I really have the same question except my wife's car has the 17" stock setup. I would like to put more tread on the ground, but I don't want to buy new wheels. According to the tire manufacturers, 255/45/17 (rear) and 245/45/17 (front) will fit. What, if any, concerns would you guys have with this setup?

 

Hello,
I usually avoid the tire question threads.
(to many "experts" & flames) but....
I would like to include my tire experience.

I previously had 255/45 r17 on the back, they were fine.

So fine, I moved them to the front & installed 275/40 r17's in the back!!!

On stock 17in(8in wide) rims

I've had 2 track days & 8 or 9 auto-crosses. (about a year now)

No bulge, no movement, even wear, great grip.

Worked just fine for me.
(this post is for informational purposes only. Don't try this at home.)

I've included some pictures for your inspection.

 

Thanks for the info. I'm getting the 255 / 245 setup on Friday. I'll post again after I run them a while.

 

This set-up is NOT the best idea for the stock wheel. Will you experience "problems"? No, the car will drive just fine on the street. However, the tire sidewalls will not be as supported as they would be with a properly sized rim/tire, so you WILL lose a bit of ultimate grip. This set up would reduce understeer compared to the stock set-up assuming a properly sized rim, but in your case, the loss of grip from the oversized rear tire might offset the increased grip in front, so you may not see a huge difference, or it may even be a wash. Maybe try 245/245 or 245/235 if you really want to optimize the handling.

Then again, if the car is just a street car, it probably won't matter that much anyway.

 

Manufacturer's recommendations for a 255/45/18" tire are for a rim width of from 8" to 9.5". The stock 18" is 8" width. So, what the heck are you talking about? This is a "properly sized rim" He will have no issues.

Lou