1315)'s post. Hollow or solid.

I really dont see a reason for using a solid bar UNLESS its for packaging. A solid bar of the same diameter will give you more spring rate. And yes, it will come with more weight, but unless you are racing and looking at ALL of your weights then thats a moot point.

BUT!! only if packaging wont allow you to fit a fatter hollow bar in place of a heavier slimmer solid bar of the same rate. If you have the clearance for a larger diameter hollow bar then you should use it.

Its about effieciency. A hollow bar is more efficient if sizing is not an issue. If sizing is taken into the consideration, for say a very tight packing on the front end then the efficiency scale is narrowed some. The weight for spring rate might be pushed aside some for the packaging needs.

But to be honest, those fitments are far and few. Usually the spring rate compared to the physical weight is gonna be the deciding factor. And a hollow bar has an edge over a solid bar if packaging is taken out of the equation.

Why, well, like some of the other guys have said. The core of a bar of spring doesnt do much for any of the spring rate. Its just dead weight.

So why does a bar thats a solid 1-1/4" have more rate than a hollow bar of the same diameter with a 1/4" wall have more spring rate? Because the 3/4" core does still have some rate to it. It would be like having a 3/4" solid bar inside of the hollow 1-1/4" hollow bar. But the last say 1/2" of that core doesnt have much rate to it. It diminishes very quickly. The center section of the solid 1-1/4" bar, the half an inch solid section doesnt have much spring rate at all. Its just along for the ride.

But a slim 1" solid bar will be very close, maybe 50lbs (lower) of spring rate, to a larger hollow bar that has an outside diameter of 1-1/4" and a wall thickness of .095" (around 3/32",, pretty thin). But the hollow bar will be alot lighter still. And still have more spring rate.

So???? Hollow bar YES!! If you can fit one in. Sooooo much lighter than a solid bar for a given spring rate. IMO anyway, and Im just regurgitating what I have read and learned. I dont have any engineering knowledge. JR

wmhjr

06-24-2010, 06:31 AM

So lighter wheels and reduced roll resistance only help a drag car??? As Norm said the physics are the same. I guess why the F1 guys use steel wheels and steel bolt no lightweight titanium stuff.

No, that's not what I said. What I DID say is that you can't assume that because it does or does not help with a drag car then it will or will not improve an autox car. The physics are DIFFERENT! And the location of weight, the distribution of weight and the EFFECTS of that weight result in very different characteristics between the two disciplines. At a very (and I mean VERY high level) there are similarities. Higher HP/weight ratio is better (assuming you maintain traction). Beyond that, the METHODS you choose to optimize performance are incredibly different. I honestly can't imagine anybody with any experience whatsoever not getting that.

I'll agree there are different optimal chassis settings for strictly straight line vs corners. But again some is theory. As I said general drag theory get rid of the front sway bar for weight and to let the front end lift for weight transfer-my car ran identical times. Open headers/no exhaust system should go faster than adding an 80 lb system-my car ran identical 1/8 mile times.

Yes there are some differences -drag cars generally do better with a taller sidewal to absorb some of the shock and not blow the tires away. Why many of the street/strip LS guys I know hook better with a taller sticky DOT even a 275/60/15 than a 275/50/17.

There are "some" differences? You're kidding, right? Serious question - have you ever built a road race car or worked on one? I don't mean that as an insult - a real question. My drag cars were frankly worthless to drive as just a normal street car much less an autox car. My best cars would launch on rails and were very consistent, but wallowed around corners like Barney the purple elephant drunk on bourbon. It's not theory - it's science. You can even look at the FAST guys to see what they do with chassis stuff just to go faster within their class. Amazing.

I'll It is generally a little easier to quantitate strictly weight changes on a drag car
.

Nope. Only for quantifying weight differences as they impact STRAIGHT LINE PERFORMANCE. Show me a NASCAR or SCCA team that uses 1/4 mile times to make changes to their cars. Just one.

I still go back to my original contention if you put the majority of In an autoX or open road course the longer time and course has more variables in driver(take a different line in a turn, brake at a different point etc etc) that can change lap time. vs adding 50 lbs. Most 11-13 second drag cars 100lbs is generally .1 seconds/1mph. I would bet on an autoX car that would be tough to measure.

folks here on a road or autoX course. Pull 8lbs, shoot I'd bet even 40 lbs, off the nose it would be hard to quantitate back to back run differences. I woud bet though lighter wheels with road race slicks they would go faster than heavy wheels and DOTs.

I don't disagree that most drivers here may not be consistent enough to be able to quantify weight changes reliably. But THAT'S NOT THE POINT. The point isn't what the driver can do, it's what the CAR can do - that helps the driver. If you're building a car, build it right considering the boundaries of your purpose and your budget. Don't just ignore obvious performance enhancements because you're not sure you will see the benefits of each individual part - remember the collective. This whole thread is ridiculous. There is certainly merit to the discussion of whether tubular can meet the same performance characteristics of solid. But assuming it can from the particular application point of view (ie, handling the relationship between chassis and lower control arms) then the only question is how much a difference, and how much is the cost. And, if you're already going to replace the bar anyway, there is simply no logical discussion whatsoever.

BTW, how about you find me that drag racing Busa with extended rear swingarm that's road racing? That would be a great video :)

Skip Fix

06-24-2010, 08:21 AM

Most of us probably wouldn't notice, and haven't picked all the low-hanging fruit anyway. Exactly! And I'd bet juggling tire pressures might pick you up as much time.

