So, I'm sure everyone is of the understanding that when one tire on an AWD car needs to be replaced, replace them all so the transfer case isn't tricked into thinking one wheel is slipping due to a smaller diameter.

I'm wondering the limits for this. That is to say, how far off can the tires be without being worried about this?

My vehicle is an 03 RX AWD, and I am running Uniroyal Laredo all terrain tires. Below are my tread depths.

LF 8/32 RF 9/32
LR 6/32 RR 9/32

Clearly, the left rear is much more worn for some reason. Any advice on future rotation patterns? Should I buy one new tire? One used tire? Leave it as it is? Is my transfer case at risk with these different tread depths? Should I try to convince my wife to buy 4 new Dueler H/Ls ?

 

As far as why they are wearing like that, hard to say - have you had the alignment checked, and, have you been rotating them ~regularly~???

The general rule is 4/32" maximum difference... For instance, when tires are new, many are 10 or 11/32", so, if the current tires are 6 or 7/32" respectively, then you are within the generally advised limits... Your maximum difference is 3/32" and it is only the one, so I would think you should be fine...

I have seen both sides of this story - I have seen people who have replaced two tires with completely different brands/tread depths and no issues, but, I've also see people who have replaced two tires that are identical to what they currently have, but two were new, two were worn out, only to have driveline issues only a few months down the road...

The driveline can handle some differences of course, its the prolonged difference in speed that does the damage over time...

 

Thanks for the reply. I have found a used tire on ebay of the exact type, with 8-9/32 of tread depth. If I purchased this and replace the worn one, all tires would be within 1/32 of each other, and I would be able to keep it that way by properly rotating. Have not had the alignment checked since purchasing the car (1 month ago).

 

There is no exact ruling from Lexus regarding the tread depth, they simply say the tread depths must match on AWD vehicles. However, our stance has been no more than 2/32nds tread depth change from tire to tire. In in a case where the new tire will be more than 2/32nds different in tread depth than the existing tires The Tire Rack will shave the 1 new tire down to match the tread height of the remaining tires. The service charge is only $35 and beats buying a new set of 4.

 

Wow, 2/32" thats even less tolerance than most...

I have actually had customers order tires from TR because they can shave them if needed to match...