Alfine 8-speed ?clutch? problem in gears 2, 3, 4

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AndrewJR
Posts: 14
Joined: 26 Nov 2017, 10:58am

Alfine 8-speed ?clutch? problem in gears 2, 3, 4

Postby AndrewJR » 26 Nov 2017, 11:32am

Hi,

I have a new and sudden problem with my Alfine ?clutch? slipping in gears 2, 3, 4.
It is mostly a "gentle" slipping, in a virtually noiseless manner, when going uphill or accelerating hard.
Feels exactly like the back wheel is slipping gentle on some wet leaves, but it isnt!
Just occasionally, there is a more violent "cracking" sound, which is more perturbing.
Gear 1 is rock solid. Gears 5-8 also have no apparent problems.
It's an Alfine SG-S501, ~4-5 years old, on a commute bike, perhaps 12-15,000km on it.
It's been serviced 3 times in its life, at the bike shop, in the Shimano oil bath.
The most recent service was 3 weeks ago and the problem started immediately after that ...
The weather is also colder, coinciding with the service, if that could be relevant.
I know the shop didn't dismantle the inner "core" - just cleaned the hub, removed the core, oil bath, refit (with a new 20-tooth cog).
It is not the chain slipping on the cog - and the shop has re-tightened the chain since the oil-bath service.
The "yellow dots" are aligned perfectly. I have also carefully experimented with different "misadjustments" both ways - with no improvement - so I am back with the dots aligned as they should be in gear 4.

I can't tell, by looking at the Shimano exploded diagrams, exactly what might be wrong. I can't visualise how this "clutch" works I also can't find any forum posting or online video/picture which describes this kind of behaviour, or explains to me how this "clutch" works. This is NOT a problem with slipping from one gear to another, which seems to be described in many online forums. It doesn't feel like it is dropping out of gear, just "slipping".

Anyone got any ideas?

I wonder perhaps if my clutch (or one of them; is there more than one in the Alfine?) is just worn, and perhaps the new oil is allowing it to slip more?
Or, is there something really subtle like a washer spacing which could possibly have gone wrong when is was reassembled?
It does have a new 20-tooth cog, but since gear 1 is so solid, I can't see how the new cog could be causing the problem.

Andrew

Brucey
Posts: 34245
Joined: 4 Jan 2012, 6:25pm

Re: Alfine 8-speed ?clutch? problem in gears 2, 3, 4

Postby Brucey » 26 Nov 2017, 6:38pm

there are only a few clutches in an SG501 hub. There are two (roller) clutches that take the drive onto the hubshell (one used in gears 1 and 5, the other used in 2,3,4,6,7,8 (*),(**), a sliding clutch that is only engaged in 5-8, a roller clutch (or pawl clutch in some variants) that is used in 1-4 (*) (and is takes the drive from the driver to the primary ring gear) and three pawls that lift from the axle and are used in 2,6 or 3,7 or 4,8 (*), (**) respectively.

That the slippage occurs in the gears you describe suggest that it is a problem with the clutches marked (*) above. That the slippage does not occur in gear 1 suggests it is most likely a fault with the clutches marked (**) above. That the slippage does not occur in gears 6,7,8 may be because the torque on the affected parts is less in those gears than it is in 2,3,4.

The secondary ring gear to hubshell roller clutch is, I think, spring preloaded. There is a cage around the rollers that is free to slide a little and it is preloaded very slightly in the drive direction by a small spring. If this spring is broken, absent, misplaced, or the cage is too sticky, or rollers are misplaced the roller clutch may slip under load. If the hub bearings are not correctly adjusted (or for some other reason eg a bent axle) the parts are not perfectly concentric, the roller clutch will slip under load. It may well feel like a 'soft' slippage, and may not make much noise. It is easy enough to check the condition of this clutch since it is on the outside of the internal parts when they are removed. If the hub is so worn that the rollers may drop out of the cage, the roller clutch should be renewed. If the steel drive band inside the hubshell is broken, again there may be problems.

The axle pawls can only be inspected by disassembling the internal. If the pawls are not full lifted at the correct time , or are worn, or have burrs on them, the gear may slip under load. This slippage is abrupt but of the same (limited) extent each time and rarely occurs without any noise. Often the timing marks on the cassette joint are not accurate and a revised timing is required. There may also a fault with the cable that means that the gear selection is not the same on upshifts as it is on downshifts. You can check this by seeing if the timing marks are exactly the same alignment on upshifts as well as downshifts.

Cable faults are commonplace. You would be amazed at how many 'faulty hubs' are actually faulty cables.

