Specs on subframes?

[touring67]

With all the popularity of Pro Touring, there have been many manufacturers to come out with complete kits for many muscle era cars. Among the kits there are complete bolt in subframes that offer "vastly improved" geometry and handling for your specific car. In my case I look at the first gen camaro parts and kits, specifically the 67. In many cases the information provided by the manufacturer is of how complete the kit is or how easy it is to adapt or install. My question is, do they offer specifications for their complete kits (because anyone would be hard pressed to offers specs for a kit that could use any number of LCA, UCA, spindles etc) or do they just tell you that it's a "vast improvement"?

I would just like to know how well a subframe was to perform under the rigors of racing or aggresive street driving. Some may state tubing thickness or frame rail thickness, possibly advertise 0 bumpsteer but do not usually give out characteristics like camber, caster, how much it changes FRCH, COG or pivot points. Would there may be a way to calculate some of these characteristics that some of you know and might be so kind as to impart on me and others of this board? Or would it just be best to contact each manufacturer and ask?

Namely, I bring this topic up because I think that if one was to use a bolt in subframe (complete kit) and spend a good amount of money on it, that they may like to know what they are getting. Also it might help to clear up some issues with using the bolt in subframe (non complete) and substituting DSE or GW or AFCO arms, taller UBJ's etc. Since some of these arms have built in changes, it might be overkill with said frame.

Was just wondering if anyone has used subframes that did vastly improve their handling and if they have measured the results or characteristics after installing one. Right now I can think of Wayne Due, Fatman Fabrications, Chris Alston Chassiworks, Art Morrison, modified Corvette, and custom...and from there my memory fails me.

There are also kits such as DSE's stage 3 that use the stock subframe but substitue almost everything. And one could use a stock frame and do the Guldstrand mod with different parts as well. But my main question here is the 'other' subframes that are for sale. Any info??

[touring67]

Ok, how about just some personal experience with some of these subframes. I know that this may have been a hard to judge question so I'll just simplify it. What do you use, and why do you like it? Did it significantly help, and if it did in what ways? Lower COG, less roll moment, better geometry, no bumpsteer, less unsprung weight, instant center adjustability, and lighter frame etc are all good things. What did you gain from using a different subframe?

[JohnUlaszek]

For starters it would be nice to see more of what Pozzi has done, publish your numbers and tell everyone how you got there.

[David Pozzi]

For starters it would be nice to see more of what Pozzi has done, publish your numbers and tell everyone how you got there.

Sorry I haven't contributed before now, I've been buisy.

I'm a ways from getting my Camaro running but let me offer a fiew observations on suspension.

THE WHOLE PACKAGE:
The whole driver/car combination is critical to accomplishing a performance goal or benchmark, if any one thing is deficent, the goal won't be met. You can have a killer car but if the driver can't handle it, nothing is accomplished, likewise a poor tire or spring choice will shoot down an otherwise good car from setting a good time, etc.

SUBFRAME
It must have good torsional rigidity, - at least as good as the factory sub. Some of the aftermarket subs look rather flexable in this respect. At least GM put some thought and engineering into trying to make the sub rigid. The geometry sucks but can be fixed, how good is perfect geometry if the subframe is wanking around?

SUBFRAME WEIGHT SAVINGS
I hear different claims of saving weight from the factory sub.
Here's what a GM sub weighs:
SUBFRAME WEIGHT additon list
Bare sub 110
knuckle assys 92
springs 22
A arms - upper 20
A arms - lower 22
Shocks 6
Ctr link and tie rods 17
Trans Crossmember 10
Sub total 299

PS box, hoses, pump 44
TOTAL 343
================================================== ======
SUBFRAME WEIGHT additon list
Bare sub 110
knuckle assys 92
springs 22
A arms - upper 20
A arms - lower 22
Shocks 6
Ctr link and tie rods 17
Trans Crossmember 10
Sub total 299

man steering box 16.5
TOTAL 315.5
=================================
A fiew lbs can be saved over stock, but not hundreds of pounds in my opinion.

I like Rack and Pinion steering, if I got a sub as light and stiff (or stiffer) as stock and it had a front steer power rack, low scrub radius, good neg camber gain, lots of pos caster, zero bumpsteer, good brakes, I'd be pretty happy with it. But it seems there can be lots of little things that can creep in to cause extra or unexpected problems. Most aftermarket subs don't have as much neg camber gain as a stock Camaro with Guldstrand mod. My experience has shown you need -2 to -2.5 deg neg camber static setting even with the Guldstrand mod on an open track Camaro. One thing that helps the late vettes get by with less neg camber gain is very very low chassis roll and high amounts of positive caster.

