Car manufacturers push it too. Subaru even goes to the extent of showing how to disable AWD in order to avoid damage to the system.
I still think it’s somewhat BS. Does Subaru disable the AWD if the tire pressures are out of spec? I will correct my previous post, tire pressure does not affect actual tire circumference but it does affect the rolling radius, plus introduces other stresses that the drivetrain must deal with, which IMO has a larger effect than tread depths not matching between the tires. A drivetrain designed to handle the constantly change of tire pressures should not be that affected by one tire having a tread depth a few fractions of an inch different from the other three.
And yet every AWD manufacturer recommends keeping the tires in sync. They also recommend keeping your tire pressure at the correct levels.
I wonder if there is a market for used tires for these situations. Perhaps someone else with the same car and size tire had to replace all four because one was damaged, and there are 3 usable tires available somewhere with similar tread wear? I mean, you would think someone will be trying to make some money off the usable tires pulled off Subarus and other AWD vehicles where this is an issue. Maybe a scrapped Subie in a junkyard has a set of tires with similar wear. I am just thinking outside the box.
Used tire retailers are a real thing. I’m sure that tires with any decent treadlife are sold to them for resale value. Common sizes will find a new home.
I actually asked if there was any way to recoup value from the 3 good tires, but the tire dealer said no. I could keep them and try to get something for them, but he didn’t know any way to.
It occurs to me that saying this is a good strategy for the tire dealer, because most people, me included, don’t want to take a partial set of tires home. He got the tires for nothing, and probably doesn’t lose many free tires with this approach.
I thought one main difference between AWD and 4WD was that AWD was not as sensitive to different tire sizes between front and back and that as long as the two tires on each axle had the same radii you were good as long as the difference between front and back were within 4/32"
With room in my car/garage I would convert one to a full-size spare and then keep the other two on the off-chance something similar happens in the future then swap out two tires you already have instead of buying 4 new tires.
that!
1 new tire, slightly underinflate to reduce the OD … et voilá …
they also recommend purchasing that $120 SUBARU cabin filter element… and a $45 SUBARU wiper blade (generic OEM part that can be purchased at a fraction of its price) ;o)
Right, but since they don’t really tires they have limited interest in you buying them as opposed to OEM equipment. From the manufacturers standpoint, it appears they believe it puts a strain on the AWD system.
I think this is the critical point. If the manufacturer believes that, in other words believes the consumer’s options are replacing all 4 or risk damaging the AWD system, we consumers have to place our bets with a potentially very expensive downside. It’s not so much choosing between good enough and really nice. It’s choosing how risky a very expensive problem is.