wineandkeyz said:I wonder if anyone else has encountered this problem. My wife and two other women in our neighborhood all own Specialized Sequoia Elite bikes (with Shimano 105 derailleurs, etc.). All three bikes have problems with throwing the chain, usually when going from the middle to smaller chain ring.
We husbands all ride different bikes (Cannondale, Fuji, and Performance), but with the same 105 hardware. And none of us has yet thrown a chain on our own bikes. At first we thought maybe the women were doing something wrong, but when we've tried the Sequoias, the same thing happened. All three Sequoias have been back to the shop for adjustments, but the problem still crops up.
Could there be some quirk with the Sequoia Elites that is causing this?
Eight things I can think of effect this:
1. Inner stop... and the shop most likely checked/adjusted that first
2. Height of the derailer... also likely checked at the shop
3. Angle of the derailer.... maybe or maybe not checked/adjusted
4. Chain line.... 50/50 in my estimation if it is likely or even likely that it is checked.
5. The chain itself can be an issue with lateral flexibility. Even new chains vary considerably in flexibility by up to 50%. How a chain falls off the middle ring to the inside is also a matter of shaping of the chain ring teeth and side plate shaping of the chain.
6. Chain length can contribute if the chain is too long you may be getting too much slack
7. Rear derailer B-tension adjustment
8. Derailer chain ring mismatch. If 105 is designed for 52/42/30 and you are ruuning smaller chain rings, then shifting won't be as well controlled.
Take a close look at the Front derailers, chain rings and chains of the various bicycles that shift well and compare/contrast them to the troubled ones.
However, even if all these things are perfect... or at least operating within specification... it can still happen. You might want to install a device that will always keep it from happening: Jump Stop by N-Gear.
Many shops carry Jump Stop for resolving this issue and you can order direct:
<http://www.gvtc.com/~ngear/whatis.html>