Folding Bikes - Story about the Nexus-8 hub

Since there are a few people on the forum that use it, I thought you would be interested in something that just came over the Bike FRiday YAK group. You can pick up the discussion there if you are really interested.

................................

in reference to the Nexus-8 hub

I broke one, on a Pocket Llama. Every time I fold/unfold the bike,
the shifter goes out of adjustment. Ride it a while with the shifter
out of adjustment and you can destroy the hub. Royal PITA. Had it
apart a half dozen times both with and without the service manual, and
wasn't able to fix it (despite being something of an expert on the
repair of the Sturmey-Archer hub gears).

On that topic, would anyone be interested in buying a year old Pocket
Llama built for a 5'11" tall rider, with non-working Nexus 8 in the
rear wheel, working Schmidt SON hub generator front wheel and Inoled
20+ headlight? Comes with folding rack, and Brooks B-17 saddle,
broken in. If you don't appreciate Brooks, let me know and I'll ship
it without the saddle. Hoping for $600. Make me an offer.

Chip

--
Charles M. "Chip" Coldwell
"Turn on, log in, tune out"

Wow, I will be interested to follow this, since I just bought a Dahon Mu XL with a Shimano redline Nexus. I will have to carefully read the manuals to see if this is cautioned about or otherwise addressed.

Thank you for posting this thread, invisiblehand. This is one topic of interest to many here who are users of this brand of internal hub-even those who own other brands like the Sturmey-Archers and the Srams. I do wonder why the owner of this bike chose to work on a hub like this. Even the bike shop where I take mine do not work on these hubs. They told me when the hub breaks, they simply swap a new rim with the hub already on or build a wheel around the one of the customer's own choice. He has the same option available to him. I hope there is someone to point this out to him before he tries to dump the bike on someone else (that is one of the reasons why I no longer buy used bikes-I don't want to inherent someone else's headache or lack of warranty).

I don't know anything about the Nexus-7 and -8, but I can attest that keeping the Nexus-4 in adjustment is difficult.

You're supposed to line up two tiny little yellow marks, which should be pretty easy, but it turns out that when everything is covered with grime from your daily commute (who'da thunk it?) and it's all located somewhere on the other side of a pannier bag that's held on with zip ties, they get hard to see. So yes, it is a pain....

If it actually goes out of alignment as a result of a design flaw related to folding the bike, it seems that you might have a valid warranty claim against BikeFriday, for replacement of the hub/wheel.

Thank you for posting this thread, invisiblehand. This is one topic of interest to many here who are users of this brand of internal hub-even those who own other brands like the Sturmey-Archers and the Srams. I do wonder why the owner of this bike chose to work on a hub like this. Even the bike shop where I take mine do not work on these hubs. They told me when the hub breaks, they simply swap a new rim with the hub already on or build a wheel around the one of the customer's own choice. He has the same option available to him. I hope there is someone to point this out to him before he tries to dump the bike on someone else (that is one of the reasons why I no longer buy used bikes-I don't want to inherent someone else's headache or lack of warranty).

He wrote that he had a lot of experience with internal hubs. They can be fixed (at least the three-speeds can) so he probably gave it a stab.

By the way, a local bud and bicycle-mechanic-whiz Harvey replied to the YAK group and wrote the following:

....................................

I can't speak about all hub gear packages, but at least for the
Sturmey-Archers and SRAMs, I strongly recommend frequent checks that the
shifter is properly aligned at the hub ("fiducial marks correct"). With
the S/A and SRAM, if you're a bit loose in second gear, two things are
likely, and neither is fun:

1) gear slips into a neutral/freewheeling zone, rounding the gears as it
goes. Takes a while to destroy, but a good start.
2) when it slips, you dive. Crank goes straight down, immediately,
generally with painful effects one way or another. This is not highly
recommended as part of the zen of BF.

This is why I use a "Proper" indexing shifter designed to mate with the
hub, and will no longer use a regular bar-end shifter to control the hub
gear.

