Why does it seem everyone goes from 225/45's to 245/40's? I get the width increase (225 to 245), but why the decrese in sidewall height? Doesn't it make it not fill out the wheel well as well? Is there a rubbing concern if you go with 245/45's? Thanks for the info.

edit: Nevermind. I just realized that the second number is a percentage rather than an actual measurement in millimeters. If you had 245/45's they'd be 18 millimeteres larger diameter than stock tires. The 245/40's are 6.5 millimeters smaller diameter and 20 millimeters wider than the stock 225/45's. Everyone here probably knew that. But now I know and knowing is half the battle!

 

check out this site: tire size calculator (unfortunately it requires java, but it's worth it)


you will never wonder about tire sizes again.

the main reason most people switch to 245s is it looks so much better. the 225 tires look like they are too small for the wheels. look at the pics I posted.

 

The manufacturers specifications for a 265/35/18 are:

Mounting Rim Width Range......9.00" to 10.50"
Measured Rim Width....9.50"
Section Width........10.7"
Overall Diameter.....25.3"
Revs. Per Mile.......820

 

245/40/R18 Nitto's

 

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%
245/45-18 4.3in 13.3in 26.7in 83.8in 756 2.7%
245/40-18 3.9in 12.9in 25.7in 80.8in 784 -1.0%
245/35-18 3.4in 12.4in 24.8in 77.8in 815 -4.7%
255/40-18 4.0in 13.0in 26.0in 81.8in 775 0.2%
265/35-18 3.7in 12.7in 25.3in 79.5in 797 -2.6%

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My question is If i can put 245/40/r18 in a Mazda rx8 with the regular shocks or do I have to put diferent shocks

 

For street use? you can safely go with 245/40 without changing a single thing