Larger tires on my C%
Thread Starter
Intermediate
Joined: Jul 2023
Posts: 25
Likes: 0
Larger tires on my C%
Hello everyone. The person that I bought my C5 from put C6 wheels on my C5, and hence, the tires are one inch taller in the front, and the rear. The fronts are 245/40 ZR 18's, and the rears are 285/35 ZR 19's. They look fine, and work fine, without any rubbing. My concern is this: I just read on a forum on Facebook, and was informed that putting a taller tire on the rear of the vehicle will change your rear gear ratio.
The person said that it will change it for the worse, not for the better, and in effect, make the car slower. I'm pretty bummed about this. Anyone want to chime in on this? Thanks
The person said that it will change it for the worse, not for the better, and in effect, make the car slower. I'm pretty bummed about this. Anyone want to chime in on this? Thanks
Drifting
Joined: Jul 2004
Posts: 1,690
Likes: 692
From: Pingree Grove IL
You won’t notice a taller or shorter tire in terms of acceleration on a 350 horsepower car. I have an auto trans and a taller tire would make my 3rd gear hit 143mph instead of 140mph. This is just an example of what a taller tire does, a shorter tire then stock will make 3rd gear hit 135mph instead of 140mph. Make sense?
You won’t notice a difference. If you like the look and it works, keep it.
I have a shorter tire on my C5 305 30 19. Guess what? You never notice a difference.
You won’t notice a difference. If you like the look and it works, keep it.
I have a shorter tire on my C5 305 30 19. Guess what? You never notice a difference.
Melting Slicks
Joined: Sep 2021
Posts: 2,555
Likes: 1,213
What you want to do is compare tire circumference. There are various calculators online to do this, Discount Tire has one.
Using that calculator we see the original 245/45 17" front tires and the new 245/40 18" are extremely close and no cause for concern.
Current New Difference
Rev. / Mile:785.32 784.16 -1.16
Section Width: 9.65'' 9.65'' 0''
Sidewall Height: 4.34'' 3.86'' -0.48''
Tire Circum: 80.68'' 80.8'' 0.12''
Tire Height: 25.68'' 25.72'' 0.04''
The results here are poorly formatted but at the calculator above they are much easier to follow.
I encourage you to compare your rear sizes and you will probably find similar results.
Using that calculator we see the original 245/45 17" front tires and the new 245/40 18" are extremely close and no cause for concern.
Current New Difference
Rev. / Mile:785.32 784.16 -1.16
Section Width: 9.65'' 9.65'' 0''
Sidewall Height: 4.34'' 3.86'' -0.48''
Tire Circum: 80.68'' 80.8'' 0.12''
Tire Height: 25.68'' 25.72'' 0.04''
The results here are poorly formatted but at the calculator above they are much easier to follow.
I encourage you to compare your rear sizes and you will probably find similar results.
Race Director
Joined: Apr 2007
Posts: 11,152
Likes: 890
From: South Western Ontario
Tire and wheel rotating inertia, which is based on weight and radius, has a bigger affect on acceleration than a small change in tire diameter. If they are factory wheels then GM did well keeping the weight down, which then means the rotating inertia is kept low. Some aftermarket wheels are heavy and have more inertia. Certain tires are much heavier than others which means they have more inertia.
