I have been looking for a good tire/wheel calculator to see how different sizes compare and how much difference there will be at various speeds.

The DML Tire Wheel Calculator looks very helpful.

http://www.dakota-truck.net/TIRECALC/tirecalc.html

 

THANKS!!!

And if you use the "Tire A" to "Tire B" comparator, it gives you equivalent tire sizes too! I've been thinking of going 18" all around with new rims and this makes selection a bit easier.

 

There is another very good calculator link somewhere on this forum that I used. Can't seem to find the link right now, If you are interested in 18's all around you will love it! That is what I did. If you want to want to keep the stock overall look you need 265/40/18 on 18/9's in the rear and 18/7.5 - 18/8 with 225/40/18 on the front. i would use 235/40/18 on the front if you go with 8 inch wide rims. You can see a picture of my car with 18's in my gallery.

 

According to the calculator a 255/40/18 is a perfect match to replace the original 255/35/19.
The selection of 18s is much better and the ride should improve.

 

God, I LOVE you guys!

 

You can also save a ton when shopping for tires. I went with 265/40 which are just a hair taller than the original 19's but are 10mm wider. This looks great on a 9 inch wide wheel. the 255 is the exact replacement. Oh and the ride is better.

 

My favorite is from the Miata.net site - http://www.miata.net/garage/tirecalc.html

 

http://www.rims-n-tires.com/rt_specs.jsp

 

This is the one I was referring to above. I really like this one! This one will also tell you if things will clear or rub.

 

This one is very interesting...if somewhat limited on tire types.

Gotta love this forum. Where else can you find this much info from so many very smart members...

 

that last wheel tire calculator if i wanted to go to a 20" rim all around. a rim that would work for the crossfire would be a 20"X9" rim with a 30mm offset. 235/35/20 on the front and 275/35/20 on the back. back would be pushed out 15mm and 7mm bigger and 5 mm closer to suspension and front would be pushed out 10mm and 7mm larger and stay same length from suspension. does that sound like it would work on the crossfire. they seem pretty close to factory specs. only a few mm.