I would like to keep the rear tires at the same diameter as stock, (this avoids any speedometer issues). In addition the consensus for the traction control is to have 0.5" to 0.7" smaller diameter front tires. The stock rim width is 8.0" for both front and rear.
Description Tire Size Diameter Rim Width
Stock Rear 245/45R18 26.7" 8.0"
Stock Front 225/45R18 25.9" 8.0"
New Rear 275/40R18 26.7" 9.0" - 11.0"
New Front 255/40R18 26.0" 8.0/8.5" - 9.5"

From a tire diameter perspective the 275/40R18 and 255/40R18 will keep the speedo accuracy and the TCS happy.
The rim width is the tire manufacturer's recomended rim width. Note that for the 255/40R18 some manucturers are OK with 8.0" while others require a 8.5" minimum rim width.
I would like to know if there would be any problems or concerns with mounting these on the stock 8.0" rims, especially with the 275's, (as this is what I would like to do).

Thanks
Derek Vanditmars

 

I don't think you can fit 275 on an 8" rim. Max I would go is 255/40 in the rear.
An if they do fit, they would bubble out a lot, maybe a 40 profile might be too big (that's IF they fit on a 8" rim).

People usually put 275 on an 9.5" rim.

 

I thought rears were wider...hmmmm. I got 265 (35 i think) on my stock 18" rears and they don't look like they bubble out...however it messes with the traction control like you mentioned...I wonder how tall you can go without rubbing...

 

ahhhh, they are the same width...bummer.