I got some rims with these specs:

Size: 17x7
Bolt Pattern: 4x100 or 4x114.3
Offset: 40mm

My car's suspension is stock (i.e. not lowered), and I want to know the proper tire size so I don't throw off my speedodomotor and my milage count.

BTW: These are the rims, but in white (the white version retains the silver polished lip, btw.) http://www.gtpower.net/adr/sokudo4a.jpg

 

225(or better 235) x45x17 are the safe ones from pot holes, curb, and softer ride.

 

Right, but out of everything, I'm looking for something that won't throw off my gauges.

 

they won't

225-235 is the width to protect the lips of your wheel from curbs, has no effect on your gauges reading.

45 - is the thicken (height), with 17 wheels, 45 is about just right (may be little tiny lil bit smaller than your stock, make real 58mph look 60mph on the speedometer - you are actually slower than your reading).

You can even go for 50, since 50 is the right size (may be just a bit larger, that'll make your real 62-3 mph look only 60mph on the reading)

 

Actually the second number is not a measurement of sidewall height, but rather an aspect ratio of width to sidewall. For example a 225/45 tire will have a taller sidewall than a 225/40 tire. That's why when you see lambos with 335/30/18, they still have plenty of sidewall height.

For 6th gen, 225/45/17 is actually the EXACT same rolling diameter as the stock 4cyl tires.

225 is also about the widest you'll want to because of rubbing issues.

Use a tire calculator to check out possible tire sizes.

215/45 or 205/50 are other options you could use as well.

 

oh well, i was making it simple

 

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

well go there for your reference,

 

I'd go with 215/45 myself

 

U would have thrown him off!!! It wasn't simplified. It was incorrect.

225/45 is not the same as 235/45.

I wouldn't go higher than 225. THe more rubber u have the harder it is for the engine to accelerate ur car but the handling is better. U want to find a happy medium. If u are worried about gas milage than maybe a 205 or 215 will suit u better. 235 is too much IMO.

 

205/50-17 or 225/45-17 will be the two closest matches in diameter for the stock tire size. Their sidewall will be about the same thickness, with the 225/45 being a bit wider tread.