I recently got a flat tire and the tire shop that I go to didn't have the BFG KDW 255/35/18 tire that I needed for my driver side rear, so they ended up loaning me a different tire (Dunlop) 245/40/18 until the new one comes in this weekend. Either way, after the Dunlops got mounted and I drove on them for two days I realized that my car steers to the right every time I accelerate. Is this normal or should I be checking my alignment?

BTW I already had an alignment done two months ago, so whats going on?

 

You have a different height and width tire on one side of the car. I would not be suprised and anything that would happen.

 

Oh ok...thanks.

 

thats pretty danger ous actually. But yes, your are veering to the right because of your mismatched tire tread and difference in profile.

 

i would change my diff oil after driving like that.

 

Well I haven't driven my car all week. I maybe drove 60-80miles total with that setup. Do you think that I'll really have to change my diff oil?

 

You might have to change you whole differential. I would only have driven to somaplace safe to keep the car. 60-80 miles you'll probably be OK, but you put a ton of wear on your diff doing that. Depends on how different the rolling diameter of each tire is.

 

I also noticed this (but the car leans to the left when I accelerate) after changing only my rear passenger side due to a flat. But the tire size and brand is the same. Am I subjecting my diff to extra stress?

 

It depends on the wear, 11mm of tread depth on one tire and 2mm on the other gives you a whopping 18mm difference in diameter. It's generally advised to replace both rears at the same time if the 'good' tire is worn down past 50%. If that's not the case with yours, your pressures could be off, I can usually detect a 2-3 PSI difference in the rears during acceleration on this car which I have never been able to do on any other car I've owned.

 

the difference in tire height in the rear can seriously damage your diff...