Are solid axles dead?

[another69]

I love my Ford 9" based Strange rear end, but the leaf springs not so much. They move side to side and I have a good amount of axle wrap, not to mention its tight around the gas tank and exhaust. Anyway, I had pretty much settled on installing a torque arm next winter to replace them. Then I started thinking, why am I putting money into keeping a live axle rear suspension? If this was a drag car then it would be a no brainer to keep it, but once they launch the next gen Mustang there will be 0 production cars that still retain a live axle (as far as I know). That tells me something. Although there are very few choices on IFS kits out there I think that things may change in 5 or 10 years. I know that each type of suspension has its own advantages and disadvantages, but I think that IRS may be better for pro touring. Please tell me that I am wrong, I really like the simplicity of my 9"!!! I have to admit though, my current rear setup is more pickup truck than Corvette.

[raustinss]

Irs are obviously awesome but yes can be a lot more involved with fabricating a custom install... weight...and then tuning. having said that yes solid axles are cheap and easy but, if your were to dig around a Lil bit ( Detroit speed) etc. There are quite a few companies that have managed to make a solid axle set up work and work quite well... bad penny...Mary pozzi has a sweet camaro...my two cent opinion its what you can afford

[dontlifttoshift]

I still run 'em on both ends......

Due to cost, I don't think they are leaving our segment anytime soon.

[another69]

Weight seems like it would be an advantage. Less unsprung and (maybe) more in the rear for better balance. As far as cost, an aftermarket solid rear end costs over $2k plus a link type suspension $2k - $5k and you're looking at over 4 grand pretty easy. I'm kind of surprised that the only aftermarket IRS that I've seen is from Heidt's, but it would seem that a decent aftermarket IRS could be sold for around $5k. Or adapted from another platform for about the same amount of cash. Wouldn't it be great to dial in some camber on your rear wheels?

[raustinss]

Again do some more home work lot at some hotrod magazines there are lots of other manufacturers for its and then yes stock set ups swapped in, putting weight in the rear of the car can help but it still will make your car heavier. I don't quite see how a solid axle and link set up would cost north of 4 grand. I know that unless you've got the cash a solid axle can pull down some stellar numbers on the skid pad. Possibly hit up the guys over at sc&c they're very informative and helpful. Markus is on here but I can't recall under what name

[Todd in Vancouver]

Again do some more home work lot at some hotrod magazines there are lots of other manufacturers for its and then yes stock set ups swapped in, putting weight in the rear of the car can help but it still will make your car heavier. I don't quite see how a solid axle and link set up would cost north of 4 grand. I know that unless you've got the cash a solid axle can pull down some stellar numbers on the skid pad. Possibly hit up the guys over at sc&c they're very informative and helpful. Markus is on here but I can't recall under what name

I just ordered a rear suspension set up for my '67 and I thought about just replacing my 12 bolt with a different set up and $4K is really easy to blow past when putting a rear suspension solid axle together. Hell, a decent 12 bolt with posi and axles is over $2K and you still need suspension, brakes, c-clip eliminator, axle upgrades, shortening, etc. etc. etc. I've looked at trying to cut a corner to save some money but if you want the whole package then you'll have to pay. I'm just closing my eyes and ordering what I need and not looking at my credit card statement until after :rolleyes:

[rustomatic]

You are wrong. Jaguar had this stuff many, many decades ago (Heidt's is basically a Jag rear); note that Jags, at least off the racing circuit, have never been known as the greatest handlers. IRS is not new, and will not make your car more new or "pro-touring;" then again, maybe it will, because it will look trick and expensive. With this in mind, one of the easiest, cheapest cars to make a good handler is the MK1 VW Bug, which was technically a swing axle at first; this may just be an endorsement for light and low weight, however. Your axle is fine; many cars with live axles have been made to consistently perform at 1G+ handling for a couple of decades now. You can do the same, so long as your goals align with this concept (performance vs. bling)...

Have you installed a locating device, like a Panhard bar or a Watts link? Their primary purpose is to remove the problem you've mentioned...

73955

[Rod]

Wouldn't it be great to dial in some camber on your rear wheels?

you can dial some camber into a full floater

[Norm Peterson]

It is possible to dial a little negative camber into most any stick axle.

