Quote:
Originally Posted by hotrodhoodrat
The rims/tiers must have the same diameter ?, so why does GM offer 18's to 21's, I'm not trying to make this in to any thing big (?) I'm just wanting to clear this up ?,
people see custom rims on the car, its good info for those who don't know, yea ?
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The rim + tire has the same circumference on the 18's and the 21's. You accomplish this by changing the sidewall height on the tires, the smaller the rim diameter the taller the sidewall. On the Camaro the sidewall height of the tires on the 19's are 122 millimeters. On the 20's is it 110 mm and on the 21's it is 98 mm.
To change the sizes if you are getting new rims is simple. If you look at the size of a tire you will see numbers arranged as such xxx/xx R xx.
For example, on the 19 inch rims the tires are 245/50 R 19. The first number (245) stands of the width of the tire in millimeters which in this case is 245 millimeters. The second number (50) stands for the height of the sidewall in millimeters and is measured as a percentage of the tire width. In this case the sidewall height is 50% of 245. The third number (R 19) is the rim size so in this case it is a 19 inch rim. Now if all you're doing is simply changing the rim size all you do is change the second number by 5 per inch of change. If you're changing the rim size to 20's then you'll reduce the second number by 5 so you're new tire size would be 245/45 R 20, and vise versa if you go with a smaller rim size so an 18 inch rim would give you a tire size of 245/55 R 18.