My 240 supposedly has a bad Wheel Bearing. Because I have two 240's, I do not drive it all the time but when I do the problem is when the brakes are used. There is a kind of thumping that makes the car shake and bump. What exactly is going on and what is the worse case scenario?

 

Warpped rotor probably...

One thing you could try is get the cat up to speed, about 65mph, then brake hard almost to a stop. Then accelerate very quickly back to same speed and brake hard again. Do this untill the brakes feel like they won't stop the car then get up to a regular speed and don't not touch the brake for a few miles allowing the rotors to cool off. Best done late at night on the highway or open road.

Wait for the experts to get on...

 

Yeah sounds like warped rotors not a wheel bearing. Wheel bearing you'll just hear an annoying moan...