The Nexus and Rohloff may be different, but I have no experience with them.

harvey sachs
mcLean va
(for a quarter century or so, I've had and ridden a S/A "ASC" hub. This
is an actual 3-speed fixed-gear hub from the 40s and early 50s, and has
the same gear spacing as the 4-speed Sturmeys. It is just barely
possible to take advantage of the quirk described above to actually set
up a freewheeling neutral between second and high, but rather too chancy
for me to do regularly.) Sheldon Harris has diagrams of the hub on his
site.

If it actually goes out of alignment as a result of a design flaw related to folding the bike, it seems that you might have a valid warranty claim against BikeFriday, for replacement of the hub/wheel.

Well, Bike Friday will put anything you request on the bike. Although they usually warn you of its particularities.

I wonder why this doesn't seem to be an issue for other folders ...

EDIT: Maybe it has to do with the distance between the shifter, hub, pivot point, and the method that the cables take to the rear. They can flop quite a bit on the Bike Friday.

Wow, I will be interested to follow this, since I just bought a Dahon Mu XL with a Shimano redline Nexus. I will have to carefully read the manuals to see if this is cautioned about or otherwise addressed.
The Mu is probably set up differently, so other than just checking the alignment I don't think you will have this issue.

I assume the root cause of the misalignment is related to the fold method, where the rear triangle folds in such a way as to affect the slack on the chain.

This was discussed here (http://www.bikeforums.net/showpost.php?p=3648208&postcount=836) in the Swift thread.

Almost all BFs have vertical dropouts. I've seen pictures (http://www.bikefriday.com/node/1000) of a BF built with a Nexus 7, and using some sort of tensioner like the Surley Singleator, to make up for not having horizontal dropouts. Don't know much about the subject, but could this contribute to it going out of adjustment frequently?

Or it could just have been a defective hub.

I've had no issues with my Swift and the Nexus 8R25. Honestly I have never ever had to even adjust it yet. Maybe the frame fold is the secret here. While BF makes good bikes, I am sure at times they have made something that wasn't quite as good as the other ones. I never thought of my BFs as a commuter bike but more as a travel bike.

I have noticed that the SA 8 speed is more sensitive to adjustment than the Shimano is. As my cable stretched on the SA I had to adjust it a few times.

In general any time you travel with a bike its not a bad idea to check everything before you ride. While I always checked my Swift, it never needed adjustment. My Dahon SpeedPro on the other hand required a lot of tweaking everytime it came out of the suitcase.

Keep in mind that folding moves components in ways the original designer may have not imagined. Just keep an eye on everything anyway. Consider it part of your pre-flight checklist.

Bike Fridays often have cable problems. There is always a compromise.

I first met Chip at the '03 PBP, I wonder what bike he'll ride this year.

I had the 8-speed Nexus on my Dahon P8. It's now on my Swift. I agree that the fold pattern on the Dahon caused all of my cables to be compromised somewhat. It felt like after 2-3 folds, I would need to adjust the cables to the rear portion to maintain the proper tension. The swift doesn't suffer from this nearly as much. I would imagine it's worse on Bike Friday's based on the anecdotal evidence with their cable routing.

I had a Nexus 8 for nine months. After riding one pacific northwest rainy season the seals didn't hold up and allowed water to get into the hub which eventually fouled the grease. Over time this made the hub very grindy and harder to pedal. I think the internals (and grease) needs to be checked once or twice a season in a wet climate, but finding a mech to work on them is difficult. Anchor bolt adjustments are no fun either. I've been thinking about building up a more maintenance free commuter using a single speed rear wheel, derailleur for tension and just a triple crank for gear range.

Would one of those cable splitters have helped?

A cable splitter ...

Pro: you are forced to adjust shifter cable tension every time you unpack/unfold the bike, so at least you're checking it "regularly"

Con: you are forced to adjust shifter cable tension every time you unpack/unfold the bike, and a wrong adjustment is fatal to the hub and risky for the rider.

