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Old 06-03-2014, 12:56 PM
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67Rally 67Rally is offline
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Quote:
Originally Posted by OBeer-WAN-Kenobi View Post
I'll have to do some more research and relearn how to decipher the tire sizes again (it's been a while since I speced out anything). Then I'll see what I can come up with. I do have a 4.10 rear and probably really should have a 3.90 so if I go a bit larger in diameter in the back I may have to go a bit narrower.
Understanding tire sizes are as follows:

275/40/18

1st number is width = 275mm wide (divide by 25.4 to find inches)
2nd number is sidewall height = 40% of 275mm (from lip of wheel to edge of tire)
3rd number is wheel diameter = 18"

A narrower tire would be a 265/40/18, or a 255/40/18
A tire with less sidewall would be a 275/35/18

Simple right?

Now the confusing part...Keep in mind that since the sidewall is a percentage of the tread width, a 265/40/18 will be 10mm narrower and have 4mm less sidewall than the 275/40/18. That translates to 8mm overall shorter tire since you have to count both both sidewalls (above and below the rim).
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