Tire size diff from stock affect speedometer?
 

Hi, my stock tires are 205 60r 16 with H rating tires and i just bought tires taht are 215 55r 16 with t rating cuz they were a good deal.
would this affect my car at all and would there be any problems?
thx

http://www.miata.net/garage/tirecalc.html

+1.5% difference is fine.

wow thx for the quick reply.
that site to calculate is awesome

3% is the rule of thumb..

width x aspec ratio x 2 divided 25.4 + diameter = OD"

I used that website as well but it isn't the best, there's actually a better one out there but i forgot what it was.

for instance my situation.
Stocks 195/60/15
Aftermarket is 235/40/17
Now on the website it says that the difference in diameter is only 1/4 of an inch.

Problem is my wheels are 9" wide and a 235 is is for a 8" so it's a bit of a stretch even so, when i line up the wheels the aftermarkets are much larger.

but it's a good tool just for general use.