REAR SUSPENSION
I've been told by Herb Adams personally and read in several books that the multi-leaf spring layout as used in a Camaro is pretty darn good, (not the springs themselves but the overall design). Is there better? Sure, but how much better, and did you do the "better" system properly or is the better suspension have some geometry errors hurting it's performance?

There are most likely certain conditions where one suspension might do better than another, I think on a pretty smooth surface like Laguna Seca, there would be little to gain from a three lnk rear, but on a rougher surface it might do better.

I'ts important when comparing to compare best to best, and the best leaf setup I suspect is the Global West Cat 5 leafs. It is the most free from bind and I'm guessing the rate and design are good for handling and pretty much eliminate wheel hop. I haven't tried these leaf's but the design looks good to me. I don't know the best three link design geometry but some of the books have starting suggestions.

There was mention of Corvette composite leaf designs. The major benefit of this design was isolating the wheel vibrations from the chassis and convienient packaging, - coil springs take up room, require extra chassis bracing, and make the CGH slightly higher, but the leaf springs can be slung underneath where there is more strength in the chassis down low. The chassis is probably easier to make or assemble too. I've had a couple of C3's with rising rate multi-leaf rear cross springs, and they rode terrible in the rear, and they had lots of drivetrain and wheel noise. GM put composite rear springs on them in 80 or 81, and it was an improvement in ride quality. From a handling perspective, the chassis really doesn't know if the spring is a coil or leaf the way the C4 or C5 vette suspension has them connected. Race Corvettes are converted to coils because they are easer to change to different rates.

I have read several posts of the Vette Brakes fiberglass Camaro springs breaking, also of wheel hop problems. If the horsepower is low, they seem to work OK but when you get close to 400hp, they don't work.

TESTING/COMPARING
I guess I'm a bit too skeptical to believe it can be done well enough to be of use to "us". As Salt Racer more-or-less said, it only takes one thing amiss and the car won't do well. The car or cars would have to be well developed, not just a subframe thrown on and timed in a slalom, etc. Most guys who have bought aftermarket subs say they are great but say they are not experienced in suspension tuning or mods.

I would like to see comparisons of chassis stiffness in ftlbs per degree for each subframe system. Comparison of neg camber gain, roll center height and movement, SVSA, FVSA, bumpsteer weight added or saved, F/R weight changes, rear RCH, and movement, rear anti-squat/anti-dive.

Things that stick out in my memory:
I attended a road race at Laguna Seca in the early 90's, I saw a worn out looking 69 Camaro in vintage TA configuration running in second place with a bunch of tube-framed plastic bodies GT1 Corvettes and Camaros! The leader Corvette fell out with mech problems and the 69 was LEADING THE RACE!

After a fiew laps, he got in a little over his head at turn 9, and spun off while leading all the other guys. This car had LEAF SPRINGS but it must have had a pretty good overall package! ;)
The guy found the car parked by a garage, bought it, and threw an engine in it, hopped in and just flew! The car was previously owned by a very successful local racer who parked it long ago.

My point here is, sometimes a simple plain combo that is well sorted will win over another car that is much more exotic. I stress the "sometimes" part!

A plain "stick" rear axle has lots of benefits when putting the power down when exiting a corner, leaf or coil/three leaf, it compares very well to an independent rear axle if the pavement is smooth.

I'm going with rear leaf on mine so I can get my car going in my lifetime... I have lots of other projects. I'm going to count on driver talent and a superoir driver/car package to get me by others on the track. If the talent thing doesn't work out well, I'll try other rear setups if I can find the time to do so.

For those who want to try a three link, I think there is a little to be gained, maybe a little better feel powering out of a turn, - stability kinds of things. More traction? - maybe, faster track time? could be a tenth or two but if comparing to a dynamite leaf combo maybe not much. This is just my speculation, not based on solid on-track comparisons, so I may be wrong on the gains possible for rear suspensions.

[Salt Racer]

...You can have a killer car but if the driver can't handle it...likewise a poor tire...

Hey, that sounds like me!!
A set of $84 18" tires didn't work so well either!

