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Check out Tirerack's site... (more) Posted by Karl [Email]  (#161) [Profile/Gallery]
(more from Karl) on Wed, 14 Feb 2001 12:41:42
In Reply to: Confused Over Tire Sizes, Bill Cannastra, Wed, 14 Feb 2001 11:37:12 Members do not see ads below this line. - Help Keep This Site Online - Signup |
Hi,
On Tirerack's site you'll find info on the diameter of each tire, and thus info about it's circumference.
In this case a 225/40-16 is definetely smaller (lower) than stock 205/55-16. The equivalent of a 205/55-16 is a 225/50-16, which will give the exact same circumference, and thus no speedo error.
To calculate, just calculate the tire's height on each side of the wheel as "tire profile in %" x "tire width in mm" (one inch=25,4 mm for reference). Add to this the height of the wheel.
Example:
225/40-16 = 225*0,4 + 16*25,4 + 225*0,4 = 586,4 mm
225/50-16 = 225*0,5 + 16*25,4 + 225*0,5 = 631,4 mm
205/55-16 = 205*0,55 + 16*25,4 + 205*0,55 = 631,9 mm
That's the height, i.e diameter of the wheel. Circumference is easy to calculate.
My question above was more in reference to the width of the tire in relation to the width of the wheel, as 225 is on the limit in terms of how wide a tire can be fitted on 6,5" wide wheel.
Hope this clarifies things a bit.
Oh, almost forgot... Since older Saabs (pre 92') run 205/50-16 standard, the difference won't be AS big for an older car running 225/40-16. Personally I would have gone with 225/45-16 which is an exact match (almost) for the stock 205/50-16. But, hey...at least the car will seem to go faster...LOL...
/ Karl
, Tue, 13 Feb 2001 13:40:59, Wed, 14 Feb 2001 12:41:42 <-- Viewing This Message, Tue, 13 Feb 2001 14:11:32
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