Problem with internal cabling to hub gears

[Brucey]

the cable is doing the right thing, anyway!

.... I presume you are suggesting there may be some slack in the cable which might be take up by a slight tightening.

sort of; I'm actually suggesting that with some hubs there is slight mismatch between the insides of the hub and what the CJ marks are telling you. This appears to occur because of a manufacturing fault.

Does the adjuster tighten clockwise or anti-clockwise?

Daft answer I know but it depends which way you look at it. For N8 and early Alfine hubs (which are both 'low normal' i.e. they default to 1st gear with the cable disconnected) you need to unscrew the barrel adjuster on the shifter (i.e. turn it so that the top of the barrel adjuster moves forwards, i.e. in the direction of travel of the bicycle). Try two clicks (from 'perfect adjustment') first, then three, then four. If there is a CJ/hub mismatch then one of these settings should make the hub work better.

If there is an internal fault with the hub, then none of these settings will provide a perfect result.

A caveat is that I have seen hubs where the sun locking pawls have become slightly damaged/worn through persistent slippage. In these hubs only a period of use with the correct setting (using lower power pedalling) with no slippage allows the parts to settle into one another properly again. Obviously there is no perfectly reliable way of making a determination that any slippage is caused by poor adjustment or by weird pawl wear; without opening up the hub all you can do is find the setting that works best, and use that.

cheers

[vandjq]

After almost giving up on this bike, it has finally settled down. The hub has not slipped at all since 4 May. This is the longest I've gone since Dec 2016. I am now convinced that it was the re-routing of the housing outside the frame combined with the lubrication of the cable which fixed the problem. But I'm not impressed that the bike was so badly designed that this problem with the housing arose in the first place. And if lubrication of the cable is so important, why do Shimano not mention it in their tech docs?

Anyway, I am very grateful to everyone on this forum who gave me excellent advice and helped me sort out the problem.

[firedfromthecircus]

After almost giving up on this bike, it has finally settled down. The hub has not slipped at all since 4 May. This is the longest I've gone since Dec 2016. I am now convinced that it was the re-routing of the housing outside the frame combined with the lubrication of the cable which fixed the problem. But I'm not impressed that the bike was so badly designed that this problem with the housing arose in the first place. And if lubrication of the cable is so important, why do Shimano not mention it in their tech docs?

Anyway, I am very grateful to everyone on this forum who gave me excellent advice and helped me sort out the problem.

I wouldn't wish to dispute anything Brucey has said on this issue as he has probably forgotten more about hub gears than I ever knew, however, I think lubrication is the cherry on the cake in this context. It likely tops it off, and will ensure that a dry cable isn't a contributing problem, but the reason Shimano don't mention it is because a new quality cable in a new quality housing that is routed correctly will work perfectly without extra lubrication 99.9% of the time. There is also the problem that lubrication done badly can end up with a sticky cable that would have been better without any extra in the first place.

All that said, I'm glad you now seem to have a trouble free gearing system. Enjoy!

[Brucey]

lubrication of cables is standard workshop practice.

IME the longer the run the more important it is to lube the cable. There are a few (very few) cables that are designed to work bone dry and last a reasonable length of time but the vast majority only work properly/for any length of time if they are lubricated.

IME Nexus/Alfine 8 cable runs which are installed dry are especially vulnerable to water getting in and causing problems.

cheers

[vandjq]

I was tempting fate when I posted that my problem was solved. Today my hub slipped 3 times in 3rd gear. On all three occasions it happened when I put more pressure (torque?) on the hub than usual. I was accelerating quickly from junctions to enter gaps in traffic. But I never stand on the pedals so this should not have been too much for the hub to handle. On each of the first two occasions there were two rapid and loud cracking noises, but only one crack on the third occasion. This was a bit unnerving, given that I was entering or crossing a busy stream of traffic each time it happened.

What is unusual about this episode is that all my previous problems with this bike have been to do with slippage in 4th gear, which now works fine. And on those occasions the slippage did not appear to be related to torque, but it certainly is now. The cable is still working OK and the yellow marks line up when shifting up from 1-4 and down from 5-4.

I've got 7 days left on the Shimano 2-year warranty. Should I make a claim?

[Brucey]

warranty? - I would. At least you can show that the cable isn't at fault now.

BTW just for fun, today I took a spare nexus 8 shifter, inner cable, cable housing etc and assembled it bone dry (i.e. without additional lubrication) for test purposes. The ferrules supplied appear to be the sealed type which are a little bit draggy anyway, but the overall result was pretty hopeless; I easily got an error of 0.5 to 1mm in cassette joint position depending on shift direction. I don't think this setup would work very well or for very long without decent cable lube.

FWIW the hub I was checking manifested both the most common faults when slippage is reported and continues even when the cable is in good shape;

1) the timing marks were slightly out
and
2) the sliding clutch was slightly mistimed vs the pawl lifts.

The latter fault means that even if the setting is adjusted so that the pawls are lifted perfectly, you still get slippage in gear 5.

cheers

[vandjq]

Well, I claimed on the warranty 2 days before it expired. The shop sent the wheel away to Madison, who replaced all the hub internals. I was over the moon until I tried to fit the wheel to the bike. When I tightened the axle nuts I was unable to stop the axle from moving because the non-turn washers had chewed about quarter of an inch out of the dropouts on both sides.

