"Cupped" tires

[indianhead]

I have a set of Michelin tires on my mini-van that have 22,000 miles on them. They have been rotated, balanced and wheels aligned according to the manufacturer's schedule.

After I had them rotated this week, there was a light thumping noise from the front left tire.

I took them back to the dealer and he said that the tire was "cupped",
from not being maintained properly and this was not covered by the warranty.

As far as I can see, all of the tires are worn evenly.

If I follwed the maintenance schedule and kept them properly inflated,
how did they get cupped?

Also, I would prefer not to replace 1 tire and surely don't want to replace all 4 with the mileage that they have. What harm to the tires ( or me) can happen if I don't replace the cupped tire?

Thanks.

[CapriRacer]

Cupped tires can be caused by a variety of things, including worn shocks, misalignment , and out of balance.

Just for background - Most vehicle manufacturer's alignment tolerances are pretty generous - far too wide to state that any vehicle "in spec' will not generate irregular wear.

What will happen if you don't replace the one tire? It is going to continue to get worse.

Hope this helps.