My front deraileur needs adjustment after every ride

Question

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

Answer 1

Sounds like you are getting slack during the ride.
This will happen with new cables but if you get it every ride something then else is going on.

My thought is that your barrel adjuster is not holding.
Does it look like this?

The barrel adjuster should have a lock nut or something to hold it in place.
Mark the position with tape or a marker and see if it moves during the ride.

The M 191 is a lower end Shimano but you should certainly expect much better performance than this.

And congratulations with getting up to 20-25 miles a day.

Answer 2

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.

Answer 3

Make sure cables are properly attached.

Make sure that the housing has ferrules on each end. If they don't , they will start to "cave in" to the inside of the gear lever switch mechanism and you will feel as the cable gets play when its not exactly that the problem.