LEAVINU

Just did a test mount of all four C5Z wheels and tires on my C6 and drove @6 miles to get some gas. I got the "TC System Active" message three times on the way there just cruising along at normal speeds. Got gas and returned back home and didn't see the message on the way back after re-start. This is the first time the car has been driven with these wheels/tires.

Any thoughts on this?

Found it odd it didn't do anything after the re-start so was it just not happy then learned the difference?

Running 285/35R18 square where my stock wheels are 255/40R18 up front and 295/35R19 in the rear.

longdaddy

i'd be more worried about ABS, you can always turn TC off. try some hard stops, if ABS functions more or less normally, I would not worry too much.

LEAVINU

Was thinking the same about TC after I posted this, but didnt even take into account ABS. I'll look into that, thanks.

gkmccready

ABS should be fine, it just uses the wheel speed sensors to see if you've locked a wheel, right? I'd be more concerned about a confused AH/TC computer that is used to seeing a difference between front and rear wheel speeds. Let us know how it goes, but I've always assumed that if you want to run a square set up on a C6 you're going to have to turn everything off all the time...

froggy47

Depending of the tire sizes, you may get away with going to comp mode for street driving.

LEAVINU

Surely hope not! Crossing my fingers comp mode will fit the bill.


Exactly what my next test will be.

gmccreary

The reason you're getting the message is that you're running a square setup on all four corners. The computer is calibrated to see a different rotaional speed of the stock front and rear wheels since it's a staggered setup. Now that the rotaional speed of the front and rear is the same the computer is confused and it thinks the rears are spinning because it's rotating faster than predicted.

255/40-18 = 775 revolutions/mile, diameter 26.0 in
295/35-19 = 743 revolutions/mile, diameter 27.1 in

You need to turn off your traction control/active handling to run a square setup.

LEAVINU

That makes complete sense. I'll hope comp mode allows me to run some AH when running around the track.

gmccreary

If it gives you issues in comp mode just turn it off and take it easy. Will you be at Road Atlanta this weekend?

LEAVINU

Yes sir I will be. I wasn't able to make the registration in time due to just getting tires mounted the other day. I'll come up and chat a bit and learn a few things I'm sure though.

I'll be ready for CMP in late April with NASA though. Hoping to get 1 or 2 smaller events in before then as well.

DRUGschnorr

AH on track? unsettles the car and ruins time...
Turn it all off as soon as you get comfortable w/ the feel of the car
my 2 cents..

LEAVINU

That's the plan.

Bill Dearborn

You won't see any problems as long as you are in Comp Mode. When I ran equal diameter tires front and rear on my C5 I could go for very long distances and never activate TC while other people running the same tire configuration would have it activate within a short distance. I suspect there is some variability between EBCMs in this area. I did experiment with my C5 by swapping the stock front and rear wheels so the front tires were rotating slower than the rears. Within a few feet TC activated and would apply the rear brakes to bring the car to a stop while coasting downhill in nuetral. I suspect the C6 TC will do the same.

AH mostly doesn't care what size the tires are.

Bill

sperkins

You actually sound like you know what you're talking about for a change.

LEAVINU: If you send Julie Pantas an email, you can probably still get in for this weekend. Be sure to stop by and say hello.

gmccreary

At least I only have one screen name