Bad Shifting
 

My 2 years old Cannondale Synapse has a boat load of problem since I've owned it. The latest is the front derailleur stops working in the middle of the ride. Then for some reason, it starts working again. It's been in the shop several times but still nothing. I think part of the problem is it is internally cabled and something is making shifting a nightmare. Does anyone have any ideas of how to fix this piece of junk?

Derailleurs are really simple devices. Pull the cable and they move. Release cable tension and the derailleur's spring pulls the derailleur back the other way. So I think you may be on to something when you suspect a cable (friction) issue. When you upshift, the shifter pulls the cable and the derailleur moves. When you downshift, if there's excess cable friction, the derailleur's return spring doesn't overcome that friction and the derailleur sticks.

This type of problem is generally easier to troubleshoot on a bike with exposed cabling. Not only can you see the cable run, but you can pull on the exposed cable midways to see if you can actuate and release the derailleur by hand, isolating the problem without having to disconnect anything. Without the ability to do that, you may have to resort to disconnecting the derailleur cable to check for excess friction. Grab the cable and keep it taut by hand while shifting up and down. Does it take a lot of effort to pull the cable when the shifter releases tension? With the cable disconnected, you'll also be able to actuate the derailleur by hand to verify it's working properly.

It's a straight forward effort to check the der's movement freedom, then the cable's, then the lever's. It's rare that a movement problem comes and goes. About the only reasons that I can think of are road crap getting wedged in the der parallelogram (and then drop out only to have another get jammed in, then again fall out.....). A cable that is starting to fray at a rub/port point. But this usually gets worse and worse, again not likely to fix then "break" then fix over and over. Then there's cable corrosion. But like a fraying cable rust never sleeps, then awakes, then sleeps, then awakes. It is possible that the shifter's internals are the problem. But ONCE AGAIN, these types of mechanical issues usually only get worse and more frequent and noy fix themselves over and over. There are some situations where a too tight cable WRT the limit screw adjustments can cause a lever to not release. But this is well known by good mechanics so if this is the problem and your shop didn't catch this (or created this when they last worked on the bike) you might seek out a different wrench.

So we're left with the wild card which can be very different form mile to mile. But before we go there have a competent wrench check every thing out fully. Consider having the cable replaced as much as a preventative step as one that might reveal something.

After all the mechanical aspects are found to be in good order take a look in the mirror:). The rider is the wild card.

I have gone out on a bit of a limb without having any real info. Just a lot of experience in seeing fellow riders not shifting well at times. I hope I'm off base since fixing a mechanical issue is just $ and not changing behavior. Andy.

I had a problem for with a sticky FD. Turns out it was the sports drink leaking from my water bottle and causing the FD to stick