What happens if one of your tires (right rear) is in good shape, is the same size as the others, but is not the same brand as the other three? Will this damage the transaxle and in how many miles if the car has a lot of miles on it but has run excellently in general ('93 suburu Impreza, all wheel drive, standard, no ABS, 240K miles)?
Wasn’t this discussion just up and active?
This one is different. He’s got tires of the same size, presumably the same ratings, but different manfacturers.
We have no data on this situation. But since the only warning is about the consequence of different sized tires, we have no reason to view this situation with alarm. Indeed, drivers who have inquired have been advised there are no consequences at all if a fourth new tire is shaved down to the size of the others, tire brand notwithstanding.
What type of car? Does it have AWD or a limited slip differential? for most open diff, cars/trucks this should be no problem at all.
Sorry I just re-read the original post. I would have to say that the tread wear rating is only part of the equation. Two different brand tires with the same size say may actually have slightly different diameters. It is usually something small say 1/2 an inch. This may cause a problem with prolonged use.
Also, just because the tread ware is the same the traction given may not be. The tread ware is based on, among other things, the traction of the tire and how hard the tires rubber is. So while the tread ware might be the same, the one different tire might be significantly “grippier” causing a difference that may, over time, damage the AWD system of your Subaru.
Different models of the same standard size within the same or different brand can have a different circumference (distance around that touches road). The important thing to consider is that the circumference of a new or different tire is within 1/4" of the average of the three matched tires on Subaru AWD.