Slipping Gears?



jwroubaix

Member
Jun 6, 2007
177
6
18
Went out for a ride and nearly had an accident. I was a climbing a steep hill in my lowest cog and was standing when the gear slipped. This is happening quite frequently but only in my lowest cog. What causes this? Is this a chain problem or some sort of derailer problem? I guess it it's time to take it in for a tune up.
 
Worn out chain, most likely, followed by worn out cassette cogs, and last, worn out chainrings.

Measure the chain stretch. It might be the chain because the tension can be so high in your smallest cog.
 
jwroubaix said:
Is this a chain problem or some sort of derailer problem? I guess it it's time to take it in for a tune up.

It could be caused by either, but basically it's when the chain doesn't mesh on the cog just right (either due to stretching, a stuck link, or a misalignment). Yes on the tune up and a chain replacement (and possibly a new cassette) might be in order if there is sufficient wear -- ask them to check it for you.
 
IME, no. Most shops recommend a re-tune for new bikes after ~300 miles of use, as the cables will stretch when new and that will affect derailleur adjustment. If you haven't done this, then that could be the issue.

You can measure the chain for wear yourself using the method near the bottom of the page here. Chain Maintenance
 
Do you ride on the gears a LOT. Like do you change gears when you are loading the chain. That could cause faster chain wear. How long did it take you to crank out these 700 mi. What chain/ gruppo is it? Where were you on the front cassette?
:) Some questions that I had.

Could be a dérailleur issue too, i.e. if the chain is not aligned to the front and rear cassette.

Anyways take it to you LBS to get it checked up.
 
If this began suddenly after changing the cassette and chain, it would seem like it would have to be your front chainrings. Does it only happen in the small chainring in front or on both equally. A chainring has to be pretty worn for this to happen and usually the small one is more worn since people generally spend more time in it. It's possible the 9 speed chain is designed for narrower chainrings than what you've got. But if the chain looks to drop down into the teeth fully, I don't know that that would be it.