any information on rear steer

[Steve25]

I was just wondering if anyone knows of any articles that talk about the disadvantages of rear steer. I can think of one disadvantage, but are there a lot of disadvantages to this system. Since this is one of the 1st gen's downfalls, I would like to learn about its shortcomings.

Thanks,
Steve

[MrQuick]

you know I haven't read anything on it but always suspected it was the cause of oversteer. One of the guys actually cut up a 2nd gen front frame and modifyed it to fit his 69 Camaro. It handled nice on the street but I never talked to him after he raced it. I think someone was even talking about doing the same with late model metric subs? I think we will be hearing on a rack & pinion set up that actually works nice soon. wait I know one thing it makes it a bits to mount big headers sometimes...

[David Pozzi]

Rear steer puts more compression load on the steering linkage when you hit a bump or just turn the wheels. The linkage tends to get flexed up and down more and has to be twice as stiff to do well BUT IT CAN DO WELL. The idler arm needs to be stiff too.

BUT, rear steer has better ackerman correction.

[Salt Racer]

Another problem is when you have lot of compliance in suspension (eg, rubber bushings). Under hard cornering, the lateral loading try to deflect components in lateral direction. Since tie rods are more rigid than rubber bushings, rear steer configuration causes the outside tire to toe in, causing oversteer. It's called compliance steer.

The effect will be even more pronounced when heavy cast iron calipers are mounted behind the steering axis b/c centrifugal force will pull heavier side more.

The effect of compliance steer reverses on front steer (outside tire toe out = understeer).

[Steve25]

Do you guys think that it would pay off to convert a 1st gen. to front steer or do you think it might just be a waste of time. If it would help the steering, I don't think it would be hard to convert because of the a-arm geometry. What are your opinions?

[PAI Racing]

Wasn't rear steer pretty popular in Nascar? As I recall there were guys at least into the '90s who had a strong preference for rear steer chassis. Don't know why though.

[David Pozzi]

Rear steer was liked in NASCAR because the steering box was more protected in a crash.

The first time I read of deflection steer was a Herb Adams article.

But from personal experience driving my camaro in autocross and on the street I found the main effect felt was bumpsteer understeer. The Camaro toes out under bump and the outside tire is more heavily loaded and controls the car's direction. I would steer into the turn, then as the chassis rolled, I had to make at least one large extra steering correction giving additional turn of the wheel to keep the car aimed at the apex. When autocrossing, I got pretty good at "double steering" the car! After bumpsteering the car but still using rubber lower bushings, I only had to make very fine steering adjustments to keep the car on-line.

[Salt Racer]

Yeah, I remember you told me about that last August.

My guess is that the height of tie rods are so low on 1st gen (especially after you reduce bumpsteer), and that you had stiff bushings in UCAs, the deflection was probably not in pure toe angle. Either that, or the spray angle of LCA pivots have something to do with it.

I have no problem with mine after I replaced factory strut rods with new ones with rod ends.

As far as whether it's worth converting the 1st gen to front steer, I'd say no. It's more involved than most people realizes. At bare minimum, the steering arms need to be changed or modified to correct Ackermann. More than likely you'll have to make the arms shorter due to rim interference (tie rods need to be outside of steering axis on front steer). It is tough to locate the R&P properly due to the presence of crossmember. You can't simply move the R&P forward and think you've solved the problem (it takes Ackermann away). Then you'll have to determine the correct width for R&P. The height of tie rods is not the only factor that defines bumpsteer curve.

You really have to know what you're doing to execute something like this properly, not to mention the cost involved (custom width racing R&P cost $700+).

When you have good fab skills, it is very tempting to try stuff like this. But without at least some basic understanding of suspension/steering geometry, you could very well end up with something inferior than what you started with. Remember, great fab skill DOES NOT necessarily equal proper engineering.

If you really want to modify the suspension yourself, please do some homework first. For your own sake, and for others who share road with your car.

[Steve25]

Salt Racer and/or David Pozzi, if I could get the geometry perfect, would there be any benefit to having front steer anyway. David, are you saying that if you could make the steering stiff that rear steer would work just as good as front steer anyway? Would a rack and pinion on the rear steer help because it would do away with the extra joints and some linkage which should cause less play. I have been reading a ton on how to find instant center and all the things that will affect bump steer. Until I know all the dimensions I can't put numbers into the formula to figure out where a new rack and pinion would go, but it I would probably have to cut a sizable chunk out of the crossmember so not to affect ackerman. It still could be done but what a pain in the butt if you won't notice a performance difference.