Yes I've worked on road race and autocross cars. My TA was autocrossed for 15 years-stock and CP(cam change at that time was not allowed in ESP where it would have fit).SCCA member for 20 years.

And yes the physics is different. My point on the weight is on a drag car the driver variable is not as much as a road/autoX. So there is a direct correlation between weight and times generally. As I said before go do a run, then pull out 8 lbs but brake slightly different spot was the lap time different because of the weight or because of the different braking is what I am saying. And yes I know the NASCAR boys don't use a 1/4 mile to tell if their weight reduction made them go faster. But since even at the same weight juggling wedge, stagger(yes I've been around circle track guys too-got a late model car sitting in the garage) all can make bigger impacts in their lap times than an 8 lb weight change(a little more than 1 gal in the tank)-my entire point in this discussion and that IS on a scienced out professional combination-different lap times same weight different chassis settings. Since unless you fill up during laps, race at the exact same gas tank fill you can make an 8lbs weight change during a race! How many guys exactly fill up their tank to autoX-especially if they drive to the event?

Again a wider tire different tread compounds do have different rolling resistance and can impact times if you over do it. Again something easily quantitated on a drag car and theory IS used in going around corners. A taller tire or one out of the wheel well can affect aerodynamics esp on formula cars. As Norm stated most of our cars unless they are tubbed or a tube frame that will not be as much a factor. Most class racing have specs for tire sizes.

Also Norm I would bet most of those cars winning jackets have enough lap times to dial in the car for it's class and current chassis setup and the variable in lap times is driver.

Since weather can significantly impact HP on the same engine even on the same day we'll leave that out of the discussion for lap time comparisons.

And yes my car when switched to drag only no front bar, loose convertor etc etc wasn't much for cornering. But actually even the drag times improved putting my tighter Guldstrand/Bilstein road race shocks back on it:) So much for 90/10s and rapid weight transfer being the ticket! Now a 22lb front sway bar and road race shocks are on it and same improved times.We get back into theory vs track results. Why did a drag car get faster with tight shocks and not get slower adding a 22 lb weight out on the nose that also slows front end travel? Only difference now from it's CP suspension days are front and rear springs.

And no weight distribution being balance helps both type cars. More weight off the front and balanced toward the rear helps drag traction also.

silver69camaro

06-24-2010, 08:50 AM

"BUT, every manufacturer will bump the OD up 1/8" or so to compensate for the lack of inner material." I would bet though most folks brains are assuming that the hollow since it is "bigger" by 1/8 would act like a bigger solid bar. So they buy a bar that is bigger but get comparible stiffness to the smaller solid bar. So did the car handle better or they get the placebo effect from "bigger is better"?

I give up!

Skip Fix

06-24-2010, 09:24 AM

Matt I'll agree if a hollow bar gives me the same feel and track performance as the solid I'll use it to shed a few pounds. I'll agree a knowledgeable guy will buy it for all the same reasons listed here.Most of the guys here would probably fall in that category.

I'm just saying that your average Joe car guy buys for "bigger is better". Why lots of motors are over cammed,over carbed etc etc.A common concept we all see. It also relates to their suspension choices. Did they buy the slightly bigger hollow bar that as was said has the same stiffness as the smaller solid bar to save the weight to go faster because they are lighter and not the rigidity/flex or do they buy it because it is listed as bigger and that is what they though they needed to go with that Victor intake with an 850 DP on a 350 with a 250@ 0.050 cam with 2" headers to drive on the street and wonder why his power brakes don't work.

JRouche

06-24-2010, 10:59 PM

I'm just saying that your average Joe car guy buys for "bigger is better". Why lots of motors are over cammed,over carbed etc etc.A common concept we all see. It also relates to their suspension choices. Did they buy the slightly bigger hollow bar that as was said has the same stiffness as the smaller solid bar to save the weight to go faster because they are lighter and not the rigidity/flex or do they buy it because it is listed as bigger

I have to agree with you somewhat with this. And I have to blame the aftermarket dealers and manufactures.

A guy wanting to improve his car re: the suspension, and more to the point, the sway bar, anti-roll bar or what ever the term is used is relying on the dealer or manufacture to supply some info on the bar. THEY DONT!! They give sizing specs and thats all. I dont EVER see spring rates associated with aftermarket bars.

So hell, whats a guy to do but guess or take the dealers opinion. And all the dealer has to offer is the size of the bar. Well what the heck does that mean. Nothing at all. It just means the dealer is saying the bar is "this" large and will increase the performance. HOGWASH!!!

All they are saying is its a larger bar and should give you more roll control. So YEAH, why wouldnt a guy think a larger bar is in his best interest. Even if he (and the dealer) doesnt know exactly what the amount of spring rate for that bar is.

So yeah, the dealers and manufactures make sure to put a certain spring rate for the suspension springs we buy. But hell no. No way to nail down a certain spring rate for a roll bar.

