I just bought an 05 X sedan. It wears 215 55 17 original size Michelins. Front is at 70%, rear around 45%. I want to get a set of 2 tires for the front, and throw the fronts to the rear since front gets worn faster.

My question is, should I go for 225 55 17, 225 50 17, or just original size? I want slightly wider but without affecting gas mileage and/or power. Any advice on what size to go with? Should all 4 be the same size?

 

With AWD, all 4 tires need to be the same size. What you'll find is that a lot of tire shops won't replace just 2 tires, since they don't want to be liable is it causes mechanical issues with the vehicle.

Technically, they are right since you want the front and rear wheels to spin at the same time, otherwise there will be excess slip in the transfer case, which generates heat and can damage it.

So, with all that jazz out of the way, I usually suggest that if you NEED to change only 2 tires, to do so with 1 on each axle. That way, the different rotation speed is absorbed by the open differential instead, which is designed to have two wheels spin at different speeds....like when turning. Not ideal, but it won't damage your transfer case.

As to tire sizes,

215/55/17 (stock size) is 26.3" in dia
225/55/17 is 26.7"
225/50/17 is 25.9"
235/50/17 is 26.3"

So a 235/50/17 is the same diameter as a (new) 215/55/17. However, that's a 9.25" wide tire, which is at the very edge of what you would mount on a 7" rim.


Ideally, buy 4 new tires, sell off your used tires. Be proactive in rotating and keeping the wear the same.

 

So what youre saying is that a 235/50/17 would fit on the stock 17x7?

 

It would fit, but it would bulge slightly. It's done all the time on Muscle cars where guys try to squeeze a little extra rubber on their rims for grip. Complete opposite of the "stretch" look in the import world.




Just picture that sort of sidewall bulge on a G35.

 

Haha. Because i just got brand new 215 55 17. I wanted wider tires on my factory 17. But i guess i got get bigger rims