Bicycle Mechanics - Rear wheel problem

I crashed my bike onto the curb a week ago, and was finally able to get replacement front wheel. Everything's in place and seems to be in good shape except for the rear wheel.

The Circular plastic plate that shields the wheel bars from the gears (I don't know what it's called, see the attached photo) keeps spinning instead of just rotating with the wheel. The movement is something like when you rotate a big ring around your index finger (I can take some video clip if you don't know what I'm talking about).

Did someone have this problem before? Can someone tell me what to do to fix this? I'm a complete newbie so I apologize if the question sounds silly.

Thanks in advance.

--Ben

When I had my old Magna it would spin once in a while. What my friend showed me was how to take off the rear cogs so I could remove the damn thing. It looked a lot better. Now that I have my Trek, the first thing I did was take off the rear cogs and remove the plastic frisbee. What does that thing do anyway?

Just something to think about.

The plastic disk is to keep your chain from going into the spokes in the event of an overshift. If the bike is well maintained and tuned regularly, the disk is not necessary. Otherwise it should be left on.

The reason the your disk is spinning is because either the little tabs that lock onto the spokes are broken, or when your bike crashed the disk came loose from the spokes. Look on the wheel side of the disk and see if the tabs are still there. If they are, move the disk until you see how the tabs line up with the spokes to lock on. Worst case is you will have to buy a new disk. Not expensive

Don't worry about it spinning. It can't hurt anything.

Originally posted by Chi
What does that thing do anyway?

Just something to think about.

I heard once (after I had just taken mine off) that it can help in protecting your spokes if the chain jumps off the cassette . I don't know if it works I do know that without it it cost me a new rim when my chain jumped on a ride last fall. Personally I always thought they were good for collecting road grime just another thing to clean.

Ouch ... :( So it does work? Oh well, I guess good maintenance is best in this case. Besides, after a while those things turn yellow and become an indicator of your bike's age. :p

Thanks for the explanation. Looks like the thing is broken. I can't see thing on the plate that would allow it to lock with the wheel. Is there anywhere on the web that I could find direction on how to remove the rear wheel?

Seriously it's not hurting anything as is.
That and, honestly, if you have to ask how to remove it.... To be nice I'll just say leave it on. I personally don't think you're quite knowledgeable enough to not have the free extra protection that little piece of plastic provides against bad adjustments. Give yourself time.

I wasn't intending that to sound snotty just in case anyone thought that I did.

Originally posted by Raiyn
I wasn't intending that to sound snotty just in case anyone thought that I did.

No offence taken, though I was asking just so I can get replacement and put it on. There's always two sides of the same coin. I'm doing this so I'd know more about bike mechanics hands on. Everyone has to learn.

What Raiyn said.

But if you must, you'll need to remove the freewheel, so you'll need a freewheel remover (http://www.parktool.com/tool_indexes/catindex_fr.shtml), probably the FR-2 or FR-3 model, and a chainwhip. That's an old bike, your shop probably won't have the right tool in stock. You may just want to let them do it, since if it hasn't been removed in a long time, it can be reeeeaaaaal tight.

Heck, just leave it alone and instead adjust your tube so that the stem isn't jammed against the edge of the stem hole.

If you want to keep it, the quick and dirty way is to punch a couple of small holes in the disk near the edge and use a couple of wire ties to tie it to the adjacent spokes.

For the record, it's called a "spoke protector." If you ever shift your chain into the rear spokes for even an instant, you will bugger up the 8 outside spokes on that side. After that happens it might take a while, but you will eventually break all eight of those spokes one at a time.

Originally posted by Spoke Wrench
If you want to keep it, the quick and dirty way is to punch a couple of small holes in the disk near the edge and use a couple of wire ties to tie it to the adjacent spokes.

For the record, it's called a "spoke protector." If you ever shift your chain into the rear spokes for even an instant, you will bugger up the 8 outside spokes on that side. After that happens it might take a while, but you will eventually break all eight of those spokes one at a time.

Good idea. Thanks. I think I'll just do that.