Nexus hub: shift cabling?
 

(Visiting here from the Classic & Vintage forum)

For the first time in over 50 years, I am going to have a bike with an IGH (internal geared hub); I am having wheels laced to include a Shimano Nexus 8 speed hub. So, it comes with a shifter & cable. Do I have to use the supplied cable, or specifically the housing, or can I change it? I am hoping to use conventional derailleur (or brake?) housing so I can change the color to fit the desired aesthetic. And does this technology require uninterrupted fully-housed cabling from shifter to hub, or can there be open segments in the run?

While the current new bike with an IGH is usually using a full length casing I suspect this is to try to keep the cable/casing from becoming contaminated, the fewer ports of entry the less grit/water will get in. However sectioned lengths of casing work well too, just as has been the case with IGHs for decades. Do take some acre about the casing's bends, smooth large radius curve will have less friction than tight bends will have. How the hub's casing stop clip is aligned and where along the stay the last casing stop is the usual spot of greatest friction and/or contamination possibility. I suggest using casing stops that are slotted so casing removal for cleaning and lubing the inner cable is easily done.

The inner cable is typical der (1.2mm diameter) with the common Shimano head. The casing doesn't need to be gear/SIS stuff. Any quality lines casing can do. Just be sure to square off the ends after cutting to reduce the casing wiggle within the stops.

Not asked about but... I set up my IGH bikes so the flat land riding gear is one of the higher ratio ones (on my old SA AW that means 3rd gear). One can always coast down the steep hills if you can't spin well, but up hill and there's no cheating:) Andy

Thanks! :beer:

Sounds like exactly the answer I needed, so I'll order cabling in the color I want for this project (brown to go along with a Brooks B17 "honey" saddle). So I do not need 100%-sheathed cable, that's great; to complete the retro look it would be fun to locate one of those metal clamp-on pulleys instead of a cable guide although using the modern hub, I presume I'd have to mount it near the bottom bracket instead of the seat cluster.

The guy building my wheels sent me a gearing chart, expressed in ratios... and this is a far wider range than I am used to (I'm a flat-lander, basically). Supposedly 5th is the 1:1 gear and I spend a lot of time riding, on other bikes, in the 75 to 78 G.I. range so I'll select chainring and cog to achieve that... but it makes 8th gear about 129 G.I.! Wow.

You can use any compression less shift housing and do not need to run full length housing. Spiral wound housing works fine for 3 speed but hubs with more speeds should definitely be used with compression less. I would also stick with metal ferrules.

Which way to route the shift cable? For the modern IGHs that have the cable casing entering the cable stop clip that is attached to the hub routing along the chainstay works well. The cable and casing will travel under the BB and stay. To use an above the shell pulley would require the cable to wind around the stay to it's underside at some point, more bends more friction. To run the cable along the seat stay (and thus a top of stay pulley) will place the hub's casing stop clip in an awkward position to work with the cable's anchor bolt and how it is manipulated to attach to the cassette joint. Not impossible but a pain to due to the stays blocking access for your fingers.

Now if your IGH had the cable attaching to an indicator chain (like SA AWs) of a bell cranl (like Shimano 3 speeds have) the cable will be outboard of the stays as it travels from the BB or the seat stay top. If the chainstay is short or your feet are long one can clip the cable with the insides of your right heel. For these routing along the seat stay is better. Here's a shot of my self made SA AW (alloy hub shell, one of my gems:)) and its ultra light control cable pulley at the top of the seatstay.

I suggest for your hub routing along the chainstay. Andy

https://cimg8.ibsrv.net/gimg/bikefor...422c42219d.jpg

Thanks. To get the desired color -- brown -- I was planning on using Velo Orange's kits: VELO ORANGE So, I just e-mailed them about "compressionless" as I have no idea.