Looks like I'll be heading down to San Bernadino in March for B'ville tech inspector meeting, and Speed Ventures will be at Buttonwillow on March 11th. Maybe I need to set the idea of 18x10s aside for a while and get a set of 255/45R18 Yokohama AVS Sport....

Good point on torsional stiffness, but I feel some people may be better off buying a subframe w/ better suspension geometry unless they know how to alter it. It's easier to tie the frame to firewall, add some tubings here and there to improve chassis rigidity.

Great story on the 69 Camaro leading a bunch of GT1 cars! I love it!!

Thanks for chiming in, David. If you can come out to the SoCal track event I'll be attending this year, you're more than welcomed to drive my car. I know it's a totally different platform, but you may be able to tell some differences in behaviors between leaf and 3-link.

[Cdog]

DP, Great post. I've seen the vintage race out at the Tustin Marine base and the first gen. Camaro's were pretty damm fast.

[Salt Racer]

Yes, you're totally right that for fair comparisons, all cars have to be well developed.

The way I look at those testings are a bit different. I think any legitimate suspension manufacturer need to be able to provide baseline setting that are close enough to ideal setting to their customers, via calculations and/or extensive testing. Subtle/small things like sta bar arm length, shock valving, tire pressure, etc, are still up to customers preference, but I have a doubt that minor under/oversteer would result in huge differnce like 0.10G in skid pad performance (for a given tire, of course).

Many of today's best street tires are capable of near 1.0G traction on a well-developed car weighing in 3000~3500 lb range, so if some car put down some miserable performance with those nice tires, personally I'd be skeptical of the engineering behind the products used on the said vehicle (ie, manufacturer was unable to provide baseline settings).

I agree that the testing results won't tell you the whole story, but they at least give me rough ideas

[JamesJ]

One problem with asking consumers what differences it made to their cars would be that every person can represent it differently and every person reading there responses would and will interpret it differently. Even if you did the same mods to two cars, many different factors would come into play such as tires, size of wheels, shock, springs, and all those mods to the rear as well, so unless you had the same person drive the car and you used the same car it can and probably will vary. I would be much more interested in the actual manufactures data, if they had any.

[Tom Nickols]

I'd think it'd be great if one of the magazines took all the aftermarket frames and a standard one and tested the frames for stiffness. Just from looking at the new ones they don't look that ridged. The existing one has a large section center member that looks as if it'd be more stiff than the 3x3 /3x4 exc that the aftermarket ones use.

As for using the corvette a arms, they are built for the corvette, so do you really think it's going to work better than the existing set up? may be, may be not. Are you really going to spend a huge wedge without finding out? Like the emporors new clothes, every one standing aroud saying its's from the corvette- it must be good. (eh, are you sure?) The corvette has the engine in a different place it has a different wheel base, track, CENTER OF GRAVITY, any of this making sence to you??? LOTS of bucks and you dont even know the return.

Stiffness of frame is probably easiest to read and may be most important. any undamped chasis flex will mess with the handeling even with the 'perfect' A arm geometry.

Safest course of action is to stick with the standard frame, stitch the frame joints together and may be looking at a Detroit Speed and Engineering style upper A arm relocation. (Preferably if the can proove it works, control tyres, shocks, springs etc on a before after comparison)

[Tom Nickols]

Here's a thought chalange the makers of the frames to do a few controled tests. run a car over a slalom etc. then change only the frame. Hopefuly they'd use a car with all new bushings and shocks. After all if they want us to buy there product the least you'd expect is they could proove its better...

Any Manufactures already done this, I'd be very interested in the results.

[baz67]

What does "vastly improve" mean? You could vastly improve a first gen with better rims and tires. Hell add the Guldstrand mod and look out corners.

~Touring67, one bias I see is that I do not think anyone has had a modified factory sub and then went and put on an aftermarket sub on. Someone correct me if I am incorrect on that. If you go from a unmodified stock sub to the aftermarket sub I would think there would be a noticable difference. It may also be just the "wow" factor that drives the purchase. You may loose some weight over a stock frame or gain stiffness. Right now all I see is the magazine marketing and no hard numbers.

I, like Tom, prefer the modified stock frame approach. You have the ability to relocate the upper pickups fairly easily to improve geometry.

