Tires: Front End Shake / Tire Cupping, brake rotor, brake rotors

Question
I've got a 2001 Tiffin Allegro motorhome with about 20,000 miles on it.  Under braking on serious down grades (say 5%+) at more than 40 mph, I get a horrendous shake in the front end (first time it happened I thought a tire must be flat).  Once I get it under 40mph, things smooth down. Over 40mph, the shake continues whether the brakes are applied or not.  I recently noticed the tires are wearing on the outside edge and are cupping.  Worn shocks? Wheel Balance?  Alignment? Demonic Possession?  Thanks for your help

Answer
David,

I think what is happening is that the brake rotors are warping and causing an "imbalance".  This, in turn, caused the tires to wear irregularly.  There is probably some wear in the suspension components - most likely ball joints - and that allows the vibration to continue after it is generated by the brake rotor.

I suggest you have someone look at the brakes - and the suspension - and even if they replace some parts, the vibration may still be presesnt because of the wear in the tires, so you may need to replace them, too.