tire size/ speedometer reading
 

Hi,I came across a fantastic deal on craigslist. I bought a brand new tire and wheel for my Mercedes for $50. The only thing is that it's a 16" and my other three are 15". I can't really notice a size difference when it's on the car. I mounted it on the driver's side rear. It's a directional rotating tire. Should I be concerned with the size difference and will it throw off the speedometer? Thanks.

The important thing is the outside diameter. If it's the same as the other three, or very close, then you should be mostly good. If it's shorter or taller it will affect the speedometer reading as well as adding extra wear for your differential.

I'd be somewhat concerned about the driving dynamics of running on three 15's and a 16. The cornering stiffness can't possibly be the same. I think I'd only do it if those were the only four wheels and tires I had.

tires
 

Thanks, I might try to get another 16" for the passenger side rear. It was such a good deal that I couldn't pass it up.