So they sell it as bigger is better. Thats so stupid. Ummm, thats why I went with a straight bar. I know what my spring rates are, anyone else with a one piece bar know the spring rate of yer bar??? I have yet to see any published spring rates for a one piece roll bar. And I have looked. Not found yet. They always SELL by size. Just looking to make some money is what I see. JR

wmhjr

06-25-2010, 04:22 AM

I'm just saying that your average Joe car guy buys for "bigger is better". Why lots of motors are over cammed,over carbed etc etc.A common concept we all see. It also relates to their suspension choices. Did they buy the slightly bigger hollow bar that as was said has the same stiffness as the smaller solid bar to save the weight to go faster because they are lighter and not the rigidity/flex or do they buy it because it is listed as bigger and that is what they though they needed to go with that Victor intake with an 850 DP on a 350 with a 250@ 0.050 cam with 2" headers to drive on the street and wonder why his power brakes don't work.

So what? The point you've been seeminly trying to make is that the tubular bar is a waste of money because of your 1/4 mile "test" (which again, I personally think provides no value - JMHO). So you're also saying the bigger cam, the 850DP, etc are also wastes of time and money?

I guess we're on two different viewpoints here. I agree completely that uneducated people buy stuff that won't help them or will actually hurt them because they haven't done their homework. OTOH, that doesn't make the part "dumb" or "useless". My .660 lift roller cam sure isn't "too big" for my motor. It would be on a 8.5:1 1975 stock motor. Not on mine.

I'll say it again and maybe it'll start to stick. The OP was asking a question and trying to do his homework. On its own merits, a tubular sway bar may not make a measurable difference. As part of a "total build" it may be the right part. It all depends on all the OTHER things you're doing. A cake is not measured by one ingredient. Its quality is measured by the combination of ALL ingredients and processes.

Norm Peterson

06-25-2010, 07:42 AM

And yes the physics is different
The physics is not different; it's the details of how you apply it that are. There's a difference.

How many guys exactly fill up their tank to autoX-especially if they drive to the event?
Quite a few autocrossers will run with the minimum amount of fuel that does not result in loss of fuel pickup. I've found out where less than minimum was in the Malibu, and I've heard when others have tried to save a little too much fuel weight . . . and this is at the regional level, no less.

Also Norm I would bet most of those cars winning jackets have enough lap times to dial in the car for it's class and current chassis setup and the variable in lap times is driver.
Autocross at that level is three shots to learn the course, starting from square one where all anyone has is a few course walks. So I suspect that the variable is more about how well a given driver can learn a given course. You still can't be leaving any 0.040's on the table.

And yes my car when switched to drag only no front bar, loose convertor etc etc wasn't much for cornering. But actually even the drag times improved putting my tighter Guldstrand/Bilstein road race shocks back on it:) So much for 90/10s and rapid weight transfer being the ticket! Now a 22lb front sway bar and road race shocks are on it and same improved times.We get back into theory vs track results. Why did a drag car get faster with tight shocks and not get slower adding a 22 lb weight out on the nose that also slows front end travel? Only difference now from it's CP suspension days are front and rear springs.
Perhaps there is such things as optimum damping and optimum balance between bump and rebound even for drag racing . . .

As far as the front sta-bar vs rate of nose rise goes, the bigger reason for removing a front bar almost certainly has more to do with shifting the roll couple rearward than it does on allowing more or quicker nose rise. When the roll stiffness is mostly out back, engine torque reaction is mainly reacted in a fashion that re-plants the RR tire instead of also trying to load the RF. And more equal tire loading means greater total forward bite even with a posi, a locker, or even a spool (they just keep the wheel with less forward bite from falling off into purely sliding grip until the other side also does).

That the LF will rise more/more rapidly is the unavoidable consequence of allowing more total chassis roll rather than something actively sought for primary benefit.

Chassis torsional stiffness matters, with a torsionally stiff chassis being beneficial (your CP build may be mitigating the presence of a front bar more than a stocker or a purpose-built dragstrip chassis would).

I doubt you'll find many drag racers who think in such corner-carving terms as roll stiffness and its distribution or chassis torsional stiffness, but I can't see this situation being anything else.

Norm

Skip Fix

06-25-2010, 11:34 AM

"On its own merits, a tubular sway bar may not make a measurable difference. As part of a "total build" it may be the right part."

We agree here! But is IS advertised as being better. Maybe it works as part of a package but is the one piece definitely better than what it is replacing?

The other main point maybe I wasn't making well that JRouche touched on does relate to this discussion and solid over hollow is the advertising by the suspension(or intake or carb folks). They are marketing their bar as "bigger" to the general public that might need a bigger bar and that hollow is as stiff as solid and "will" handle better when it may or may not handle any different. Any independent verification?? Edelbrock swore to me on the phone their Pontiac performer(before the RPM was out) would out perform a "factory"intake even a RAIV or HO. It is advertised as such besides what their tech spouts. On my RAIV heads it KILLED airflow by 10% over an HO intake-wouldn't have made the motor perform better than a factory intake.

Does a plain Baer brake system with the same size rotors work better than a factory single piston with a larger pad surface area? They sure have advertised they do, or a Wilwood smaller rotor smaller pad Dynalite system on a 3600lb car?

Unfortunately in our hobby there are not "peer reviewed" testing as in medical,scientific or engineering fields. The magazines doing them take ad money which often influences results-even most medical lecturers now have to disclose if they do studies for the drug companies and have a conflict of interest in the results. My machinist built a motor for one of the big magazines-somehow once in print many of the components got changed to bigger advertisers products for the build. So I guess I'm just a skeptic when it comes to auto advertising, even if it is actually a better product. Kind of like racing a flow bench or dyno numbers-what does it do at the track is the real deal.

