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I have a Cannondale Women's Adventure 1 that I got this spring and have been riding on local (paved) trails every weekend. I started off riding about 6 miles a weekend and recently have progressed to 20-25 miles in a day.

About halfway through a ride, my front derailleur seems to need adjusting, I have to wiggle the shift knob to get the chain to change gears. For example, if I'm in 1 and go to 2, I have to pull the knob slightly ahead of 2 (between 2 and 3) to get it to change. To go from 2 to 1, I have to adjust the back gears a few times, or sometimes backpedalling will get it to change (but that's hard to do on a hill).

I keep taking it to my LBS (where I bought the bike) and they adjust it so it works fine in their parking lot, but again after riding for a few miles it's messed up again.

I don't know if I'm doing something wrong in technique or if there's something wrong with some piece of the bike, nor do I know enough about what's wrong to find anything that's helpful. It can be adjusted to shift correctly, but that adjustment doesn't stay for very long. What should I be looking for? Or, could I be somehow doing something when riding to cause this problem?

Some specs on my bike that might be relevant:

Shifters Shimano Revo Twist Type

Cog Set Sunrace CSM66, 11-32, 8-speed

Chain KMC 8-speed

Front Derailleur Shimano M191

Rear Derailleur Shimano Alivio

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When you're riding on level ground and you change gears, the gear change should happen easily and reliably. If that's not happening then keep pushing the LBS to make it right. –  Carey Gregory Nov 3 '13 at 6:30
    
Are you adjusting with the barrel adjuster? If so, is it possible that it is slipping? (Normally they should click -- if not then the mechanism may be toast.) The other possibility is that you have a cable that is failing. Or (bike shop should have checked this) the cable clamp is simply loose. –  Daniel R Hicks Nov 3 '13 at 14:00
    
I agree with @DanielRHicks it sounds like it's losing cable tension. –  Aaron Nov 4 '13 at 14:41
    
@DanielRHicks I'm not sure if you're asking about the shifters on the handlebars or some other parts. The shifters do click when I try to up/downshift, but the click isn't in the right place. The LBS will fix it to be in the right place, but about halfway through the next ride it'll be wrong again. –  Zaralynda Nov 4 '13 at 16:49
    
@Carey-Gregory Even on level ground it doesn't shift right. I keep taking it and explaining the problem, and they'll fix it so that the gears are right for a short while but it doesn't STAY fixed. I'm not sure if I'm asking them to fix the right part or what. –  Zaralynda Nov 4 '13 at 16:52

1 Answer 1

Depending on how many times this has happened, it could be a couple of different things. One possibility is that the clamp on the derailleur is loose and allowing the cable to lose tension over time and stop shifting properly. Another is that if at some point the LBS replaced the cable and adjusted it properly, the cable will naturally stretch, also causing it to lose tension and stop shifting properly. However, the break in period for new cables is usually relatively short and they should stop stretching and stay adjusted. This all goes out the window if the LBS has replaced the cable multiple times, however. You end up replaying the break in period and associated period of a stretched cable and no adjustment. There is also the smaller possibility that you have both going on, however, I'd hope the LBS had checked the cable clamp on your first visit.

I'd try politely asking for clarification from the shop what they have done. Shift cables are very inexpensive (for a shop) and I know several mechanics who will replace ANY less expensive shift cable out of hand to rule that out as a problem. Many shops will attach old/replaced parts to a repair bike so when you pick it up, you know what has been done/replaced. If you are just dropping it off and saying it doesn't shift right, different mechanics (or even the same mechanic who doesn't remember) may be replacing the cable and you may be replaying the break in.

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