Soloontario

This pertains to a C5 Zo6. I gather that alterations in tire diameter can screw up the traction/active handling control in these cars. How much alteration from stock is acceptable? I am thinking of going to a smaller diameter rear tire like the Yokohama Advan 08 which in 295/30-18 is apparently only 25" tall. vs a 25.3 " tall front tire. Asking for trouble??

Bill Dearborn

It won't bother the Active Handling. AH is triggered by steering wheel input and the car's response to that input as determined by the yaw and lateral G sensors.

The stock tire diameters are 25.4 for front and 26.4 for rear. The front to rear ratio is 26.1 divided by 25.4 or ~ 1.03 as long as you stay within the 1.1 to 1.5 range with the front to rear ratio you should be fine no matter what diameter wheels you go with. Sometimes you can get by with equal tire diameters front and rear. I was able to on my C5Z but others couldn't drive very far before TC started triggering. Probably due to the slight tolerance differences that exist between various EBCM modules.

The tire you are thinking of will not work unless you turn traction control off every time you drive the car. With the front tire being a larger diameter than the rear tire TC will activate with the car coasting down hill in neutral with the engine at idle. It will apply the rear brakes and bring it to a stop. You can try this yourself if you don't believe me. Just swap front and rear tires to try it.

Bill

AU N EGL

Turn AH/ TC off. many guys run square set ups without any problems

all the difference needs to be is less, the rear slightly larger then the front, so only a 1/4" to 1/2" difference if you leave AH/TC ON

Bills Z06

Very well stated!

froggy47

I have run a short rear tire with all TC/AH off and it works ok, but your ride height /balance will need adjusting. It's generally better to have a taller rear and not have to deal with all the issues of running a shorter rear. I am not a big fan of the full square setup as I think the car needs more rear tire for many reasons. My Suburban truck has a full square setup & I like it on that vehicle.

Bill Dearborn

You don't necessarily have to run a square setup to have equal diameter tires front to rear. Running a 275/40/17 front tire with a 315/35/17 rear tire will net a 25.3 in diameter front and rear. I ran that combo for 5+ years before switching over to 315s at all 4 corners in 06.

Bill

froggy47

You are correct, of course, what I ASSUME is that when folks talk about a square setup they mean the same wheel/tire on each corner.

Soloontario

Is the system sensitive enough to pick up a difference of 0.2 " larger at the front? Nitto NT01s in 275/35-18 are 25.55 tall while the 315/30 -18 for the rear are only 25.35. (Certainly smaller difference than the Yokohamas)

VetteDrmr

The system is sensitive enough when you have AH and TC enabled. I have never run those on the track, either autocross or at a DE, unless I was in wet conditions.

If you really want to you can run with TC disabled (Competition mode), but I wouldn't bother.

With AH/TC disabled the car doesn't care. C6s are a different beast, one of the things I like about the C5s.

HTH, and have a Merry Christmas!
Mike

Bill Dearborn

On my C5s I never had a set of tires with that differential. I swapped front and rear stock tires to see what would happen. As you know the difference is ~ 1 inch. On my C6Z I have run 305/35/18 R888s in the front and 335/30/18 R888s in the rear and TC will activate almost as soon as I start driving. Have to remember to turn it off.

Bill

taken19

I have a C6 Z51, but the data point may be useful to you...

I run 275/35/18 and 305/30/19 at the track and the comupter activates AH and TC on hard acceleration above 90 mph. With stock sizes (245/40/18 and 285/35/19) OR TC turned off, no issues.

I think the size difference is just enough that the computer gets confused at high speeds.

Sean

VetteDrmr

C6 nannies are much more intrusive and harder to get around than C5s.