When jeep gets between 50 and 55 wheel starts shaking . I get up to 60 and it stops. Had new tires put on 2,000 miles ago.

When you hit the brakes, or just driving down the road ?
Most wheel balancing machines only duplicate road speeds of 40 mph. So it could be a tire or wheel.

Tire bouncing (not shaking) is generally caused by a bad shock absorber. If you have 30k miles on them or you see any oil leaking form the top (but could be long gone), replace them. (front pair, rear pair, all four but never just one) If it's shaking, check ball joints, all other front end components and wheel balance.

Is it possible the tire is defective? How many miles are on this Jeep?

no its your wheels well out of balance get them looked at first fitting a damper wont stop this shimmy

you are getting an oscillation .you need to put the front tires on the back and try it again as it could be bad tires.
if it is still the same,put the vehicle on a hoist and check the tire/rim play side to side and up and down.
turn the wheel and check for bearing noise.
common things are wheel balancing,tires,tie rod ends,worn axles and bearings.

lol Make sure you wash the inside of your rims after you go playing in the mud. a small amount of dried mud will make your wheel shake at a high speed. It will unbalance your wheel.

It could be worn starting parts, Not ballanced wheel, and broken or worn struts. Start with the wheel getting ballance and go from there if there was no problems before your got the new tires put on.

hmm.. im just taking a shot in the dark but when my car did this i needed new wheel bushings. It would shake and sound louder than usual.. not crazy, but a little louder. Anyhow, I changed my bushings and the shake was gone! :) justa suggestion..

Balance your tires, if you did not have that done with the rotation........check for proper tire pressure (with cold tires)

New revised calipers. and have the new rotors machined right out of the box before installing