dabac

Hi guys,

I'm looking to flip a bike with a 7-speed Nexus hub.
Doesn't seem to be heavily ridden, but its been left outside - no roof - for a considerable time.
Only thing that's obviously wrong is the indicator in the shifter that's out of synch.
Any pointers on how to fix that?
While riding, it does feel like all gears engage as they should, but it also feels like the hub runs "dry" - if that comparison is understandable.
Do these hubs dry out and need relubing?

Do I need to pull it apart for that?

I've looked at the disassembly instructions, and it didn't look too bad.
Is it that simple, or are there any hidden complications?

(I have worked on IGHs before, replaced an axle on a S-A 3-speed for instance)

Or should I leave well enough alone and sell as-is?

wschruba

The inside does need to be regreased/oiled, as they come from the factory greased (and sparsely, at that). The procedure is fairly simple, as you've noted; pull the cassette joint, sprocket, and RH dust cover (snap-on or screw-on, left hand thread, depending on the model), unfasten the left cone entirely, allowing the internals to be withdrawn from the hub shell. You don't touch the RH cone/wheel bearing during normal service (and indeed, it's not possible on most Shimano IGHs, without the proper drifts to remove/install it).

The proper grease is fairly thin stuff. I imagine finding a local supply of something thin enough would be difficult enough that you should just bite the bullet and buy the Nexus grease. For home service, without total disassembly of the internals, you should drop them in/otherwise inundate then with oil; ATF is a popular choice, if not wildly off label usage...20wt non-detergent oil works fine (so, 3-in-1 small-engine oil).

The easiest way of dealing with it, without a dipping vessel, is to grease the LH bearing, grease the bearings/clutches on the internals, then tilt the hub shell on its axis, so the bottom of the right and left bearing races are level with each other. Nearly fill the space you created (a few mm below spilling), then insert the internals, and install the left cone (don't flip the wheel RH side down while doing this). Grease the hell out of the exposed bearing on the RH side, then put the dust cover back on, followed by all the other stuff, and adjust the LH bearing as necessary.

Racing Dan

"Do these hubs dry out and need relubing?

Do I need to pull it apart for that?"

I have an inter 8 bike. The factory lube was very dry/stiff grease. It did get a dry feeling after some time. To lube it without disassembling all the tiny parts, pull out the whole mechanism, from the drive side, and lube it with gear oil in an oil bath. I used generic gear oil, as the Shimano oil is very expensive, and I just brushed the oil on the mechanism with a brush. Worked out very well.

From my experience you can not "fill the hub with oil". I tried that, but the oil leaked out the big black seal/dust cover in the drive side. You can try it out, but be prepared for some clean up. I believe dunking/brushing it generously and letting it drip for at while, before reassembly, is the way to go.

dabac

Ok, Thanks all.
Time allowing I'll have a go at it this weekend.

dabac

Pulled the hub apart today. Found the culprit. DS wheelbearing dry. Probably should be replaced. No parts available. Settled for a clean and lube instead. Disassembly became a bit more thorough than intended. Fumbled a bit at the first reassembly attempt. Didn't think of which way I held up. And suddenly had parts all over the floor.
Am awaiting the results of the test ride with some trepidation...

JaccoW

1. Go to Sheldon Brown's website for maintenance manuals and part lists so you know what goes back where.
2. Go look up the part number on Hollandbikeshop.com and get the necessary replacement parts. There are a ton of bikes with these hubs driving around and while they should be pretty bomb proof (most Dutch people just leave them standing outside most of the time) but they certainly appreciate a bit of love from time to time.
3. Triple check your gearing cable settings. If they are slightly off the hub will feel like crap.

Mickey2

To adjust the 7 speed Nexus gears there's usually an indicator near the hub-wire end. Mine had a two red marks that should be aligned to get adjustment right. The shifter was to be set for 4. gear when adjusting, but this migh vary a bit between models. I have sneakily opened the side of 7 speed Nexus hubs and added oil meant for the Alfine hub, as well as another synthetic oil. It works fine, but it needs to be added now and then, and it's a bit of a fuzz to have the wheel, and parts off to get access to the inners.

dabac

I found the service manual a bit misleading. Mine showed a hub w/o the attachment for the shifter cable, but with the DS locknut in place. Not really a "natural" configuration IMO.

Anyhow, I found enough 3/16" balls to replace the DS wheel bearing, so I went ahead with that. The new balls stuck a lot better in the cage, so I think I'm OK there. Hub felt considerably smoother. It seems to shift OK, although I tend to run out of consistent road conditions before I've really sampled all the gears.
So I think I'm good, and thanks for all pep and support.

28027

Hi there. This is an old thread but i have a similar problem with a nexus 7, model SG-7R50.

Itīs not mine, is from a friend. She asked for help and i though it shouldnīt be so difficult. Big mistake. First i saw a tutorial where it recomended fully dissasemble the sproket side for cleaning. Now i have a nut that if i thight it the sprocket stops turning freely, if i let loose, the mechanism wobbles.

Thatīs the first problem. The second, i did the oil bath and the mechanism started to roll much worse. Donīt know what happened, i used ATF oil. Wonder if someone had a similar problem or have a clue on what to do.

Thanks in advance.

Geepig

I am not familiar with that hub, but I suspect that nut might be used to set the clearance on the sprocket cones, much like one would do on a classic front wheel.
For the second issue, some hubs only work with sparse lubrication.

28027

Thanks for the answer and sorry for my english.

I have solved the first issue. The nut is supposed to sit in a kind of shoulder the axle has. My problem was that one of the pieces below was not fitting correctly on it's place. Found it, placed it and now i can adjust the nut withoul compromising the wheel turning.

For the second problem, i was skeptical with the oil bath but i saw Shimano has a videos about this process with a very similar model. I have been cleaning the excess of oil, put the grease back and assembled the hub. It turns pretty well, it shifts, but it also drags a lot (pedals keep turning). It didnīt happen so much when i did the oil bath so maybe it is necessary. Donīt know for sure, the oil bath leaves a great excess of oil that have been leaking and kind of dissolving the grease i put on the other attemps of assembling.

Now that i know how to assemble the hub properly maybe i'll give another try to the bath and see if the drag gets any better.

28027

I update myself. After the oil bath and greasing i put all back together but still have some drag in the pedals and also makes a not really pleasant noise when i try to ride. The wheel turns and it shifts gears but the noise came when it has to freewheel. Am kind of desperated with this thing.