[Mr Self Destruct]

Key in your old tyre size, then your new tyre size, and it'll tell you the difference to your speedo.
Very useful when you want to replace 6 x 15 standard bug wheels with 8.5 x 18 Audi RS2's!:D

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

[kenny]

how cool is that,hours of fun.the 205/55-16s on my bay are 2mph out at 60. took me ages with my thinking cap on to work out that the rolling circ was pretty close before i fitted them.

[Coxy]

Very useful when you want to replace 6 x 15 standard bug wheels with 8.5 x 18 Audi RS2's!:D

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

:D :D :D

Although mine are 17's!!

18" RS2 rims were a very limited optional extra and are like rocking horse shit.

[Mr Self Destruct]

Yeah, if I win 'em on ebay and can't find someone with a T25 to swap with, I'll need oversize wings!:D