Bicycle Mechanics - Bicycle gear and chain is off.

Note that I discovered this the day after making the horrible mistake of listening to my family about riding in wet, muddy conditions when my bike is not properly equipped for such terrain.

My problem is the gear setting is off from where the chain is, my bike is 21 speed, but here's the example:

Setting 6, chain is in sprocket 7, a light rattly sound can be heard when moving the pedals.

Setting 7, which is where it should be regarding the chain's location, eliminates the rattling sound. Switching back to set 6 does not move the chain to sproc. 6, it remains in 7 and the rattling returns.

A similar problem with the lower gears. Setting 1, chain is in sprocket 2 and rattling, etc.

I'm not fully sure on what the cause may be, but I have slight suspicions of mud being clogged somewhere.

I tried manually moving the chain and trying manipulate the gears and hoping it would 'sync', but no go. Basically, the chain is one gear lower than the setting. It wasn't like this during my brief ride yesterday.

Clean all components thoroughly and find the instructions for setting up and adjusting derailleurs at www.parktool.com. Follow the instructions in detail from the beginning leaving nothing out. Your problem is likely to be related to the shifter cable tension, but there are other possibilities including a bent derailleur or derailleur hanger.

Clean all components thoroughly and find the instructions for setting up and adjusting derailleurs at www.parktool.com (http://www.parktool.com). Follow the instructions in detail from the beginning leaving nothing out. Your problem is likely to be related to the shifter cable tension, but there are other possibilities including a bent derailleur or derailleur hanger.

Absolutely. If everything is clean and the derailleur/hanger is straight, then its a cable tension thing. Put the shifter in the lowest gear and adjust the barrel nuts until the cable is quiet on the lowest cog. That should solve most of the problem except for minor tweaking. Cable too tight = won't shift high to low. Cable too loose means wont shift up. Also make sure the stop screws allow for the derailleur to move laterally enough to cover all the cogs. Start loose and tighten them until they prevent movement beyond high and low gears.

No derailer geared bikes are any better "equipped for muddy terrain." The drivetrain is completely exposed, so yeah, it'll get dirty.

But that alone won't break it or ruin anything, as long as you clean it afterward. Have you washed the bike yet? You may just have mud clogging something. Otherwise it's possible you ran into something and bent your rear derailer/hanger.

After you clean the bike it would be good to lubricate the derailleur pivot points and jockey wheels with a high-quality light oil; Tri-Flow is often recommended. Then go through the Park Tool procedure step by step.

I had done a wipe down, but it turns out (much to my surprise) that it wasn't mud, rather it was the cable needing adjusting. I was relieved that it was such a simple fix, though a full cleaning could still be in order.

Thank you all for your help.