As noted with respect to the Jaguar IRS, a well done stick axle arrangement is better than an indifferently done IRS.


FWIW, at the recent SCCA San Diego Solo event it was a solid axle Mustang over a WRX for the win in E Street Prepared. Not by much, but good enough evidence that a stick axle suspension still doesn't have to be considered a performance handicap.


Norm

[cornfedbill]

Having worked in the OEM auto industry, I learned not to put too much stock in the argument that what is being sold is the best technology.

I remember that argument being used to eliminate pushrod engines. Luckily the Corvette team did more analysis than to look at the market. The result was the LS1 that broke all the rules.

I think there is still life in a properly set up live axle. I anticipate fewer leaf springs and more full floating axle shafts though.

[another69]

I love the simplicity of a solid axle, don't get me wrong. It is really easy to spend more than 4 grand on a decent one though- I have close to that in my Strange rear with Hotchkis leafs.

I have not installed a locating device because it may just be better to ditch the leafs than to band aid them. The locating device would help the side to side (as well as affect rear geometry I think), but than what about the wheel hop? add some Caltracs maybe? I would be left with a leaf spring mess for about the same cost as the torque arm I originally considered.

As far as low weight, my car is now 3160# with an iron block SBC. 55% front / 45% rear. Wouldn't the car perform better if it was closer to 50/50, even if it gained some weight in the rear?

I know that some permanent camber can be set on live axles, but it would not be possible to dial in any kind of a camber curve (not even sure how important that is in the rear) without IRS.

There is no doubt in my mind that a well set up solid axle would outperform a poor IRS, but what about a well set up IRS ( corvette, porsche, nissan, viper, bmw, ferrari, etc) ? I know that the jag type IRS is pretty much all we are offered, but that doesn't mean that a well adapted IRS would really perform great. I especially like the corvette setup with the torque tube and trans in the back. I know that IRS is really nothing new, it just sticks in my mind because as a kid I saw it under one of my favorite cars- a Shelby Cobra.

[another69]

Rustmatic- Thats a nice panhard bar you have under that pickup truck! JK

[raustinss]

My apologies..i was wrong I was going with someone already having a solid axle and building it vs purchasing a IRS. Now if you aren't using a stock gm rear end...add gears..posi type unit.. springs...shocks...and now someone decided to add brakes to the mix then, yes I can see maybe 3 grand. I've got a stock 12 bolt..add gears and posi...600$ ish brakes 1300$ rebuild kit 100$ etc etc etc. Now if we are "Spicing Up" a solid axle...we need to do th same to the IRS and I know heidts has advertised a independent rear based off a jag design.. add a few goodies an your closer to 6 grand
Solid axle cheap simple can be tuned to "Pull a g"
IRS axle expensive complex..wow factor easily tuned to "Pull a g"
Either way you look at it its money spent and the need to evaluate what really are you going to do with the car. 98% of us will never drive the car to the fullest extent. I guess this is where and why the majority of us just stick with the stock type rear axle set ups.

[Norm Peterson]

[QUOTE]I have not installed a locating device because it may just be better to ditch the leafs than to band aid them. The locating device would help the side to side (as well as affect rear geometry I think), but than what about the wheel hop? add some Caltracs maybe? I would be left with a leaf spring mess for about the same cost as the torque arm I originally considered.
That's the beauty of either a torque arm or 3-link suspension, or with a bit more thought even a well-designed and performance intended triangulated 4-link. All of the band-aids are essentially built in to the four individual connecting elements and there is no unwanted wrapping or other flexibility to be crutched. You get to choose the geometric roll center height and the basic anti-squat and roll steer geometries yourself instead of settling for what was there by OE design (or for what any of the "band-aids" do to revise it), and you get to avoid situations where the geometry dictated by the "band-aids" starts competing with the geometry that the leaf springs want to follow. That leaves the choice of bushings and/or sphericals of some sort as detail design matters, for which there are some good general guidelines.



