[Z06] Why are vette rims two different sizes?
Drifting
Joined: Oct 2006
Posts: 1,773
Likes: 2
From: San Diego CA
Safety Car
Joined: Oct 2004
Posts: 4,816
Likes: 132
From: Plano TX
Its a Conspiracy between GM and the Tire Industry.. They figured with different size rims we would not be able to rotate our tires, forcing us to buy new rear tires at an accelerated rate, thus stimulating the tire industry
Melting Slicks
Joined: Aug 2004
Posts: 3,003
Likes: 89
From: Indy IN
A very good friend was one of the ride and handling engineers on the C5. When the car was in development we were discussing the front tire size and rim width that they were working on (we were both with GM at the time) and he indicated that they needed to skinny down the front tires to make aerodynamic performance numbers.
BTW he was confident that the car would be fine with narrower rims on the front and that it would be as fast with the with 255's as the older C4's (Z07 C4's had 275's up front) and we all know that wasn't the case.
Once they went with different width rims and tires on the front, it wasn't any stretch to go to different diameters. Remember that they went with skinny rims on the front of late model base suspension C4's, so as early 1993 you couldn't rotate tires on the base suspension car although Z07 cars had a square setup.
BTW he was confident that the car would be fine with narrower rims on the front and that it would be as fast with the with 255's as the older C4's (Z07 C4's had 275's up front) and we all know that wasn't the case.
Once they went with different width rims and tires on the front, it wasn't any stretch to go to different diameters. Remember that they went with skinny rims on the front of late model base suspension C4's, so as early 1993 you couldn't rotate tires on the base suspension car although Z07 cars had a square setup.
Thread Starter
Safety Car
Joined: Oct 2007
Posts: 4,028
Likes: 3
From: Matthews Nc
Interesting! Someday I may want to buy new rims and tires and the advantage of the same size rim is obviously now I can rotate and not feed into the corporate tire companies ploy to sell more tires! I just didnt know if it was anything other than just a looks thing or had a actual performance gains.
Team Owner
Joined: Sep 2003
Posts: 43,084
Likes: 33
From: Raleigh / Rolesville NC
Interesting! Someday I may want to buy new rims and tires and the advantage of the same size rim is obviously now I can rotate and not feed into the corporate tire companies ploy to sell more tires! I just didnt know if it was anything other than just a looks thing or had a actual performance gains.
And some ppl even the same wheels and tire combos on all four corners. ( I did for a year)
Challenge with four identical wheel tire combos come from AH / TC. If you turn AH/TC Off there are no problems.
Ideally the rear tire should be 1/2" taller then the front to have no AH /TC issures
Most performance tires are directional tires. so moving from left to right, is not really a good idea.
For performance gains, if that is your objective stick with 18s or 17s on all four corners. This is mostly a weight issue. Large rims and tires weigh quite a bit. And Rotating wt from tire/wheel combos are the death of performance.
For each one pound removed from rotating weight, ~ 6.5 lbs removed of static weight our of the car.
each 100 lbs out of your car, or 12.5 lbs less wheel weight is equivalent gaining 10 rwhp more.
Good Luck
HTH a bit
Last edited by AU N EGL; Nov 14, 2009 at 11:17 AM.
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Thread Starter
Safety Car
Joined: Oct 2007
Posts: 4,028
Likes: 3
From: Matthews Nc
Ouch so same size tires will cause issues with active handling but doesnt really affect performance. This actually alters my original idea of same size rims. I use active handling to keep me from getting out of control. Even today pulling out in traffic with cold tires the traction control kept things from possibly going bad. Thanks for the info guys.
Team Owner
Joined: Sep 2003
Posts: 43,084
Likes: 33
From: Raleigh / Rolesville NC
Ouch so same size tires will cause issues with active handling but doesnt really affect performance. This actually alters my original idea of same size rims. I use active handling to keep me from getting out of control. Even today pulling out in traffic with cold tires the traction control kept things from possibly going bad. Thanks for the info guys.
I ran 18x25.5/11.5 on all four corners. It handled fantastily. Grip was great. Yes these were Good Year G19s Slicks. R450 compound.
best handling my car had. But must turn off AH/TC too allow the car to drive and handle the best.
But 18x12 rear and 18x10 front with Nitto NT555
Nitto NT555 305/35ZR-18 101Y B & 285/35ZR-18 97Y B
Thread Starter
Safety Car
Joined: Oct 2007
Posts: 4,028
Likes: 3
From: Matthews Nc
This is great info. My car is a street car only. I think if I do decide to go with rims and tires It will be 18"front and 19" 11 rears. Forgestar f14 rims has just offered an 18" 9.5 for front but is limited in availability. I really appreciate the info because Its an expensive decision and I would have been unhappy with having to turn off my tc/ah all the time.
