Rear suspension on Jimmy Johnson's 67 Camaro

[Payton King]

I posted this over at Lateral-g and thought that I would do the same over here. For those who do not frrequent that site, Jim Pettigrew is building a 67 Camaro for Jimmy Johnson (#48 Lowes car). It is running a de-tuned cup motor, 21st Century front subframe, richmond 5 speed, etc.

Anyway, Pettigrew came up with an idea for a new suspension for the rear. Well, it is really not new, in the 60's when Chrysler was drag racing they used this system to get around a few rules that stated their cars must run leaf spring rear suspensions. Austin Healy 3000's ran this type of suspension as well. That is where Jim got the idea. Many years ago he had an Austin Healy and droped a small block in it. He stated that it handled really well and would hook like nobody's business.

So here is the deal. It is a poor man's 4 link. The leafs act as locator, springs and lower link. The housing is on a swivle link and the upper link is standard fare.

Take a look and give me your opinions pro or con. Jim is thinking about producing these as a low cost alternative to what is presently available.

[silver69camaro]

I smell roll bind with the short upper link.

[David Pozzi]

Early stick axle vettes had something like that but I believe the axle was just clamped to the leafs in a stock manner, not with a pivot.

A year or so ago, one of the magazines had a similar setup shown that one of the LA shops built. Again, it may not have had the lower pivot under the leaf. If the upper arm is kept parallel to the leaf, it may not bind in roll, it's hard to say but I'd guess the upper link should be near the same length as the lower to be sure, -the closer the better.

Thanks for posting that.
David

[CarlC]

I'm pretty ignorant about most of this, but was this type of link used to help reduce spring wrap in a drag racing situation caused by a weak leaf spring?

If so, would a more elegant solution, especially in our cases, be an optimized spring without the links?

[Mean 69]

Many of the vintage Trans Am cars use a similar arrangement, on some cars you can see them clearly, on others, they are hidden. Basically the same as the "over-rider" bars on the early Shelby cars, the idea of which was borrowed in various guises by many, many other teams. All of the crew chiefs that I spoke with, that would share "anything" about the arrangements, didn't have particularly good things to say about the setup, corner exit oversteer seemed to be the biggest issue, likely due to (roll) bind. Rules in the series won't allow them to do too much about it, T/A cars are expected to run as they did in their day.

The fast vintage cars that use leafs on the East Coast use a single upper link in the middle, it helps control spring wrap, pinion angle change, and further helps "define" anti-squat, it's a coupled argument with the leafs and isn't nearly as straightforward as a pure link setup, or a straight leaf setup. Rather than a hard link, it's sprung, albeit very tightly, I think it might be damped too. There is no doubt that you can use this type of setup to improve the handling of a leaf car, but it is not trivial by any means, I'd guess there is a better chance of harming the handling than helping. Vintage racers are extremely competitive, so I doubt you'll get a whole lot of setup secrets out of them, I know I have tried with very, very limited success.

Mark

[Payton King]

Jim has been wanting to try this out on a car for years and now he gets his chance. Good thing about it is there is very little alteration to the car itself. It should be running by January and he will do a little real world testing and see how it drives. My car is very similar in that we are both running the 21st subframe and leafs in the rear...same spring rates, shocks and sway bar. Obviously I do not have a de-tuned Cup motor that should make upper 600 hp, but we can do a side by side test and drive and see the difference.

Should be an interesting comparison...I am curious myself

Any other thoughts?

Again this is an old school approach to trying something new, or not so new. Get an idea, build it and see if it works. No modeling or computer analysis.

[justanova]

The fast vintage cars that use leafs on the East Coast use a single upper link in the middle, it helps control spring wrap, pinion angle change, and further helps "define" anti-squat

do these cars use the pivot mount on the springs? or are they bolted to the springs normally?

[vintageracer]

The "overide" traction bars used in an early Shelby are a bad idea for racing as outlined in a previous post. My 66 Shelby GT350 had them originally. For ****s and giggles we hooked them up one time to see what they did to the handling. Bad news! The rearend would bind up making corner exit a handfull as stated above. The single bar in the center as sold by Kurt Vogt at Cobra Automotive is one of the hot setups now in Vintage racing. You are starting to see this setup in Camaro's also!

[Mean 69]

The single bar in the center as sold by Kurt Vogt at Cobra Automotive is one of the hot setups now in Vintage racing. You are starting to see this setup in Camaro's also!

You devil, yep, that's the one I meant. Damn Cobra Auto guys. Fast as snot, as I understand, but don't try to get near the details. Unless you have a fat wallet.

