chain drops during xc

I've got chain-drop problems even every setting is right.
The chainline, shift-mech, chain lengh are all correct and function
normal during the ride. However, during the downhill session, the
chain often drops inward to the frame. I tried set the RD cage at
higher tension, no use. Also I tried shift the gear to the middle
while riding, the chain still falls.
Can anyone help?

On Nov 2, 7:55*am, Luke Forward wrote:
I've got chain-drop problems even every setting is right.
The chainline, shift-mech, chain lengh are all correct and function
normal during the ride. However, during the downhill session, the
chain often drops inward to the frame. I tried set the RD cage at
higher tension, no use. Also I tried shift the gear to the middle
while riding, the chain still falls.
Can anyone help?

Is this during a shift or just out of the blue when descending? If
out of the blue, I think the mountain bike people need to chime in,
because to me (a mostly roadie), it would be caused by a momentary
slackening of the chain along with an impact sufficient to dislodge
the chain from the chain ring -- but modern rear suspension (which I
assume you have) does not change chain line length when the suspension
is compressed. Slack n'whack -- but where is the slack coming from?
If this is happening during a shift, you can get uneven shifting if
you have cable stick or lack of lubrication in the FD, so apart from
checking your FD adjustment, make sure it is lubricated, and the
cables are lubricated.I suspect, though, from what you say this is not
the problem. -- Jay Beattie.

Luke Forward wrote:
I've got chain-drop problems even every setting is right.
The chainline, shift-mech, chain lengh are all correct and function
normal during the ride. However, during the downhill session, the
chain often drops inward to the frame. I tried set the RD cage at
higher tension, no use. Also I tried shift the gear to the middle
while riding, the chain still falls.
Can anyone help?

Good idea to be in big ring on true descents. Also, try removing a link
(make sure to accommodate cross-chain scenario though).

Bill S.

On Nov 2, 10:55*am, Luke Forward wrote:
I've got chain-drop problems even every setting is right.
The chainline, shift-mech, chain lengh are all correct and function
normal during the ride. However, during the downhill session, the
chain often drops inward to the frame. I tried set the RD cage at
higher tension, no use. Also I tried shift the gear to the middle
while riding, the chain still falls.
Can anyone help?

Sounds like the inner stop on the FD could use a small tweak, or
perhaps the chain could be a touch long. I wouldn't be as quick as
jay to assume you have rear suspension, based on the XC mention. Is
the bike FS, or hardtail? Have you worked with the front derailler
inner stop? How much chain is on there? Can you (of course you
wouldn't, but for the sake of conveying chain length) be on the big
ring and the large rear cog at the same time? If so, how much slack
is left? I've seen this issue when the chain is too long in the
past. If you have any slack when on the large rear cog and large
chain ring, I'd say the chain is too long. You shouldn't use that
combo anyway, of course. The only reason to even have the chain long
enough for that to be possible is in case you accidentally switch into
that combo, so you don't bind the chain. My XC bike has a chain that
won't allow that combo to be used, and trying to do so will bind the
chain. It also has a larger-than-normal gear range, and running the
chain any longer results in slack on other, usable gear combos, so I
run the chain shorter and avoid using the large/large combo, which as
mentioned shouldn't be done anyway.

Another helpful thing to know would be if this is happening pedaling
or coasting. I assume the latter, since it's unlikely you'd be on the
small chain ring while pedaling downhill. I tend to be on the middle
or big ring on descents, depending on what is at the end of the
descent.

wrote:
On Nov 2, 10:55 am, Luke Forward wrote:
I've got chain-drop problems even every setting is right.
The chainline, shift-mech, chain lengh are all correct and function
normal during the ride. However, during the downhill session, the
chain often drops inward to the frame. I tried set the RD cage at
higher tension, no use. Also I tried shift the gear to the middle
while riding, the chain still falls.
Can anyone help?

Sounds like the inner stop on the FD could use a small tweak, or
perhaps the chain could be a touch long. I wouldn't be as quick as
jay to assume you have rear suspension, based on the XC mention. Is
the bike FS, or hardtail? Have you worked with the front derailler
inner stop? How much chain is on there? Can you (of course you
wouldn't, but for the sake of conveying chain length) be on the big
ring and the large rear cog at the same time? If so, how much slack
is left? I've seen this issue when the chain is too long in the
past. If you have any slack when on the large rear cog and large
chain ring, I'd say the chain is too long. You shouldn't use that
combo anyway, of course. The only reason to even have the chain long
enough for that to be possible is in case you accidentally switch into
that combo, so you don't bind the chain. My XC bike has a chain that
won't allow that combo to be used, and trying to do so will bind the
chain. It also has a larger-than-normal gear range, and running the
chain any longer results in slack on other, usable gear combos, so I
run the chain shorter and avoid using the large/large combo, which as
mentioned shouldn't be done anyway.

Another helpful thing to know would be if this is happening pedaling
or coasting. I assume the latter, since it's unlikely you'd be on the
small chain ring while pedaling downhill. I tend to be on the middle
or big ring on descents, depending on what is at the end of the
descent.
Bought a Shadow rear derailer do not have a chain drop problem any more
it's amazing how a simple design change can make so much difference in
the shiftability of the whole drive train and on hard rough (North
Shore) descents hardly any chain slap and no chain drops.