Shimano Nexus Hub gears.

:shock: Bought Carrera bike fitted with these, with which I am impressed with, however I realise that the cabling ,ie length etc is not at all user friendly. removing the back wheel and disconnecting the cable at the wheel is practicaly impossable as there is a lack of adjustment?

Anyone the recognised expert on these? or is there a Shimano super service centre that knows the full ins and outs of this, most cycle shops just look blank if you ask?.

Thanks The Rat Gloucester area 07788510474

I'm probably the resident expert on all things Nexus.

What do you want to know?

Thanks,as the bike is set up it appears that a rear wheel puncture is a bit of a problem. The cable is designed to disconnect at the hub, this requires some slack cable perhaps as much as 18mm, to be able to rotate the connector and disengage. Unlike the drum brake fitted (Carrera Subway eight) with mid adjuster the only adjustment is at the handlebar and thats not a great deal. It may be that you are required to remove the twist grip unfeed the cable from the frame and then remove the wheel? seems like a bit of a chore. Surely Shimano would not have designed this, it appears to be the application of their gears to this Carrera bike is where thre is a design issue. Initialy my solution would be to make a bespoke cable and at the hub end remove the present end stop for the outer sheath and install an adjuster of 30mm or so. This you could then remove the cable and more easily adjust the aligning marks when setting up?
Aslo interested in preventing ingress of crap and lubrication I assume its some form of liquid greese. In fact any info is welcome. Recieved no book or any information at all, although have 30 years eng experience. The Rat

I have a similar Alfine hub bike and find Sheldon Brown is awlays a good start for info

This link is for the Nexus that may be of help

http://www.sheldonbrown.com/nexus-mech.html

Basically, Nexus was never designed for easy wheel removal. It was originally designed for commuter bikes with full chain guards and wotnot -- the sort of bike people PAY other people to work on.

It was never aimed originally at the type of bikes it became popular on in Denmark - sporty, chain-guardless bikes - and which now seem to be catching on elsewhere. This led to endless problems with seals and water getting into the hubs - which all appear to be sorted now.

Anyway, back on track.

The easiest way to get your wheel off (and I can end up doing this several times a day) is to drop the shifter down to the lowest gear which will free up slack in the cable. You then tug on the cable outer so it hops out of its slot near the sprocket. Undo the wheel and drop it out of the frame and unhook the cable. DO NOT UNDO THE CABLE NUTS unless you can remember where to put it again - it is millimeter critical. Barrel adjuster is a red herring - it's easy enough to do without one. Thinking again was that it should be as sealed and low friction a system as possible.

Alternatively, take the wheel out, then undo the plastic lockring and pull the changer system (proper name is cassette joint) off. The yellow dots will show you how to assemble it again.

Compared to quick release and derailleur gears it's a fiddly system but compared with SRAM super 7 it's a dream to work with when you get the knack. I remember the original versions and they wer a nightmare and Shimano really have improved it a lot since then.

Re. ingress of gunk....

Firstly check you have the correct hub version - 8 gear should be and 8R30+ - these have excellent seals. Earlier than that, you may need a dustcap upgrade.

Shimano never fitted grease ports as firstly it works better with oil ( they found out later) and secondly they didn't want idiots flushing hubs with WD40.

There is no easy service method unfortunately. But if used with the right dustcaps it shouldn't prevent any problems. Even in Danish conditions, if serviced once anually (pull innards out and dip in oil bath) it'll be fine.