I'd be really grateful to hear from anyone who has experienced and solved this problem.
My Shimano alfine 8 hub gear is slipping in gear 6 - the other gears seem fine. I have it on a Revolution Shadow with belt drive.
The issue is that this is the second hub gear that this problem has occurred on. Edinburgh Bicycle Co-Operative replaced the previous hub gear and said they'd tested this one before sending to me. I've had it for a couple of weeks now and the issue has re-appeared.
When riding in 6th gear there is often a slip and clunking noise. I had heard that hub gears need to be 'run in', so was willing to live with this. Now, particularly when free wheeling in 6th gear, it will drop out of 6th into what seems like 'neutral' with a torque similar to 4th. I've had the cable adjustment checked by a bike shop to make sure there isn't something simple I'm missing.
As this is the second hub gear that this has happened to I'm wondering whether the root cause might be something else: gear shifter, alignment of dropouts, etc (although wouldn't this affect all gears)?
Many thanks for any replies.
Simon
Alfine 8 hub gear slipping in 6th
Re: Alfine 8 hub gear slipping in 6th
Check the cable adjustment - but that is likely to affect more than one gear.
Check the cable inner for kinks. I had problems after I accidentally trapped the gear cable in the dropout when putting the wheel back in one time & got a slight kink in the inner. I could get some of the gears right but not all as the cable effectively adjusted itself depending on whether the kink was out in the open or flattened out inside the cable outer.
Rick.
Check the cable inner for kinks. I had problems after I accidentally trapped the gear cable in the dropout when putting the wheel back in one time & got a slight kink in the inner. I could get some of the gears right but not all as the cable effectively adjusted itself depending on whether the kink was out in the open or flattened out inside the cable outer.
Rick.
Former member of the Cult of the Polystyrene Head Carbuncle.
Re: Alfine 8 hub gear slipping in 6th
I would automatically replace the gear cable in this circumstance, if there is the slightest doubt about it. I know of people who won't warrant their work on IGHs unless the shifting system is also overhauled.
Re you fault (assuming it is SG-S501 or SG-S500, some Nexus 8 hubs will be similar; NB Alfine 8 SG-S7000 may be slightly different) there are a few causes I can think of;
1) that there is a shifter/cable/cassette joint fault that leads to erratic position of the cassette joint and therefore erratic/imprecise gear selection. A common cause of this is if the cable is accidentally set to the wrong gear, eg should one cable ferrule be unseated in either adjustment or use. [A quick 'sanity check' is to select 4th gear and check the marks on the cassette joint line up OK, whether you select 4 via upshift or downshift. If you have the 'weatherproof' cassette joint, do be sure that the rubber boot isn't getting dragged into the shift mechanism.]
2) That your hub is one of those whereby the best adjustment is not when the marks line up exactly in '4th gear' (NB you should be absolutely clear that you have a matching hub and shifter; please tell us the exact model numbers of all the parts; I think there are now some combinations of shifter and hub -which have been fitted to production bikes....
- whereby you need to adjust when the shifter indicates 5th not 4th, and with these combinations '8th' is a low gear and '1st' is a high gear).
3) That there is something peculiar going on in 6th gear.
Given the history of the bike/hub I'm inclined to think that it is 3), but that the problem is somehow related to the installation/adjustment rather than the hub itself.
From your description what I think is happening is that the high gear clutch (which is held in position using a spring in gears 5-8) is being pushed out of engagement in gear 6 when freewheeling. The effect of this is that (until it re-engages) when you start pedalling again, you might well have second gear, not 6th, for a fraction of a turn. Because the high gear clutch re-engages under load, there is a real danger that the clutch can slip and be damaged when it tries to go back in.
If so.... why 6th and not 5th? Well, the drive is transferred to the hubshell via a set or pawls (or IIRC on alfine models a small roller clutch) on the left side of the hub in 1st and 5th gear. In all other gears there is a larger roller clutch that drives the hubshell. So in 5th the large roller clutch is 'already freewheeling' when the hub is transferring drive but in 6th it isn't; it needs to release before the hub will freewheel forwards in the normal way. If the roller clutch doesn't disengage quickly it drives the carrier unit forwards and with it all the other parts in the gear train. If the pedals are not also to turn forwards, the only place it can slip (in 6th gear) is the high gear clutch, which will disengage and then re-engage when forwards pedalling is resumed (noisily, probably).
If so, what is causing the roller clutch to jam (and then lift the high gear clutch) in 6th and not other gears? Well, if the roller clutch jams, it exerts the most torque on the high gear clutch in 6th (rather than 7th or 8th gear). Why should it jam at all? Well, sticky grease, badly assembled drag/preload spring (there are variations in roller clutch design), lack of lube, damage or wear in the roller clutch parts, could all cause it.
However my guess is that there is something screwy in the dropout alignment or the belt tension (vs bearing adjustment); either of these things could cause a slightly flexed (elastically bent) axle when the hub is in use, and/or a radial preload on the roller clutch. This could make it reluctant to disengage when freewheeling. BTW although the same gear train is used in 2nd gear the drive between the driver and the high/low range gearing contains an additional freewheel element (pawls or roller clutch depending on model) , so the main roller clutch can jam without causing any problems.
