southpawboston

I recently built up a new bike for my wife around a Nexus 8 "red-band" IGH. She reports skipping when she's in 4th gear. By that, she means that there is a loud "chunking" noise along with the crankset slipping forward under torque. She insists that she eases up on pedaling while shifting, so the gear changes should be occurring properly. It often happens within a few seconds of her making the shift into 4th. It doesn't seem to happen in any other gear. I have not been able to reproduce the problem with me riding the bike, but she's reported that it's happened at least 3-4 times in less than 50 miles of riding.

Is this a common problem? This is my first experience working with an IGH other than a Sturmey Archer 3-speed (many of which I've taken apart and rebuilt). And yes, the cable is adjusted perfectly-- the two yellow lines on the cassette line up perfectly in 4th gear and there is no cable binding anywhere.

One thing I did that may be a little unorthodox is that I didn't run continuous cable housing from the shifter to the hub. Rather, I utilized a downtube cable stop and the frame's built-in cable guide on the BB, designed for the rear derailleur cable, then used a vintage clamp-on cable stop on the chainstay, with a short piece of housing between that stop and the hub's cassette. Shimano doesn't specifically say not to do this, and I see no reason not to. The adjustment does not seem to vary using this type of cable routing. Just putting this out there in the interest of full disclosure...

Here are pics of the bike and hub for reference:

Mr IGH

Most shifting issues are the result of a binding cable that's not free to release the hub when downshift. Your setup is kinda tight, perhaps a different washer set will allow a smoother path. Or maybe a longer housing (requiring the cable stop to be moved towards the bb).

southpawboston

Thanks. I'm pretty certain that the bend in that final stretch of housing is less kinked than, say the last curve of housing that feeds into a rear derailleur. Plus, the cable is sharply kinked inside the shifter mechanism. When I run through the range of gears with the bike on the stand, the cassette moves freely in both directions.

But anyhow, I guess I've still deviated from the recommended configuration, so I'm going to replace the cable stops with continuous housing from shifter to hub and see if that solves the problem. For what it's worth, I wasn't thrilled with that kinked housing, either, but the cable stop wouldn't fit further forward on the stay as the stay gets wider as it gets closer to the BB.

krome

On my bike with the Nexus 8, I ran housing to the DT stop and then naked cable from there, past the BB guide, to the Nexus directly. I turned the cable stop arm on the nexus up out of the way. For an instant I thought about cutting it off, but then cooler heads prevailed. The cable comes close to the tire, but there is ample clearance.

This is installed on a bike that had been left in the weather for some time. When I get around to painting it, I want to put braze on housing guides all the way to the nexus. It is working well for me, but I would rather run housing all the way to the hub, as recommended.

Basically, just remove that clamp on cable stop on the chainstay and the housing and see if you can change the washers to turn the bracket out of the way. (I bought extra washers and found some that worked the way I wanted)

Aquakitty

I have an alfine I built up for the b/f. At first I did a cable setup something like you did but I could never get the shifting clean. I went back to the recommended "straight line" with just some zipties on the downtube and it shifts cleaner, however no matter how clean I get the setup it does not like shifting under pressure at all... for experienced people this is no big deal but for people not used to this they will get miss shifts.

Mr IGH

I run my Nexus/Alfines with continuous housing and I cinch the zipties loosely to be sure there's no cable binding.

southpawboston

I don't like zip ties, so what I'll probably do is drill out the down tube cable stop and run the housing straight through it, then replace the bottom bracket cable guide (which is screwed in to bottom of the BB shell) with a nylon P-clip, and route the housing through that. Those two anchor points should be adequate to hold the housing in place.

tcs

I'm mystified as to why poor cable routing/binding would cause skipping in only one of the gears - as the OP said, just ratio #4. Anyone care to educate me?

Aquakitty

I have no idea what the technicalities are of the IGH's but that's what mine did as well, in order to set up the IGH you have to put it in 4th and then line up the dots on the cassette joint, maybe the kink in the line makes that lineup inaccurate. Could be the steps from the base ratio, or sumpin like that.

southpawboston

Yeah, I was scratching my head over this as well... it could be that the alignment is more critical in 4th than in others. I'm also not 100% certain that the cable pull is equal between all gears. At this point the only thing I can reasonably try is to route the cable more conventionally. It doesn't cost much and takes only a few minutes... easier than tearing the hub apart!

tcs

Ah. With the Shimano 8 a sensitivity downshifting from 5th to 4th makes sense. As you say, low normal, so the hub's spring is reeling in the cable slack, and from 5th - direct drive on the Shimano 8 - it has to engage both the super low (0.53) and the super high (1.62) planetaries to create fourth gear's 0.85 ratio.

southpawboston

Interesting! Yes, the slipping happens in 4th exclusively, but I believe it's after downshifting from 5th, not upshifting from 3rd.