Norm on my car and the sway bar and shocks for drag-drag shocks let the front end lift and transfer weight too quickly. It would hook then drop the front end and unload the rear tires. Slower weight transfer allowed to to stay hooked. Something the Pontiac guru Jim Hand even found on his 11 second wagon,tighter shocks worked better. Also the "new" thing for drag cars is adding a rear "anti roll bar" to help them go straighter. Alot like a sway bar! Also many drag guys have found the rigidity of their chassis can help consistency, not to the extent a roundy round corner carver of course.

"So I suspect that the variable is more about how well a given driver can learn a given course." I agree but still a mistake or change in braking point/accelerating point on the course would change the times more than a 8lb difference in weight on that same car. On a road course where there is less rapid changes in inertia once you are at speed and a longer lap time I would bet that 8 lbs difference would be even less per lap, and the gas used during that lap could sure change 8 lbs, I know one drag pass can do it from rolling across the scales myself regularly.

So do a "double blind study" using a solid vs hollow bar-same end links and bushing durometer hardness and then I can go for it:)

Norm Peterson

06-25-2010, 12:11 PM

Also the "new" thing for drag cars is adding a rear "anti roll bar" to help them go straighter. Alot like a sway bar!

It IS a rear sta-bar ("sway bar"), just sold under a slightly different but entirely accurate name. And it does the same thing, shifting the roll stiffness distribution. If your unmodified car roll stiffness is distributed 80% front/20% rear and you want something like 40%/60% you can either throw away front stiffness (smaller or no bar), add rear stiffness (add big bar), or even do both. I imagine that there are limits to what you can do with just the bars or would even want to, but that's the idea.

I think we have to agree to drop consideration of driver errors from this discussion. Sure, it affects the results more - miss a 2-3 upshift or screw up and early-apex a corner and run out of pavement on track out might be "worth" several hundred or a thousand lbs added to a properly driven car. Or a wreck if you find a wall or a catch fence. But as near as I can tell, . . . . the likelihood of making such errors isn't a function of making any of these small mods. So either the driver is good enough to never make them or is unskilled enough and always does; the errors just can't come in a pattern that favors the outcome of either arrangement over the other.

Norm

wmhjr

06-25-2010, 12:23 PM

What you're talking about exists everywhere, and not just in our hobby. My problem with your position on this is that you're targeting tubular sway bars, but I don't see you making the same claims about tires, wheels, frankly every single product on your car. At some point you have to do your homework, talk to people who work with this stuff, and make a decision. If everyone waited until there was "scientific proof" in some sort of "double blind study" - we would frankly have no options to even consider.

If you read carefully my position from the beginning, it's quite clear. There are things I used in my build that I KNOW work. Some of that was tested on a dyno, and I also had the advantage of up front data from engine builders, etc who have proven concepts and combinations. Some things were more a leap of faith based on perceived expertise and experience from people like Marcus at SC&C, Frank at Prodigy and others. So far, am I confident that my choices are the absolute "best" combination? Heck no - I have no idea. Am I confident that they are "good" solutions that have been proven to work? Heck yeah!

Just because you cannot measure the difference one part makes by itself does NOT mean it is OR is not a "better product". And again - I absolutely do NOT agree that testing on a drag strip necessarily correlates to anything on a road course. Not going to change my mind there. Been down TOO many passes to start believing that.

Back to the topic at hand. The OP didn't just go out and buy something based on some magazine add. The OP asked a question here - far from just believing marketing hype. There is certainly some question as to the performance of tubular vs solid. People here who seem to know what they're talking about weighed in. I wish some others had also done so. I would also agree that tubular or solid, a straight splined bar would allow for the best calibration and testing. I should also be up front that I'm not a Jim Hand disciple. He's another guy - not a god. There are things that many people including myself don't necessarily agree with. His book is good. And outdated. If I want to measure changes for a drag car, I'll do test and tunes at a strip. If I want to measure changes for a road car, I think I actually need to turn the wheel in at least one direction :)

wmhjr

06-25-2010, 12:31 PM

I think we have to agree to drop consideration of driver errors from this discussion. Sure, it affects the results more - miss a 2-3 upshift or screw up and early-apex a corner and run out of pavement on track out might be "worth" several hundred or a thousand lbs added to a properly driven car. Or a wreck if you find a wall or a catch fence. But as near as I can tell, . . . . the likelihood of making such errors isn't a function of making any of these small mods. So either the driver is good enough to never make them or unskilled enough and always does; the errors just can't come in a pattern that favors the outcome of one arrangement over the other.

Norm

So Norm, would you also agree with the following as to why driver errors or variation should be removed?

It's just like target shooting. In bullseye pistol shooting I've got a .45 that has been bench tested and proven to shoot 1.5" groups at 50 yards. Now, I KNOW I can't shoot 1.5" groups. The biggest improvements in my scores will be the result of better technique. BUT - since it's all about consistency and predictability, having a TOOL that performs at a higher level reduces variation (and therefore the probability of error) just a little bit more, giving me a greater chance of an optimal result. If I'm shooting like crap, that 1.5" pistol capability won't be able to be measured during a match. BUT - if I happen to shoot really well, my chances are better. BTW, I still don't shoot well enough.

Road cars are the same way. A crappy, overweight and inexperienced driver can do a terrible job even in a top notch prepared race car. But without considering budget, every little advantage you build in increases your potential just a little bit more.

Make sense?

