My wife's Cherokee is driving me crazy.  It has a bad front end shimmy, right up through the steering wheel.  But it only occurs between 55 and 60 mph and only when braking.  Does not have the death wobble when running at any speed over bumpy roads, railroad tracks or pot holes.  Only happens when braking.  Does not happen all of the time, but often enough to be a problem.  Brake pads are good, rotors are well within run out, tested with dial indicator.  Tire shop says tires are good and not cupped or causing the problem.

Thanks,
Bill  

check the ball joints, tie rod ends, drag link ends, track bar ends, and wheel bearings. if all that checks out then look at the steering stabilizer shock.

the front control arm bushings could be worn to the point that braking causes a severe caster change which can start the wobble  

I think you should be looking for warped rotors. The fact that it only does it braking is the big clue here. I had a similar problem with wife's Cherokee a few years ago and it was the rotors.  

If it only happens when you are braking, then it's most likely bad rotors.  You'll want to replace the pads when you do the rotors as well.  The good part is that it shouldn't cost much more than $100.

Try either your local Advance Auto store, or some online place like Cherokee parts

Terry