1994 corcisa

[swisher]

if I put 215R70 14" tires on it how far off will my speedomerter ben off.

[J-Ri]

Originally Posted by swisher

if I put 215R70 14" tires on it how far off will my speedomerter ben off.

first we would need to know what's on there now. You first need to figure the circumference of each tire

215 is the section width in milimeters.
Multiply that by 10 to get centimeters.
There are 2.54 cm in an inch
so 21.5/2.54=8.46 inches wide

70 is the sidewall height as a percent of the width
so 8.46 x .7 = 5.92
there are two sidewalls and a rim to get diameter
so (5.92 x 2)+14 = 25.84" diameter
25.84 x 3.14 = 81.14" circumference

find the circumference of what you have on there and find the percentage that they are off.

I figured it out on my beretta, and going from 195/75/14 to 205/70/14 was about 98% of the indicated speed (215/70/14 was less than 105%, but both numbers are just the best that I can remember, so at 55mph you'd be about 3mph over). I was concerned about rubbing, so i went with the ones I did, but I was wanting to get 215/70/14. (195s wore way too fast on the shoulders, going wider causes more wear in the center of the tread) If you end up trying it, please PM me and let me know if they rub, I've got 2/32" tread left and will be replacing them before winter