Skip Fix

06-26-2010, 11:18 AM

"I don't see you making the same claims about tires, wheels, frankly every single product on your car. At some point you have to do your homework, talk to people who work with this stuff, and make a decision."

I did make the same claim if you looked at my post about more carb, more cam. Why I and lots of racers have shelf full of carbs, cams, headers, mufflers,springs, shocks, convertors, rear gears, tires that have been tried for my conversation. Nitto drag DOTs sure don't stick like M/T just at the top of the list I recently swapped out. I DO buy and personally try lots of products and freely will tell what helped or hurt my combination. My current pump gas motor in my TA got over 20 pulls. 3 carbs, 2 intakes, three different rocker ratios,timing settings. I've had Guldstrand, Herb Adams, Global West parts on the TA back when you could pick it from Adams place in Monterrey. Heck I autocrossed a 1" rear Adams bar with a stock front bar and did fairly well but LOTS of parts in my garage,attic,storage spaces,on multiple cars(my kids high school driver 81 TA was built from spare parts) etc. that were actually tried.

So lets get back to the original question then-even on a well tuned car NO other changes, same driver, same good line around the track,tires, bushing hardness etc etc --will a 1 1/4 hollow bar give faster lap times or noticeable better handling than a 1 1/8 solid bar(since it was mentioned that generally they increase on a 2.5 mile road course or typical moderate length autoX course for the majority of cars and drivers? And we know that because it was actually done and compared how many times?

It seems you guys are not just implying but saying it will make a difference on the clocks and the seat of the pants. That is my skeptical nature in this discussion as I've swapped enough parts and enough track time to doubt that more than 1% of us would feel or measure that improvement even if the bars actually have the exact same rate(something still not shown comparing one bar to a different one). But then who would have guessed a fresh better tranny and a new looser convertor would have picked my drag car up almost 0.7 seconds!

"It IS a rear sta-bar ("sway bar"), just sold under a slightly different but entirely accurate name. And it does the same thing, shifting the roll stiffness distribution." You and I know that but the drag guys say its different:)

JRouche

06-26-2010, 08:04 PM

Road cars are the same way. A crappy, overweight and inexperienced driver can do a terrible job even in a top notch prepared race car.

Come on now. Just cause a guy is fat and overweight. Im 5'8" and 160 so, not fat. But give the fat dude a chance. Oh, and my rule. NO FAT chicks. LOL

No, no!!! I know that was just a typo right? You were thinking of the car and started writing about the driver. I get it. Im just trying to humor up the post a lil You WERE talking about the overweight car right, not the driver? LOL Never know.

My take? I think all of you guys have some solid points and are knowledgeable when it comes to cars. Sometimes the waters can get muddied up a lil though with differing ways of talking about similar points of view. In the end you folks might actually get to the same point but on different roads.

Kinda cool. I like to get all the opinions from several folks. Pick out the bits and pieces that are common and a guy like myself, or the OP can get a good understanding of whats involved.

Its good chatter and thanks for sharing your opinions. We all learned something. I did anyway. JR

Norm Peterson

06-27-2010, 06:26 AM

So lets get back to the original question then-even on a well tuned car NO other changes, same driver, same good line around the track,tires, bushing hardness etc etc --will a 1 1/4 hollow bar give faster lap times or noticeable better handling than a 1 1/8 solid bar(since it was mentioned that generally they increase on a 2.5 mile road course or typical moderate length autoX course for the majority of cars and drivers? And we know that because it was actually done and compared how many times?

It seems you guys are not just implying but saying it will make a difference on the clocks and the seat of the pants. That is my skeptical nature in this discussion as I've swapped enough parts and enough track time to doubt that more than 1% of us would feel or measure that improvement even if the bars actually have the exact same rate(something still not shown comparing one bar to a different one).
The advantage is really there, or at least is potentially there. Whether a given driver takes full advantage of it on any particular run or lap is a separate question.

But then who would have guessed a fresh better tranny and a new looser convertor would have picked my drag car up almost 0.7 seconds!
Depending on what was in there before (OE or mild street/strip?), it's not hard to guess that there would have been improvement. If you know enough about the two torque converters involved and the engine's torque curve, you can estimate the effect on rear wheel torque and hence acceleration. Do this for every mph of speed increase enough times and you'll have an estimated effect on ET (and mph).

"It IS a rear sta-bar ("sway bar"), just sold under a slightly different but entirely accurate name. And it does the same thing, shifting the roll stiffness distribution." You and I know that but the drag guys say its different:)
Yeah, it's kind of hard to get lots of folks with the straight line mentality to see any connection between what they're tweaking to go straight better and what some of the rest of us do to turn corners better. I've met exactly one drag racer who understood this particular topic well enough to realize why you don't need a rear antiroll bar with ladder bars.

Norm

Norm Peterson

06-27-2010, 06:40 AM

So Norm, would you also agree with the following as to why driver errors or variation should be removed?

Make sense?
I think so. At a level corresponding to banging away at tin cans and bottles, mechanical excellence hardly matters. Every round is either a hit or a miss - if anybody is even bothering to "keep score". Consistently closer groups doesn't even figure in, since missing by 1/4" might as well be by a foot or more.

At a more serious level, the better tool starts to have influence on the results. There's got to be a bit of "picking yourself up by the bootstraps" going on unless you're also receiving instruction and guidance. Maybe even if you are.

Norm

Skip Fix

06-27-2010, 08:25 AM

The advantage is really there, or at least is potentially there. Whether a given driver takes full advantage of it on any particular run or lap is a separate question.

