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Builder's Corner Restoration and preservation. Keep them running in perfect shape. What size is your bottom bracket?

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Old May 14th, 2012, 12:11 PM   #1
dmarvin
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Default Chain Falling Off...A lot.

I'm running 1x9 set up on my 87 Wicked. Recently the chain has started falling off while going over roots, logs etc in the woods.

What could be the cause of this? Could I have all of sudden developed a lot of frame flex? I was thinking it might be the rear wheel?

Any feedback is appreciated
Dean
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Old May 14th, 2012, 3:39 PM   #2
chainline
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Quote:
Originally Posted by dmarvin View Post
I'm running 1x9 set up on my 87 Wicked. Recently the chain has started falling off while going over roots, logs etc in the woods.

What could be the cause of this? Could I have all of sudden developed a lot of frame flex? I was thinking it might be the rear wheel?

Any feedback is appreciated
Dean
Has this just started to happen? it could be a host of problems. first i would check to see if your chainring bolts are tight and there are no bent teeth on the chainring, then I would check to see if the torque on the crank bolt is 35-40 ft lbs.are you running the chainring on the out side or the inside of the crank? what is the Chainline like ?. if you use the front chainring as your guide if you use ruler it should fall inbetween the fourth and fifth cog. or you can use the chain. it also could be bad runout on the bearings in the bb.. good luck....lots to check...
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Old May 14th, 2012, 6:44 PM   #3
yo-Nate-y
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Also: chain length. If it is when going over stuff, maybe you just need to clean and lube---i.e., quick back pedal before you go up and over, and the chain grabs/bounces/ goes AWOL when you start to pedal again.

Why not grab a Third Eye or other stopper?
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Old May 15th, 2012, 12:09 AM   #4
tvcreative
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sounds like a worn out chain, freewheel, and derailleur tension spring
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Old May 15th, 2012, 2:17 PM   #5
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Quote:
Originally Posted by dmarvin View Post
..
Any feedback is appreciated
when the chain line is ok, then it can only be caused by wrong chain length.
There is a way to calculate the chain length

for example

Chainstay length in mm --> 400
Number of teeth of the largest chainring --> 46
Number of teeth of the largest sprocket --> 23

the result is

Chain length = 100 members = 127.4 cm
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Old May 16th, 2012, 4:08 AM   #6
theredchili
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Most people over here running a 1x9 or 1x10 , tend to use a chain device up front to stop this happening .

Also your chain could have stretched-maybe worth checking.

just a thought
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