So, having checked that the parts are compatible and that the cable/adjustment checks out, I'd try;
1) checking the hub when the belt is less preloaded
2) checking the hub (with a slacker belt) when the track nuts are half-tight instead of fully tight (on the workstand only if you don't have good chain tugs)
3) checking the hub for roller clutch jamming; does the fault occur or not on the workstand depending on how hard the forwards engagement is made when under load?
4) checking the hub for bearing clearance adjustment; if there is really any detectable free play at the rim, this may (indirectly) lead to roller clutch jamming.
hth
cheers
Re you fault (assuming it is SG-S501 or SG-S500, some Nexus 8 hubs will be similar; NB Alfine 8 SG-S7000 may be slightly different) there are a few causes I can think of;
1) that there is a shifter/cable/cassette joint fault that leads to erratic position of the cassette joint and therefore erratic/imprecise gear selection. A common cause of this is if the cable is accidentally set to the wrong gear, eg should one cable ferrule be unseated in either adjustment or use. [A quick 'sanity check' is to select 4th gear and check the marks on the cassette joint line up OK, whether you select 4 via upshift or downshift. If you have the 'weatherproof' cassette joint, do be sure that the rubber boot isn't getting dragged into the shift mechanism.]
2) That your hub is one of those whereby the best adjustment is not when the marks line up exactly in '4th gear' (NB you should be absolutely clear that you have a matching hub and shifter; please tell us the exact model numbers of all the parts; I think there are now some combinations of shifter and hub -which have been fitted to production bikes....
- whereby you need to adjust when the shifter indicates 5th not 4th, and with these combinations '8th' is a low gear and '1st' is a high gear).3) That there is something peculiar going on in 6th gear.
Given the history of the bike/hub I'm inclined to think that it is 3), but that the problem is somehow related to the installation/adjustment rather than the hub itself.
From your description what I think is happening is that the high gear clutch (which is held in position using a spring in gears 5-8) is being pushed out of engagement in gear 6 when freewheeling. The effect of this is that (until it re-engages) when you start pedalling again, you might well have second gear, not 6th, for a fraction of a turn. Because the high gear clutch re-engages under load, there is a real danger that the clutch can slip and be damaged when it tries to go back in.
If so.... why 6th and not 5th? Well, the drive is transferred to the hubshell via a set or pawls (or IIRC on alfine models a small roller clutch) on the left side of the hub in 1st and 5th gear. In all other gears there is a larger roller clutch that drives the hubshell. So in 5th the large roller clutch is 'already freewheeling' when the hub is transferring drive but in 6th it isn't; it needs to release before the hub will freewheel forwards in the normal way. If the roller clutch doesn't disengage quickly it drives the carrier unit forwards and with it all the other parts in the gear train. If the pedals are not also to turn forwards, the only place it can slip (in 6th gear) is the high gear clutch, which will disengage and then re-engage when forwards pedalling is resumed (noisily, probably).
If so, what is causing the roller clutch to jam (and then lift the high gear clutch) in 6th and not other gears? Well, if the roller clutch jams, it exerts the most torque on the high gear clutch in 6th (rather than 7th or 8th gear). Why should it jam at all? Well, sticky grease, badly assembled drag/preload spring (there are variations in roller clutch design), lack of lube, damage or wear in the roller clutch parts, could all cause it.
However my guess is that there is something screwy in the dropout alignment or the belt tension (vs bearing adjustment); either of these things could cause a slightly flexed (elastically bent) axle when the hub is in use, and/or a radial preload on the roller clutch. This could make it reluctant to disengage when freewheeling. BTW although the same gear train is used in 2nd gear the drive between the driver and the high/low range gearing contains an additional freewheel element (pawls or roller clutch depending on model) , so the main roller clutch can jam without causing any problems.
So, having checked that the parts are compatible and that the cable/adjustment checks out, I'd try;
1) checking the hub when the belt is less preloaded
2) checking the hub (with a slacker belt) when the track nuts are half-tight instead of fully tight (on the workstand only if you don't have good chain tugs)
3) checking the hub for roller clutch jamming; does the fault occur or not on the workstand depending on how hard the forwards engagement is made when under load?
4) checking the hub for bearing clearance adjustment; if there is really any detectable free play at the rim, this may (indirectly) lead to roller clutch jamming.
hth
cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~
~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~
Re: Alfine 8 hub gear slipping in 6th
PROBLEM SOLVED Many thanks for the replies to my question.
I think Brucey accurately identified the problem and solution in point 3 of their post - many thanks for your detailed description, you're a life saver.
For the record, I have a Shimano Alfine hub (SG-S501) and shifter (SL-S503).
I double checked the cable and it was fine; no kinks, etc.
I reduced the belt tension by a fraction and was ultra careful with checking the wheel alignment in the rear dropouts.
I adjusted the cable tension by a fraction too.
I've now done about 15 miles after the adjustments and think it's safe to say that the problem is fixed - happy days!