farmington

old motorhead

The ratio of front to rear diameter needs to remain the same. Don't think you can change that in the tune and keep the nannies happy. So, if you add a 10% taller tire in the rear, you need to similarly get a 10% taller tire in the front. The rears need to be about 4.6% taller than the fronts no matter how tall the rears are.

HOXXOH

IIRC there is no tire size adjustment for front tire size in HP Tuners, only the rear to correct the speedometer/odometer. If that's true, you can't fix the ratio if it's out of the limit. If my memory is wrong, and it happens more frequently anymore, then you can fix the ratio.


Here's a method that assures the minimum ratio limits and can be used with replacement tires, especially when only replacing one axle pair. BTW, not all tire manufacturers tire data is accurate, but short of measuring the tire properly inflated and on the car, it's all we have.

Find the OD of the OEM front tire and the tread depth. Do the same for the rear tire.
Calculate the circumference of each with full new tread and also when no tread remains.
Calculate the percentage of difference between full tread on the front vs no tread on the rear, then do the same for no tread on the front vs full on the rear. Those are the known limits. It may be more, but GM doesn't appear to let that information be public.

KW Baraka

Going with taller tires in the rear on raises the rear end. Whether this will impact handling o aerodynamics in a Corvette.....I don't know, but I wouldn't chance it.

Going with rear tires that are more than an 1" taller than stock while keeping stock diameter front tires has been known, in the 94-96 B-bodies to disrupt/disable the ABS.

KW