When I Googled the problem I found these comments from Aaron Goss:

'It is extremely important to make sure your axle nuts are tight (30 foot-pounds each MINIMUM!). Grease or heavy oil the threads prior to installing the nuts. Check the torque once in a while... If the axle does manage to rotate, your frame or hub may suffer frame damage (as pictured below).



Also note the marks and recess created by the non-turn washer's teeth. This happened because the axle nut threads were not greased and torqued to 32-35 foot-pounds. Axle movement is the enemy! But since bicycles are put together by folks that may or may not know all the proper methods, dropouts should be built with replaceable steel inserts. Better yet, a steel frame!

Below is what happened to a Shimano Alfine 8 speed hub when the axle rotated.'



I strongly suspect that this is what happened to my hub when I heard the horrible cracking noise before I claimed on the warranty

I have always tightened the axle nuts to 42nm as recommended by Shimano, and I greased the threads. So this should not have happened.

Now my question is: Is it possible to repair this aluminium frame, or do I need a new (steel) one? BTW my dropouts are tiny compared to the ones in the picture, so I can't turn the washers around.

[Brucey]

the axle dog failure shown by Aaron has not arisen because of the axle rotating per se, it has been caused by excessive torque in the low gears. This may also have caused the axle to spin, of course, loading up the NTWs. The cracking sounds from your hub may have been a similar breakage, or may have been bearings or roller clutches at fault. There is no way of knowing which.

The chewed up frame with the NTWs is a more serious issue, and is depressingly common. Sometimes you can fit (single-tang) NTWs inside and outside of the dropouts (facing opposite ways) and this improves matters. However if the dropouts are short vertical ones, this is less easy to make work well.

You can get the dropouts welded, or sometimes fit large diameter, thick washers to spread the load over the damaged area.

cheers

[vandjq]

Thanks for the advice Brucey. Where would I get the welding done? (I mean what type of workshop) The main damage is a quarter inch square chunk out of each side where the tang has chewed the top of the dropout (with the bike upside down). I'm guessing that on one of it's many trips to the bike shop they didn't tighten up the axle nuts to 42nm. And the axle is slightly loose in the bottom of the dropout. I should post some pictures really. Is it possible to repair it with epoxy resin?

[Brucey]

aluminium welding is a specialist skill. Ask in a local car repair shop or bike shop if they know of anyone who does it nearby. There are a few wrinkles that may trip you up

1) heat input; the paint will be burnt away for some distance around the repair, and any adhesively bonded joints near the weld repair will fail.
2) filler material selection; if you know the material in the frame tubes, it should be possible to work out what filler material will work for building up the dropouts. Good welders are sometimes bad at choosing the right filler material.
3) post weld heat treatment; basically with this repair there won't be any. This might be fine, it might turn out to be a problem.
4) dressing of the weld repair; the weld repair will be all blobby right after it is done, and will need to be dressed back
5) distortion; it is possible that the alignment of the parts won't be perfect after welding; this is usually accommodated during the dressing (post weld machining) of the weld. In extremis the original dropout slots will be completely filled with weld metal, and new slots will have to be cut. Obviously this requires some very accurate work.

Before you embark on this route, check that the frame isn't covered by the manufacturer's warranty, and/or wouldn't be cheaper to replace anyway.

cheers

[vandjq]

As per Brucey's advice I claimed on the Shimano warranty for my Nexus 8 hub and the Cube warranty for my frame and have collected the bike today after 5 months in the workshop.

Firstly, when I checked them today the axle nuts were not tight at all. Using a beam wrench I was able to tighten them to 35 foot-pounds.

Secondly, the chain is far too tight. The new frame has an eccentric bottom bracket which is a different design from the old one. That had two holes in the side which allowed adjustment using a two-pronged Park tool. The new one has a hole in each side marked L and R. A 4mm Allen tool can pass through the bracket from one side to the other but I'm not sure how to adjust it. It is held in place by a clamp with two Allen bolts.

Thirdly, the yellow marks on the cassette joint line up when moving from gear 1-4, but not from 5-4. On 23rd May I posted that this problem had been sorted by external routing of the cable housing and lubrication of the cable. But it has appeared again after re-assembly of the bike in the workshop. I’m really not sure how this could have happened.

Some people might advise me to return the bike to the shop I bought it from and complain. But I have completely lost confidence in them after the bike has spent 8 of the last 12 months in the workshop. In order to get compensation I would probably have to get an expert report and take court action, which would be too expensive in relation to the value of a 2-year old bike.

[gregoryoftours]

I'm afraid I haven't anything to add about your hub gears, other than that if the bike came back to you with cables internally routed again I'd refit them externally. There are many, many more badly designed internal cable run routes than good ones in my experience. As far as comfort goes marathon plus have pretty stiff sidewalls and feel harsh to ride. I'd go for something more supple. You could also try fitting sponge grips and maybe a suspension seat post.