Bicycle Mechanics - Gear problem

Hello,

I'm new to this forum, hope I'm posting in the right place. I've got a mountain bike with 21 gears. When the change the (back) gear the chain easily slips on to the correct one, but when I try and change the (front) gear, it doesn't change, rather it stays the same (stays to 2). When I change it to one, the chain starts making a awful noise!!! I hate this, how can I fix it ?

Thanks.


P.S: You can call me a newbie in bike maintenance!

take it to a shop. It most likely needs the limit adjustment screws fiddled with.

What kind of bike is it? Sometimes it is actually cheaper to upgrade a part than to fix it a number of times.

Chipmunk,

You may want to refer to your shifting problems in terms of the gears you having trouble with, rather than the numbers.

If I understand your question, your rear shifting is fine, but your front shifting is not.

I'm sort of an old-timer in some respects (started racing mountain bikes when they were mostly rigid!), so I always remove those goofy numbered index indicators, but "2" must refer to your middle chainring (assuming you have a triple crankset).

If your chain won't go up to the big ring ("3"?) when you shift, then that usually means you do not have enough cable tension. There is a small barrel adjuster on your front shifter where the derailleur cable enters it. You need to rotate this counterclockwise as if you were trying to unscrew it form the shifter. Just do a half rotation at first, and keep making half-turns until the chain wants to go up to the big ring.

If your chain makes a lot of noise when you're trying to go into your small chainring ("1"?), then that usually means the chain is rubbing against the front derailleur cage, and you need to adjust that. There are two screws on the top of your front derailluer. One adjusts the position when you are in "1" and the other adjusts the position when you are in "3". Put your front shifter into "1" and then try moving each one a half-turn in each direction, returning it to the original position if nothing moves. One of those rotations should move the derailleur cage inward towards the bike frame. Again, make small adjustments - just enough to allow the chain to fall down onto the small ring. If you go too far, the chain will fall right off the small ring onto your frame. If this happens, put the chain back on, and un-do your asjustment one-half or one full rotation.

See the "Read Me" post above for Barnett's Manual, Chapter 33.

Also, try opening a beer while you do this. It seems to help.

Dave:beer:

In addition to the limit screws on the derailleur, you may have cable tension
problems. The cable tends to stretch with time. Put the derailleur in the position where the cable is loose, usually on the smallest front chainring, but rarely the opposite. It will be obvious. Loosen the cable clamp screw/bolt on the derailleur (just a little) enough to take a pair of plyers and pull the cable tight. Tighten the clamp, adjust the derailleur stop screws, of which the stop screw for the small chainring is more important. That establishes the rest position of the shifter system. If the cable is loose again after this stop screw adjust retighten. Try to avoid loosening the cable clamp so much that the cable falls out of the clamp, some clamps have "two" clamping positions, only one of which is correct. Now shift into the largest chainring. If it won't go then the large chainring stop screw is probably too far in. Unscrew it 3-4 full turns and see if the shifter will put the chain on the largest ring. If so put the rear der onto the smallest cog and see what the chain clearance in the front der cage is. In general the largest chainring should be usuable on the outer most cogs of the cassette upto cog 3 or 4 (8 or 9=smallest cog in back) before the cage gets chain rub. Adjust the large chainring stop screw for cage clearance on the smallest rear cog. Steve