Toque

Guys:

So this has me curious.

Does anyone know for sure how far outside of stock diameter (difference between front/rear) you can go before you have active handling/traction control issues ?

Everyone seems to throw out 0.5" as the number to be close to. I don't know if anyone knows for sure though.


Stock C5 (97-04):
Front
Tire Size = 245/45/17 = 25.7" Diameter
Rear
Tire Size = 275/40/18 = 26.7" Diameter
So the rear tire is 1.0" larger than the front tire on a stock C5.

Stock C5 Z06 (01-04):
Front
Tire Size = 265/40/17 = 25.4" Diameter
Rear
Tire Size = 295/35/18 = 26.1" Diameter
So the rear tire is 0.7" larger than the front tire on a stock C5 Z06.

The setup I'm running now is:
Front
Tire Size = 275/30/19 = 25.6" Diameter
Rear
Tire Size = 305/30/19 = 26.3" Diameter
So my rear tire is 0.7" larger than my front tire. This is the same as my stock Z06 setup. I don't have any Active Handling or Traction control issues.

So my question is.... How far away from 0.7"-1.0" (Diameter) can you get before you start to have active handling issues ? Does anyone know for sure what the magic number is ?

If anyone here have had issues with Active Handling/Traction control I would love to hear what sizes you were running. Maybe if we get enough numbers on this post we can figure out what works, and what does not work.

Thanks !
Toque

AustinVetteFan

Everything I've read suggests that as long as you're 0.5" or more, you're ok. If you go below 0.5" difference, that's when things start acting up. Of course, I got that from reading opinions here on CF, and what the hell do these people know?

m6 c5

Im going to guess that if you are greater than 1.5 then you will have issues as well, but I guess the software could be written to only try to intervene when the rear tires are spinning faster than what is expected because as long as you are on the throttle its not really possible for the front tires to be spinning faster than the rears...

Vetteman Jack

What I have heard is 1/2" on either side of the 1" factory number too, but I have no first hand knowledge if something less/more than that would be a problem. When I have bought tires, they have either been the exact factory sizes or as close to the 1" difference as I can get.

Maybe someone will give some info if they have tried something outside the boundaries so to speak.

AU N EGL

as long as the rear is "slightly" taller then the front you are OK.

Slightly taller could even mean a few PSI more in air pressure in the rear tires vs the front on identical size tires. I have done this several times.

that said, just get tires with a min of 1/4" OD difference or greater and you will be fine.

Toque

Ok everyone makes some good points.


What I'm taking from comments made is that, the closer you make the front and rear diameters the same, ... the greater chance you have of having AH/TC issues.

I have been chatting with a forum member about his stock Z06 sizes. He wanted to go to a 275/40/17 in front as apposed to the 265/40/17. That would put his rear stock 295/35/18 tire at only 0.4" larger. He said he had spoken with other members and they were not having AH/TC issues. It must be close to the magic limit though I suspect..


The other side of the coin is... will you have AH/TC issues if you make your rear tire even larger than the front ?

A friend of mine just installed :
Front - 265/35/18 (25.3" diameter)
Rear - 345/30/19 (27.2" diameter)
That's a 1.9" diameter larger tire in the rear. He said he went for a quick drive yesterday and never had AH/TC issues.

So am I to assume that AH/TC issues are ONLY caused by having the front and rear tire diameters too close to one another ? Increasing the rear tire size is not relevant to AH/TC ?

Thanks !
Toque

SaberD

From what I have read, it seems some vettes are more sensitive to the difference in height than others. I don't know if there was any trend.

hotwheels57

I upgraded to 18/19" tires recently. I searched high and low on the internet, asked every tire "expert" and no one had the definitive answer. I think much is supposition (it is the internet). And it seems there's as much supposition/information on corvetteforum as any other C5 reference site.

Spending $2000 for tires that won't work wasn't in my plans. I chose to stay conservative in my selection to avoid the issues and I didn't want to stay with 17/18" tires.

I decided to stay as close to oem OD as possible. Front tires are exact OD as oem. Rear tires are .1" larger. No issues...and I sleep well at night.

corvettebob1

The last time I bought tires I went from the stock sizes 245/45/17 & 275/40/18.
To as close to the Z06 size I could get 275/40/17 & 295/35/18, and since I have a 98 w/o active handling I have no issue with this.
But I have to say the traction control is much more intrusive with the closer size stagger.

TXGS507

I am one of the "friends" Mark (toque) is referring to. I recently changed from a 19/19 combo w a 265/30/19 up front & a 325/35/19 out back (19X10 / 19X11 CCW SP500 wheel)

Went to an HRE 18/19 combo along with T2 Flared fenders (rear).
Started w fronts ( per Marks theory) w a 265/40/18 up front.. Granted, my car is lowered on Coilovers.. and the tires rubbed badly. Changed to a 265/35/18 fit like a glove.. Running a 345/35/19 out back.. Mark thought initially that i would have AH/TC issues... Drove the car 01 Z06 for approx 20 mi... NO issues..

Just my experience.... FWIW...

AU N EGL

Can we say MAJOR under steer problems ??


If one runs 345s in back they need 315s up front.