Shaking front (?) BRAKES

[James Scott]

I just got back from a weekend trip to the local mountains and foothills, including Yosemite and surrounding small foothill goldrush towns. When going downhill, I experienced a frequent pulsating braking, shaking the steering wheel a little, without pulsing the brake pedal much(?)! It felt like one of the front wheels was going to shake right off the car! This occurred even on light braking - It seemed to smooth out at heavier braking! Thought this might be the ABS kicking in too soon, but why would it smooth out at HEAVIER braking?

Once it pulsated so bad I thought one of the front brake calipers came loose or some equivalent disastrous part failure! It shook really bad on light braking at about 70 mph going downhill at a fairly steep angle!! I pulled over, expecting to find some major failure. . . . . I seriously thought I would have to be towed!!!

Couldn't see anything, continued on, pulsated less (but still substantial!), when road flattened out the brakes smoothed out alot.

HELP! Is this an ABS problem? Weird brake fade? YIKES!!

Thanks for any help!

BTW: Can I have these rotors (fronts cross-drilled) turned by a regular shop lathe or do I need to have them ground as someone suggested to me here?