spanwar

I noticed that the stock settings for the C5 & C6 specify the same camber F & R:

C5: -.2 degrees
C5 Z06: -.7 degrees
C6: -.45 degrees
C6 Z06: -1.0 degrees

But I see lots of folks are running more front camber, usually by .5 degrees, the suggested "moderate" alignment for the C6 is -1.5* F & -1.0* R.

Assuming the car is near neutral in the stock alignment, and you increase negative camber all around to improve cornering, what's the advantage of adding more in front than rear?

davidfarmer

more neg camber in the rear takes straight-line grip away. You don't see any dragsters with neg camber.

Also, the slip angles of the front need more camber. The front is doing quite a bit more work especially in a front-engined car, and the rears are just following along the arc.

Personally, I'd run the same front and rear up to about -1.75 to -2.0 for ultimate grip. THEN, if need be, I'd go higher in the front, but not the rear.

John Shiels

after 1.5 in rear you start to loose your straight line traction.

davidfarmer

oh a final note. These cars are not neutral in stock configuration, they are set up to push slightly. You need a little more relative front grip to get the slight throttle oversteer that rotates you out of the corners.

spanwar

I'm not sure I follow. If the fronts do need more camber because they do more work....then why would you still stay the same F&R all the way up to -2.0? Sounds like you'd always want more on the front (unlike the factory specs).

VetteDrmr

The stock alignment is *not* neutral, but understeers; therefore more negative camber helps up front.

HTH, and have a good one,
Mike

spanwar

Ok, that helps me understand what the purpose is. But I'm still new at this. There seems to be a dozen ways of adjusting the balance toward understeer or oversteer. Given all those choices, why would one prefer to adjust camber instead of tire pressures, tire widths, swaybars, etc, etc?

TooManyIDs

http://www.articlecity.com/articles/...cle_1600.shtml

Solofast

The reason you want more negative camber in the front doesn't have anything to do with the basic understeer relationship.

The answer is in the geometry....

The reason that you need more negative camber in the front for high performance use is that you loose some negative camber due to the kingpin angle. If you didn't have a high kingpin angle (they put it in to get a low scrub radius, and hence less steering kickback) the result of turning the wheels and the effect of caster would give you higher effective negative camber settings and you wouldn't need as much static negative camber.

This is why cars running lower speed events like autocross need more static negative camber than cars running high speed events. They are putting in higher steering angles and are loosing more negative camber due to kingpin angle effect.

The tire temps tell the whole story, and to keep the outside front tire upright when cornering hard you are going to need more negative static camber up there than in the back, and that is primarily the result of the effects of kingpin angle.

And yes, you can compensate for the kingpin angle with lots of caster, the Germans (BMW and Mercedes most notably) run higher caster angles (like 10 degrees or more) to address this. There are compromises here having to do with steering "feel" and what you want the car to do, so the designer pays his nickel and takes his choice...

Some are confusing the basic understeer/oversteer relationship with absolute grip at the limit. While a car that understeers will have higher cornering grip if you add negative camber (up to the obvious point of too much), it doesn't mean that adding negative camber will make the car oversteer, it just means that the limits will be higher. The basic understeer/oversteer relationship is governed by roll stiffness distribution. While putting in odd amounts of negative camber (like lots more in the front than in the back) you could get some weird at the limit behaviour, (like snap oversteer at the limit) that isn't really what the General had in mind when he designed the car.

VetteDrmr

There was a guy I autox with that was debating whether to go to 275s up front (he was running stock widths at the time). I told him that if he went with 275s all around that the car's handling would go from a fairly strong understeer to moderate oversteer.

He then acted disappointed, saying "man, you just can't win!" I then pointed out to him that the reason is due to the much increased front grip that he would have with the 275s. He got a much happier expression when that light bulb dawned.

In fact, I'm just switching over to 275/305 RA-1s; I'm hoping the car is fairly neutral, but we'll have to wait and see.

Solo, thanks for the explanation.

Y'all have a good one,
Mike

ace996

Mike,
I run 275/315 Falken Azenis 615s for the street and 710s for autox. The set-up is very neutral. I also have a maggie so throttle oversteer is never difficult to call upon.

The T1 guys run 315s all around, but probably need to tweak alignment/springrate/pressures to dial-in.

Be good,
ace