Chain backing off
 

I promise I am trying to keep my stupid c&v questions to a minimum of like, one per week.

So, I have noticed my chain backs off every time the wheels roll backwards. I've had bikes do that before , but this is like clockwork on the new to me campy equipped Ciocc, so I wondered if it is a campy thing, the free hub?

None of my current other bikes (sram red, shimano ultegra) do this.

Shifting is noticeably smoother on the campy than all others I have now or have since owned. No dropping, no rubbing, minimal chatter, easy trimming..all good stuff. I keep a chain catcher on my red equipped cervelo to make sure I don't drop when moving to the small ring, which has never been a problem for me on any other drive trains. Granted that is while riding and shifting, not when rolling backwards.

Any ideas? Is it just me? I may have to start bringing a grease rag with me if I can't figure this out.

Rear derailleur alignment?

OP didn't state which sprocket that the chain is derailing off of, or which gear combination was being used when it derails.

I often get bikes that will derail the chain off of the big ring when the chain is on the big chainring and biggest cog. Often a too-long bottom bracket spindle (and resulting poor chainline) is largely to blame.

Just today, my new Trek 1400 (16-speed, double chainrings) needed some work to prevent this.

So there is usually one or more teeth on the chainring which have a burred, bent or distorted tip, such that they will allow a sideplate to slip to the wrong side of the tooth, effectively guiding the chain off the chainring.

So I got out my big, coarse file, slipped the chain down onto the bb shell, and positioned the file at a roughly 45-degree angle to the outer-side faces of the big chainring's teeth, then turned the cranks backward so that the file would cut and produce a bevel on the driveside of the big ring's teeth.
>>>>I had to position the file carefully to prevent a crankarm or pedal from hitting my hand or the file.<<<<
I turned the cranks several turns, while slowly tilting the file to create a somewhat curved bevel that most effectively guides the chain over the tips of the teeth.

BTW, I've even fixed problems like this using a rock on the side of the road (in lieu of a file) when someone's chain was found to be derailing because of a damaged tooth problem.

As for my Trek's drivetrain, I can now rotate the cranks backwards indefinitely with the gearing fully cross-chained, with no tendency for the chain to derail!

My bikes like to go forward, maybe yours is just showing displeasure at moving backward?

This is the Synchro bike? Despite it shifting smoothly I suspect the chain is simply not perfectly aligned with the sprocket. This happens a lot on friction bikes where the chain is fine under tension pedaling but rolling back with no tension it will slacken.

You may also want to triple check for a stiff link in your chain. A minor stiffie won't be noticeable when pedaling but again with no tension it can cause issues.

Will check it out, thanks guys. Just puzzles me because even though it is an older bike, it is a new component build and was well built.

Lay the bike on its side, for example, pick it up, and just the invariable pedal pull in reverse knocks the chain off every time.

Just find it weird and frustrating that it happens so frequently.

only a minor inconvenience at this point. Forward momentum is all good, and as you say, I should keep it in that direction.

Wait.... What components? You bought the frame used and built it up?

Have you checked the dropout alignment and the derailleur hanger? You need to find a shop that has the tools and the mechanic that knows how to use them. It is a long shot but if everything else is perfect it could be the hanger is bent or twisted and that is what is causing your problem.

+100,000 New parts on an older bike is not always a slam dunk. Drop out mis-alignment, RD hanger bent or twisted, this is really common on the old stuff. Note, my newest bike is a 1992, most are early 1980s or older. Some have modern drivetrains. All had some alignment issues when I obtained them.