Looking to get new tires and this is what is on the care now;

F- 245/45 ZR17
R- 285/35 ZR18

Stock is supposed to be...

F- 245/45 ZR17
R- 275/40 ZR18


Now that calculates (stock) to:

245 x .45 = 110.25
275 x .40 = 110

What I have:

245 x .45 = 110.25 (same)
285 x .35 = 99.75 (10.25)

The question is what effect does / did that have or am I being too AR and should just go with what will fit?

Also as I dont run 150 MPH do I really need ZR1 rating?

Thanks guys for the input.

Onion

 

Your stock wheels and tires have the following specs.
If you keep any tire/wheel changes so that the specs are very close to stock Dia/Cir and revs per mile you should be good to go. The Active Handling/traction control syst. is designed to use these specs/ratios between the front and rear wheels plus other inputs to help maintain control of the car.

Front Stock Size
245/45/17x8.5 +56mm offset
Diameter- 25.7"
circumference- 80.6"
revs per mile- 786.1
Rear stock size
275/40/18x9.5
diameter- 26.7"
circumference- 83.7"
revs per mile- 757.1

Here is a setup that keeps the stock front to rear ratios very close and should allow the AH/TC syst. to work correctly.

Front replacement size
275/40/18x9.5 +56mm offset
Diameter- 25.6"
circumference- 80.2"
revs per mile- 789.7

Rear replacement size
315/30/19x10.5 +59mm offset
Diameter- 26.5"
circumference- 83.2"
Revs per mile- 761.6

The above setup changes wheel size if you don't want to change wheel size then you don't have to, but when you change just tire sizes you will still end up changing the ratios between front and rear.
As the other poster stated the revs for the rear tires should always be less than the front or the AH/TC will interpet that as wheel spin and attempt to control the car according to those inputs as well as any other inputs it is sensing at the time.

http://www.rimsntires.com/specs.jsp

This is the site that I used to do the sizing of the replacement tires/wheels. These are not the only replacements that can be used, just some I came up with.
Input the stock sizes in the first inputs and the replacements in the second set of inputs. Play around with it and you will see that what may appear to be a minor change in tire/wheel measurements can make a very big difference in ratios between the stock set up and any replacement set up you may want to use. Keep in mind that front to rear ratios are certainly very important.
You can even put the same size wheel on all four corners and get the ratios to be very close by adjusting the tire inputs.
I am sure that many owners have used any number of tire/wheel combos without any major problems, but I am of the belief that it is much safer to keep the front to rear ratios close to stock ratios because the AH/TC syst. uses many inputs to keep the car operating in a safe manner. The system expects to see certain conditions that fall into what it considers safe operating conditions and reacts accordingly.
I have no idea how much of a deivance from the stock front to rear ratios that the system can sense and still keep the car operating in a safe manner. Although I am sure that there are forum members that do know this info. Torque is one member that has a very good tire sizing thread. I would check it out.
Hope this has been helpful.

 

See my post on the subject

http://forums.corvetteforum.com/c5-g...ah-issues.html

Toque

 

Thanks for all the info guys and 8vette7, your correct in no AH only TC.
Great posting Toque on tires.
Now I just have to see what the best combo is and what is available because as we all know just because we want dont mean its out there.
Any opinions on BFG tires and sizes?

-Onion