I have an 05 with 18" OEM sport wheels. My crappy Turanzas are down to it's last days and have been looking here to see what people are replacing them with. As I've seen 235/45/18 are very slim pickins. Kuhmos are pretty reasonable replacements but there is a nationwide shortage on those right now. Seen that I can go 245/40/18 or 245/45/18 to get more choices. Using those calculators, it says the following compared to stock size at 60mph:

245/40/18 - 61.4 mph, 2.379% too fast

245/45/18 - 59.1 mph, 1.359% too slow

My question is, does that mean it will affect the odometer reading as well? Given you can drive 35K miles on the set:

245/40/18 - 35000 * .02379 = 832.65 miles more on odometer than actual?

245/45/18 - 35000 * -.01359 = -475.65 miles less on odometer than actual?

 

Yes that is true.

 

I went with 245-45-18 due to this problem with available tires at a decent price and have been happy with them. They also fill the tire well more.

 

Wow...no kidding. Never thought about the mileage affect. Can you tell me where you found this calculator? I'm curious to know what my adjustment would be (I'd have a negative affect based on the above, running 245/40/19's). That is good to know that the odometer reading is less than my actual miles.

 

These are the best sites:

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

http://www.1010tires.com/TireSizeCalculator.asp

 

I think this one is by far the best
http://www.rims-n-tires.com/rt_specs.jsp

 

Holy $hit, that site's awesome!

 

I am mistaken! Yes, that site is definitely better.

 

That is definitely the best, thanks for sharing.

 

Wow. So helpful. This really helps with looking at offsets in relation to tire width and how it should affect the car's overall appearance.