Originally Posted by SLO_Town
As I said, my MIL is in really great shape for her age. The amount of push back she gave me when I spoke to her one the phone makes me want to drop the issue as well. She was ADAMANT that she needed to replace the entire set. If the tires were just a week old she might have done the same thing!
In your MIL's defense, I wonder if the tire shop gave her a decent discount on the new tires in exchange for letting them keep the barely-used Michelins. Getting all new tires was still unnecessary, but if she got a decent deal on her trade-in tires instead of paying them a disposal fee on them, that's less bad.
Also, an internet search on this topic will show a lot of frightened people scared of driving their Subaru around with even a very slightly mismatched tire. I assume such people get their tires rotated every 1000 miles and constantly check the tire pressure and vehicle weight at each corner and never put anything heavy in the trunk so all the tires are always exactly the same height. Actually, I don't assume they do that, because that sentence was written sarcastically.
Probably the only chance you have of helping your MIL be less tire strict in the future is if you find a Subaru vehicle manual that specifically says all the tires don't have to be replaced under her strict conditions.
Or if Consumer Reports says it. Old people love Consumer Reports.
Speaking of Consumer Reports...
shaving-all-wheel-drive-car-no-replacing-all-four-tires/
For example, Subaru warns owners that mismatched tire circumferences can cause serious mechanical damage to a car's all-wheel-drive system. Drivers with an AWD vehicle should refer to their car's owner's manual for specific guidance on tire replacement. Buying four new tires may be needlessly expensive for drivers who only need a single tire to join the three other moderately worn tires. But you can buy a single new tire from TireRack.com and have the company shave it to the tread depth that matches the depth of your other tires.
Anyway, if your wife thinks your MIL is so well off that there shouldn't even be a discussion when she replaces four new Michelins every 500 miles, that's great. And it's a good thing to remember in the future if either of them ask you to help your MIL in some financial or money-saving way.