As far as low weight, my car is now 3160# with an iron block SBC. 55% front / 45% rear. Wouldn't the car perform better if it was closer to 50/50, even if it gained some weight in the rear?
As you approach the limit, most likely. And as front weight % goes up and further away from 50/50, the more any tire size stagger will hurt you - personally I would not even consider using any tire size stagger until the front weight % was a little under 50%. Unless I simply could not fit any more tire up front no matter what I did (in which case I'd probably come down a size or two out back, conventional thoughts concerning appearance be damned).

The current Mustang is only a tiny bit better than 55/45 (IIRC 54/46 at least in the pre-2011 models), and it's not exactly a slouch on the road course or even at autocross.



I know that some permanent camber can be set on live axles, but it would not be possible to dial in any kind of a camber curve (not even sure how important that is in the rear) without IRS.
With two separate camber curves, you'd definitely want them to play nice with each other as the car moves around on its suspension.

Keep in mind that the rear tires on an IRS can also exhibit toe changes independently of each other. This is something that can easily be felt if there's much of it, and it can be a bit of an uneasy feel.



There is no doubt in my mind that a well set up solid axle would outperform a poor IRS, but what about a well set up IRS ( corvette, porsche, nissan, viper, bmw, ferrari, etc) ? I know that the jag type IRS is pretty much all we are offered, but that doesn't mean that a well adapted IRS would really perform great. I especially like the corvette setup with the torque tube and trans in the back. I know that IRS is really nothing new, it just sticks in my mind because as a kid I saw it under one of my favorite cars- a Shelby Cobra.
Well adapted being the operative thought. Maybe Suspension Analyzer can handle this (I don't know personally, as I could never get even the demo version to run on my own computers).


Norm

[BMR Sales]

We offer bolt on Torque Arm kits for 67-81 F-Bodies with 10 bolt & 12 bolt rears. We also offer a kit that comes with a Ford 9" that has been jigged and bracketed to bolt in as well.

https://static1.pt-content.com/images/pt/2012/05/kitpricing-1.jpg



The guys who want a Ford 9" can order a kit that includes a bare Strange housing for $600 more. Take a look at the link below detailing an install that a PT.com member there completed with our Ford 9 in. kit in his 1973 Firebird:

https://www.pro-touring.com/showthread.php?80483-BMR-Torque-Arm-Installed-on-my-73-Firebird/page2&highlight=TORQUE+ARM



Here is a video of a customer with a 67 Camaro who got 2nd place in Street Machine Class at '12 Kansas Good Guys. He was running air over shocks and had not adjusted the roll center via Watt’s Link….. he should be able to cut about 2 seconds off this time just by addressing these issues.

http://www.youtube.com/watch?v=Jf9qK5GLD-Q&feature=relmfu


Here is a VERY informative tech article written by our R&D manager explaining what it does:

http://www.chevyhiperformance.com/tech/chassis/suspension_steering/1206chp_torque_arm_suspension_systems/



Here is a link to the recent Two Guys garage that gives you a visual look at what our Torque Arm Suspension does:

http://www.youtube.com/watch?v=n60dENFWPFY

[another69]

Norm- you bring up some good points about tire stagger. I wonder if some people run wider tires in back to deal with putting down the power. It is just hard to run really wide tires in the front of some of these older cars. It seems even harder to have neutral handling. Your Mustang has a 3 link, right? How do you like it?

I'm glad to see so much positive feedback about solid axles. I guess solid axles are still alive, but leafs are dying.

BMR- I saw your kit at a performance expo installed on a firebird (I think) that was propped on its side. I was really impressed and decided shortly after that was the way I wanted to go. I really like the way the upward force of the pinion is transferred to one of the strongest parts of the car- the subframe. I originally was going to get a HRTH truck arm. I would, however want to keep my 9" rear. Would you offer a kit for the 9" that uses the leaf spring mounts that I already have or do I need to cut them off?

[BMR Sales]

BMR- I saw your kit at a performance expo installed on a firebird (I think) that was propped on its side. I was really impressed and decided shortly after that was the way I wanted to go. I really like the way the upward force of the pinion is transferred to one of the strongest parts of the car- the subframe. I originally was going to get a HRTH truck arm. I would, however want to keep my 9" rear. Would you offer a kit for the 9" that uses the leaf spring mounts that I already have or do I need to cut them off?

