Im looking on a couple of packages for my car.

the rim is 20X8.5 with +38offset. what rubber should i use or will both fit the car?

245/45-20 or the 245/40-20?

Please help me here if you have a tips!

Want to order wheels asap :)

RGDS UMB

I can't help you with 20s but do a search. There are several members with 20s and they give their tire size, etc.

I tend to think 40 profile is what you need. Also, tire rack gives suggested tires for wheels that you pick for your vehicle. Just enter your car type and wheel size and it chooses a tire combo that should fit.

245/40/20 will keep your rolling diameter the same as stock- 27.7"

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