Jan 9, 2002 7:51 AM
|On my 21 speed commuter bike, a shifting problem has arisen that I've never experienced before.
A little background:
1) My 7 cog freewheel tooth count is 11-13-15-18-21-24-28.
2) My chain is overdue to be cleaned.
3) My rear derailleur is Shimano STX.
4) The bike has been ridden about 5700 miles
5) All original equipment (i.e. no part has been replaced as of yet)
6) The bike has Grip Shift SRT-600 shift levers.
7) Until recently, the shifting has been flawless.
The shifting problem: The shifting works well until I shift from the 15 tooth cog to the 18 tooth cog. When making this shift, the chain does not move. When I subsequently shift to the 21 tooth cog, the chain jumps over the 18 tooth cog to the 21 tooth cog.
Will cleaning my chain solve this problem? (In the past,I have used much dirtier chains with no problems in shifting.)
Am I dealing with a derailleur problem?
Any advice would be appreciated.
|Two things try...||Cima Coppi|
Jan 9, 2002 8:24 AM
|1. Given the miles you have put on the bike, it is probably past time to change the derailleur cables (both front and rear).
2. Check for stretch in the chain and replace if necesary.
|clean and lube everything first||cory|
Jan 9, 2002 10:17 AM
|Could be just neglect and age. I'd start by lubing the cables (might as well replace them while you have them out; they're cheap), including a drop of lube where they pass under the bottom bracket. Clean the chain, cogs and derailleur and lubricate everything that moves, and I'll bet that solves your problem.
If not, candidates for replacement would be the chain and maybe the freewheel/cassette. Be sure to get the right chain, not a narrow one. Should be able to do it for $15 or less. If the teeth on the cassette are "hooked" rather than symmetrical, you'll need that, too, but I doubt it.
|New Cables AND Housing||grzy|
Jan 9, 2002 10:37 AM
|Face it - with that much time and so little maintenance it's time to replace the cables and housing. Cleaing them never really works well - you just can't ever get all of the accumlated dirt and grime out of the system. Modern indexed shifting systems are fairly sensitive to friction. Just replacing the cables and not doing the housing won't help much - it's really the housing that is the problem. Also, realize that cables often wear a groove inside the housing so even if you did get it totally clean you'd still have inherent friction. You'll be amazed at the improvement that $20 will buy. Staying out of wet and dusty conditions will really extend the life of everything, but often that's just not possible. It's like buying new tires - eventually you have to do it.|
|re: Shifting Problem||Lone Gunman|
Jan 9, 2002 10:41 AM
|Agree with the cable diagnosis/possibility. All it takes is for 1 strand of cable to break and gum up the works. Just a suggestion, I swapped out my cables this year and put all new cables and housings (Airborne, teflon coated) brakes and shifters, $20 shipped? sweet workin' shifts now.|
|re: Shifting Problem||JimP|
Jan 9, 2002 12:55 PM
|I certainly agree with replacing the cables but, you probably need to replace the chain instead of just cleaning it.|
|Cables or chain/cassette?||Kerry Irons|
Jan 9, 2002 6:04 PM
|I'd put my money on the chain and cassette needing replacing, but the cables certainly may need it too. If there's no fraying of the cables, they're probably OK, though cheap to replace. The chances of you not having AT LEAST 1/16" per foot of chain elongation are near zero, even if you had maintained things well. And with the chain elongated as much as it probably is (I'd bet over 1/8" per foot) you've certainly chewed up some of the cogs. Replace them both. On systems this cheap, and with a commuter bike, you've just got to face a regular replacement of chain and cogs. I commute year-round, and the winter salt/grit issue requires chain/cog replacement every 2500-3000 miles on comparable equipment. Mostly dry riding with regular maintenance on my "good bike" and I got 12K miles out my last Campy Record chain/cassette.|| |