One of my tires is wobbling back & forth!

Make sure wheel nuts are tight. If they are you may have broken/seperated belts in the tire. Have the tire inspected. If ok I would check for loose wheel bearing/hub assembly.

If it wobbles with your hands at 9 and 3, its a tie rod end.
If it wobbles with your hands at 12 and 6, its a wheel bearing.

Here's a long answer. It could be 100 things. But if your wobble is showing up at low speeds, look at the tread on the tires. Does it snake back and forth? If so you have a belt separation in the tire. If it's not a tire, you may have a suspension part that's bad. Or, more than one. Control arms, ball joints, tie rods, (inner and outer), bushings, and wheel bearings, and any one of them could be waiting to send you into the ditch, or worse. Many garages will give you a free check of your major components. Try them. If you can't or won't, jack up your truck so one wheel is in the air, grab the front tire with one hand at 9 o'clock and the other at 3 o'clock. Wiggle the tire. A very little play, is probably ok, but if you have more than 1 inch of movement, you probably have a bad wheel bearing or a ball joint or control arm. Now grab the tire from top and bottom. Try to move the tire up or down. You should have NO play, at all. Any movement is bad, probably a ball joint, but it still could be a bearing. When you're driving, if your steering wheel is wobbling side to side, it's a front wheel problem. If you just feel the wobble in your seat, it's a rear wheel problem. Don't let the problem keep getting worse. If you put used tires on, it's probably a tire. That, you can fix. Anything else I've mentioned, you can't fix without some very expensive tools, and an alignment machine. Good luck.

Wish I knew what vehicle but if it's front wheel drive,bet on the wheel bearing, would think it would make noise on turns,usually worse one way than the other.

WOBBLING TIRE IS A BAD WHEEL HUB BEARING.REMOVE WHEEL CHECK HUB BEARING WHERE FRONT AXLE MESH INSIDE HUB.SHAKE HUB BEARING SEE IF IT REAL LOOSE AND WOBBLY. IF YES HUB BEARING BAD.

I would start by checking your wheel bearings. Do this by pushing back and forth on the top of your tire or car near the tire. If the tire wobbles back and forth at all your hub assembly should be replaced. For this problem I would check for this first.

You need to check the hub bearing and the lower ball joint on the vehicle and make sure they are good. If you can jack the vehicle up and can grab the top and bottom of the wheel and wobble it back and forth then the bearing is possibly bad. If you can grab the front and rear of the tire and move it back and forth it could be the tierod end you can have someone watch the parts while you move the tire.

The bearing is a tapered bearing did you put it on the right way round so that the largest part of the bearing is at the back

That then matches the taper on the wheel hub

That is so you can wind in the castellated nut with a torque wrench to set the pressure of the bearing according to the manual

Possible wheel bearing failure, ball joint failure or tie rod end failure. Does the wobble seem to be when tire is moved toward center of vehicle on top and bottom or front and back??

i had the same problem,i endend up changing the hub bearings and ball joints and front u joints the main problem was the hub bearings