Silverton

What's the influence of camber change on chassis tuning: understeer vs. oversteer? For example, a common street/HPDE alignment might be something like -1.5 deg (front) and -1.0 def. (rear). What would be the affect of increasing the rear camber to something like -1.25?

96GS#007

Increases understeer / Decreases oversteer

yakisoba

Except the stock rear on the C5 will only go about -1.1 camber, unless you lower the car.

TRACKMAN2

in my eperience it has doent make a car turn better , but you can turn better with it? make sence? to me an adjustment of toe helps the car mechanically turn better. once the car is turned it will be more stable with more camber than without..
when you turn the inside wheel has less weight on it so it can turn more than the outside wheel that has all the weight on it..toe out allowes this to happen the inside tire is pulling the car twards the direction of turn and the outside tire is just "tracking" ....camber is used to get the most surface of the tire to contact the road at max turn force!!! ps too much camber and its hard to get rhe power down coming out of a turn. because the tire is all jacked up on its edge. check your tire temps for right amout of camber.. inside middle and outside..

Silverton

For those folks that run a square wheel/tire setup (i.e., same wheels/tires front and rear), what rear camber would be appropriate? In the example, above (-1.5 front, -1.0 rear), what should the rear camber be?

TRACKMAN2

what ever amount keeps the tire temps even across the surface. if the inside are 170 and the outsides are 123 you got way too much camber..
if they are close you have ballance if there 170ousides and 123 insides you need more ... or a shorter sidewall more tire ppress or stiffer spring to keep the tires from rolling over.... i like more camber in the rear tires because i tend to turn fast and voilently and i set the back of the car on the rear so the front wheels only have to wory about turning...big heavy vets can stand lots off neg canber but you have to be really bustin it to get the full befits.. look at my avitar pick see how much weight is on the outside left rear compared to the front left...

heavychevy

I agree with TRACKMAN.

I've found that - camber helps you "toss" the car around more. I've watched James Clay in an E36 M3 at time trials throw the thing around like a rag doll and those M3's run like -4 and -4.5 camber. Of course because of the longer wheel base less toss will be needed and permited in a vette. I dont feel like the cars turns better, but it does feel like the understeer threshold is increased (more steering input before understeer) and that oversteer becomes more liberal.

davidfarmer

In the front, more camber (up to around -2.25) will add more grip, it decrease understeer, increase oversteer.

In the rear, more camber (up to around -1.5) will help rear grip when in steady-state turning, but can also decrease grip coming out of a corner.

Depending on how much trouble you have putting power down coming out of low speed turns, you may find increased camber causes more harm than good. You really have to balance cornering grip and straight line grip.

In my case, in a C6Z06, I run -2.2deg front and -1.5deg rear camber. Works well with both street and sticky tires.

TRACKMAN2

great minds think alike i,d be interested in in your toe settings i run 1/8 to 3/16 out in the fron and 1/8 toe in on the rear...my buddies that run dirt cars run up to 2 inches toe out

davidfarmer

For a street car that gets some track duty, I usually go 0 to 1/32" toe OUT in the front, or up to 1/8 for a more dedicated track car. I have a write-up on my website about using toe out for creating quasi-ackerman http://www.davidfarmerstuff.com/Toe-Ackerman.pdf

In the rear, I usually run about 1/8" to In. Honestly, I rarely can tell a huge difference if I go another 1/8" either way, but this is my goal.

More toe out in the front will certainly help turn-in, but it creates a lot of drag on the straights.

C66 Racing

As discussed well above, increasing rear camber will in general increase rear grip laterally and reduce it under power. The question I'd be asking is how is your car handling in long corners? Most Corvettes tend towards understeer and increasing rear negative camber will make this worse (and cost you some straight line grip under acceleration).

If you are really serious about getting your suspension set right, tire temps are going to be critical to fine tuning. Tire temp gauges are pretty cheap compared to a typical track day. Pick one up if you don't have one and start logging your inside, middle and outside edge tire temps. You'll learn a lot about how your tires are really being used.

heavychevy

How does this affect braking, I've been told that slight toe in helps braking as the tires squat out under heavy braking.

