cambered rearend

[turtle]

Hey guys! This will be my first official post!

My question is, what would be a good starting point for camber in a rearend for a dirt circle track car.

The car will be a 3200 lb. metric chassis.
We are limited to Hoosier G60's on 8" rims.
We can change the frt. upper control arm mounts to help the moment center and camber curve of the frt end.
We can run a 9" but all rear mounts must be in stk location.
The car will be running 53%-54% rear percentage.
This car will run on different tracks, 1/4 to 3/8 mile, slight banking to medium banking.

I guess something else I should say is that I know it should be helpful, but how much would I need to before I started getting positive results? As of right now they dont have a rule against it. But if I show up with my rear tires OBVIOUSLY all leaned over, I feel they will create new rules toward this.

Thanks for any input.

[ZIGGY]

IME it is not beneficial on most dirt. Go buy some crowned axles and try it;you can't get much.

[RCJ]

When you have stagger in the tires it puts some camber in the r/r.You will have to have cambered axles because when you start bending the housing the bearing will start burning up.I think you are better off looking at r/r toe and I'm not saying anymore lol.

[turtle]

You cant get much stagger to speak of with these tires... you can buy cambered snouts for for a floated rearend (no need to bend tubes) and crowned axles and drive flanges (no burnt bearings). toe the RR out??? the car will have roll steer built in to it. or is it benificial to have the rearend toed out as well???
Thanks

[englertracing]

Back in my stock car days, I cambered a ministock rear 0.5* I feel that it helped.
Going to see how it works on a winters rear on a road race car soon.

[crazyman]

Yeah.. How do you camber a one piece unit? Bend the rims?

Seriously though, just speculation, but I think having the left tire forward (toe) would help the car steer left...

[turtle]

[/quote]Seriously though, just speculation, but I think having the left tire forward (toe) would help the car steer left...

Do you mean like, "toe out the rear tires"? kinda like ackerman angle in the front of the car?? sounds like it could work.. I would have to do some drawings or illustrations to get a better concept of the effects. (I'm a "gotta have visuals to get a better understanding" kinda guy) but the concept sounds legit.

The reasoning for my cambered rear question is that, the tracks that I run on are in the deep south and they often dry out and get very slick.
My idea was to lower my air pressures to get a larger tire contact patch. Now we all know that lowering the pressure is going to let the tire roll over during cornering. That is why I thought that you can add some camber to compensate for this condition.
Now I also know that you can't go to low on the pressures because of distortion of the tire carcass. (we know racers want to push everything past the limits)
I am in the mind set that small things add up! I also question things outside of the box and that is why I am asking this one. Now if it has been done and does not work, I would like to know. I also understand that if it has been done that some people may not let me know due to its advantages. (racing secrets) But someone could PM me and we could keep it amongst ourselves and keep it from going public! lol

[ZIGGY]

Turtle, if you have lots of money & time you may hit on a combo that gives you something. Many have tried it incIuding me. First time was about twenty years ago with a 2-link sometimes lift bar, sometimes pull bar modified on IMCA tires. Kelly Shryock was working for Bob Harris then and told me I was wasting my time. He was correct. And I haven't found any different over the years since. But I haven't been fully involved with a dirt car chassis in several years and there are many people smarter than me, so who knows? Work it and see.

[mbrooks]

it will probably take at least a 1/2 degree to be effective, and i can see that on a car, so tech inspectors might also, or your competitors. wouldn't be worth the effort imo. never toe the rear out, you will be loose like you wouldn't believe. slight toe in is not bad. you say rear pickup points must be in stock location, but if you can move the thrust line to the left i think would help, and it doesn't take much.

[MadBill]

FWIW, production tolerances on solid axle camber are often >+/- 0.5 deg.; crash repair tolerances would be more. Just sayin...

