Tires: strange wear on rear left tire, inflation pressure, toyota corolla

Question
I have a 2001 Toyota Corolla.  I have noticed over time that my left rear tire has worn differently than the right.  I don't know exactly what the wear pattern is called (cupping?), but it looks as though the tread has flat areas dispersed throughout.  It is also audible when I am driving, and the sound has increased over time (as the wear has increased).  

I am trying to determine if this is an issue with my car (suspension, etc), or an issue related to the fact that I never rotate my tires (I know, bad car owner...).  I was planning to take it in to the dealer to determine the cause, but wanted to ask here first to get an unbiased opinion (and avoid getting raked over the coals at the dealer for parts I may not need).

Thanks so much!

Alyssa

Answer
Alyssa,

This is caused by misalignment and aggravated by lack of rotation and insufficient inflation pressure.

So you have been rotating your tires, right?

How about checking tire pressures?

Mmmmmmmmm.

Try a rotation and see if you can live with the noise or vibration.

But if you absolutely want to prevent further problems, get an alignment.