I have a Z71 with factory 16" rims and was wondering if i got bigger rims like 17" or 18"s or whatever how do you get your speedometer to read right? Does anyone do this? Also if i get a bigger tire than factory tires on a set of 16"'s would i need to do anything to the speedometer?

 

If you get a bigger wheel, you don't need to worry about anything as long as you keep your tire size the same diameter as stock.

If you get a larger tire size (diameter) than stock, you will have to modify the programming in the ECM to match your new size.

 

http://www.miata.net/garage/tirecalc.htmlheres a site to tell you if you will need to get your speedo changed

 

tunes will fix it wether hand held or whatever so get whatever kind you want and fix it i dont see a sig so dont know if you already have one but that will fix it