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-   -   Backpedal = chain jumps cogs? (https://www.bikeforums.net/bicycle-mechanics/713770-backpedal-chain-jumps-cogs.html)

TurbineBlade 02-15-11 01:59 PM

Backpedal = chain jumps cogs?
 
Hey, I had a bike in the workstand and noticed that when it is in any gear, once you backpedal the chain tends to jump to the next cog...

Is this normal? What would cause this? The bike has friction shifters, and I tried many times just trimming one way or another and still -- backpedal and the chain wants to jump.

Is this normal? I've never tried to backpedal my other bike to see if it does it too.

Tober1 02-15-11 02:00 PM

I had something similar once. My chain was too long. ie. Not enough tension on it.

Maybe remove a link? Please consult others before taking my advice :)

bikeman715 02-15-11 02:05 PM

it either your chain is to long or the rear dérailleur need more tighten on it spring. also check your hanger it might be bent.

TurbineBlade 02-15-11 02:11 PM

Hanger is good - I put the tool on it last week.

Actually, I think (from reading) that most bikes do this since derailleur drive trains are meant to be used in the forward direction only. Fix is to stop backpedalling. I think the cause is simple chainline angle. Every once in a while I'll backpedal just a half kick or so pulling up to a stop light, and then start at the traffic light only to have a "pop" sound because the chain tries to grab a different cog.

Disregard- Thanks to the above posters.

Tober1 02-15-11 02:13 PM


Originally Posted by TurbineBlade (Post 12229938)
Hanger is good - I put the tool on it last week.

Actually, I think (from reading) that most bikes do this since derailleur drive trains are meant to be used in the forward direction only. Fix is to stop backpedalling. I think the cause is simple chainline angle. Every once in a while I'll backpedal just a half kick or so, and then start at the traffic light only to have a "pop" sound because the chain tries to grab a different cog.

Disregard- Thanks to the above posters.

Nope. There's definitely something more going on.
I have 3 bikes and they will all backpedal freely in any gear combo. I'd say remove a link. You might be surprised ;)

TurbineBlade 02-15-11 02:31 PM

It might be something else, but it's definitely not hanger alignment or chain length. I always install via big-big, not thru the derailleur + 1 link overlap. The derailleur is a deore long cage and in the big-big that sucker is pretty darned stretched out.

TurbineBlade 02-15-11 02:33 PM

One more detail: I spend about 95% of the time in the large chainring of a triple, using the 2nd, 3rd, and 4th largest cogs -- which makes me suspect chain angle. I do this because with a 22-32-44 crankset chainlife sucks when using the 32 chainring and smaller cogs. I'll try the middle and small chainrings tonight...

Tober1 02-15-11 02:34 PM

I'll take your word for it :) But does the jumping only happen when you're cross-chained? I thought I could live with it when it was happening to me, but I noticed that even slight backpedals would cause buckling or shifting. Ended up being a major PITA.

Nice sig by the way.

longbeachgary 02-15-11 02:36 PM

If it were indexed shifting I'd say derailure adjustment but friction? I'm at a loss.

fietsbob 02-15-11 02:57 PM

Just Don't back pedal, freewheel or pedal forward, that is the way derailleur systems were made to go.

want to go backwards, Unicycles are best at that.

LarDasse74 02-15-11 03:08 PM

It is very unlikely this is related to derailleur or hanger alignment. THe derailleur only affects the chain's path over the cogs when the chain is going forwards.

More likely chainline.

02Giant 02-15-11 07:59 PM

I had this same issue last summer when I replaced the wheel set, installed new rear cogs, and a new chain at one time. After following the derailleur adjustment instructions that came with the new cogs, the problem was resolved.

TurbineBlade 02-17-11 06:54 AM

Update: It's just chainline when on the large chainring and larger cogs. When shifted to the middle chainring the problem disappears, and when on the large chainring and smaller cogs it disappears.

So, no issue -- ;)


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