Wheel stagger tolerances for traction control and active handling
 

Hi Tadge!

I have a 2016 Z51 Corvette, and I'd like to know the guiding principles behind how wheel stagger can affect traction control and/or active handling. This is so that I can decide what size wheels/tires I can use in lieu of the stock type & size. Using an example of only Michelin, and looking at 2 different tires, I think you'll be able to see where I'm going:

Stock setup:
Michelin Pilot Super Sport ZP's 245/35/19 and 285/30/20
Diameter: 25.8" and 26.5"
Wheel Stagger: (25.8" - 26.5") = 0.7"

Potential change:
Michelin Pilot Cup2's 245/35/19 and 285/30/20
Diameter: 25.8" and 26.5"

Wheel Stagger: (25.8" - 26.8") = 1.0"

So changing to Cup2 tires will change the wheel stagger by 0.3" Is there a guideline to the maximum this wheel stagger can change without affecting the traction control or active handling? If it was known that, for example, the wheel stagger should remain within the range of 0.5" to 1.5", then everyone on the forum could be able to determine if a given tire setup would cause issues with the traction control or active handling. Right now, the general consensus is that we shouldn't stray too far from the stock stagger, which is very subjective. This old thread is what I'm currently using to guide myself.

Thanks!

https://cimg4.ibsrv.net/gimg/www.cor...0174222c75.png

Pay more attention to the revolutions/mile spec rather than the diameter or even circumference as revs/mile takes into account tire deformation and slippage. Then, take the oem ratio of revs/mile and compare that to your proposed setup. Most stability systems want that ratio to be within 3-5% of the oem ratio. Some are more sensitive than others.

I'd love to know the answer to this, but his answer is going to be a long winded, jargon thick version of "we spend a lot time doing very complicated things with multiple variables and inputs and and messing with one of them can have unintended consequences."

I have always used a ratio of 1.04 based on dividing the rear tire diameter by the front tire diameter. If you vary by more than 4% you will see more detectable issues. If you make the rear wheel diameter smaller than the front wheel diameter you will see an almost immediate activation of TC as soon as the car starts to move, even if it is just coasting down hill in neutral with the engine idling. TC will apply the brakes and bring it to a stop. The most likely thing you will notice is TC reacting sooner as the ratio starts to approach one and not as soon as the ratio grows past 1.04. On top of that each EBCM will react slightly different based on where its threshold sits in the acceptable tolerance range. That means some might trigger sooner than others while others might not trigger as soon.

Last year I ran 645 diameter race slicks on the front and 660 slicks on the rear (a 1.02 ratio) and didn't have a problem with TC when driving in the paddock although it was turned off when I was on track since I was running in either Sport 1, Sport 2 or Race Modes which have no TC.

Based on that I feel safe saying you could probably choose front and rear tire diameters that give you a 1.02 ratio and not have any detectable TC issues. The 1.04 ratio has been around since the C5s were introduced and on my C5s I had no issues running equal diameter tires front and rear although there were other people who did have some strange TC issues when speeds reached 70 mph. Those were resolved by turning TC off.

Bill