If I change to tires with a very different diameter, will this throw off my speedometer? Is there a way to fix this?

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

 

no

 

Yes it will change it the speedo reading (our speedo's are off regardless though). IF it can be fixed, the dealer will have to hook it up to a computer to reprogram the ECU to recognize the larger diameter.

But I think jjashaa's right, not sure if Honda does that kind of reprogramming for the TL's