Hi all,

I recently replaced the rear cassette, chain and rear derailleur on the road bike. Previously I had over 2500 miles on the bike and the following never happened:

Occasionally, when shifting from the big ring to the smaller ring on the front derailleur, the chain will go over "too far" and fall between the small ring and the inside frame.

This never happened before switching out the components but now happens 1:10 times. Its made me paranoid of switching on hills etc where I need shifting reliability.

Any thoughts?

Thanks much

Try adjusting the low-gear limit screw in slightly. It could be that your new chain is has a different profile inside the links to the old one or something, which is making it overshift when the old one didn't

I agree about checking the limit screw. Do that first. Then if you still have trouble, you could look at something like the N-Gear Jump Stop: https://gvtc.com/~ngear/

+1 to the limit screw... first place I'd look.

First try adjusting the front derailleur per this: https://www.parktool.com/blog/repair-...ur-adjustments Start at the beginning and don't skip any steps. Un-systematically tweaking screws can get you into trouble as the adjustments are interrelated
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I also recommend the nGear Jump Stop, I routinely install them on all of my bikes. Nothing takes the fun out of a nice ride like digging a greasy chain out and reinstalling it and properly installed this will virtually eliminate spilling the chain.

Thanks all. I guess Im not understanding why the limit screw would need adjustment as the chain will fail even when the rear selected cog is in mid-range. Not at any limit. Im also hesitant in adjusting the front derailleur as its been fine for 2500+ miles. Could any one enlighten me on the limit screw need to adjust?

Also, thanks for the nGear Jump Stop - interesting gadget.

EDIT:

Oh wait, your talking about the limit on the FRONT derailleur - makes more sense. Sorry Im such a newb in regards to derailleurs

I would guess it's the chain that makes the difference here. Was it the same chain? Perhaps your front chainrings were worn in sync with your chain? I don't really see how that makes much sense as the chain pretty much "falls" onto the smaller ring. My wife's triple had a similar problem which was a real concern as it's carbon fiber and she could have damaged it if she wasn't so experienced (she let off pressure immediately when it occurred and didn't drive the chain into the frame). I cured it by lowering her FD about 2mm. Even after returning it to the lbs their adjustment had the FD cage higher than it really needed to be so I bit the bullet and adjusted it myself so the cage only clears the big ring by a very, very small amount. Whether that fixed it or she began to be more careful about shifting under load I can't say. Typically chain suck happens when components get seriously dirty so you may also want to take a look to see if your chain rings happen to be dirty/muddy. The problem could conceivably be unrelated to the change in derailleur/chain.

https://www.youtube.com/watch?v=IDJU2KTrXbg&NR=1