I really want to switch to the Bridgeston RE960 Pole Position tires but the problem is they do not make thhe exact rear tire size of 255/40/R18 and the closest they make is 245/40/R18 which is close but is 1.2% off on speedo reading. Has anyone used 245/40/R18 and do you think this would be okay?

 

Is anyone running 245/40/18 on their rear oem wheels?

 

Why the RE960 Pole Position ??? If you must have Bridgestones, check out TireRack, they have the RE050A Pole Position as the highest rated replacement tires for the IS (with the correct sizes) . . .

 

Err, 255 is the width of the tread, 40 is the height. NORMALLY, i say normally, the speedo is affected by the size of the rims/tires in height not width. To this date i have never heard of the speedo being affected by the size of the 'footprint'.

 

255/40 = 102mm sidewall height
245/40 = 98mm

so width does make a difference

 

The first number in a tires size indicates the tread width, the second number indicates the sidewalls height but is a percentage of the first number.

 

Agreed. The width of a tire does affect the overall diameter and thus the speedometer too.

Some more specifications to put it in perspective...



http://www.powerdog.com/tiresize.cgi

 

I have the same tires and a similar problem in that I was looking for a 265 instead of a 275. There are just some sizes that manufacturers don't make. Though, I got that tire because I live in WA and its rainy and cold a lot. In TX you don't freeze too much do you? Rain performance isn't that bad on summer tires its just cold/ice/snow performance, as suggested before you might try the same tire in the max performance summer section.

 

a 1.2% change in speed.... no wonder i never heard of it... meh

 

would 265/40/18 fit on the rear oems ? im having a hard time trying to find a good deal on 255/40/18...

 

^ Try tirerack.com. They carry alot of choices for the IS in 255/40/18. IMHO I wouldn't go any wider on the stock rear rim . . .