Norm I can see in theory less weight is better for any performance car and definitely agree with it(assuming weight reduction in the right places) and try to do it!

But given a 3600 lb solid sway bar car will it go slower than a 3592 lb car with the hollow bar, a 0.002% difference in weight? And we will be able to measure it in lap times on a 2.5 mile road course? Again dropping the discussion the bars are identical rates. I'd just bet you even most professional drivers would have enough lap variablity(tank level, tire stick,track temp etc etc) on a car without the bar change to not be able to measure that much weight change improvement with the bar change. Look at the NASCAR boys lap times when at road courses, or national autoX times- I'd bet the same car same course has more variation than what even the engineering formulas would predict in perfectly identical runs is all I'm saying.

How many of you guys here that do track time have lap times the same to the 0.01 second for all laps that day?

wmhjr

06-27-2010, 04:25 PM

You keep missing the point.

It's not just the difference in weight of the two bars. It's that, PLUS the differences in other parts. A pound here, a half pound there.

You're also missing another very important point. Yes, there is clearly more variability in driver performance. So what? The perfect car with the perfect drive would in theory yield the best performance. Doesn't exist (Sorry Brian, et al...) Introducing driver variability in this discussion is a worthless activity. No value whatsoever. Just because the driver isn't good enough to always take advantage of it, doesn't mean it isn't an advantage.

By your logic, ANY change that isn't doesn't result in significant improvements should be disregarded. That would result in a pretty crappy car. I seriously doubt that replacing a well performing solid bar with a tubular lighter bar by itself will result in any measurable change.

Like I said - probably not worth pulling a good performing sway bar and replacing it on a mainly street car just for weight savings. But the really good cars are filled with well thought out details everywhere, and try to take advantage in every area. I was helping a friend at the track yesterday (drags) and that's mainly the difference between very consistent good cars, and those that were not as good. Attention to detail. Focus on the little things. The SUM of the parts and the design. You also need to recognize that not everyone is a consistent racer and that they may not have the ability to have shelves of parts. That also means that sometimes you need to find some really strong resources. There are a few here who are sponsors, and my experience thus far has been very positive. Marcus for example encouraged me to NOT replace sway bars until I had a chance to drive the car with the other suspension changes we implemented. It's a credit to some of our sponsors that they give what I consider good, experienced advice rather than just trying to sell every part they carry.

BTW, my car has a tubular Hellwig front bar. I needed a new bar. Since I needed one, getting a the Hellwig bar was a good choice.

MrQuick

06-27-2010, 11:10 PM

I know a bunch of guys that spend thousands just to loose 15lbs. But good discussion.

Skip Fix

06-28-2010, 06:30 AM

"I have a 79 Z-28 with Hotchkis springs/Bilsteins and Nitto 555's. I have a 1 1/8" factory sway bar on it now. I am looking at either the hollow Hotchkis sway bar 1 3/8" or the Addco solid sway bar
1 3/8". Losing the weight would be nice, but would there be much difference in the cornering capabilities between the two bars? Any advice would be great."

We ARE talking about the difference between a hollow vs solid. I get it's part of the whole package, total weight loss with other light weight components- I'm not that dense to figure that. But the question and most of the discussion from the start is swapping a bigger hollow bar going to perform better than a solid bar? The engineering theory that most is the outer portion so the hollow can be effective-part of the debate but we'll ignore that for this. And the advertising pushes that and the lighter weight WILL be better just from the sway bar and you go faster. Then just doing a sway bar swap and saving 8 lbs should be able to be verified on the track. Tell us-using a scienced out car(assuming his has all the other bells and whistles or using a pro car, pro driver, already a good solid front bar for it's set up) and swapping a hollow bar for a solid bar will it make a change in lap times or a seat of the pants feel?

Simple question-not debating a 100 lbs lighter will make a difference for all that light weight stuff also added on-just bar A vs bar B.

wmhjr

06-28-2010, 12:28 PM

"
Simple question-not debating a 100 lbs lighter will make a difference for all that light weight stuff also added on-just bar A vs bar B.

You mean like when I said....

Most important, like I said - if you're replacing the bar anyway, no reason to NOT get a tubular bar as opposed to a solid bar. If you don't need to replace the bar, then it's probably not going to make a measurable difference.

:)

79T/Aman

06-28-2010, 03:49 PM

Here are a couple pics where practice trumps theory, FEA shows the arm under the most stress, this supports my concerns that the arm of the sway bar should not be ignored and a hollow arm will flex more than a solid one, reducing performance, and as seen in the pic eventual failure (yes, no need to tell me that solid bars also fail)
And as you will notice in the pic how a tube bar bend starts to collapse on itself when formed.
And as I mentioned before why would you spend 2 to 3 times as much for a hollow sway bar that needs to be larger and cause interference problem on some cars with zero performance gain

David Pozzi

06-28-2010, 04:26 PM

That is a lousy attempt at making a hollow bar!

The hollow bars I've used have no visible shrinkage in the bends. Budget allowing, I would go with a hollow bar for the weight savings, even though it's a small savings and not something you are going to be able to measure. I installed taller upper balljoints on Mary's 2nd gen Camaro, I couldn't measure that either, but I know it SHOULD be better.