~Tom, your idea about a head to head test is great. The problem is that it would be marketing suicide to all but one company. I would be surprised, but happy to see that happen.
Brian

[touring67]

This is exactly what I was hoping to hear about. Yes, it is quite true that it is very hard to judge different frames for different cars and different drivers, tires etc. However, all I seem to hear about when searching for different frames is that it will "vastly improve" the handling performance. The reason I have not really gone into a modified stock subframe is because it could be harder to judge because any small change could affect the results and it's based on the user's judgement not on the marketing of the manufacturer.

I am sorry if I have come off with a bias towards a different subframe ( I think it is easier to judge that way) as I would prefer whatever worked better than just what 'looked good'. Meaning, if the modified stock one worked better then I would be all over it, and if not I would much prefer to weigh the difference against an aftermarket sub and if the difference was significant enough by my standards then get another frame I suppose. I would love to see some test numbers or some comparison data of aftermarket subs or modified stock ones vs each other. IF there was data out there I highly agree that it would be very beneficial to know it. And to baz67, it would be great if the manufacturer could weigh their own subframe against a modified stock one. And I also agree that it seems to me that all I hear is that it will 'vastly improve' the handling etc and this is just marketing hoopla.

That is sorta why I asked the question of what people use and why they like it so that I/we could get a rough example of the characteristics of different frames and modified stock ones. It may not be so exact as test data but it is a start. Since the first post I made in this thread may have asked too much on specifics I figured I would ask a more open question. Any info could be helpful on this topic and I wonder what some of the more experience guys have used and found that worked, that is what I hope to find out.

[Payton King]

I am trying to get my car together as quickly as I can so I can provide real world numbers. I am looking at the first or middle part or April at a completion date. I will not have any before numbers to compare to as my car had the stock 1st gen suspension before I took it apart 3 years ago. Will my set-up be the ultimate...I doubt it. There will always be someone with more money and resources to best anyones effort. I, like most of you, would have liked to have seen a comparision of performance data inwhich to make my desision. So, when my car is done I have access to some data acquistion equipment and someone that knows how to use it and I will provide numbers good and bad (hoping for no bad numbers) My car is a 69 camaro with an LS1/T56 combo. It will have a 21st Century C5 frame, DSE connectors, DSE rear leafs, Global West rear shackel kit and I will be running C6 tire and rim package. No mini-tub...unless I have a weak moment in the next few weeks.

Soon as I can get it together I will post numbers. I would hope that others would do the same. Even though I have committed to the 21st Century frame, it can only make our hobby better to have actual data on all of the products that are offered. Would I like to have a head to head test with other products...yes! I think that would be an absolute ball. To address the same car concept: way too much work. Not only would you have to swap frames, probably tires due to offset and headers/exhaust systems. I think similar cars with the respective manufacturers parts installed and same tire compound would be as about as close as you could get. If I am not mistaken **** Guldstrand and Herb Adams had a shoot out in the 80's with 2 cars in one of the magizines...I think it was a 1st gen and a 2nd camaro.

Payton

[Steve1968LS2]

The problem is that it would be very hard to quantify. You would have to use the same car with the same driver on the same track under the same conditions. Swapping out the subframe is not a quick proceedure so you would have to invest quite a bit of time. It could be done though, a sort of "subframe shootout". It would far more complicated to pull off than say horsepower comparisons.

Would be nice to see how much better the "best of the best" subframe system compares to a highly modified stock subframe. Hmmm, I have an idea for a tech article.

[Cdog]

The problem is that it would be very hard to quantify. You would have to use the same car with the same driver on the same track under the same conditions. Swapping out the subframe is not a quick proceedure so you would have to invest quite a bit of time. It could be done though, a sort of "subframe shootout". It would far more complicated to pull off than say horsepower comparisons.

Would be nice to see how much better the "best of the best" subframe system compares to a highly modified stock subframe. Hmmm, I have an idea for a tech article.

Hey your in Anaheim Hills too. We should meet up sometime and check out eachothers projects.

[touring67]

As far as swapping subs on a certain car to do back to back testing I think it is nearly impossible due to so many variables and this has been stated before. It would be very hard to limit the variables as there is certain tuning that would be required with each one resulting in a difference in another variable so as far as that is concerned, yes I agree it would be very hard to quantify. IF it was to be tune for the skidpad as much as you can and THEN test the results may be informative but only if the variables were measured. One could say, well if they had adjusted xxxx more then they could have pulled more g's etc. So as far as a subframe shootout goes, either one would have to be loaded and have a multitude of resources and people on hand to assist or two identical cars that ran back to back with the same driver, again requiring lots of time and money.

