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When I installed my wife's snow tires last month I noticed nasty cupping on the inside shoulder of the left rear that I took off. It's bad enough that you can easily pick the tire out of the stack from across the garage. She took it for an alignment today and the rear toe came back at +.34 degrees on the left, -.05 on the right. Spec is +.03 to +.28, with "not adjustable" written on the print-out. I guess this explains the road noise as well as wear being a bit faster than I would have expected for a set of 80k-rated TripleTreads. This might have something to do with the solid 3mpg difference between her car and mine in the same conditions & speeds as well.

I just ordered a pair of EZ shims in hopes that I can bring it back in-spec. These tires are shredded but maybe I can prevent it from happening again. Probably ought to check my own car out when I'm done with hers.

Didn't Al (Hobbit) have to fiddle around with his rear alignment, too?

When I get mine done next year I'll have them check the rear. When I got it aligned this summer the dealer said you only have to check the front wheels. Lucky for me it was off so very slightly and I have no wear issues that I can see at the moment. Still I'm definitely going to have a four wheel alignment done on her next summer just to make sure it is with in spec.

Didn't Al (Hobbit) have to fiddle around with his rear alignment, too?

I don't know about Al in particular, but there are plenty of other Prius running around with the same issue. If I had been smart I would have looked into it tens of thousands of miles ago. But tire wear seemed fine and it tracked straight so I assumed the rear wheels must have been alright. I think the difference is that we have directional tires now (in her case tripletreads with ~50k on them at the moment) so uneven wear due to one bad wheel doesn't get covered up. The tires aren't rotated from side to side.

On the bright side, EZ shims are relatively cheap at ~$12 a piece. (Shim stock would be cheaper but I don't entirely trust myself to cut them correctly from scratch.)

I tried to fix this today and failed miserably. The rear hubs are rusted solid onto the rear axle. I loosened all four bolts but no amount of persuasion would get it un-stuck. The best thing I can think of is to apply a liberal quantity of PB to the area, tighten everything back up, and try again next weekend in hopes that the penetrant will work.

Any other bright ideas? I have a 3-jaw puller but I don't see any good way to apply it.

Here is a hobbit thread on his rear alignment. Not much help at a glance, but it might lead somewhere as he tends to resolve such things. I'd pm him for some links.

http://priuschat.com/forums/gen-ii-prius-care-maintenance-troubleshooting/47177-wooba-wooba-wooba.html

And here is a thread that may help others with the basics, but does not address your issue at a glance:

http://priuschat.com/forums/knowledge-base-articles-discussion/43197-tutorial-rear-tire-alignment.html

Take a small propane torch and lightly heat it in the center. Lay a 2x4 on the hub and hit it with a hammer. Do this around the circumference. It should pop off. Hit the board with a hammer. Don't beat it.;)

Ooh, hadn't thought of heating it. I would have to be careful because there is an ABS sensor in the mix somewhere, and the brake components. But maybe I can get those out of the way somehow. Good idea!

I wouldn't recommend that to just anyone. Yes, light heat, but Quick. If you linger too long, you may heat the axle end too and that would negate the expansion of the hub. The hub is cast so it will heat up pretty quick anyway.

I vote with msirach on 'heat and beat'. Unless driving for a while after your de-rusto sprayng helps.

Indeed since the Dawn of Prius this has been one of the bug/features that many folks have noticed and thought of ways to correct. Those folks conspicuously not including official Toyota shops.

Do such quirks make Prius dearer to our hearts? Um probably not. But it can sure keep you from running tires 5+ years, to the point where they are starting to get lost in the ozone. That's the 'feature' aspect of it. Um maybe not.

Yes everyone who entrusts their lives to 4 small rubber contact patches at high speeds ought to attend to tires. But that's just one of my unbearable sermons.

DAS

Success! Letting the lubricant soak in for a week and whacking the hub assembly with a 3 lb drilling hammer did the trick. Now all I have to do is get it on the alignment rack to make sure I made it better rather than worse.