Toyo Proxes T1R - $208/each
Michelin Pilot Sport - $254/each

All 225/45/18

What do you think of these two tires? Any opinions on either? Or should I stop around to other places?

I just want decent grip, great rain performance, and longevity.

Also, I've seen other owners installing different size wheels (like 245/40/18) - will 245/40/18 make my spedometer inaccurate?

 

1% difference = you will not notice it.

From this site ==> http://www.miata.net/garage/tirecalc.html

Tire Size Comparison

Specification Sidewall Radius Diameter Circumference Revs/Mile Difference
225/45-18 4.0in 13.0in 26.0in 81.6in 777 0.0%
245/40-18 3.9in 12.9in 25.7in 80.8in 784 -1.0%

 

i recommend the T1R's in 245/40. i absolutely love mine. i would try Edge Racing, which is where I got mine. the price was far better than $208... i think i paid like $167/tire, & i got more rubber. Here is the link:

Edge Racing

 

Go with Michelin PS2 in 245/40-18. It's quiet and the grip is amazing.

 

I agree with zaglo. EdgeRacing.com has the T1R for less than $160, and it should be about $20 a tire from a good shop to install them, all of which will be less than they quoted you.
Kramer Tire is a local tire store, I assume, right?
I would ask them how much they charge to install 4 tires if you bring them in, and if that is anywhere near $20 per tire, tell them you can get the T1R's for $150, so why don't they cut you a deal? You pay $180 per tire installed and everything, they get the business and you don't have to wait for shipping or anything. Just a thought...

 

For the money the T1R is a great tire that has everything you are looking for. Can't say anything bad about the PS2's. Damn fine tire. probably the best overall tire on th market, just expensive.