Rear wheel stuck (not moving)

Question

I have a Mongoose XR-150. Just brought it from Craigslist a month ago.

Suddenly while biking today, the rear wheel got jammed. It just stopped moving, however hard I tried to pedal. Immediately after this, when I tried pedalling, the pedal moves but none of the wheels move with it. There's a weird tension on the pedals though.

I would really like to get this fixed as cheaply as possible. Does anyone have any ideas/advice?

Thanks

Answer 1

At a guess, you suffered chain suck where the chain got stuck between the smaller chain-ring and the frame, or you dropped the chain between the rear cassette and spokes. The forces you then used have possibly been more than the QR skewers could handle and the rear wheel slipped in its mount. The weird force is the tire rubbing the frame.

My real concern is the "However hard I tried....." - you may have done significant damage to drive train components. Never put pressure on a jammed drive train - a modern bike is actually a very highly tuned, lightweight and fragile piece of machinery. Forces it is not designed to take will break it.

You do not say how you went from jammed and not moving to moving and not driving - was there a bang/crack/snap involved?

There are a few things that can be wrong, and based on what you said, you probably now have more than one fault. You need to isolate parts to find out what it is. Most of the of these checks can be done almost instantly without removing anything. The chain will get in the way - you won't need to remove it though.

1. Remove the wheel from the bike and check the freewheel. It should be moving freely in one direction and locked up in the other

2. Check the rear derailleur - is the chain running freely though it. If not, check the chain line and make sure the small sprockets are free spinning.

3. Check the chain line though the front end. Is the chain clear of the derailleur and sitting properly on the chain ring.

4. Spin the pedals and check the bottom bracket is not jammed up somehow. check the pedals and cranks are properly aligned and attached to the bottom bracket.

Answer 2

Most likely, from your description, the chain has jumped off a sprocket on one end or the other. This would normally suggest a misadjusted derailer, but can occur on older bikes because one of the chainrings is slightly bent.

The other likely cause is that the rear axle has come loose and the wheel is cocked and is rubbing against the frame. But then the pedal would not move.

There are mechanical failures that can occur in the bottom bracket or rear axle, but they rarely occur catastrophically -- you usually get considerable grinding first.

Note that if the chain is jammed somewhere you can do serious damage to stuff by attempting to force it. For instance, if it's jumped off the rear large cog and is stuck between cog and spokes you can do serious damage to the spokes (if there's no spoke shield). If the chain is jammed between the front sprockets you can seriously damage both chain and sprockets by attempting to force. Forcing the chain in such situations hardly ever improves things -- it almost always makes things worse.