Derailleur appears to be too tight
10-10-21, 04:45 AM
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Derailleur appears to be too tight
When I back pedal my bike in low gear the chain will not pass freely through the rear derailleur. The rear cassette Shimano 8 speed and the problem occurs on all lower half positions.
Chain on 3rd lowest rear cog
Chain refuses to pass backwards
Chain on 3rd lowest rear cog
Chain refuses to pass backwards
10-11-21, 10:13 AM
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I'd suspect the cassette mechanism binding (but that would affect the behavior on all cogs) or the rear derailleur not centered on each of the cogs at the time.
10-12-21, 08:39 AM
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Yep, could be a "gooey" (thanks, Sheldon Brown!) freewheel, which you could test by taking off the chain or removing the wheel to see if it resists being spun backward. Could be that one or both of the derailleur pulleys is also gooey, or that something is bent so that the chain is not running straight.
Despite the admonitions against backpedalling, some situations call for backing up your pedals by a partial rotation (like lifting up one pedal to get ready to start at an intersection), and the bike should be able to support that. It's very satisfying to have a bike on the stand, and to be able to turn the cranks backward with minimal resistance, and the rear wheel in no rush to turn with the chain. You can rule out a few suspected sources of friction that way.
Despite the admonitions against backpedalling, some situations call for backing up your pedals by a partial rotation (like lifting up one pedal to get ready to start at an intersection), and the bike should be able to support that. It's very satisfying to have a bike on the stand, and to be able to turn the cranks backward with minimal resistance, and the rear wheel in no rush to turn with the chain. You can rule out a few suspected sources of friction that way.
10-13-21, 01:04 PM
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Not necessarily - the amount of torque (turning force) put into the cassette is a function of what gear the chain is on - the same chain tension on smaller cogs will cause less of a turning force than it will on larger cogs. It is very likely that the freehub mechanism has more drag than idea, but that using the large cog provides enough torque to overcome it while smaller cogs do not.
10-13-21, 01:09 PM
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Response 2:
It is also possible, although less likely, that one or both of the derailleur pulleys are gummed up. This would be easy to determine by pulling the chain clear of a pulley and just using fingers to try to spin each pulley. They should have virtually no drag when the chain is not engaged.
Much more likely that it is the freehub mechanism,.
It is also possible, although less likely, that one or both of the derailleur pulleys are gummed up. This would be easy to determine by pulling the chain clear of a pulley and just using fingers to try to spin each pulley. They should have virtually no drag when the chain is not engaged.
Much more likely that it is the freehub mechanism,.
