Question/concern About My 2006 Is250 Awd

[Jetson]

I apologize for the length of this in advance.

I bought my IS250 used in May of 2009. At the time, the previous owner said the car had pretty new tires, which, when looking them over, looked to be true. Unfortunately, what I didn't notice was that the left front tire was a different brand than the other 3. So, after about 2 months, I noticed that the tire was wearing faster than the other ones(and that it was a different brand). So I had the left front tire replaced with the same brand and model as the other 3 tires.

Then, last week, I hit a pothole and got a flat right front tire. When I was having it replaced, they(different place than the first time) told me about the tires on the AWD model needing to be within 3/32 of each other, to prevent problems(transmission and rear differential I think? don't remember specifically).

So, my first concern is I don't remember anyone saying anything about this the first time last year I got the left front tire replaced. I'm guessing it's because they took a look at them and it was obvious it wouldn't be a problem, since the tires were so new? I doubt it was an issue, since everything last week was within 3/32(2/32, actually).

My bigger concern is the fact that I was driving the car for a while with the bad/worn left front tire before I replaced it, and I'm pretty sure that tire was outside 3/32 of the other three.

So my questions are, how much damage could I have done already? Is there anything I could do or check to see if I should have anything done to the car?

Thanks in advance.

[bartkat]

If you're talking about tread depth, I doubt if you've done any damage at all. My opinion would be that they suggest keeping tread depths close in order to have "equal" traction on all four wheels.

[Sidney07]

Here's some interesting information about "mismatched" tires on AWD vehicles...http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=18.

[Jetson]

Thanks to both of you for your responses. That link from tirerack was interesting. I guess I'm hoping that being off for a month or two didn't do significant damage, but I'm still not sure who I'll know. I did have the rear differential serviced when I bought the car.

The other interesting thing was that even at 2/32 difference, there is still stress.

At this point, I probably have 1 tire that's off 2/32 from the other two, so maybe I should check if any a local places offer the tire shaving service.

[sktn77a]

The concern here is that the AWD differentials will be be "working" if the tires are not all identical diameters. Well, gee, that's what a differential is for! Every time a 2WD car goes around a corner the differential "works". Same if you get a flat in a drive wheel tire and replace only that tire. Nobody worries about that for a 2WD car, and nobody needs to worry about an AWD car either. Remember, Costco (the worst ones for this) and tire rack sell tires. If they don't sell tires, they loose revenue! And Lexus would rather you didn't chance anything on their dime - you pay for the tires, why should they risk potential (note, "potential") warranty claims when they can just have you buy 2 (or 4) new tires!

I'd lke to see some data on differential durability/failre before I recommend some poor sap to go out and buy 4 new tires for his AWD every time he needs to replace only 1.