STEVEN13

On my C4 this past season I went with -1.5 camber front 0 toe and just shy -1.5 camber 1/8 toe in rear. It seemed that the harder I went in the corners the more neutral.

With this set-up my lap times were a little slower at Pocono but faster at Lime Rock. At Lime Rock I flip the tires on the rims-this may of helped for the lower lap times and could of helped at Pocono.

For this season I will have new tires and I am keeping the alignment the same (for the first event anyway).

Steven

davidfarmer

front and rear tires are "dragged backward" all of the time, and especially under braking. Front tires do nearly twice the work as the rears under hard braking, so you will gain toe out in the front, and likely go from toe in to neutral toe in the rear.

I've never attempted to measure toe change during braking, but I'm sure the <500lbs of load (per corner) does move them 1/8-3/16" at least.

Anyway, for most of us, braking is the easiest part of racing, so getting the camber dialed in for cornering is more important than losing a bit of stability under braking. A bad tie-rod end or bad/loose bearing can certainly lead to some very noticable imbalance under braking, however.

heavychevy

So in your opinion, the change in cornering ability is drastic enough to be worth the extra drag and possibly extending the braking zone slightly?

Just asking, this is all news to me. Parts of setup I havent explored.

Silverton

Referring to my second post, consider the case of running the same tire width at the front and rear (or a front tire width only slightly less than the rear). The motivation for using the larger front wheels/tires is to reduce understeer.

Having reduced understeer with the larger front wheels/tires, would an increase in (negative) camber at the rear help balance the car? Another option, would be to reduce the rear sway bar stiffness. If the front was -1.5 and the rear -1.0 before going to wider front wheels/tires, should the rear camber be increase to balance the car? If so, how much?

C66 Racing

Hard to say. Have you driven the car yet with the same size tires front and rear? When you went to larger front tires, did you increse the rim width or just put wider tires on the same rims? I ask this because in SCCA T1 we must run a 17x10 front rim and a 17x11 rear rim. I've run 275/40-17 front and 315/35-17 rear as well as 315/35-17 all around. But when shifting from the 275 to 315 fronts its still on the same 10" rim. As a result, the 315s are somewhat bulged and the whole contact patch is not on the ground. Front grip in cornering is not as improved as you might imagine. I find that the biggest improvement with the wider front tires is in braking performance... but this comes at the cost of straight line drag. I found that when shifting from 275 to 315 fronts, I didn't change the rear setup at all, but ran a slightly lower front camber with the 315s. Still think best bet is to go out with what you've got, take some tire temps and go from there.

Slalom4me

Balance the car? Does this mean you seek to further reduce understeer
or does it mean you want to dial understeer back in to counter the
move to oversteer by increasing the front tires?

Reducing the rear roll stiffness with either the rear stabilizer or rear
spring will generally shift balance in the direction of understeer.

.

Silverton

I'm interested in a good guess for an initial alignment. The tires [front: 295/30-18 on 18x11 Corsairs (thanks, John! ); rear: 295/30-19] go on tomorrow. The alignment will be done next week after the Hardbar camber/stud kit (thanks, Gary! ) is installed (along with the Pfadt "street" sways; thanks Mike Boman and Aaron! ). Because of the wide front tires, I need approx. -1.5 deg. camber in the front. The usual recommendation for rear camber is -1.0 deg. for cars with narrower front tires. That will certainly work OK. Gkmccready (on this forum), who is also running 295/30-18's on 18x11 Corsairs, has posted that he has reduced his rear sway bar stiffness (by going to a "base" sway bar) to improve handling balance. Since I'll be installing adjustable sways, I can experiment with different settings.

A lot of forum members run wide front tires. Subdriver's suggestion of reducing the front camber is another approach. However, it achieves the same thing: bring the the rear camber closer to the front.

gkmccready

I'm thinking of going back to the Z51 rear bar. I found that adding rear toe-in brought the car into a happier place so I'm going to put the stiffer bar back on.

I also have a set of the Pfadt Pfatty bars in my garage still, and I may experiment with those again this season now that I've settled a bit on an alignment that keeps the back end happier.