Yes the car you seen at PRI was "Freedombird" project:

https://www.pro-touring.com/showthread.php?49145-OLDFLM-s-(Ty)-71-Firebird-comes-to-Fletcher-s-Customs!!-Giving-back-for-my-Freedom!!&highlight=freedombird







We could sell you the leaf spring mounted lower control arm brackets, but the brackets that need to be welded to the Ford housing will be tought to put on yourself unless you borrow our fixture/jig....


https://static1.pt-content.com/images/pt/2013/04/IMG_20111216_103415-1.jpg

https://static1.pt-content.com/images/pt/2012/07/BMR9inch-1.jpg

I would recommend selling your housing empty for a guy who just wants to upgrade to a Ford in his 67-69 F-Body or 68-74 X-Body and order our kit with the same spec'd Ford and use your internals/brakes in/on it.

[Norm Peterson]

I wonder if some people run wider tires in back to deal with putting down the power.
Bet money on it. Either for that reason or for reasons of appearance and "stance".



It is just hard to run really wide tires in the front of some of these older cars. It seems even harder to have neutral handling.
Absolutely. I remember putting a lot of time into finding an acceptable way of fitting even 245/50's on 8.5" wide wheels to the 1979 Malibu that I used to have. Still had to do a little "clearancing", and the car never was happy about running through slaloms at autocross.



Your Mustang has a 3 link, right? How do you like it?
Love it. Enough that when I ever get around to lowering it, it won't be by any of the usual amounts and the axle-side LCA pickups won't be at any of the usual relo bracket heights. I do see a Watts link in the car's future, though.

The car can be made to steer just a little on the throttle in 3rd gear at ~45 - 50 mph with only the ~300 HP 4.6L (that has only a cold air intake and a very conservative tune). And it'll do a 3-cone slalom maneuver around scattered truck tire debris at 65 mph without breaking stride, you just steer around the stuff on constant throttle.


Norm

[Skip Fix]

One thing to remember about an IRS is when you start adding a lot of power things start breaking . Half shafts which generally also have extra U joints to spit besides the ones in the driveshaft. How stout are the axle shafts coming out of the center pumpkin to the half shafts? How stout is the posi in it?

Many of the older Vette guys use a modifiedd pumnpkin to take a 12 bolt posi vs the10 bolt set up as well as upgrading to larger half shafts. One guy is making a 9" pumkin to be used in the 04-06 GTOs making a lot of HP(that already have billet half shafts).

[DarkoNova]

I wouldn't call watt's links and panhard bars "bandaids".

I've seen cars with fiberglass leaf springs and watt's links/panhard bars do some pretty amazing things.

I've also heard that fiberglass springs help with ride quality considerably, which is one of the main reasons I want to ditch leaf springs in the first place. Don't discount leaves just because they're old school tech.

[Norm Peterson]

I wouldn't call watt's links and panhard bars "bandaids".
When they are added to control leaf-sprung axles in directions that the leaves aren't up to adequately controlling alone, that's exactly what they are. Additional components used to cover for shortcomings in the basic leaf spring arrangement and detail design.

Technically, adding them over-constrains the axle, with the more flexible components bending, compressing, or otherwise squishing and deforming to suit the motion that is forced by the stiffer components as the car moves around on its suspension. Usually this sort of thing adds a little NVH because the forces that are developed to do all that bending, etc. get transmitted back into the car to some extent

That doesn't have anything to do with how effective the "band-aids" can be, particularly with fiberglass leaves. The less rigid the material used for the leaves is, the greater the need for them to be crutched by an additional component for what they can't do very well all by themselves.

Fiberglass springs are not cursed with the same levels of interleaf friction that most metal leaf springs end up having sooner or later. That's a direct reduction in ride harshness, which I agree is a nice development. But that does not fix the lateral location issue, which involves both lateral bending and torsion in the leaf and compliances in the leaf spring bushings and (usually) shackles. Or the matter of spring wrap.


My position has nothing to do with leaf springs being "old tech". It's based on recognizing what structural loadings they aren't very good at resisting all by themselves, what that implies with respect to suspension geometry, and understanding the side effects of adding more suspension components to help them out. I'm a big believer in each suspension component being very good at doing one thing well, as opposed to trying to do two or more things not-so-well.


Norm