Strange rear derailleur behavior while coasting
09-10-17 | 06:51 AM
#1
Thread Starter
Newbie
Joined: Jun 2012
Posts: 40
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From: Switzerland
Bikes: TREK 1200 SL (2006?), 1996 Trek 750 Multitrack (sold, great bike), many incomplete projects in the basement
Strange rear derailleur behavior while coasting
Hi all,
suddenly, I cannot coast with my bicycle. It was working fine until before yesterday, now when I stop pedaling, the rear derailleur is "pulled" forward. After this strong and noisy movement of the derailleur, I have 2/3 rounds of pedalling without any tension (even with the fastest gear, no transmission from the pedal to the wheel), then the chain starts to spin the wheel again.
Here in this video you can see what is happening:
Do someone have a guess about what's happening?
I am posting this as a quick search in the forum did not give any idea. But I am still digging into it ... "luckily" it is Sunday and rainy here ...
suddenly, I cannot coast with my bicycle. It was working fine until before yesterday, now when I stop pedaling, the rear derailleur is "pulled" forward. After this strong and noisy movement of the derailleur, I have 2/3 rounds of pedalling without any tension (even with the fastest gear, no transmission from the pedal to the wheel), then the chain starts to spin the wheel again.
Here in this video you can see what is happening:
Do someone have a guess about what's happening?
I am posting this as a quick search in the forum did not give any idea. But I am still digging into it ... "luckily" it is Sunday and rainy here ...
09-10-17 | 07:01 AM
#2
Mechanic/Tourist
Joined: Apr 2007
Posts: 7,522
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From: Syracuse, NY
Bikes: 2008 Novara Randonee - love it. Previous bikes:Motobecane Mirage, 1972 Moto Grand Jubilee (my fave), Jackson Rake 16, 1983 C'dale ST500.
If you look carefully, you will see that the chain is sagging at the top when you coast. That can only happen if the cassette/freewheel is rotating without the cranks moving. Therefore the cassette is the problem, as it should remain still. Try this Google search result in order to fix the problem: https://www.google.com/search?q=cass...icking&ie=&oe=
Last edited by cny-bikeman; 09-10-17 at 07:55 AM.
09-10-17 | 07:05 AM
#3
Senior Member
Joined: Aug 2005
Posts: 33,657
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From: Pittsburgh, PA
Bikes: '96 Litespeed Catalyst, '05 Litespeed Firenze, '06 Litespeed Tuscany, '20 Surly Midnight Special, All are 3x10. It is hilly around here!
I expect the problem is the freehub mechanism is sticking instead of freewheeling properly. It's either gummed up or a pawl isn't releasing when it's supposed to.
09-10-17 | 07:08 AM
#4
Senior Member
Joined: Aug 2008
Posts: 2,589
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freewheel's jammed up so it doesn't coast, instead the cogs get dragged along with the wheel. Then the chain gets wrapped up and yanks the derailer around.
you can try flushing it with oil, but considering its wear prone, cheap, and the OEM ones break down... probably better to just buy a nicer new one.
'freewheel' -that cluster of gears on the back wheel. ask you bike shop for one.
you can try flushing it with oil, but considering its wear prone, cheap, and the OEM ones break down... probably better to just buy a nicer new one.
'freewheel' -that cluster of gears on the back wheel. ask you bike shop for one.
09-10-17 | 07:27 AM
#5
Thread Starter
Newbie
Joined: Jun 2012
Posts: 40
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From: Switzerland
Bikes: TREK 1200 SL (2006?), 1996 Trek 750 Multitrack (sold, great bike), many incomplete projects in the basement
Great answers, thanks to all.
Now that you gave me all the hints, I am really forced to fix it today (I have a spare wheel in the basement, under a ton of boxes and stuff from the last moving ...)
Now that you gave me all the hints, I am really forced to fix it today (I have a spare wheel in the basement, under a ton of boxes and stuff from the last moving ...)
09-10-17 | 07:33 AM
#6
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Joined: Feb 2017
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Bikes: Soma Fog Cutter, Surly Wednesday, Canfielld Tilt
The freehub is dragging.
The freehub (what the cassette mounts on) is supposed to be able to spin backwards, thus allowing you to coast. Something is causing it to drag, so the cassette is trying to spin with the wheel, thus pulling on the chain. That is why you see the derailleur tension arm moving so much.
The freehub (what the cassette mounts on) is supposed to be able to spin backwards, thus allowing you to coast. Something is causing it to drag, so the cassette is trying to spin with the wheel, thus pulling on the chain. That is why you see the derailleur tension arm moving so much.
