What causes scalloped tires?

What causes tires to scallop? I had a pair do this before and would like to prevent it from happening to my new ones. Thanks for the help.

Nick

A few possibilities: out of alignment or worn front end (wear on inside could be toe-out, worn tie rods or bad ball joints, wear on outside more likely toe-in). Too much use of 4WD on good traction surfaces can cause cupping especially on outside, and more so if front end is worn, leading to excessive toe-in. Dynamic imbalance can cause nibbling or cupping wear. Binding front u-joints maybe, but that usually will be felt. A good tire and/or front-end shop should be able to analyze the wear.

shocks......

All of the above ...

plus wheel balance

Rotating them every 7000 miles? Did'nt think so.

Rev