jediphobic

I can't seem to find the information at the moment, but does the red band nexus have the double clutch that alfine has? If it does, then that's your problem. If you are pedaling with any pressure at all, the double clutch won't engage to protect the hub. I have to stop pedaling completely to shift on my alfine. Like I said I don't know for sure that your hub has that feature.

southpawboston

I'm not sure. I do know that the hub seems to shift without hesitation even with a slight load on the pedals, but I instructed my wife specifically to ease off and freewheel for a moment during and after shifting to ensure all the gears have aligned properly (a habit that's tough to break, instilled in us from our Sturmey Archer IGH bikes). According to her, doing that doesn't prevent the slipping.

krome

Downshifting relies on a spring return. Any cable friction can affect that. Upshifting relies on your thumb pressure, cable friction is easy to overcome with one's thumb.

southpawboston

Yes, this makes perfect sense. However, when I have the bike on the stand, and I twist through the gears in both directions, the cassette moves in either direction without sticking. I especially note this when I make the 3-4 upshift or 5-4 downshift to check the cable adjustment (watching the two yellow lines align in 4th). So, I'm still skeptical that my cable routing is the problem... but I'm going to change it regardless.

krome

I think the external mechanism (cassette) moves regardless, upshift or downshift. If the gears are loaded, they will not downshift until unloaded, but I think the cable mechanism moves anyway. However, this does not explain your issue, if it works on the stand (and when you ride it).

I do notice that any out of the saddle heavy mashing of the pedals can make the silent clutch slip. However, this is a known no-no, keep one's butt in the saddle.

LarDasse74

Are you suggesting this happens even after one is in gear? I have an Alfine 8 and I have no such problems, and I am a big guy and torque the hub mercilessly. Stand and deliver, I like to say!

Edit: (to the OP) to ensure the cable routing is not the problem, simply move the clamp-on-cable-stop a few inches forward and use a longer length of housing to create a less sharp bend.

Also make sure the 'cassette joint' lock ring is fully tightened - I have noticed that if it is not fully turned toward the 'locked' position it can cause the cassette joint to bind when shifting.

krome

Yes, It can be in gear, and heavy, out of the saddle mashing has caused it to slip for me. After some searching, I came to the conclusion that mashing out of saddle is a general no-no for the Shimano [Nexus] IGHs (not speaking for any Alfine unit). I'm around 150# and I don't consider myself to be extraordinarily powerful.

Mine is a red-band 8 speed Nexus, not an Alfine. On the Harris cyclery webpage, they say this about the Alfine 8: I take that to mean they've beefed up the silent clutch so it will not slip.

I'm planning on trying out an Alfine 8 soon.

southpawboston

I don't see how they could market a hub like this that would slip... what about the liability issues? Designing an IGH is not rocket science, they've been around for 100 years. With all of Shimano's patents, you'd think they'd have the most important aspect of the hub design down pat...

I wanted to place it farther forward, but it's too small to wrap around the chainstay, especially as the stay widens as it gets closer to the BB. As it is, it took me forever to find one of those clamp-on cable stops, and had to modify it to fit the oversize stay. It can't move any farther forward.

Well, my wife hasn't mashed on this bike at all, and rarely (if ever) gets out of the saddle to stand on the pedals. In fact, she said that on one instance of the problem, she was pedaling very lightly.

krome

That is how I felt. All I can say is that since I've kept in the saddle, I haven't had the problems. Part of me wonders also if it is/was a break-in issue with mine.

All I know is that there are several 8 speed shimano models. Is this due to incremental improvements? Bug fixes? I know that if there are older products still out on the market, Shimano isn't going to say that they've added more clutch engagement to address slipping, they will say it "improves shifting" or some such. They are not going to bad mouth their older products.

I'm not bad mouthing their hubs, I'm just saying that I experienced some slipping, did some looking around (here included) and surmised that I shouldn't hammer the pedals on my 8 speed Nexus. I was disappointed, but I still like the hub.

I'm glad to hear that LaDasse74 is able to hammer his Alfine. I want to try one myself.

Edit: as far as I know, Shimano has never marketed their IGHs for MTB use. That says a lot right there, to me. Rohloff, sure, MTB, tandem, etc. hammer it at will. But you have to bring the $$$$ to play with that one.

Aquakitty

Wondering, you using the nexus revoshifter (twist shifter)?

While this is true, there are many people who use it for MTBing and run a very low ratio with no problems. There's lots of info on this over on the MTB review forum.

southpawboston

Yes, it came with the hub. So far it seems accurate enough; the yellow bands always line up in 4th.

themothman421

I've literally been having the same issue, very helpful thread!

Aquakitty

I don't know about that shifter myself, it's on my husbands bike. I took the bike out for a ride tonight and it is really not shifting that great even though I have a straight line to the hub with the cable. It feels like that shifter is a bit of a piece of crap, tbh. But, I only paid $9 for it so what can you expect. Mine seems to not like 5-6-7. It feels like the cable isn't winding nicely in the shifter, kinda sticky. $200 hub and we get a $9 shifter, lol.