I have a 2014 Specialized Sirrus Carbon with Tiagra front and rear derailleurs. Several times the chain has come off the front derailleur—a somewhat worrisome notion when you are clipped in and going slowly up a hill. Thankfully I didn't fall. It has me thinking an upgrade is necessary. My other bike has Dura-Ace derailleurs and I've never had a problem with the chain coming off. I'm thinking of just getting a Dura-Ace front derailleur to solve the chain problem. Do I have to get both derailleurs done, or can I just do the front?

Neither. Just have it adjusted properly.

I second this, get the derailleur adjusted, your limit screws aren’t set correctly

The chain came off the chainring because the derailleur isn't adjusted correctly. If you don't know how to adjust it, go to your favorite bike shop and have it adjusted. That will solve your problem.

As stated above, get the front derailleur adjusted properly. A Dura Ace derailleur will dump the chain too, if not adjusted correctly.

Assuming the chain is being dumped from the small ring, proper adjustment should fix the issue, but the addition of a chain catcher or chain watcher could help, too.

Front and rear derailers are independent of each other and can be replaced and/or mixed any old how - as long as they remain compatible with shifters, spacings and tooth counts.
But I agree with the other posters that it’s more likely an install/adjustment thing rather than an issue with the derailer as such.
IME - assuming proper install - the key aspect of good front derailer performance is to ease up on pedalling while shifting.

I'm going to jump onto the "front derailleur is not properly adjusted" bandwagon.

Here's the catch: I could teach a chimpanzee to adjust a rear derailleur but fronts can be something else. Assuming you have been fighting it for awhile, you have almost surely fubarred it beyond redemption. Here's what I'd do:

Completely disconnect the shift cable and keeping the Tiagra, pretend that you are installing that brand new, expensive, Dura Ace derailleur for the first time. Park Tool has a good set of step-by-step instructions if you think that you need them but the most important step is getting the position of the derailleur on the seat tube right. Follow all of the other steps in order because each adjustment that you make can affect the subsequent adjustments.

The front and rear derailleurs have nothing to do with each other. Rears wear out a lot faster because they have running parts; only the spring can wear out on a Front. My previous Front lasted 17 years; Rears last me about 5.

Shimano used to provide instructions for how to adjust derailleurs in the box; now they're on their website. It's pretty simple.

Also check the angle of the derailleur: if it's rotated to far one way or the other it won't work properly.

You may have another problem: worn teeth on chainring(s), worn chain, loose shift lever. A chain can come off a chainring even with a properly-adjusted front derailleur if it shifts quickly from the largest to the smallest of a triple, as it would if the lever keeps on moving after you take your hand off of it.

The Dura Ace R9100 FD that I just picked up had instructions in the box, so YMMV.

In the off chance you come back and check this thread you posted, put the chain in the big ring and small cog. Turn the outer derailleur limit screw clockwise (moving the cage inward) until just before the cage touches the chain. If the screw is hard to turn then hit the shifter paddle to give the cable some slack, adjust screw, then shift back up to check the clearance. Takes about 15 seconds.

Thanks for all the help everyone! The bike had a few other needs so I've dropped it off at my local bike shop. I appreciate all the help though—I thought I'd have to upgrade the derailleur, but am going to stick with the Tiagra and see how it does properly adjusted. Perhaps I'll put the money I saved towards better wheels!

Good to hear that you got it sorted.
Curious to understand how the chain gets thrown while going slowly up a hill, assuming it happens because you shifted the front. Good form would dictate you would be in the small ring long before you were going slowly...

a chain minder/jump stop is part of my several builds... no shifting past the inner chainring with that back stop.

Carbon, Braze on FD? K edge invented the chain catcher for those https://k-edge.com/product-category/...catchers/road/





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