Most manufacturers of subs have some variation of a 'full kit' that comes with all that one would need to modify or bolt it in, minus the small stuff. These are the types of kits that are easier to test because they are full and have less variables. The manufacturer could test the bumpsteer, test the camber curve, modify the instant center, check the roll center height and if possible test for stiffness and so on...but it seems that they don't do this, rather they say that it is a great improvement over stock or will allow more adjustments.

Although I do agree that in the end it is the ultimate choice of the user and his/her choice of settings and tuning, I still believe that it would be much easier to choose if there was some published data on any aftermarket subs and modified stock ones. It is more about the tuning than the components themselves and that is why I suggest that it is easier to do the testing on the full kits, tune them or test them for their performance and go. Because there are measurements that cannot be changed and their are limits to tuning on certain components I think it would be easier to quantify this type of testing.

That said, let's hear what some of you guys use and why you like it. What did it allow you to change that aided in performance and what measurements, if any, did you check that proved it to you. I know this is somewhat subjective and could go on forever but I think that is the point. The more info, the better.

[Salt Racer]

I remember reading shootout of SBC cylinder heads in CHP in mid '90s. I was surprised to see something like that, but it was very good info.

It would be great if the same thing happens with subframes, though it's probably tough to materialize due to complexity and higher cost involved.

But, IMO every manufacturer should have a test mule for their own benefits as well as customers'. A six-cylinder Camaro can be picked up for reasonable money, and they can equip cars with their own subframes. Then, perhaps magazine people or some influential individuals/organizations could gather some sponsors to supply spec engine, tranny, diff & gear, tires, etc (like a carb-to-pan crate motor from GMPP, 245/45R17 & 275/40R17 KDW tires from BFG...), draw out some simple rules (no interior other than front seats, no body panel hacking...) and conduct a shootout.

Afterwards, manufacturers can keep the running cars. They can take potential customers for a ride to showcase their products. Or put their new products on and have the cars tested again by the same people for a direct comparison with the baseline (ie, shootout results)....

Sounds like a pretty good idea in my head, but I probably should get back to reality...

[MuscleRodz]

I like your idea Salt Racer and just take one carburated mule with nothing on it except what is required to run and drive and go racing. I think it would be actually harder to get the manufacturers to ante up the subframes for the test. As stated earlier in the post, it would be marketing suicide to everyone but the winner.

Mike

[touring67]

I think that is the idea behind it though, it would weed out the poseurs, the idea behind capitalism. If they so choose to market their product as superior then there should be some substantial data behind it to back it up. However, this may be hard to do at this time but look at what is being accomplished these days. The aftermarket is so alive that I think it is possible. One example is the complete new sheetmetal body for 69 Camaros which just shows that if there is substantial evidence that something like that is necessary they will build/do it. For now, I think the possibly uninformed are still buying what they do not know much about and keeping the market thriving on what I consider a lack of data.

Again, now that I have said that I would still like to hear what some of you guys are using for your cars, let it be a race car, let it be a street car, let it be both. I think it can be beneficial to hear what people have to say about their experiences with different suspension products. If you had problems with a Watt's link in the rear bring it up, if you spent hours fabricating and tuning the Corvette IFS but it worked phenomenal after, then thats game here too. I think experience (along with the technical knowledge) is one of the best teachers and education when it comes to something like this, so let's hear some of it.

[Cdog]

Would'nt a well tuned and set up front suspension keep a certin degree of castor and camber all throught it's travel? If so it seems you could test that on a allighnment rack. ( Sorry for spelling). Now you could also put too big of tires in the front and scrub too much speed in the corners. Or too big of rear tires and have severe under steer. Seems to me there probably is a magic number most race car builders look for when making their suspensions. After you get those #'s correct it's all about traction, weight and shock rate.

I used to race 100 mph karts when I was a kid and learned the basic's then.
My basic thought was if you have weight savings and can run a wider front tire if needed, And you have the correct castor/camber, the aftermarket subframe has built in benifets from weight savings and wider tire avaliabilty so now it's up to you to tweak and tune to get it's full potential.
If my statements are correct, lets put the frames on a rack and check them out.