Chain getting stuck on the rings..

[Dead Man]

Howdy

Searched and only found one other thread, but it seemed to devolve into a side topic that strayed ever farther from my issue.. so I figured I'd start fresh:

7900 with unknown mileage... probably about 5,000 miles. Completely problem-free, super low-maintenance until this issue.. but quite suddenly, the chain gets stuck between the big and small rings when I drop from the big to the small. Went from no problems to it happening pretty much every single time I shift rings... I have to make sure I'm easing up and be prepared to immediately backpedal so it'll un-stick itself and fully drop to the small ring. No issues going back up to big ring.

Rings and chain are cleaned and lubed every ride, thoroughly so every few rides. The chain does have about 2,000 miles of gritty PNW all-weather riding on it, but, as I said, I do clean and lube very regularly, and it still gages good with a Park gage.

My thoughts are: clean/lube/re-tension the front mech cable and re-set limits... but that's all I got.

Thoughts?

Thanks!


-B

[Black Dog]

I would make sure the FD is moving freely and the cable is moving smoothly too. It sounds like the FD is not shifting down fully and is placing the chain between the rings.

[bart998]

Need more info.... (assuming the derailleur is adjusted properly) what model crank and what model chain? A narrow chain (11 speed) and an older crank (8 or 9 speed) could cause this. Another possibility is a weak front derailleur return spring or drag in the cable not allowing the derailleur to move freely to the stop.

[Dead Man]

Originally Posted by bart998

Need more info.... (assuming the derailleur is adjusted properly) what model crank and what model chain? A narrow chain (11 speed) and an older crank (8 or 9 speed) could cause this. Another possibility is a weak front derailleur return spring or drag in the cable not allowing the derailleur to move freely to the stop.

7950 crankset, 6700 chain

[pbarry]

Really sounds like a FD problem. Cable slippage on the anchor bolt/binding within the housing/slight rotation of the cage from a not-tight-enough clamp. Get that rig on a stand and start turning wrenches.

[oliver1850]

I had it happen once on my Ritchey. 7700 FD, R700 crank and shifters. I had to stop and pull the chain off the ring, backpedalling wouldn't free it. I put it down to waiting too long to shift and having too much load on it when I finally did. Haven't ridden it enough to know if the problem will persist.

[djg21]

Originally Posted by The B

Howdy

Searched and only found one other thread, but it seemed to devolve into a side topic that strayed ever farther from my issue.. so I figured I'd start fresh:

7900 with unknown mileage... probably about 5,000 miles. Completely problem-free, super low-maintenance until this issue.. but quite suddenly, the chain gets stuck between the big and small rings when I drop from the big to the small. Went from no problems to it happening pretty much every single time I shift rings... I have to make sure I'm easing up and be prepared to immediately backpedal so it'll un-stick itself and fully drop to the small ring. No issues going back up to big ring.

Rings and chain are cleaned and lubed every ride, thoroughly so every few rides. The chain does have about 2,000 miles of gritty PNW all-weather riding on it, but, as I said, I do clean and lube very regularly, and it still gages good with a Park gage.

My thoughts are: clean/lube/re-tension the front mech cable and re-set limits... but that's all I got.

Thoughts?

Thanks!


-B

It's called "chain suck." The chain fails to disengage at the bottom of the chainring when shifting between rings and gets "sucked" up between the chainring and the seat stay. It's a common MTB issue. It generally means the rings are worn, and it is aggrevated by dirt and grit.

First, check your chain; make sure there are no stiff links. Not to start a debate, but change your chain at around 1,500 miles to prevent wear on the rings/cogset.

Then look at the rings, and if possible, compare them to new rings. My guess is that the teeth on your rings will have hollowed out on the side where they engage and will look like shark fins. If so, it's time to replace the rings. My experience with Shimano road rings is that they last a pretty long while, but newer rings with ramped teeth not quite as long. My MTB rings (at least the bottom two on my triple) have to be replaced every season.

[oldpotatoe]

Originally Posted by The B

Howdy

Searched and only found one other thread, but it seemed to devolve into a side topic that strayed ever farther from my issue.. so I figured I'd start fresh:

7900 with unknown mileage... probably about 5,000 miles. Completely problem-free, super low-maintenance until this issue.. but quite suddenly, the chain gets stuck between the big and small rings when I drop from the big to the small. Went from no problems to it happening pretty much every single time I shift rings... I have to make sure I'm easing up and be prepared to immediately backpedal so it'll un-stick itself and fully drop to the small ring. No issues going back up to big ring.

Rings and chain are cleaned and lubed every ride, thoroughly so every few rides. The chain does have about 2,000 miles of gritty PNW all-weather riding on it, but, as I said, I do clean and lube very regularly, and it still gages good with a Park gage.

My thoughts are: clean/lube/re-tension the front mech cable and re-set limits... but that's all I got.

Thoughts?

Thanks!


-B

Chain 'dancing' most often a front der adjust issue. Make sure the Fder outer cage is aligned with the chain when in highest gear, big ring and smallest(highest) gear. That turns the tip of the front der, where off the big ring stuff happens, inward a wee bit, making sure the shift is aggressive enough to get the chain to the small ring.

Tight cable also, and inner limit screw so when in lowest gear(small ring, biggest, lowest cog), the distance from the chain to the inner cage is 'about 1mm. No more or else you may get chain to front der rub when in highest gear.

Front ders can be kinda a black art sometimes.

Not chain suck, BTW-that's a different issue when the chain doesn't come completely off the big ring, gets grabbed by the small partially and gets crammed between the chainrings and the frame.