That said, I would not try and talk anyone out of running a solid bar if the rate was correct. That one choice isn't significant either way, but if you were to choose the heavier option every time, your car would wind up weighing quite a bit more, and that would be significant. If there are clearance, fit, or rate issues, that needs to be considered in your choice too.
David

JRouche

06-28-2010, 09:43 PM

I have to agree. That bar is a poor example. Every hollow bar that I have used is not necked down at the turn. Might be the diff between using a mandrel bender and just a simple roll bender.

And the end of it? Not sure if corrosion had a helping hand in the failure. Or if it failed and was left out to rust. But the way the end is open l am curious to what it looked like new? Not a design I would put in my car. The manufacture of that bar was doing it on the cheap.

One thing that came to mind. For the issue of weight and is it worth it, for such a small weight loss.

Yeah. A driver may not get dramatic increases in performance, may be the same. Most guys like to see a measurable increase for money spent. I totally get that. Thats reasonable and sound thinking.

But thats most guys. Some guys will look at the entire picture and KNOW they have a decrease in weight, as small as it is, its still a real number. So whether their driving performance increases they know they have shaved a pound or two off the front. And sometimes the idea is to keep whittling away at some of the sections that can be lightened up and before you know it you have shaved 50 extra pounds off.

But really, I think looking for a pound or two here or there should be used by a racer. And then there are still so many places to reduce weight. I find it funny to see a guy looking to shave off two pounds at the front and he has a battery in the engine compartment. Or has a steel bumper and not aluminum bumpers. Or has a steel hood and not a plastic hood (and fenders). Or is worse yet running really large heavy wheel and tires cause they look good instead of using race wheels and tires of a correct diameter. Or too much steel and cast iron on the engine when he should have more aluminum.

It seems like there are SO many places on the front end to shave weight that when a guy starts talking about a couple pounds for a sway bar he might have missed some other areas. Racers usually dont. They have all of the stuff I talked about and MORE. Now those guys really can start to talk about the couple of pounds re: hollow or solid bars.

But unless the battery is in the trunk, aluminum top end parts for the engine (and accessories), aluminum radiator, aluminum bumper, maybe some plastic (fiber glass or carbon fiber) parts for the hood and fenders and a lot of other inexpensive changes are made the couple of pounds for the different bars seems like bench racing IMO.

Kinda makes me think of the guy that rides bicycles and spends 4500 on a bike that has titanium this and that, carbon fiber this and that and he is 30 pounds over weight. He might do better with a steel frame bike to shed his extra 30lbs. But thats a diff story.

Im ALL for reducing front end weight. But I think ALL of it should be looked at. And if a guy needs a new bar anyway, yes, I think he should go for the more efficient bar (weight to spring ratio) and continue to look for weigh savings all over the car.

But if a guy has a bar thats working for him (proper spring rate already) and is looking to replace the bar because of the weight issue I think thats a poor choice. Not saying thats whats going on here. But for anyone else looking at a new bar... Its all good. JR

Here are a couple pics where practice trumps theory, FEA shows the arm under the most stress, this supports my concerns that the arm of the sway bar should not be ignored and a hollow arm will flex more than a solid one, reducing performance, and as seen in the pic eventual failure (yes, no need to tell me that solid bars also fail)
And as you will notice in the pic how a tube bar bend starts to collapse on itself when formed.
And as I mentioned before why would you spend 2 to 3 times as much for a hollow sway bar that needs to be larger and cause interference problem on some cars with zero performance gain

Skip Fix

06-29-2010, 07:01 AM

wmhjr

06-29-2010, 08:07 AM

Originally Posted by Skip Fix https://www.pro-touring.com/forum/images/buttons/viewpost.gif (https://www.pro-touring.com/forum/showthread.php?p=688877#post688877)
"
Simple question-not debating a 100 lbs lighter will make a difference for all that light weight stuff also added on-just bar A vs bar B.
You mean like when I said....

No we're talking about a 100lb difference ONLY a 8 lb sway bar swap! You seem to be missing the point he asked for just a sway bar swap.

Skip, no - you're still missing the point.

I have a 79 Z-28 with Hotchkis springs/Bilsteins and Nitto 555's. I have a 1 1/8" factory sway bar on it now. I am looking at either the hollow Hotchkis sway bar 1 3/8" or the Addco solid sway bar
1 3/8". Losing the weight would be nice, but would there be much difference in the cornering capabilities between the two bars?

The OP was for some reason unhappy with his factory sway bar, and was considering replacing it either with an Addco solid bar or a Hotchkis tubular bar. THAT is what this thread was about. It was NOT about whether or not replacing the existing bar simply with a lighter bar made sense.

If the OP had been asking about the performance of the tubular compared to an existing solid bar, then OK. He was not. Since he had already decided to replace the bar, it was a question about whether the replacement solid would outperform the tubular, and vice versa. In this specific situation, there is certainly no ADVANTAGE to a heavier bar assuming the tubular bar can meet the suspension requirements. And since the price difference between the two is negligable enough to be called non-existent, I continue to be baffled by the way this thread has turned.

Furthermore, in a later post the OP stated that he had purchased and installed the Hotchkis tubular bar and performance was apparently improved.

Seems pretty straight forward to me.

silver69camaro

06-29-2010, 09:39 AM

I think this thread is going nowhere pretty quick.

Skip Fix

06-29-2010, 01:59 PM

"Losing the weight would be nice, but would there be much difference in the cornering capabilities between the two bars? Any advice would be great." So in fact cornering comparisons for a similar sized solid and hollow was the initial question.

