I've got an '03 BMW 745i that's still under warranty and was told today that I needed to replace my 'thrush rods" as they're wearing down. At first I was told it would be covered under warranty..later I was told it would not be, as I've got after-market wheels that according to the dealer are causing the excess wear.

My main question is, what are thrush rods? How come I've never heard of them and a google search yields zero results for anything remotely related to cars.

My second question is, since when does a simple after-market wheel that's DOT certified void a warranty?

Any suggestions as to how I can avoid getting ripped off?

Thanks!

P.S. They're the only show in town. Awesome.