[turtle]

Turtle, if you have lots of money & time you may hit on a combo that gives you something. Many have tried it incIuding me. First time was about twenty years ago with a 2-link sometimes lift bar, sometimes pull bar modified on IMCA tires. Kelly Shryock was working for Bob Harris then and told me I was wasting my time. He was correct. And I haven't found any different over the years since. But I haven't been fully involved with a dirt car chassis in several years and there are many people smarter than me, so who knows? Work it and see.

well heck.... now I am second guessing this idea because you are familiar with the tire and the idea.... but I question now, why does the USMTS rules restrict cambered rearends if there is no advantage??

it will probably take at least a 1/2 degree to be effective, and i can see that on a car, so tech inspectors might also, or your competitors. wouldn't be worth the effort imo. never toe the rear out, you will be loose like you wouldn't believe. slight toe in is not bad. you say rear pickup points must be in stock location, but if you can move the thrust line to the left i think would help, and it doesn't take much.

I was thinking of trying 1/2* because i felt that I could somewhat disguise that amount with some manipulation of the body panels. (cambering the rearend is not illegal yet, just don't wanna make it obvious) I also wasn't sure if there would be any advantage with that small of camber, BUT, every little bit helps, right?

FWIW, production tolerances on solid axle camber are often >+/- 0.5 deg.; crash repair tolerances would be more. Just sayin...

just askin, but how can you get camber on a production rearend? I have seen bent axle tubes lean the top of both tires inward.... is that what you mean??

[MadBill]

Yes, frame repair shops regularly chain down and pull solid axles to straighten crash damage.

There is no 'zero tolerance' part in existence, and axle housings are far from precise. A factory repair manual or a frame shop reference gives ranges for how bad is acceptable and how close is OK after repair.

Twenty-odd years ago I was responsible for providing tech specs for a showroom stock road race series for Camaros and Firebirds. Early on, we noted up to a degree of negative rear camber appearing on some cars. I dug into it and was surprised to find the factory tolerances were something like + 0.75/- 0.5 degrees per side. Verifying -in-tolerance rear camber became another post-race inspection item.

Bottom line, any series that declares: "No cambered rear ends" better publish acceptable limits. An axle with zero point zero one degrees (either positive or negative) is cambered.

[ZIGGY]

why does the USMTS rules restrict cambered rearends if there is no advantage??

Also been in IMCA class rules for years. So are restrictions such as to one battery. (Yes, I've run two for ballast & backup, and a higher voltage wheel chair battery for my HEI;but when I dynoed with/without, no hp gain over good single.) IMO sometimes they're just trying to simplify or economize, not address some well-recognized performance advantage.

I'm not saying rear camber is useless on dirt, just that it's no revelation and some of us mere mortals haven't found it generally worthwhile. But you might be able to make it work for you with your combo, track conditions & driving style. I dunno. Try it. It's always a good feeling to find something where others didn't.

[ZIGGY]

I was thinking of trying 1/2* because i felt that I could somewhat disguise that amount with some manipulation of the body panels.

P.S. - Use the ancient but useful trick of putting some other glaringly obvious attraction elsewhere on the car for the techs & competitors to focus on while you conduct your camber trials.

[turtle]

I'm not saying rear camber is useless on dirt, just that it's no revelation and some of us mere mortals haven't found it generally worthwhile. But you might be able to make it work for you with your combo, track conditions & driving style. I dunno. Try it. It's always a good feeling to find something where others didn't.

I think I might try it around mid season after I have gotten a good and consistant feel of the car and to see if I can notice more corner speed or better tire wear. Also think I'm gonna try it because I can not think of any adverse side effects from running it. I thought about trying it on a pull bar modified but I figured with as much pinion movement that it would be turning the camber into a "toe to the right and left" movement during acceleration and deceleration. Granted it would not be much, but it might be enough to give some sort of side effect that would need more tuning to compensate for. (if it could be compensated for)

P.S. - Use the ancient but useful trick of putting some other glaringly obvious attraction elsewhere on the car for the techs & competitors to focus on while you conduct your camber trials.

I like the way you think! I have seen this Jedi mind trick in the past and it ALWAYS works on the simple minded! LOL