Bike trouble!?!?

My front derailleur sometimes has the chain come off into the pedals, also when I鈥檓 pressing hard on the pedals (Going up a hill or gaining speed) the chain breaks loose it doesn鈥檛 come off, I don鈥檛 really know how to explain it. Can someone tell me what鈥檚 wrong?

Sounds like a couple of possible problems here.

I'd be especially suspicious of improper adjustment if you are hearing the chain rub the front derailleur as you pedal. When really mashing the pedals, your frame can flex a bit which may accentuate the rubbing of the chain on the derailleur enough to dump it. You may simply need to adjust the front derailleur cable a bit using the barrel adjuster for the front derailleur.

You may also need to adjust the "high" stop on the front derailleur.

You can find instructions for adjusting the front derailluer at the Park Tool Website:

http://parktool.com/repair/readhowto.asp...

If you are riding along and the chain is not rubbing the derailleur, but suddenly the chain pops of the big ring you are probably suffering from a worn out chain or worn out chainrings. This is a potentially dangerous problem. Having the chain pop off can cause you to fall especially if you are standing up and really mashing. Lots of grunge on the bike's drive train makes the problem worse, as well.

Also, you describe, "the chain breaks loose," under some circumstances. This could be an issue with rear derailleur adjustment. If your rear derailleur isn't quite right, the chain can hop off a rear cog and skip about. Again, you might only need to adjust the rear derailleur's barrel adjuster to fix the problem.

http://parktool.com/repair/readhowto.asp...

If you are completely unsure of adjusting your derailleurs, and the information on the pages above doesn't help, I'd take the bike to your local shop. You probably need some very simple adjustments and they'll be happy to show you what they are doing.

Hope this helps.

your deraileur isn't set properly.

you can correct this by adjusting the high and low adjustment screws on the der. I cant remember offhand which one does what though.

The issues you are having can be fixed by getting your derailleurs adjusted. The front needs to have the high limit screw adjusted, the rear needs a cable adjustment. If you are unsure how to do this take it to a bike shop.

Everyone seems to be telling you to adjust your derailleurs, but you should also look at your chain-rings, your rear cassette, and your chain. Worn parts can cause your chain to skip off the gear teeth under a load.

you need a tune up!

adjust the derailleurs and check your rings and cogs....you may need to replace those as well.

Hi,

I experienced the same problem not that long ago. A bike repair shop inspected everything and discovered that one of the sprockets was worn and had to be replaced. The new sprocket completely fixed the problem. I had literally thousands of miles on the bike, so the problem was caused by simple wear and tear.

Please note, however, your problem could also be caused by a too-stretched chain or if the deraileur needs major adjustment.

You said your problem sometimes occurs by "pressing hard on the pedals." That is one symptom of a worn sprocket.

CycleMan