Front clain dropping when transitioning from Big Ring to Small Ring

Tech
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Evening

I bought a new Specalized Roubaix 105 Sport and the last two rides I have been done, had my chain slip off when moving from the front big ring to the small ring. Assuming it is a user issue, but wanted to ask for any recommendations or suggestions to prevent this?

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I’d start with the FD position and setup: Is the FD cage parallel to the chain rings? Is it set to the right height? Are the limits set correctly? I haven’t setup a Shimano FD in about 15 years (I’m Campy guy), but that’s where I’d start. Surely Shimano has setup instructions somewhere on their site or YouTube. I’ll also bet some mechanics will chime in here with instructions for that.

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Hi there @Eric_Fine, if you’re comfortable working on the bike yourself, you might want to try and follow Shimano’s instructions under, “Checking gear shifting and fine adjustment” right near the bottom of the page at this link.

Installing the inner cable and adjusting gear shifting

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Actually, if you bought it new you should have the shop check and set the derailleurs because they apparently did not do that correctly. As others have pointed out though it’s a DIY skill worth learning and doesn’t need special tools. I highly recommend bettershifting.com for learning how to tune your bike.

You also asked about prevention. There’s a product for that called a chain catcher that mounts to the derailleur and stops the chain from slipping between the small ring and your frame. They’re easy to install (but you’ll need to remove/remount your derailleur which usually means tuning). I use Deda Elementi Dog Fang but there are perfectly fine and low cost options on Amazon.

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@Eric_Fine this is not user error and the chain should not fall off the smaller chainring when shifting from a bigger one.

Definitely take it back to the shop where you purchased the bike. The fix should be free of any charge and something they should be able to do quickly for you.

I often see front derailleurs set up incorrectly from shops, I.e. incorrect height, cable tension, alignment, support screw not being used. The shimano documentation, linked in post above, is clear and easy to follow if you did want to try to resolve the issue yourself.