What are the negative effects of putting 2 different size tires on the rear, (e.g.175-65-13 and a 175-75-13). placing the tires next to each other they looked to have a noticeable size difference so i was wondering if it would be bad to use them.

 

I would think that using two different size tires would throw off your alignment. Also if they are different brands you should consider that they have different performance characteristics, which could lead to problems.

 

Short answer: Bad idea.