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

AndrewJR
Posts: 14
Joined: 26 Nov 2017, 10:58am

Re: Alfine 8-speed ?clutch? problem in gears 2, 3, 4

Postby AndrewJR » 26 Nov 2017, 8:17pm

Thanks. Struggling to take all that in, having never been able to see the innards of my hub, and neither the Shimano exploded diagram nor online photos really allow me to visualise this.

I agree that quite likely, the non-appearance of slippage in gears bigger than 4 feels like it could just be that there is less torque going to the hubshell, with the gearing. I was really surprised today when I found that gear 1 was so solid, considering how slushy 2-4 have become. So, most likely the roller clutch you describe to the hubshell which is active in 2-4, 6-8. I'll check gear 5 by stamping on it really hard next time, to see if I can get any slippage in 5 at all. If not, it would be more evidence.

After that, sounds like my best shot is to first ask the shop to check the hub bearings are just right. There's no obvious play, or stiffness, which we checked already, so it must be something more subtle with the bearings, or perhaps something has broken or dropped out during the service, or just died at random.

Andrew

Brucey
Posts: 34245
Joined: 4 Jan 2012, 6:25pm

Re: Alfine 8-speed ?clutch? problem in gears 2, 3, 4

Postby Brucey » 26 Nov 2017, 8:52pm

Heed me well; item #1 is always to check that the cable is working properly and that if you upshift to the timing mark on the cassette joint, it aligns exactly the same as if you downshift to the timing mark.

If it doesn't do this the cable is probably faulty and the hub stands zero chance of working properly.

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

Mike_Ayling
Posts: 131
Joined: 25 Sep 2017, 3:02am
Location: Melbourne Australia

Re: Alfine 8-speed ?clutch? problem in gears 2, 3, 4

Postby Mike_Ayling » 27 Nov 2017, 5:01am

Time to start saving for a Rohloff!

Mike

Roadster
Posts: 443
Joined: 26 Jul 2016, 2:12pm
Location: E.Lancs/W.Yorks border

Re: Alfine 8-speed ?clutch? problem in gears 2, 3, 4

Postby Roadster » 28 Nov 2017, 2:47pm

Mike_Ayling wrote:Time to start saving for a Rohloff!

Not necessary in this case: the Alfine 8 may not be quite as good as a Rohloff but it's still the best of the rest at a fraction of the price.
As Brucey has stated and indeed restated, the three primary suspects are the cable, the cable and the cable, which must be checked and if necessary replaced before doing anything else. Like most indexed shift systems, Alfine 8 needs a good quality cable with linear-wound (compressionless) outer in order to establish consistency in both adjustment and use. The Jagwire Universal Sport is an excellent, reasonably priced choice which will ensure that the problem, whatever other causes there may also be, is definitely not due to the cable:-
http://jagwire.com/products/diy-cable-k ... -shift-kit
A new/better cable may be all that's required and, needless to say, costs a lot less than a Rohloff.

vandjq
Posts: 86
Joined: 16 May 2007, 11:30am

Re: Alfine 8-speed ?clutch? problem in gears 2, 3, 4

Postby vandjq » 29 Nov 2017, 10:23pm

I second all posts which advise changing the cable. My Cube Travel Pro with Nexus 8 hub was about 6 months old when 4th gear started slipping. I too feared there was something wrong inside the hub. But on adjusting the gear cable with the shifter there was a slight difference in the yellow mark position when moving from 3rd to 4th gear compared with 5th to 4th gear. As per Brucey and Roadster's advice I installed Jagwire Universal Sport wiring and housing (£16), which solved the problem for about a year. But now it has started slipping again in 4th. I don't like the internal routing on this bike as I feel the cable run is a bit sharp where it enters the down tube. So I am thinking of upgrading to Jagwire Pro (£31) which seems to have better lubrication and a stronger housing. I might even consider the top model Elite, which has aluminium housing (£50). I would also keep an eye on the cassette, which can get pretty mucky and may be another reason for a sticky cable. I clean it with alcohol and do not put any lube on it as that attracts dirt.

Brucey
Posts: 34245
Joined: 4 Jan 2012, 6:25pm

Re: Alfine 8-speed ?clutch? problem in gears 2, 3, 4

Postby Brucey » 29 Nov 2017, 10:44pm

having encountered dozens of draggy gear cables in IGHs there are only a few different modes of failure.

Occasionally water penetrates from the shifter end but by far the most common thing is that when the gear cable runs along the chainstay, the last foot or so of cable goes bad. Some combination of water ingress from the cassette joint end and lack of lubricant when the cable is first installed makes the cable go draggy.

In extremis water pools in the cable housing at the low spot and the conditions inside the housing can go anaerobic, which can cause even stainless steel inner cables to start to corrode. They turn black and then start to crumble to nothing.

