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Author Topic: Chain Jumping  (Read 2035 times)

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Offline Ken

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Chain Jumping
« on: February 13, 2008, 08:44:33 AM »
Anyone have any ideas about this? It happened the other night on the night ride. While in the big ring and riding fast over the choppy roots under power, the chain tends to jump down to the middle ring. I never go any lower on than the third cog so as not to cross the chain up at a bad angle. The cassette and chain are almost new with maybe about 300 miles on them.
If you don't crash occassionaly, you're not riding hard enough!!

Offline treadlight

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Re: Chain Jumping
« Reply #1 on: February 13, 2008, 08:53:49 AM »
Anyone have any ideas about this? It happened the other night on the night ride. While in the big ring and riding fast over the choppy roots under power, the chain tends to jump down to the middle ring. I never go any lower on than the third cog so as not to cross the chain up at a bad angle. The cassette and chain are almost new with maybe about 300 miles on them.
Its time to switch to the otherside, one of the reason why I went singlespeed. ;) ;) ;)

scooter

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Re: Chain Jumping
« Reply #2 on: February 13, 2008, 09:04:35 AM »
When this happens is the chain against the outer edge of the derailer cage? If so this would indicate that your cable has streched and needs a slight adjustment. Try turning the barrel adjuster at your shifter counter clockwise effectivly lengthing the cable housing. You should be able to visually watch your derailer cage move outward and stop rubbing the chain as you make this adjustment :)

Offline Ken

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Re: Chain Jumping
« Reply #3 on: February 13, 2008, 09:17:35 AM »
I'll try that. I actually thought about that but didn't have time to try it on the last night ride. i got in with the A and B+ mixed group and hardly had time to breath let alone adjust anything. Thanks Scooter

Tread, If I came home with another bike my wife would kill me!! :( I have been looking at Marcel and yours and thinking how cool that might be. I don't have one of those. The new Specialized Stumpjumper Pro Fully and/or Allez or Roubaix road bikes look good also! 8)
If you don't crash occassionaly, you're not riding hard enough!!

scooter

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Re: Chain Jumping
« Reply #4 on: February 13, 2008, 09:22:41 AM »
Got my eye on one of those Roubaix too ;D

Offline Garry

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Re: Chain Jumping
« Reply #5 on: February 13, 2008, 10:11:56 AM »
Anyone have any ideas about this? It happened the other night on the night ride. While in the big ring and riding fast over the choppy roots under power, the chain tends to jump down to the middle ring. I never go any lower on than the third cog so as not to cross the chain up at a bad angle. The cassette and chain are almost new with maybe about 300 miles on them.

It is dropping to the middle ring because likely the chain rings are worn out.  Since you have a new chain and cassette that should give you smoother quieter shifting in the back, but the chain can't hold it's position on the front if the ramps and teeth are worn on the chain rings.  The smallest ring up front lasts the longest as it is just a straight sprocket.  The other two have ramps and different teeth to help lift and drop the chain.  When they get worn they don't hold very well or shift to and from smoothly.

Offline Harvey

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Re: Chain Jumping
« Reply #6 on: February 13, 2008, 01:19:11 PM »
It could also be the height of the derailleur relative to the chainrings. I suffered through this problem all last year and finally figured out that moving it down about 1mm made a world of difference. The outer plate should just clear the big ring. Check it all the way around because the teeth can be different heights.

Offline Ken

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Re: Chain Jumping
« Reply #7 on: February 13, 2008, 01:25:37 PM »
Good info all. I've changed the chain regularly to avoid premature wear and the teeth on the chainrings don't have that shark tooth look to it yet but there are alot of miles on them. I'll do that Harvey. Once it jumps down it doesn't want to jump back up and I have to push the shifter further to make it happen which sounds like maybe it's the cage or maybe the ramps are worn on the chainring also.
If you don't crash occassionaly, you're not riding hard enough!!

Offline Harvey

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Re: Chain Jumping
« Reply #8 on: February 13, 2008, 02:42:57 PM »
Once it jumps down it doesn't want to jump back up and I have to push the shifter further to make it happen
That would indicate a cable adjustment issue.

scooter

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Re: Chain Jumping
« Reply #9 on: February 13, 2008, 02:47:47 PM »
 ;)

 

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