I had a Nexus 8 for nine months. After riding one pacific northwest rainy season the seals didn't hold up and allowed water to get into the hub which eventually fouled the grease. Over time this made the hub very grindy and harder to pedal. I think the internals (and grease) needs to be checked once or twice a season in a wet climate, but finding a mech to work on them is difficult.
Does your bike have full fenders and a decent mud flap on the front?

Sheldon "Dry" Brown

Is it true there's a hole in the bottom of a Nexus where you can let out all the ground pepper after a days riding? :)

I guess there is a reason people buy internally indexed Rohloffs. Do Sram and sturmrey archer have the same adjustment problems.

Well, Bike Friday will put anything you request on the bike. Although they usually warn you of its particularities.

I wonder why this doesn't seem to be an issue for other folders ...

EDIT: Maybe it has to do with the distance between the shifter, hub, pivot point, and the method that the cables take to the rear. They can flop quite a bit on the Bike Friday.

This isn't a problem on any of my Dahon folders and I've had three. I think the OP destroyed her hub by riding it out of allignment and just needs to buy a new one and replace the internals.

I also happen to think Bike Friday has issues with regards to cabling of their bikes. You always hear how someone received the bike and needed to take it an LBS for a turnup.

Dahon has an unattractive system where the cables are extra long but this allows the bike to fold and unfold without having to adjust the shifter.

The only internal gear hub I've used is my SRAM dual drive, but I haven't had a problem with it after riding it in all kinds of weather and 3000-4000 miles. I've been through rain, sleet, and snow and have used both the original shifter and Shimano Sora road brifters without a problem. I am interested in maybe using a 7-8 gear internal hub for one of my folders though. I've been following this thread and am now undecided.

Juan

Does your bike have full fenders and a decent mud flap on the front?

Sheldon "Dry" Brown


My bike is a current model, had factory fenders, mud flap, chainguard and was dealer serviced a few months prior to the problem. I had previously owned another Nexus 8 bike and two Nexus 7 bikes, that never got wet and were perfect. Up until my problem, I thought the Nexus was the perfect drivetrain. It is a bit disturbing that many (most?) dealers don't work on these hubs, but just replace them. It would also be nice to see internal hubs with lube ports again.

[EDIT] Sorry, ignore this. The forum is acting odd today, switching up posts and shuffling them into the wrong thread

This thread really is about the design of the Pocket Llama, not the faults of the Nexus 8. The Nexus goes out of allignment when the cable is stretched. To bring it into allignment the cable tension is reduced. So the design of the bike, and the placement/length of the cables, and then the riding the bike with the Nexus 8 out of allignment would have damaged the hub. The hub didn't destruct because it was a Nexus.

It is a bit disturbing that many (most?) dealers don't work on these hubs, but just replace them. It would also be nice to see internal hubs with lube ports again.

Most dealers won't work on them because an hourly mechanics rate working on a used Nexustakes a chunk out of the value of a new hub and most mechanics are still derailleur-centric...and not because of some innate fault with the Nexus itself.

This thread really is about the design of the Pocket Llama, not the faults of the Nexus 8. The Nexus goes out of allignment when the cable is stretched. To bring it into allignment the cable tension is reduced. So the design of the bike, and the placement/length of the cables, and then the riding the bike with the Nexus 8 out of allignment would have damaged the hub. The hub didn't destruct because it was a Nexus.

Well, it seems to me that it is hard to decompose the problem that way. For instance, the indexing mechanism in the Rohloff is in the hub itself. So the cable stretching described apparently has little/no effect on the hub.

Anyway, the point of the thread is if you have an internal hub that cost less than a $1000 USD then you should check the alignment every once in a while and/or learn to recognize when it is out of alignment.

A cable splitter ...

Pro: you are forced to adjust shifter cable tension every time you unpack/unfold the bike, so at least you're checking it "regularly"

Con: you are forced to adjust shifter cable tension every time you unpack/unfold the bike, and a wrong adjustment is fatal to the hub and risky for the rider.

