Is it ok to have 245/40/19 and 275/35/19 tires - tires with different sidewall heights? Does this affect rolling diameter and the feel of the ride at all? (I'm putting these on 19x8.5 and 19x9.5" rims).

Thanks.

 

See VQRacer's sticky thread at the top of this forum or just go here: /www.miata.net/garage/tirecalc.html
Would be better to go with 35 series in the front (w/ 245's)and 35 or 30 series in the rear (w/ 275's)

 

So basically the only problem I may have running those sizes I wrote above is that my speedometer may be off by a bit? Will there be any difference in ride/performance? Lastly, is the speedometer measured by the front or rear wheels? Thanks.

 

By the transmission. However, differently sized wheels / tires (in this case the rear tires) will give slightly inaccurate speedometer readings.