i HAVE GATHERED THAT 17" X 8 RIMS WILL FIT ALL ROUND A S5, WITH 225/50/17 (F) 245/50/17 (R)
My question is, A- is this correct without spacers or anything?
B- Does this affect the speedo?

 

If I did the math correctly, you would have to have a 245/45/17 in the rear the keep the rolling diameter the same as stock. Anything different than that should cause your speedo to be off. I don't know about the fitment, though.

 

depends on the offset of the wheel, but it is my understanding (and someone may correct me) that a 245 will be too wide.

 

I believe 245s will fit just fine with the correct offset rims. I have heard of someone going even wider, its the offset that matters though.

 

I will be running these tire sizes once my dang wheels get off the slow boat from japan.

stock T2 is 205/55/16 24.9 tall

225/45/17 front 25" tall
255/40/17 rear 25" tall

front 17X8 +35
rear 17X9 +35

wheel is Enkie RP-F1

you could run 245/40/17 in the rear if you only have 8" wheels. this size is 24.7 tall so your speedo will be a litte off



what offsets are other people running with 8" wheels?

 

http://www.miata.net/garage/tirecalc.html
use this tire size calc to find the right size