hi i have a nexus 4 speed revoshift on my giant lafree.trouble is when i put into 4th gear it sounds like the drive chain is jumping teeth.(like a worn chain)but its all brand new sprockets and chain that ive replaced. and the red lines on the unit are aligned as per manual when in 4th gear.a while back i had a similar problem and had to go into 3rd gear as 4th gave same results as now. but this was due to worn chain and sprockets because eventually i had to go to 2nd gear and eventually first.its as smooth as anything in 1st,2nd and 3rd but click to 4th and i cant even pedal just horrible jumping of the chain. its driving me crazy.anyone care to have a guess.
nexus revoshift problem
- Thread starter subevo
- Start date
It seems most likely to be the gearhub, but another possibility is that the rear wheel fore and aft adjustment is putting the motor chain idler arm is a position where it's allowing the chain to ride up on the motor drive sprocket.
I'd say first try riding the bike without power and see if you get the slipping when you stand on the pedals and apply full leg thrust in 4th gear. If you get the slipping then, it's the gear hub. If you only get the slipping when the motor is switched on, it's the chain jumping, almost certainly on the motor sprocket (I'm assuming the motor drive sprocket is also new).
Just one more possibility though. The Lafree only uses 3/16" chain, the chainwheel and motor sprocket width is too great for 1/8" derailleur chain, and if that is used the drive will jump under high load as in 4th gear. The chain measurement is the roller width between the side plates.
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I'd say first try riding the bike without power and see if you get the slipping when you stand on the pedals and apply full leg thrust in 4th gear. If you get the slipping then, it's the gear hub. If you only get the slipping when the motor is switched on, it's the chain jumping, almost certainly on the motor sprocket (I'm assuming the motor drive sprocket is also new).
Just one more possibility though. The Lafree only uses 3/16" chain, the chainwheel and motor sprocket width is too great for 1/8" derailleur chain, and if that is used the drive will jump under high load as in 4th gear. The chain measurement is the roller width between the side plates.
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It's really a job for a cycle shop familiar with hub gears Subevo. There's a large number of small components internally so not something to tamper with lightly. This webpage shows the internals of the 4 speed.
A common way to repair is new complete internal assembly, but there may be an issue with spares availability since the 4 speed hubs have long been discontinued.
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A common way to repair is new complete internal assembly, but there may be an issue with spares availability since the 4 speed hubs have long been discontinued.
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