david58

I get about one chain drop per ride - Saturday was an exception, but it got me today.

This is a 105 group, crank and all, with the 50/34 in front and 11/28 in the back.

I will shift from the front big to small, typically about 3-4 cogs from the big, and the chain will drop. I have also had it drop when I have been in the big/big combination, and when pedalling backward to get my pedal to a position for a start.

Took it to a reputable LBS and described the issue. They worked on it, but when I rode Saturday the front was noisy as all get-out, but I didn't drop the chain. Took it back to the shop Sunday, asked why all the front D noise, she spent 63 seconds or so fixing it, and off I went. Then rode today, quieter, but dropped the stinking chain.

Any suggestions as to what is going on, what I should do? A different LBS is one of my first thoughts...

MudPie

See Park Tool's advice on adjusting, https://www.parktool.com/blog/repair-...ur-adjustments

Mr. Beanz

Sounds like she's trying to adust the front d on the limit screw alone.

She tightened it so the chain wouldn't drop but allowed the chain to drag on the cage. On your return, I'd bet she loosened the limit screw allowing the cage to move to void chain drag. This put you back to point A.

First time she should have adjusted the limit screw, then adjusted the tension to keep the chain off the cage. Sounds like she just bounced the screw back and forth....find a better mechanic.

Proper front der adjustment is finding the right combo of tension and limit screw position.

onespeedbiker

Sounds a bit like user error. First your bikes drivetrain is not designed to pedal backwards, sure it will, but you might, well drop a chain do so. Second you have a much better chance of dropping a chain with a compact crank than a standard because of the differences between the chainrings; your rear derailleur has more chain to take up when you down shift. My recommendation is not to wait until you run out of cogs before you shift into your small chainring and when you do so make it a smooth transition. If you are in the middle of a hill climb and try to force your chain off the big ring, there a good chance you will spin the crank before the chain takes hold and that can throw a chain. Probably the best answer for you is to get a chain keeper; it's a little gizmo that mounts at the level of you small chainring and creates a fence to stop the chain from flying off.

FBinNY 

The primary cause of chain drop on front shifts is incorrect low gear limit adjustment. Other minor adjustments, like cage alignment can also contribute.

But the other possibility is rider habits. If you shift the front under load the tight chain will spring inward like a plucked guitar string. Higher chain tension produces more spring action.

This used not to be a problem. For example my old Sun Tour and Campy front shifters simply won't shift if there's too much tension in the upper loop. But to make indexing crisper, makers stiffened FD springs and cut shift gates into the outer chainring so it'll shift under power. (it's easier to change bike parts than rider habits). It's nice to be able to shifter under power, but chain drop is part of the price.

Since the OP's issue is sporatic I suspect it's more the rider than the FD, but it could be a combination.

There's a third possibility, which I wouldn't mention except that the OP has chain drop when backpedaling. Depending on where on the cassette the chain is, and whether it crops to the inside or outside, it could indicate a chain line issue, with the crankset being a bit in or outside of ideal chainline (center of chainset lines up with center of cassette). if all else fails I'd take a moment to check this.

sideshow_bob

Irrespective of the cause, might I suggest a $10 chain catcher be installed. Basically impossible to drop a chain on a bike that has one fitted.

If your bike has a round down tube, then the Deda dogfang is the better option. If it's not a round tube, then one of the ones that goes onto the backside of the braze mount will do the job.

I install them on all my bikes.

Retro Grouch 

I could train a chimpanzee to adjust a rear derailleur but fronts can be something else.

Whenever a front derailleur doesn't respond to normal tuneing, my recommendation is to start completely over. Disconnect the shift cable and start with the position of the derailleur on the seat tube. Then follow the Park Tool recommended steps IN ORDER.

If I were to guess at the OP's problem, I'd say the yaw angle of the derailleur on the seat tube.

david58

OP, here. Rode today, in the hills as opposed to yesterday totally in the flats - more shifting today. No chain drop. Danged FD is noisy as all get-out, but no chain drop.

I understand about shifting under load, and as I am trying to teach myself to spin better I shift sooner rather than later. I generally shift from big to small when I am 3-4 cogs away from big-big - was spoiled by my CX setup, where I can ride all 10 in the big ring. But I'm learning.

I am going to a different LBS to get the FD set up again, hopefully that will fix it.