Shimano Hub Gear Innards

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.

The rusty hub

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.

The new hub

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.

I ran the new hub in its standard configuration for about a year, and there's a page about the design changes and how the new hub performed during that time, including what the innards looked like at the end of it.

The Oil-Port Modification

I then 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 the new hub is doing, I'm not sure it's needed, but I decided it probably wouldn't hurt.

Long-Term Performance

There's a page about the performance a year after the oil port was fitted, when the hub is was almost two years old.

(Compare this with the picture at the top of the page - both mechanisms are about the same age. What's glistening wet in that picture is water, what's glistening wet here is oil.)

Now it's eight years old, so there's an eight years of use page too.


Obviously, I've dismantled my hubs several times. It's actually relatively easy to get into one of these hubs, and there's a page about how to open them up (and put them back together). If you don't want to modify the hub, you can re-lubricate with the same oil by dipping it, but you still need to open it up to do that.

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