Even quite competent cycle mechanics are often fooled by slightly draggy cables, and are prone to diagnose failed hubs instead of failed cables.

To reiterate, if there is the slightest difference between an upshift to the timing marks vs a downshift, the cable is bad.

The cheapest solution is to fit a new inner cable (stainless ones of adequate quality are available for ~£2 eg at decathlon) with lots of lube, having flushed and cleaned the housing. If the old inner cable comes out looking cruddy enough a new housing is a good idea too.

NB with CJ-8S20 especially, it is absolutely imperative that you use the correct (metal) ferrule at the cassette joint end of the housing. The ferrule is supported on two small projections and plastic ones can just fail. The shimano cable (which comes with 8s shifters) has an aluminium ferrule that is crimped onto the cable housing. A loose metal ferrule will work but the cable housing can pop out the ferrule which throws the indexing off.

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

vandjq
Posts: 86
Joined: 16 May 2007, 11:30am

Re: Alfine 8-speed ?clutch? problem in gears 2, 3, 4

Postby vandjq » 29 Nov 2017, 11:00pm

Thank you for that Brucey, it never occurred to me that it could be just the cable itself causing the problem. I'll try changing it before paying out a lot of money. I might try that Shimano housing as well, in order to get the correct ferrule. I should think it's a lot cheaper than Jagwire.
:)

Brucey
Posts: 34245
Joined: 4 Jan 2012, 6:25pm

Re: Alfine 8-speed ?clutch? problem in gears 2, 3, 4

Postby Brucey » 29 Nov 2017, 11:23pm

this is what the correct metal ferrule (for use with CJ-8S20) looks like on the end of a Nexus/Alfine 8 cable.

Image

I don't know what the part number is for the cable/housing/ferrule alone; I've mostly seen this arrangement on cables that come with the shifters eg SL-8S20.

If you have CJ-8S40 (sealed type) cassette joint it is still a good idea to use a metal ferrule but it isn't such a disaster if (in a pinch) you use a plastic one instead.

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

Winfried
Posts: 81
Joined: 29 Sep 2014, 1:46pm
Location: Paris, France

Re: Alfine 8-speed ?clutch? problem in gears 2, 3, 4

Postby Winfried » 30 Nov 2017, 12:10am

To add to the above picture: With the Nexus/Alfine 7/8 in the lowest gear (cable loosest), the anchor bolt must be located specifically at 101mm from the end of the ferrule:

Image
https://www.sheldonbrown.com/nexus-mech ... bleinstall

FYI, Shimano sells this very useful accessory, for use with Alfine/Nexus 7/8/11 IGHs:

"TL-S700-B Inner Cable Fixing Bolt Setting Tool"
https://www.sjscycles.co.uk/tools/shima ... y72a06000/

Brucey
Posts: 34245
Joined: 4 Jan 2012, 6:25pm

Re: Alfine 8-speed ?clutch? problem in gears 2, 3, 4

Postby Brucey » 30 Nov 2017, 12:24am

IIRC the correct cable length varies with the cassette joint in use.

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

Winfried
Posts: 81
Joined: 29 Sep 2014, 1:46pm
Location: Paris, France

Re: Alfine 8-speed ?clutch? problem in gears 2, 3, 4

Postby Winfried » 30 Nov 2017, 4:09am

Are the cassette joints different between the eight-speed Nexus and the Alfine ?

As noted in the SB article, the distance is different for the Alfine 11 (184mm).

Brucey
Posts: 34245
Joined: 4 Jan 2012, 6:25pm

Re: Alfine 8-speed ?clutch? problem in gears 2, 3, 4

Postby Brucey » 30 Nov 2017, 8:43am

IIRC there are at least three CJs for the 8s hubs

CJ-8S20 (standard)
CJ-8S40 (sealed)
and another one that fits the latest (top normal) 8s Alfine hubs

The first two fit the Nexus 8 and the original series of (bottom normal) Alfine 8 hubs.

I think the cable length is different for each.

There are other CJs that fit 4s and 7s hubs; there are multiple (different) versions of those too.

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

Roadster
Posts: 443
Joined: 26 Jul 2016, 2:12pm
Location: E.Lancs/W.Yorks border

Re: Alfine 8-speed ?clutch? problem in gears 2, 3, 4

Postby Roadster » 30 Nov 2017, 5:25pm

It's not actually necessary to position the fixing bolt at precisely 101mm from the ferrule because this distance is widely adjustable after installation by means of the barrel adjuster at the shifter end - provided, of course, that the correct distance falls within that adjuster's range. What's important is the initial alignment of the yellow marks in 4th gear and the consistency with which the mechanism returns to its optimal setting in service.