Thanks. Hopefully the wheels arrive soon, now that you mention it I need to be careful about "cable will be outboard of the stays as it travels from the BB or the seat stay top"; thanks for the warning! I seem to understand that there are parts keyed to the dropouts that dictate the direction of the cable forward of the hub. The frame is old enough that there are no braze-ons, including on the chain stay. Having full housing all the way up the chain stay and downtube, secured with zip-ties... ugh! I must be able to do better than that.

Here's a couple pics of my Nexus 7, it looks the same as the Nexus 8 (sorry the background makes it kinda hard to see). The cable attachment point is inboard of the stay, you might be able to find a vintage metal clamp-on cable stop to mount halfway between the hub and BB shell. Then you'll use one groove under the shell (if it has them) to run the inner wire up to another stop on the downtube. This is for chainstay mounting, I don't know enough about vintage frames to figure out how you would use seatstay/toptube.

https://cimg1.ibsrv.net/gimg/bikefor...39a9f1cc2f.jpg
https://cimg5.ibsrv.net/gimg/bikefor...135396f1ce.jpg

Great photos -- thanks.:thumb: Not having IGH experience in half a century, I somehow had it in my mind the cable had to go outboard of the chain stay. Apparently not! If I can get a clamp-on chain stay guide that can mount far enough forward on the stay, this looks right. Interestingly, if I combine this with downtime shifting, so little housing will show that one wonders why I'd bother ordering a different color!

Per earlier post, there are no braze-ons on this frame, I need a single-sided clamp-on guide (wish me luck!) or a pulley.

Sort of recall that the stub of the anti-rotation washer needs to face the closed end of the dropout. Perhaps to minimize the force on the arms of the dropout.
I am sure more experienced members will clarify.

Think through how you're going to release cable tension so you can disconnect the cable (removing the wheel to fix a flat).

Suggest setting 6th gear @75g.i. ish on your Shimano 8-speed IGH so gears 7 & 8 will actually have some utility and you'll use the draggy 4th gear less often.

Hmm. I presume the Nexus does not have a way top do that?

So, you feel the 6th ratio is not significantly less efficient in terms of friction than 5th? 18T/50T should get me there, then. Finding a 50T 50.4mm BCD ring should be doable.

With the recommended 'housing run from shifter to hub', one grabs the cable housing and pulls it free of the cable mount on the hub, allowing enough cable slack to easily release the cable end from the shift hook on hub. If you're going to run bare cable, you need to consider how you're going to create that slack.

6th is the second most efficient gear on a Nexus/Alfine 8. 4th is the least efficient.


PS - Folks fret over efficiency on IGHs. Nobody ever thinks twice about the efficiency difference among various derailleur gears. Unless you're going to time trial or randonneur on this IGH bike, I wouldn't worry about it. But that's just me.

Not trying to derail the thread but.....

We very rarely get these 8 speed hubs in, but we have gotten some 4 speeds. We learned the easy way to set the cable anchor bolt for them by measuring 101mm from the center of the bolt to the end of the cable housing (shifter in lowest gear). Just curious is this the same measurement for the 8 speed hubs?

I’m following along on this. I’m new to 8 speed IGHs & have a Sturmey Archer on a recumbent trike. Anything I can learn about them in general is bound to be valuable.

That depends on which cassette joint you have. Every one I have dealt with (and it's a lot of them) have the 101mm spacing to the anchor but there is a long arm cassette joint that requires a longer setting.

On my chrome cruiser with a Nexus 7 I've used a continuous run of spiral-wound housing for nearly 20 years, and once I get the hub properly adjusted I've had no problems keeping it that way. A 7-speed IGH shifter pulls a lot more cable per increment than a comparable rear derailleur system.

Far be it from me to argue with what works, but the length of cable pull is far less important than the precision of the increments, so I will be sticking with compressionless.

...and I think we'll both be satisfied.

No braze-ons there but I am seeing plastic add-on under-BB guides, if I find one and tech on how to drill & tap the shell, I rather like the idea! :love: