Nexus 8 Skipping/Slipping
12-06-12, 09:59 PM
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Nexus 8 Skipping/Slipping
Has anyone had non-cable adjustment related issues with shifting on a Nexus 8?
I've adjusted my cable about a dozen times, lining up the yellow indicators on top. (The bottom indicators were not painted correctly, and one is a small yellow line that crosses diagonally at 45 degrees out of the notch, so adjusting to the marks on the bottom is a no-go)
4th gear sometimes has a problem shifting that seems to be non-cable related. Looking at the indicator, when shifting from 5 to 4 while stationary, it does half the shift, and then the second half slowly. All other gears shift instantaneously when stationary. If I hold the actuator in place while downshifting, then turn it with my hands, I can feel a rough grinding spot where it slows down. I'm not sure how that translates into slipping while riding, but it happens occasionally.
A more frequent problem is 8th gear slips, it engages, then disengages, then engages off-and-on. I've also had it completely slip like a false neutral on a SA hub. I can never seem to perfectly replicate what causes the slipping. It has happened when torque was applied to the crank, no torque, and even backpedals while shifting. Some days are better than others but it never consistently slips. Sometimes it slips in 8th half the times, other days it works fine. I loosened up the cable on the chainstays and around the bottom bracket where the bends seem the tightest, but it still has problems. It uses suboptimal anti-rotation washers so that the cable is pointed into the chainstay, but Shimano says it should be fine. (Black/gray on 20 degree dropouts)
Any ideas?
I've adjusted my cable about a dozen times, lining up the yellow indicators on top. (The bottom indicators were not painted correctly, and one is a small yellow line that crosses diagonally at 45 degrees out of the notch, so adjusting to the marks on the bottom is a no-go)
4th gear sometimes has a problem shifting that seems to be non-cable related. Looking at the indicator, when shifting from 5 to 4 while stationary, it does half the shift, and then the second half slowly. All other gears shift instantaneously when stationary. If I hold the actuator in place while downshifting, then turn it with my hands, I can feel a rough grinding spot where it slows down. I'm not sure how that translates into slipping while riding, but it happens occasionally.
A more frequent problem is 8th gear slips, it engages, then disengages, then engages off-and-on. I've also had it completely slip like a false neutral on a SA hub. I can never seem to perfectly replicate what causes the slipping. It has happened when torque was applied to the crank, no torque, and even backpedals while shifting. Some days are better than others but it never consistently slips. Sometimes it slips in 8th half the times, other days it works fine. I loosened up the cable on the chainstays and around the bottom bracket where the bends seem the tightest, but it still has problems. It uses suboptimal anti-rotation washers so that the cable is pointed into the chainstay, but Shimano says it should be fine. (Black/gray on 20 degree dropouts)
Any ideas?
02-04-13, 12:32 PM
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An update in case anyone in the future has non-adjustment problems. The problem hasn't been fixed, but appears to be diagnosed. Hub skipping can be caused by things other than poor cable adjustment, but still caused by cable issues and the revoshift.
One is that the cable housing ferrule can jump out of the barrel adjuster with aggressive shifting (multiple gear drop), bumps and slightly suboptimal cable routing, then the ferrule will hang on the edge of the barrel adjuster throwing cable adjustment completely off. This sometimes fixes itself with shifting when moving the cable will cause the housing to nest itself back into the barrel adjuster. Cable length and routing should be adjusted to an appropriate length to minimize the chance of this happening. (I will add that cable routing and length was not bad, but perfect routing should help). In the case of rapid shifting, the knowledge of this issue should be sufficient, as it is quite simple to move the cable back into the adjuster while riding. The problem is difficult to diagnose because it fixes itself after shifting a few times, and will likely be fine by the time you get out to inspect for problems.
The second is holding onto the twistgrip, especially when changing hand/body positions. Even if the shifter does not index to the next gear, twisting slightly can put tension on the cable, causing the clutch to be between gears. Unfortunately most Nexus 8 bikes have handlebar grips and bars that are designed to run with half-length grips mater to a twist shifter. This is generally a rare condition because Nexus 8 hubs are used on upright bicycles (where one tends not to tuck), or mounted in an alternative fashion where the shifter if mounted to a device such as a hubbub, so that the hand does not rest on it at most times.
The problems can likely be rectified with the purchase of a higher quality Alfine 8 trigger shifter or by using a gentler riding style.
One is that the cable housing ferrule can jump out of the barrel adjuster with aggressive shifting (multiple gear drop), bumps and slightly suboptimal cable routing, then the ferrule will hang on the edge of the barrel adjuster throwing cable adjustment completely off. This sometimes fixes itself with shifting when moving the cable will cause the housing to nest itself back into the barrel adjuster. Cable length and routing should be adjusted to an appropriate length to minimize the chance of this happening. (I will add that cable routing and length was not bad, but perfect routing should help). In the case of rapid shifting, the knowledge of this issue should be sufficient, as it is quite simple to move the cable back into the adjuster while riding. The problem is difficult to diagnose because it fixes itself after shifting a few times, and will likely be fine by the time you get out to inspect for problems.
The second is holding onto the twistgrip, especially when changing hand/body positions. Even if the shifter does not index to the next gear, twisting slightly can put tension on the cable, causing the clutch to be between gears. Unfortunately most Nexus 8 bikes have handlebar grips and bars that are designed to run with half-length grips mater to a twist shifter. This is generally a rare condition because Nexus 8 hubs are used on upright bicycles (where one tends not to tuck), or mounted in an alternative fashion where the shifter if mounted to a device such as a hubbub, so that the hand does not rest on it at most times.
The problems can likely be rectified with the purchase of a higher quality Alfine 8 trigger shifter or by using a gentler riding style.