Camaros?!?! NO! Really?

Kidding aside, like every single possible thing you can imagine (i.e. beyond suspension), there are SO many ways to skin the cat, some good, most not so good. This isn't intended, by any means to shoo folks away from trying new things (even if they aren't "new"), in my humble opinion, it's all about the tour, not the arrival. Always something to learn.

Mark

P.S: Mr. Vintage, going to SEMA this year? We won't have a booth, which means I'll have a little more social time. Drop me a line!

[vintageracer]

Kurt's (Cobra Automotive) stuff is fast but the mechanics don't last! Sebring and Daytona, their cars never are able to finish the 2-3 hour Enduro races we have at those 2 tracks.

You want fast AND Ford mechanics that last, call Gary Jones of Gary Jones Motorsports in Augusta Georgia. Gary's 66 GT 350 is the HSR (Historic Sportcar Racing) Rolex Endurance Challenge Champion 2 years in a row. This is the first time ANY American car has won the title once much less 2 years in a row. HSR is the "Run What Ya Brung" group. Vintage race cars that run with HSR are a WHOLE LOT FASTER than when these cars were new! Cup motors, Jericho's, Brembo's, Dry Sump, that's what you will see in HSR. I know as I had to compete with this stuff for 9 years! Ever see a 66 Mustang or 67 Camaro out brake and out corner a 911 RSR? That's what you see in HSR and I would not have it any other way. Good, clean competitive racing with less regard for period mechanics than any other Vintage race group. I wonder if that's why HSR is also the largest Vintage Race Sanctioning body in the USA?

I will arrive at SEMA Wednesday morning. I have to Trick or Treat with the kids Tuesday evening. I will be at the Lateral G party Wednesday evening and the PT dinner on Thursday eveninig. I look forward to seeing you at SEMA!

[CarlC]

Seems like a bunch of us have the same itineraries for SEMA! We should set up a track day in L.V. next year sometime during the week of SEMA.

Mike, I look forward to meeting you. It's always good to put a name with a face.

[Mean 69]

Not to highjack the thread here, but the last two years NASA had a track event, including American Iron just up the street right after SEMA at LVMS. The other local track, Pahrump, might be fun to look into also, never been there.

No question, Steve Earl's events are more for the "upper crust," wine and cheese folks, and require the cars to have the correct heritage (brass tags, SCCA log books, etc). Several other organizations, HSR included are far more liberal with the rules, and I agree, Mike, this is WAY cool. And you are right, them cars is fast!!!! I'll be at SEMA for the events also, it'll be good to meet up with you guys.

Back on topic, this is one of the cases where there are a lot of opinions on a particular setup, but in this case with theory (on paper) matching demonstrated execution. Does it mean that the car is going to be completely unmanageable? Probably not, but there will be issues with it at the limit. I'd guess that Jimmy will be able to handle them. :drive1:

M

[Payton King]

I would like to find out more about the HSR deal. I will see if I can find Gary Jones as well. Just to take a look at the car.

As far as Jimmy racing around in this car...it is pretty much just a street car. He does not want a roll bar or cage in the car. I am sure if he wants to go racing he has plenty of cars at his disposal.

When you are speaking of the center bar on the Vintage racers...like a center link on a 3 link system but using leafs?

[vintageracer]

Gary Jones Motorsports 706 840 3206. Tell him Mike Strinich refered you to him. Gary can give you the low down on what is going on with the rearends. There is a little rear-end bending and tweaking to get better camber going on these old vintage cars.

As far as HSR, go to HSRrace.com for all the information, results and schedule.

[Payton King]

Thanks for responding

[wendell]

Vintage racing is a mixed up crazy world. Regardless of how well the floating housing-over rider set up works, I know there are more eligant solutions ot the same problems.

[PT Goat]

Not to digress too much, but I thought that West Coast Customs already built JJ an early Camaro with a Cup engine - Randy Dorton's last build before he was killed. JJ bought the engine at a charity auction. I think it was featured on Rides?

Is this the same car, a second Camaro, or a redo of the first?

[Payton King]

you can see more over at lateral-g. It is on the home page on the left side.

[Damn True]

HSR sounds bitchin, and daaaaayyyuuuum they have some nice stuff in their classifieds. Too bad all their events are on the East Coast.

[David Pozzi]

There is an HSR West, but they don't seem to have a Trans-Am class.
http://www.hsr-westracing.com/

[zero g]

It was called a leaf link. The instructions for builing one are in the MOPAR Chassis Bible.