First time building a bike and having this issue with the rear derailleur pulley jumping when I stop pedalling. Only seems to happen at the 2 highest gears.
The group set and wheelset are all new. I read that this could be an issue with the hub. Should I get it warrantied?
Rear derailleur pulley jumping and chain slap
byu/DrKorok inbikewrench
by DrKorok
9 Comments
Freehub body has drag. If you let go of the pedals do they keep “ghost pedaling”?
This is normal. You can reduce it slightly on gravel/MTB derailleur with a clutch. You could also tension the chain more. But basically it’s the inertia of the cassette if you stop pedalling too quickly pushing the chain forward.
If you look at a lot of pro sprinters, they often lose their chains crossing the finish line for exactly this reason.
Does your RD have a clutch? Is it engaged?
Nothing wrong here. What you’re seeing is momentum from stopping the cranks far faster than you would ever want to while riding. Stopping this fast can actaully throw the chain off the chainrings on the road, so it should be avoided.
The derailleur is working as designed in this video. There is no issue. Just don’t stop your cranks instantly, in an incredibly jerky manner, and you’ll be fine.
You’ll notice that you’re actually pulling the derailleur cage forward by slightly backpedaling every time you stop the cranks. The top run of chain operates in tension, the bottom has only minimal tension. What you are doing reverses that.
Ride it outside and see if it keeps doing it
B-Tension to start
A drop of lubricant between the freehub & hub body is usually enough to deal with the drag that’s causing this
Free hub isn’t freely hubbing. You can tell because the chain goes slack on the top indicating the cassette has kept rotating.
This just physics doing its thing. You would realistically never be pedaling like this. As long as it’s all adjusted correctly you will be just fine. Go out and ride