I don't think this is true: you shift to smallest cog (least derailleur tension), undo the cable splitter then fold the bike. Then the cable housings aren't being pulled as much as the fold pulls the cable inside the housing instead of the housing itself.

While I haven't used these for a folding bike yet, I have used them for 2 S&S frames I have. I really didn't have to fool with derailleur adjustments after undoing these.

So,

con: needing to split cable everytime you fold (at least on davinci designs ones , the ferrule is large enough you can do this with your bare hands)

pro: things stay in adjustment

This thread really is about the design of the Pocket Llama, not the faults of the Nexus 8. The Nexus goes out of allignment when the cable is stretched. To bring it into allignment the cable tension

I think it would be better to say that it's the cable [length] installation, not the bike design itself. Add $2 worth of new cable housing to make the derailleur portion 2 feet longer and less susceptible to misalignments during folding.

con: needing to split cable everytime you fold (at least on davinci designs ones , the ferrule is large enough you can do this with your bare hands)

pro: things stay in adjustment

I stand by original comments. I have a travel bike with S&S couplers. If one isn't careful, it is possible to reconnect the cable splitters without their being fully seated, which adds length to the cable run = hub out of adjustment.

BTW, S&S has some good hints at http://www.sandsmachine.com/guide_s.htm .

For those not familiar with cable splitters, see http://bessasandackerman.com/blog/?p=14 (pix near the end)

I stand by original comments. I have a travel bike with S&S couplers. If one isn't careful,

Weren't you talking about a folding bike in your original post, though ("unpack/unfold")?

S&S are too time consuming for me. A good indicator of when the coupler has become undone a bit is when the shifting starts making noise. Then most likely the sleeve needs to be retightened, because what you said above has happened: a small amount of "extra" frame has appeared throwing off the shifting. I think there's maybe max 1-2 mm tolerance before you start to have the noise.

jasong, I think I was talking about both, folders and separables, anything with cable splitters. I've found that if I don't get the metric wrenches out to tighten each cable splitter when reconnecting, the high tension on them will quickly loosen them. IOW, finger tight is asking for trouble.

reconnecting, the high tension on them will quickly loosen them. IOW, finger tight is asking for trouble.

That's never been an issue for me. Both S&S frames have the davinci splitters. What kind do you have? I've only finger tightened mine, in fact. PS - at least the shifter cables aren't under high tension, it's very low. You can pull these cables with your fingers and maintain proper tension. That's not the case for the rear brake splitter, but we're talking about shifting performance.

Since there are a few people on the forum that use it, I thought you would be

IH - please see private message.

PS - at least the shifter cables aren't under high tension, it's very low.

??? I agree, low tension on the smallest cog ... what about tension at cogs 2 to 9 or 10?

"Most dealers won't work on them because an hourly mechanics rate "

Are there enough Nexus problems to justify learning how to repair them? I doubt the typical bike shop mechanic ever looking inside one. They have a lot of parts, not something you can figure out without training or study.

Are there enough Nexus problems to justify learning how to repair them? I doubt the typical bike shop mechanic ever looking inside one. They have a lot of parts, not something you can figure out without training or study.

Probably not ... although it is hard to tell whether the few problems are due to small numbers of Nexus 8 internal hubs, high reliability, or both. As someone else posted earlier, if you look at the hourly labor charge, it might be the case that it is more cost effective to simply replace the hub than try to repair it.

??? I agree, low tension on the smallest cog ... what about tension at cogs 2 to 9 or 10?

Same tension, different position. You can shift youself with by pulling a cable with your fingers.

In regards to my Nexus failure comments: my use of this bike was as an off-season rainy day commuter. I rode this bike in drenching winter rains. I believe that the hub could have been saved if the mechanic cracked open the hub and inspected the grease (proprietary grease from what I understand). Replacing the fouled grease and being aware that there was a seal problem would have saved it. However, at the hourly shop rate, it won't take long before you spend enough to buy a new hub. It is all hind site now, but an expensive lesson.