Thread: Chain Dropping from Front Derailleur

I'm having an issue with my chain dropping from my middle ring. It only happens on techy downhill rock sections when not pedaling. It's dropping from the bottom of the chainring not the top. I ride left foot forward and tend to be in the middle/bottom rear cogs during the downs.

It started when I replaced my cranks from Raceface to XT. Was tired of the BB issues and crank bolt problems on the RF setup.

-Chain and rear chainrings only had about 50mi on them when I switched cranks
-Have checked derailleur alignment of FR and Rear . Even took it to the shop to have it checked. Shifting wise everything is smooth.
-They also took a link out of the chain even though I've been running the same length since I've had the bike (about 3yrs).

Is it possible that the rear derailleur spring tension is just not enough given it's a few years old? Is the tooth config on XT chainrings much different than RF? Any other thoughts?

I've been running in my big ring a little more because it doesn't happen in that ring but I'd like to keep using my mid for those times where I need to grab lower gears for those quick uphill shots after a rocky downhill.

I had the same thing happen rallying my hard tail. I'd just put it in the big ring and not worry about it. I mean, you can drop it into the middle ring for those quick uphill shots.

Yeah I can keep doing the big ring thing but I have had times where you throw a chain dropping to the middle on a quick up. Still strange that for 3years it's not been a problem but now it is. Not like I'm any faster on the downs that's for sure.

Get rid of your pansy granny ring, and just rock the middle and big ring. Then get you a dual Chain Guide, and BAM...problem solved.

The chain dropping is pretty common... If you are running any lower-model shimano rear derailer, they swing in such a way that it loosens the chain tension over any bump, if you hit a big enough bump, the derailer cage will swing far enough to have your chain jump off your sprocket.

Solutions:
- Is your chain too long?
- Get rid of granny-gear and put in an inner-bash. Dual chainguide is sometimes overkill.
- Get a saint, or sram derailer, I know the srams have delt with the issue of derailer cage pivoting in that direction, I THINK the new saints have also adopted a new idea.

I personally would just go sram if you want the granny gear, or put an inner bash if you don't need it.

No explanation as to why this is happening more with the XT cranks (and assuming rings) than the XT set up other than it is possible that maybe the RF rings had slightly taller teeth.

That's besides the point. Powtron and kalisto are on the right track. I would strongly suggest ditching the big ring. I have no idea why they are even run anymore even on a dedicated XC mountain bike. With an 11-34 on the rear you can pretty much have all the gearing you will ever need (read: I have no idea why or where you would need more) running a 24 + 36 + light bash up front. Then, to alleviate any chance of chain drop you can run a guide, or you can eliminate 99% of chain dropping with a Blackspire Stinger...which is really just the bottom roller of a guide but works very well and weights about 90 grams. Plus either a guide or a Stinger will silence chain slap which is wonderful thing to not have to hear on the trail.

^^^^ Yeah, what he said...

Two rings is what I have on my FR/DH bike, and I have one ring on my XC bike (8 speed Redline).

The Sram idea would help the problem at least a little, as would a shorter chain. However, the reality with a triple ring setup is that in rough terrain the chain will always want to drop off to the small ring or lower, especially if you have a particularly active/little chain growth suspension design. I have three lacerated organs right now thanks to this phenomenon.

Considerations(not really suggestions but just thoughts):
-Try to focus on your shifting so you don't end up in those small cogs on rough downhills, this puts more tension on the chain and makes it less likely to happen albeit not impossible.
-If you buy a new Shimano rear der., buy one of the shadow ders(saint, xt, slx, etc.) as they have the same limited b-tension idea that sram does now. Though I feel that the steel arm that mounts the shadow ders is stupid flexy and causes as many problems as it's worth. In short, ride Sram!
-Whether you buy Shimano or Sram, try buying the shortest cage that you can get away with. This means that you will have to be very careful with what gear combos you go into, as going into the wrong one can mean a der. cage ripped in half(seen it on a number of X-0s). This allows you to run both a shorter chain and it minimizes that swing length of the derailluer cage and thus moving the chain less.
-If none of that fixes it, look toward a chain retention device. That's most likely where I'm headed now that this issue has cost me 6-8 weeks of my summer

*Sidenote: As a little highlight for Specialized, I will say that the modified E-type front der. that Specialized mounts directly to the swingarm of many of their FS bikes now drastically reduces the likelihood of this happening as the front der moves in sequences with the suspension rather than the chain moving around the front der when the suspension moves. Rarely did I have this issue arise on my Pitch all of last year. However, with the ultra active suspension design of my Remedy and a conventionally mounted front derailluer, I came around a set of corners that I've hit a hundred times in the last year, went to grab some throttle and ended up in the ICU since the chain wasn't on. Not so much a recommendation but a little design props to Specialized.

Was away from the computer for a few days. Thanks for the input. I guess I never thought of getting rid of the ring. I don't use it all that often, if ever anymore.
Couple notes
- I'm running a Sram X-9 Rear Der long cage. Maybe my original thought on the spring tension is correct. After a few years of beating up the rear der it's lost some of it's tension.

-Shortened the chain during the last tuning.

If you drop the big ring, get a medium cage der, and adjust chain length accordingly, you should be able to get rid of the issue. The thing about dropping the big ring is you can adjust your front derailer a bit more to the right than you normally would because you don't have to worry about the chain rubbing against it in the highest gear (because you don't have one). Keep's the chain from jumping down...

Minor hijack - anything special need to be done to run a Stinger on a dual-ring setup? Looks like they're made for single rings, but this is like the 3rd thread I've seen where people have suggested the Stinger with a dual-ring setup.

Just a quick update.
New derailleur = problem solved.

^ What'd ya get?

I replaced the old Sram X-9 with a new X-9. You could feel the difference in the spring tension between the two. The old one was pretty worked.

Originally Posted by Big E

Minor hijack - anything special need to be done to run a Stinger on a dual-ring setup? Looks like they're made for single rings, but this is like the 3rd thread I've seen where people have suggested the Stinger with a dual-ring setup.

Sorry for the late reply as just happened to see this thread bumped up.

Stinger is designed for dual ring.

It will work with a single (but I'd be more inclined to run a guide with a single since you no longer have a front D to actually keep the chain on).