Shimano Nexus Rear Hub Cap Nuts - made of cheese?

[CAMRAMan]

I seem to have stripped the threads on the cap nuts of my Nexus rear hub. The serrated spacer washers are also somewhat worn down.


The hub is fitted to an electric bike, which may - or may not, make a difference.


There seems to be only 3-4mm of axle thread for the nut to grip on one side - though this will increase as the nut is tightened, but only by 2-3mm. Is that enough thread for a nut to fully grip the frame?


I've got replacement nuts and serrated spacers on the way, so I hope that fixes things, but I was wondering if anyone else has had this happen...?

[Brucey]

There seems to be only 3-4mm of axle thread for the nut to grip on one side ….. Is that enough thread for a nut to fully grip the frame?

No. There should be more than that.

FWIW if the e-power is routed through the IGH, the fitment will be unusually sensitive to any slack between the NTWs and the frame; the axle tries to spin both forwards and backwards, in high gears and low gears respectively.  With leg power alone and a little slack it tends to settle in the latter position and stay there.

However  with motor power as well the axle can rotate back and forth until it works loose. Often this causes so much damage the frame is ruined.

cheers

[mzjo]

I seem to have stripped the threads on the cap nuts of my Nexus rear hub. The serrated spacer washers are also somewhat worn down.

I've got replacement nuts and serrated spacers on the way, so I hope that fixes things, but I was wondering if anyone else has had this happen...?

1) Yes
2) They're not cheese; they're chocolate (which is why they get eaten!)

On a more serious note yes I stripped a lh nut on an Alfine 8 (same as the Nexus; SG501). I thought at the time that the reason waas possibly a torque reaction overtightening the nut due to the rh not being tight enough. I now keep a pair of nuts in stock. This was on a normal bike, not an e-bike. There isn't a lot of thread sticking out lhs but I think more than you have. The roadside fix would have been to swop the wheelnuts side for side, letting the longer axle rhs grip on the unused part of the ex-lh nut.

[vorsprung]

I have also broken an Alfine nut of this sort.  Doesn't always happen though have some that have lasted years and years

[Brucey]

FWIW the nuts are 3/8" x 26tpi which is a very common bicycle axle thread. Any bike shop will have nuts with this thread in.

cheers

[Kim]

I've noticed the nuts seem a little cheesy, and assumed this was strategic to prevent damage to the axle.

[CAMRAMan]

Thanks. That seems to confirm my opinion of their durability.

I bought the bike secondhand, so don't know how well it was treated prior to my ownership. It's useful to know the nut size, so I can get something other than Shimano to replace them if things go awry again.

[mzjo]

FWIW the nuts are 3/8" x 26tpi which is a very common bicycle axle thread. Any bike shop will have nuts with this thread in.

cheers

Not in my part of the world they won't; must be about as common as Alfine hubs (of which I have the only one I've ever seen). However it is useful to know that a proper imperial wheelnut should fit.

[Brucey]

Maillard/Normandy and all kinds of random British  nutted rear hubs were 3/8" x 26tpi and yer average cheap nutted rear hubs and some front hubs are still 3/8" x 26tpi. Any bike shop that has no nuts in this size is not worthy of the name.

Needless to say you don't need domed nuts, ordinary ones will do.

cheers

[CAMRAMan]

Nuts and washers arrived - eventually - and fitted today. All seemed to go together well, but I need a test ride post-rush hour to check they have fixed things.