[Kerry]

On the back with the 285 35 20 on the front or put another way.
this much difference it how tall the tires Im wondering about how it will affect traction control. Anyone try that much difference?

[enzia35]

I believe it’s best to keep the diameter difference to under an inch.

[drewspr00]

I'm running 285/35R20 with 315/30R20. No issues for me. Non-MRC

[arpad_m]

I'm not 100% sure he'll be fine with 315/35s. The front-to-rear delta vs stock is +3.3% at these sizes, which is straddling the line (~3%) where many began to experience traction control system issues, and it's mostly on the wrong side of it.

In addition, depending on the tire and previous harness/wheel well liner relocation preps, the rear tire may well rub the liner and potentially the main body harness on the driver side.

[grampa_ss]

You’re probably right. I thought I saw 30, not 35. Maybe I should delete my comment.

[Kerry]

Originally Posted by arpad_m

I'm not 100% sure he'll be fine with 315/35s. The front-to-rear delta vs stock is +3.3% at these sizes, which is straddling the line (~3%) where many began to experience traction control system issues, and it's mostly on the wrong side of it.

In addition, depending on the tire and previous harness/wheel well liner relocation preps, the rear tire may well rub the liner and potentially the main body harness on the driver side.

Thank you Im not sure that link works right but 315/35 to a 285/35 is 2.8% 28.7 and 27.9

[arpad_m]

Originally Posted by Kerry

Thank you Im not sure that link works right but 315/35 to a 285/35 is 2.8% 28.7 and 27.9

The comparison of ratios vs stock is what yields 3.3%: these fronts are 0.7% taller than stock, while the rears are 4% taller.

Now, nobody apart from the Camaro engineering team knows exactly how much the margin of tolerance is for wheel speed differences, but similar gaps did trigger traction control issues for others if I remember correctly.

I would go with a much safer 305/35/20 instead, or even the standard 1LE sizes of 285/30 and 305/30.

[Kerry]

Originally Posted by arpad_m

The comparison of ratios vs stock is what yields 3.3%: these fronts are 0.7% taller than stock, while the rears are 4% taller.

Now, nobody apart from the Camaro engineering team knows exactly how much the margin of tolerance is for wheel speed differences, but similar gaps did trigger traction control issues for others if I remember correctly.

I would go with a much safer 305/35/20 instead, or even the standard 1LE sizes of 285/30 and 305/30.

Interesting. How does the car know what size tire it has if nothing to compare to. Ie front rotation vs back.

[Baddawg53]

I ran nitto nt01 315/30/20 rear and 285/35/20 fronts and it totally confused the car. Was fine on the street but on the track I had to turn the traction control off. Same issue with my current 315/30/18 square setup.

[arpad_m]

Originally Posted by Kerry

Interesting. How does the car know what size tire it has if nothing to compare to. Ie front rotation vs back.

It does have something to compare it to: OEM tire sizes (circumferences) are listed in the tune (see below), and the car checks actual wheel speed on all 4 corners compared to what it expects.

The concern is that the static wheel speed difference with these much taller rear tires might be enough to spuriously trigger traction control and/or ABS because the car may "think" the rears are stuck, given how much slower they rotate compared to the fronts despite expectations set by the tune.

Again, this is all conjecture and a precautionary measure, because (apart from the tune) we/I have no exact knowledge of how these algorithms are actually programmed. Nobody is trying to prevent you from giving it a try, but it may be an expensive experiment if you end up having to replace those 315/35s.

Of course, adjusting the tire size in the tune to resolve this is always an option, leaving only the potential rubbing as an issue, plus of course the "standard" small disadvantages of taller tires.

[KingLT1]

As long as the front and rear are under 1" difference then you will be fine. The tire height overall doesn't matter...just needs to be changed in the tune with the gear/tire calculator under the edit tab. I always use the rear measurement. No issues with my car running 245/40/20 up front and 305/35/20 rear.

[Kerry]

Yes it would be an expensive mistake hence the reason I ask. I always adjust in the tune to get the speed odometer correct. With a 295 35 20 i have a setting of 27.57 seems to be correct.

I use spacers so That opens up alot of room. I have 11 inch rims on the back and have had a 335 30 on the back. But they were 6 year old mitchlens and had aged out they were hard and it was spin city.

Thinking hard about the 315 nitto 2 (running 295 now) but limited on what size tire on the front. The vert will not take as big of a tire on the front that the coope body part of the car is different or I would run the 295 35 up front. Works on a 9.5 rim with a 15 mill spacer, a 20 mill might work but might rub fender too.

I had a 305 30 on the front for a little bit and I caint rember what was on the back probly a 295 35 but it was too much and it would shut me down at times going wo close the throttle and flash the traction light. Car Thought it was spinning because of the speed difference in front to back. turn off traction control and all good. I just dont want to drive around all the time with it off

[Kerry]

So I know I can still go into launch mode with out rear pressure sensors. I know that if bthere are no fronts then it will not let you. Low yes gone no.
So in doing some tire sizeing I had a 28 in tire on the back and a 27 on the front. When I first pulled out and got up to about 40 or 50 I noticed the traction control blinking. I though O great this wont work. Now heres the funny thing, I drove around 30 minutes fast slow from a dig ect It never came on again. Recon it learns for like the sensors when you say go to the track with different tirs with no sensors maybe they make an allowence for a taller tire as well? Can any one confirm. thanks obtw if you go the other way big front small back it will hit traction control so hard on a stomp it will close the throttle. Turn traction control off and no problems.

Man this is embarrassing. I answered my own question. So I guess I tried this in 2020 and thought I had small on front but turns out that works but not small on back. I had forgot witch way it was!