Hi,
I have a mountain bike which has an issue with the back wheel

I suppose you could call it vertical shaking. I have no idea how to fix it or if i need a replacement part.

The way it happened was my back tire got a puncture. While punctured the bike was cycled for a short distance, hitting some bumps.

When the back wheel is spun in a stationary position it (holding the back wheel in the air) there is no obvious bend in the axle or anything.

But it is possible to see the back wheel shaking!

Has anyone had this problem before or could give me some advice. I would rather not bring it to the bike shop and get charged.

Thanks

Are you saying that it moves from side-to-side, up-and-down, or both?

The first thing that I'd check would be that the tire is seated properly. Deflate the tire and check that the tube isn't stuck between the tire and rim. Next inflate the tire to about 10 psi and check that the tire is seated about the same way on both sides of the wheel. Then inflate to the pressure that you ride and check where the tire touches the wheel again.

Other problems could be a bent rim or even a defective tire as you rode on it uniflated.

Its not side to side, its more up and down.

like an elliptical motion of the wheel as it turns around i did suspect it was bearings or axle more so than the tire as the tire looks fine

+1 This is the most likely cause.

Sounds like you have flat spotted or dented your rim. it is out of true radially. You can try to identify the low spot, loosen the spokes in that area and try to push or pull the low spot out of the rim.

Here is a thread about ways to fix a flat spot. https://www.bikeforums.net/showthread...-spot-on-a-rim

Or you could take the rim to a bike shop and have them verify that the rim is bent and see if they can true it up.

I agree that it sounds more like a misaligned wheel or bent rim than anything else. Of course, it's possible that it's only a poorly seated tire, which would be great news for the OP. But riding a wheel for any distance with a flat is usually death on the rim. The test is to spin the wheel and watch the rim at the brake shoes (or a fixed reference if you have disc brakes) and see id the rim runs true or not.

I actually took the advice given and deflated my tire. Upon inflating the tire it seems to have worked.

Thanks a million for your help!

OP; Your description sounds like just what it would take to put a flat spot on the rim and/or bend an axle.

- So, flip it on its back and give the wheel a light spin. Put eyes on the cogset/freewheel. If you can see it moving up and down, then you have a bend axle.
- If axle is not bent, then spin again and watch the rim see if it goes around smoothly and suddenly drops down a few millimeters in one or more places. If it does, then it has a flat spot.

Depending on what you find and on what quality/price range of wheelset you broke, you may be way ahead to just buy a replacement wheel or wheelset. If the wheels are fairly ordinary, you can get a set of F & R for under $100 easily. Eitherway, save back about $30 to have the new rear one tensioned before you ride it the first time.

/K