Yaris newbie, trying to find out max tire size....

[dingbat]

Originally Posted by ilikerice

maybe i am misunderstanding this.. ill back out of this one..

Dude, The middle number is simply a percentage of the tread width.

185/60/15, 60% of 185 = 185x.6 = 111 sidewall height.

195/60/15, 60% of 195 = 195x.6 = 117 sidewall height.

The difference in sidewall height is 6mm between the two sizes. Because the sidewall is on both sides of the wheel when measuring diameter, or total height, double the difference for 12mm total height difference. Really you're only talking about a 6mm difference in ride height, but the real issue is with the gearing and speedo. reading. Circumference is diameter x Pi (3.14) so the difference in circumference would be about 38mm. between the two sizes which is just under a 6.5% difference. A 205/60/15 would be a 12mm increase in ride height (bout 1/2 an inch) and aprox. 12.5% increase in gear ratio. That's going to be significant.