I am getting 18 x 7.5 rims and I want to know what tires I should get the 225/40/18 or 235/40/18. Thanks

 

225/40/18 is the correct tire size

 

I've got 235/40/18. Rides well and I think a lot of guys out there would tell you to go with that size.

 

225s will look "flatter" and not bubble out like how the stock ones do. A lot of people would say it's more visually appealing to have the tire sit flush with the rim, but either set will fit. They will also have less sidewall flex due to the tire being more stretched out over the rim.

I personally run 225/40/18 on my 18x7.5.

 

225/40/18

 

i would say 225 because the wheel is only 7.5" wide

if you had a 8" wide wheel then i would say 235.

when i had 18x8.5" i had 245 and the roads here are bad (NJ). i needed the extra rubber.

 

these are about an inch smaller than stock! I'd go with the 235s but 225s will work as well.

 

speedometer is the most accurate with 225/40/18 on a 18 x 7.5 rim..thats to my understanding at least..

 

What about 18x8 wheels, should i go with 235/40 18 or 245/40 18?

 

Here's the tire size calculator for you to use. 245's are closer to you original 17" tires, and they fit on 8.0 - 9.5 wide wheels. Use any of the specs pages from TireRack to check.
http://www.miata.net/garage/tirecalc.html

Mike

 

On the same subject. I am going purchase 18/7.5 rims and am going to run 225/40/18 tires .. but before i get there how do i know what offsets do i get for the rims .. and will this setup it snug under stock height 2000 GXE ?..

 

get an offset thats between 35 and 42 and you shoudl be fine. youll still have a lotta wheel gap..get some lowering springs

 

on a 18 x 7.5 proper size supposed to be 225 or 235, it honestly makes a little difference. wider tires, grips the road better. i would say 235/40/18 because that is what im using and it does NOT look weird at all! looks better than 225.