[David Pozzi]

There really isn't much room for a rear steer rack on a first gen Camaro. If you want a road race type oil pan and low car, the rack can get pretty tight to fit in there. I think in Tony Huttmer's PT book he had to remove his Steeroids rack to install the BB engine. Then re-install the rack. Unisteer makes a rack but I don't know if it's a Power Steer rack. The rear steer racks have lots of U joints and at severe angles which isn't cool... One guy posted he had to grind on the U joints to prevent them from binding on a Steeroids application. Header clearance to the steering shaft is a problem with BB engines and some SB engines.

A C4 crossmember can probably be spliced into the first gen frame rails, but lots of work.

Try driving someones car with a re-done suspension and late style Saginaw PS box and see if that's good enough for you before re-designing everything. Re-read Stielows post on the Mule and how he has tried several racks in it, lots of pitfalls in building suspensions.

Year One built a first gen Camaro with factory subframe and a front steer rack, look that one up.

If I were shopping subframes today, with Rack and Pinion in mind, I'd look over the new Wayne due sub, and the Alston sub. The Alston seems to have a good camber curve.

[Salt Racer]

I'd also add 21st century's C5 based subframe to the list. Very small scrub radius (63" hub face with C5 knuckles), and I like their adjustable FVSA length.

I don't see much benefit of front steer over rear steer IF everything is reasonably rigid (nothing is absolutely rigid) and there's no packaging constraint. Front steer seems to require longer tie rods than rear steer for a given UCA/LCA length and IC location. That means more range of suspension travel before geometry goes haywire. For this reason, front steer is probably more desirable for long-travel suspension (like on Baja racer). But within the range of suspension travel we're dealing with here, the difference is negligible.

Aside from the obvious weight advantage, I don't see much benefit of R&P over a well-designed box system either.

Box can be made to work very well. I'm happy with my AGR box (12.7:1, 0.235" T-bar). The only complaint I have is slight slop when it's at the center. DSE has a nice, light weight box with modified spool valve. Supposedly they have addressed this issue, so I might try it one of these days. Like David said, find someone who has a nice box setup. Bribe him with a 6-pack and talk him into letting you drive it.

One thing that is often overlooked is the height of tie rod inner pivot when wheels are steered. On R&P, it stays constant. But typical steering gear box setup has pitman/idler arms mounted at an angle. This changes the inner pivot height. This affects the bumpsteer curve under cornering. It's difficult to get this right and still have desirable SVIC location and good bumpsteer curve when wheels are straight. But you certainly don't want the outside tire go 3 degrees toe-in when it hits a bump at the limit. If you're designing suspension from scratch, constant inner socket height of R&P is easier to deal with, but I'm guessing the height change of inner pivots can be used as an advantage in some cases.

If you have to have a R&P for whatever the reason (I honestly think most people want R&P b/c it's the kewl thing to have), then go ahead and study what it takes to make a successful conversion. There's nothing wrong with your idea and I'm sure it is possible, but I'd still say the return isn't worth the effort unless you're trying to engineer a kit to market.

You should know that these opinions are coming from a guy who'd rather spend his money on tires and entry fee for OT events and enjoy driving the ***** out of his car, than working on it. I don't have to have trick gadgets on my car as long as I can kick some butt on road course.

[Steve25]

Salt Racer and David Pozzi, thank you for your input. The only reason that I was interested in a front rack and pinion is because I thought that maybe there would be a performance advantage. Since you guys don't think that I would be gaining any performance, I am no longer interested in the idea. My only goal is to have a very fast car that is very capable of cornering. I don't care about aesthetics at all because I don't want to have to feel bad about running the car so hard in races anyway. I just want to be competitive and have a good enough of a car that my driving will allow me to win races. Thanks for the good advise. This advise is especially good because it will save me a lot of money. I guess I would still engineer a kit to market if I thought it would be profitable. Since it sounds like the rack and pinion is more for looks, the people that would want this setup might as well spend the money and get the pretty vette parts too.

[racingpartsales]

Your car in competition can gain some all important rear weight percentage when your running rear steer. The suspension geometry on your 1st generation car has many desirable features, The 2nd gens are great subs too and found on many stock cars to this date.

Just last year I sought out and built a rear steer nova for a local class of stock cars. The front sub weight is much, much lighter and the engine set back is easier to achieve on the rear steer cars. All advantages when cornering is prime consideration.

The second generation cars have more anti dive built in the upper control arms than first gen stuff. This can cause more caster gain upon braking. All of these are considerations circle track guys must think about. If your looking for massive performace improvements over your 1st gen sub, It wont be there. I would install a decent anti roll bar and stout bushings throughout. That will make a world of difference in your handling. I also would install solid body mounts in the front if ride compliance is not of primary importance. Jeff