When you are driving an all wheel drive vehicle EX:STi. Would it be any harm to your engine/tranny if you have one different tire brand on your car, it's the exact same size just a different brand.

 

no, you will be fine.

 

well, tire companies are like pants companies. even though you wear one size, they are all cut differently and dont fit the same.

for example, hoosiers typically run 10-20mm wider than they actually say, so that people can get more grip and still stay in a lower class with their cars

 

and technically, even different tread patterns can mess up your differentials. Granted it would take a really long time, me thinks, for different tread patterns to ruin your diff. Much longer than your tire would last anyway.

 

agree with all above.

 

Different tire companies have different size circumferences than other brand tires even if the "size" is the same. On AWD Subies the acceptable tolerence is no more than 1/4" difference in the circumference of the tire. You have to measure a mounted tire around the center of the tread with a flexable tape measure to get a proper measurement. Compare all 4 tires, if they are all within that 1/4" then you are good.

The tolerence is pretty thin, that's why rotations are so important to keep the tires wearing evenly. The easiest way to ensure the tires are the same circumference is to replace them all at the same time with the same brand/size/style.

I've seen mis-matched tires damage a center diff in only 5,000 miles...