vanguy

My wife got into a little accident and punctured the side wall of her tire which has about half the treads still on it. I was going to buy just one new tire but the tire guy told me that with AWD, if there is a slight difference between the diameter of the tires, it can damage the transaxle. I actually remember reading this in a car magazine about a Jeep owner and he was in the middle of no where and had a put a tire on that is different size and he burned out his transaxle or transfer case or something. However, I have no ideal how sensitive the RX300 is to a slight difference of tire diameter but decided not to take a chance. Any comments?

Lexmex

I had this happen to me, through an act of vandalism about 3 years ago. Had to buy two tires as a result. It was actually possible to patch for about $25 USD but my uncle said such sidewall patches down down here are pure garbage, but decided since I had some cash on hand to get 2 new tires and then a few months later another 2 for the fronts.

I don't have personal experience with the RX300 on different diameters, but my uncle can tell you quite a bit of stories about mixing and matching on different size tires and all the long term ill effects. People are notorious down here for not doing tire rotations, balancing, though they will do alignment. And when those front tires wear down too much, the results are predictable.

HarrierAWD

No, it will not damage the AWD transaxle & differential (otherwise you won't be able to make even the slightest turns.) The Jeep most likely had the part-time offroad 4WD setup, which could be damaged with different size tire on dry pavement.

Assuming your current spare tire is of the same type and brand new, you can buy just one and swap out the other used one on the same axel with the spare. A half-worn tire is perfectly good for spare duty. Save the punctured one for your backyard swing.

TunedRX300

As Harrier indicated, the difference is diameter is small enough. I have three relatively worn Pirelli Scorpion Zero tires and bought a new one to make it four. Drive around for one year and not a single problem.
If thread depth can tear apart transaxle and transfer case, by definition, the spare tire should not be used even in emergency because it is not as evenly worn as the other four. Also if you don't rotate tire often, you got to replace all four tires or face damage? Doesn't sound right at all using the logic.
The tire shop may be more motivated to sell you two tires than telling you the actual impact, which is none.

Raoul

Would you really buy four more if this happened again?

TunedRX300

If one is concerned about cost, might as well to buy road hazard insurance.
If even wear is your primary concern, why not buy used but perfectly good (no puncture, patches) tire off ebay that has similiar thread depth?

Lexmex

When mine had the side puncture, the tire was already worn down, but still several months away from needing a new tire, so that is why I got the two tires then.

Raoul

I wasn't concerned about myself.

I wouldn't buy an airline ticket for a four engine plane that won't fly on three engines.