emptnest

I am prepping my newly acquired 1993 C4 for HPDE tracking. Being a newbie, I will take the advice of experienced track drivers, and initially run on street tires; then as my skills grow, I will move up to stickier tires.

So for now, I am running a square 275/40 x 17 set up, on 9.5 saw blades. In preparation for eventually running separate track tires, I have two extra sets of wheels. One set is another set of 9.5 x 17 saw blades; the other is a staggered set of 9.5 and 11 x 17 A molds.

I expect to run primarily on either the PIR track in Pittsburgh, and at Summit Point. I may occasionally visit VIR.

So the question is this:for the track should I run a square set up, or staggered?

obviously a staggered set up denies tire rotation. So over the course of two tire sets, and assuming fronts wear at twice the rate of rears, I will replace two fronts at the end of cycle 1, then all 4 tires at the end of cycle 2. Total 6 tires over 2 cycles. A cycle being whatever time it takes for the fronts to wear their corners to an unacceptable degree.

But if I run square, I will only rotate front to rear, and not have to buy tires at the end of cycle 1. Then at the end of cycle 2, I will replace all 4 tires. Total 4 tires over 2 cycles.

Is that the conventional wisdom? Or is the assumption of less rear wear incorrect?

Two more questions:

Is there a performance advantage to running larger rears?

Does anyone running a staggered set up rotate side to side for extended life on fronts? Or is that ill advised ( as discouraged for regular street tires).

Looking forward to your thoughts.

Bill Dearborn

Run a square setup. Get two more 11x17 A Molds and run 314/35/17 tires front and rear. If I remember correctly there were a number of people who ran that setup while C4s were still popular on the track. To find out try your rear A Molds on the front. One thing to check is to see how the clear the lower control arm. When I ran that setup on my C5s I had issues with turning the wheels too far in the garage and paddock and the rim would rub against the control arm and strip the wheel weights off the rim. Since your car is a 93 you will need to get the GS Offset A Molds. The ZR1 offset will make the rims stick out too far and may not work well on the front.

Bill

FASTFATBOY

Square setups allow for much longer tire life, you can rotate and flip tires on the rims.

Saves mucho dinero.

Black89Z51

I'm running NT01's on my car, staggered A-molds. I couldn't be happier with this setup. The front doesn't push at all and tires are wearing pretty evenly.

rkdc5z06

315/35/17 all around here

used to run R888 but they runout quick..
so went with NT05s to stay within SCCA rules of 200 thread wear.. for auto X
wheels are
17x10 F 17x11R ccw classic race ver.

emptnest

So, posters 4 and 5, are you rotating? If so, how?

Scooter70

I run 305 square on 18x10.5 Z06 rear wheels on a C5. Yes, rotate every event by putting the best tire on the left front, second best on right front, and the most worn on the rears. Every couple of events, flip the tire on the wheel to put the worn edge on the inside. (Assuming that your tread pattern allows for running them in both directions of course.)

Hat_Trick_Hokie

I do this as well.

I run slicks, so I can put them on any corner. And when the outside edges start to wear down (because I do not run enough camber) then I get the tires flipped on the rim to even the wear on the other side of the tire.

rkdc5z06

Just like above said,

I take the tire off the wheels and put left tire on the right and vice versa.


Cheers!

Bluefire

Curiosity question:
Does running a square setup make the car more prone to encountering ABS "ice mode"?

VetteDrmr

I never have with my '00 hardtop, but IDK about the more modern systems.

Bill Dearborn

Can't say, since I have never encountered the fabled "ice mode" other than when really driving on ice covered with a layer of water. Touched the brakes and all 4 instantly locked at the same time. That was a real "Ice Mode". There was so little friction the ABS never saw a difference in in wheel speeds and never activated.

Bill

rkdc5z06

+1
When I drive hard in the canyons and get the hops, All I get is

"Active Handling activated" for a second it and goes away.

never had Abs or other light came on.

emptnest

Will 10.5 c5 Z rears fit all around on the 93 C4?

Solofast

C4's run best square,,,, period....

The reason is that the car is a bit nose heavy and putting big tires on the back gets you nothing but makes the car push. If you try to run bigger tires on the back you can't put enough bar on the back before the rear end jacks due to the rear roll center height.

It's embedded in the DNA.. Just run it square and don"t waste time trying to figure out a setup that will let you run bigger tires in the back. To do it and make it worthwhile you need to rework the rear geometry to lower the rear roll center or you are wasting your time.

Solofast

It used to happen in autocross in C4's all the time. Or if you are on the track it can happen often. The reason is that sometimes you have to hit the brakes when the car is really light on one or more wheels and it goes right into ice mode. You will probably not see it on the street much, but if you have one wheel on a really dirty surface (like at the edge of a street where the road has a patch of gravel on it) and if you are braking really hard it can get into ice mode in a heartbeat.

emptnest

Ok I'm sold on the square set up. I appreciate everyone's advice.

So, given that, will c5 z rears (18 x 10.5) fit on all four corners, or should I limit myself to the 17 x 11 A molds mentioned in the initial posts above?

Black89Z51

No I'm not rotating. The tires are wearing nice and evenly.

I've heard a lot of AutoX guys run square 315 setup.

A lot of people here say that a staggered is going to push, but I've yet to have that happen at all. Next year I'm going to Hoosier R6's in the 275 fronts and 315 rears.

Solofast

You would most likely be faster with the 315's all around. You could put in more front bar and have more grip on the front with the bigger tires, provided you can keep them flat on the ground.

This goes back to the thread on how much tire is "enough" and is more better after that. Typically if you have "enough" tire more doesn't help that much. If you don't have "enough" then more tire brings big benefits. It is very dependent on the tire, the setup, what the tire likes, and the velocity of the relative wind....

Armycop

What he said. Except I'm running 315's all around. MOAR TYRE PLZ!