Since it is advertised by the manufacturers and said by folks here -the hollow has the same torsional resistance as solid(although one statement was that they are often made larger to be sure they do) due to torsion in the outer portion only and they are better in performance because they are lighter-usually 8lbs or so. It should then pull more gs and have a better lap time if it is in fact better and has an advantage over the solid-not a wash-ie perform the same. Otherwise it is a coin toss.

My entire question was -can we in fact measure this difference between these two bars? Your comment the solid bar has no advantage does not mean the hollow one does have one unless it can be measured. A simple engineering and scientific concept-it is not different if it can not be measured. And all I have questioned-can we measure a 8 lb difference in a cornering car.

Here's a quote from David Pozzi "and not something you are going to be able to measure." Which is my contention.

If not we get back to the coin toss for the decision.

He made a decision, it performs as he would like so we're OK with how it handles-but is it "better"?

wmhjr

06-29-2010, 02:40 PM

I give up. I'm going down to my shop in a little while and will hang barbells on my sway bar.

David Pozzi

06-29-2010, 06:48 PM

There's a reason I didn't post in this thread sooner. It seemed like it was going to go on and on and on no matter what. I think enough information has been discussed that anyone could make an informed decision on what anti roll bar is best for them.

Skip Fix, what exactly do you want, a vote?
I don't see the point in further discussion, but I'm not going to lock this thread.
David

MrQuick

06-29-2010, 11:00 PM

It seems to be one of those threads where everyone is arguing in agreement. I could be wrong.

vince

Roadrage David

06-30-2010, 01:07 AM

mmmmm just pickt this tread up and i think its a good one. Nothing wrong with a serius discusion. I have something to say myself . i didnt go tru all the posts so it might have been said alredy, But if there is no mesureble diferense in a hollow ore solid sway bar, could it be that when you have a all out race car with all the ""exstra"" weight savings on the car that are availeble today , that the hollow sway bar is the one to go for, iven the hollow sway bar critics should see and understand that the ""mutch"" lighter car would not put the hollow sway bar under enoughf presure to have it work any diferend then a solid sway bar!!!!!. just in case i runn Helwig solid up frond!. nothing in the rear as i have a mini tubt car with fat tires. simple Hodkish coils DSE leafs koni classic shoks.( no airbag ore coil over stuf just stuf that works) only cars that past me on the former F1 cirquit in holland was the Ariel Atom and a 2010 corvette C6 Z06. i had to let them go due to radiator cooland leak producing smoke!!. caught some c5 c6 corvettes and brand spanking new saleen mustang and new shelby mustang. my car weights in at 3692 lbs with halve a tank, and im the 320 lbs fat guy driving it!oohh pasenger weights in at 175lbs.. http://www.youtube.com/watch?v=mbq-yN8DGn8&feature=player_embedded http://www.youtube.com/watch?v=Opza1XD_Y9M&feature=player_embedded http://www.youtube.com/watch?v=QSWpnguqiZM&feature=player_embedded

Skip Fix

06-30-2010, 05:53 AM

David I guess arguing ineffectively with wmhjr that neither bar has an advantage if track times/performance are the same regardless the advertising or engineering theory. Around too many engineers and scientists to take statements as truth without measured backup.

wmhjr

06-30-2010, 06:27 AM

I'm convinced. I rode my harley to work today. It had less than half full fuel tanks and I couldn't notice any difference in performance, so I'm not going to fill my tanks anymore. Tomorrow I'm going to check whether or not there is any difference in performance if I disconnect my lights. I'm testing everything on a 1 mile stretch of road, and anything that doesn't result in measured performance differences is going to be discarded.

:)

zbadone

06-30-2010, 07:03 AM

Wow, this thread has really taken on it own life. I appreciate everyones input, but like WMHJR said, I was just wondering which bar someone would choose given that the bars were the same diameter, very close to the same price, and that one happened to be hollow vs solid. If they performed nearly the same, then I believe it would be to my advantage to have less weight on the car. Also, just an FYI, the hollow Hotchkis bar was actually $20 less then the solid so I figured it was a win-win. Do love this new bar however. It really keeps the car flat and doesn't push out the front end at all. Maybe I'm just not pushing it hard enough......:smoke:

Skip Fix

06-30-2010, 09:16 AM

"Tomorrow I'm going to check whether or not there is any difference in performance if I disconnect my lights" Well the correct theory to test there is disconnecting the alternator to reduce the HP draw spinning it uses:) Why do you think so many drag guys are hooked up to battery chargers between runs? Although depending on the electronics and ignition you may loose more than you gain as some folks that do that test have found.

zbadone-glad the sway bar deal worked out and gave you the performance you wanted-after all that's all it is about anyway.Since the two choices would probably be a wash in performance on your car the the hollow was cheaper it was a win-win. The rest is just engineering theory exercises unless you want to buy that solid and do a back to back test them for us:)

FWIW my old NMCA Top Stock RAIV motor was dynoed with 3 different intakes(all made within 1 hp of each other even the factory HO intake vs the aftermarkets).2 additional on car tested. Had 5 cams, 2 different header sizes, mufflers,2 rear gear ratios,shocks, as well as different timing/jetting setting-so I really don't believe in real world testing to prove what the theories are at all;) So what can I say I guess I'm not so bright to want to try things-even free mufflers for the manufacturer that swore theirs will go faster.