I commute on a bike (Carrera Subway 8) with hub gears and brakes, using the Shimano Nexus range of componentry. For a commuter / utility bike, I think hub gears (and to a lesser extent brakes) ought to be much the best setup.
This is some notes about my experiences.
My first hub gear only lasted two years before failing
catastrophically. Before it failed, it was running rough and dismantling it
after failure it was evident that it had let water inside and there was lots
of corrosion. It's not a pretty sight, but the full detail
(and nasty pictures) is listed on another page.
Amusingly (or not), it actually lasted less than one month over two years - I collected the bike on 21 October 2006 and the hub seized solid on 19 November 2008. The hub had a two year guarantee. Hmmmm. Yes I know that fitness for purpose is not constrained by guarantee periods. No I couldn't face the hassle of arguing about it with either Shimano or Halfords.
I've since heard from several owners of this specific model of hub that
theirs has done likewise. I think there is a design fault with the seals.
Other superficially similar models don't seem to suffer.
So, I bought a new hub.
The two hubs are externally pretty similar. Both are 'premium' Nexus 8.
The older one was a SG-8R25, the new an SG-8R36. Functionally, the new one has
a 'silent clutch' rather than a ratchet freewheel, but otherwise they are both
8 speed, roller brake compatible, and use the same shifter and connector.
What has changed is the sealing of the end where the innards are withdrawn.
On the old hub, the end of internal unit protrudes out through a plastic cap. The plastic cap is a tight press fit into the alloy shell - it rotates with the hub shell. The dark metal bits on the axle rotate with the sprocket, and the silver bits are fixed with the frame (ie, don't rotate). At the interface between silver and dark there is a lugged washer which is what the shift arrangements connect to - it's more visible on the new hub, but it's in the same place on the old.
On the new hub, the sealing is much more complex. The plastic push-fit cap is in the same place, but it now has ridges and lips and stuff on it. The outermost lip overlaps a new metal cover which is tightly clamped against the sprocket (ie, rotates with the sprocket).
If you imagine a drip rolling down the face from the top, on the old, it
would roll down the cap, then settle on the protruding (dark metal) axle.
It is now resting against a single wiper seal, behind which is all the
gubbins. On the new hub, however, it starts down the cap, is deflected
out on the lip, and if it drops off the tip of that lip, it is outside
the metal disk, and does not get to any seal. In fact, it will come up
against the sprocket, and
presumably be deflected off to the teeth and ejected. If the water does
get behind the metal disk, it still has the same seal to penetrate as on
the old. Whether this arrangement is enough of an improvement, only time
would tell.
Since the hub was behaving itself, I left well alone. However, in January
2010 (ie, after just over a year of daily commuter service) curiosity got the
better of me, so I opened it up.
I'm pleased to say the new hub is very nice inside. Yes it only has a little over half the mileage the other one had at failure (though actually it has done two Decembers and two Januarys, which is all the first hub managed), but it still has clean white grease, and nicely smooth-polished balls, rollers and races.
The contrast with the picture at the top of the page is quite striking!
The carrier at extreme left is what got mangled in the first hub.
This is exactly how it came out of the shell - I haven't cleaned it up or
re-greased anything at all here. All this is the original grease, after
about 14 months daily use, including two Decembers and two Januarys.
This is the race that those balls run on (I've wiped grease off this to look
at the surface).
The whole of the inside of the shell looks good
(this is also after being wiped clean).
At the same time, I've fitted the oil port I
first thought about when the new hub was brand new. There's
a whole page about the planning and implementation
of that. Given how well it's doing, I'm not sure it's needed, but I decided
it probably wouldn't hurt.
It's actually relatively easy to get into one of these hubs.
The 'maintenance manual' images accompanying my description here are copied from the truly excellent Sheldon Brown's web site. He has the full service manual online. It's actually for an older, non-premium, model (SG-8R20), but at least the first few steps follow the same dismantling sequence. Obviously, I can't guarantee that any particular hub you have will be exactly the same, but steps 1 to 10 work the same for both the SG-8R25 and the SG-8R36 that I have tried, and I've been told they work for an SG-8R30 as well.
This is as far as you need to go if the innards are OK. You can keep going following these instructions from the service manual if you must. I've never gone past step 10 of page 15, because soon past this point is tight metal to metal push-fit so you start hammering things using a special tool (see step 16 on page 16). At step 10 you can get grease well into the internals, so that's enough for me.
Just do it all backwards.
Actually, it's fairly obvious except the routing of the shifting cable. Fortunately, page 9 of the maintenance manual covers that (steps 7 to 9). Pay particular note to the bit about the 2mm allen key (in the box near the middle of the page) - this makes it much, much easier to reassemble.
The reason I refer to a 'proper job' is that actually, the easiest way to
re-lubricate is by dipping the internals in an oil bath. You only need to
do about half as much to achieve that - take the wheel out, shifter connector
thing off, brake off, undo the locknut and take cone and bearings out of the
left side. Now you can pop the innards out leaving the sprocket in place.
This assembly can then be dipped, keeping the plastic cover clear.
There's a Shimano dipping kit, with special oil, and even a plastic tub with a line on it so that when you dip the innards in the oil comes up to the right level. I bought one from Petra Cycles who seem better than most at having maintenance stuff and spare parts, certainly much better than my lbs who become incoherent if you quote part numbers at them.
The official illustration (shown here) has the sprocket and plastic cap off,
but I can't see any reason why you'd need to do that - you're not supposed to
submerge it that deep anyway, according to the pictures on the can.
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