Why am I able to shake my back tires?

Could Be many factors wheel bearings etc was the tires high speed balanced? Check inner outer bearing and tie rods etc !! More Info Please!!

Could be a bad wheel bearing. This is very dangerous, be sure and get it checked out asap. If the wheel comes off you're going to have a very bad day!

A couple of things to check. It may be a wheel bearing, shock, cv joint, or a very common cause is that one or both of your back tires are worn irregularly. This causes the car to shimmy and get progressively worse as you have explained. It usually happens on the front end of the car, but can occur in the back.

Need more information. Are you sure it is the wheel bearing? I replaced a wheel bearing on 1996 Corolla after it broke. Had to take wheel apart and replace with used bearing (from junk yard). Not that difficult, but you might check your rims on the wheel first. Have a tire shop balance your tires to see if you have a bent wheel rim. I had a tire shake until I would hit 70 MPH and it would disappear. Needed to change out tire rim to eliminate shake. It can cause bad wear on your tire.

many causes.

loose lug nuts
wheel out of balance; weight fell off
bent wheel
incorrect tire pressure; over pressure can damage the tire
faulty tire;out of round, tread separation, etc
loose wheel bearing
worn shock absorber
worn steering / suspension component; bushing, tie rod end, ball joint, etc
alignment issue

You can rotate the tires, front to back to see if the problem follows the wheels or is a front end only problem.

SOUND LIKE BAD WHEEL BEARING.SAFELY RAISE SUPPORT VECHICLE ON JACK STANDS,MAKE SURE VECHICLE PARKED ON SOLID LEVEL GROUND.GRAB WHEEL OR TIRE AT THE WITH ONE HAND TOP AND GRAB BOTTOM WHEEL TIRE WITH OTHER HAND,TRY TO SHAKE MOVE WHEEL IF WHEEL TIRE MOVES WHEN YOU SHAKE OR MOVE IT ANY.THE WHEEL BEARING MORE LIKELY BAD.IF WHEEL BEARING OKAY YOUR FRONT BRAKE ROTOR RUN OUT WORN OR WARPED.

SOUND LIKE BAD WHEEL BEARING.SAFELY RAISE SUPPORT VECHICLE ON JACK STANDS. GRAB THE FRONT TIRE WITH BOTH HANDS ONE HAND ON TOP TIRE OTHER HAND ON BOTTOM OF TIRE. TRY SHAKING TIRE.IF SHAKES LITTLE WHEEL BEARING BAD.IF DONT SHAKE WHEEL BEARING OKAY.

sounds like your front end is out of alignment check your tires for wear other than in the middle and take to tire shop to see if the tires are balanced right

3 possible answers. 1 the rim is bent 2 . unbalanced tire 3. wheel bearing needs replacement

Why drive side bearing could be a bad other.balance yes, tie rod could be bad.