Cycling UK Forum

Nettled Shin wrote:

Mark Berry wrote:My Nexus 8 (Alfine with a roller brake) froze two mornings last week. I'm quite sure it was the hub - not the cable.MarkB

I find it surprising that the increased viscosity of your oil would prevent a change occurring at all. Would it not just be delayed? I hope you've not got any water inside your hub?
Just goes to show that hubgears can't be that inefficient, else you'd expect the 10s of watts lost to heat would keep the lubricants nicely fluid.

I've openned up the hub half a dozen times and seen so signs of water .

The thick oil seems to make something 'stick' rather than just get sluggish. I have a stiff climb on the way to work, which I did out of the saddle, with a slack changer cable, expecting a sudden, noisy change but just didn't.

I quite see your point about efficiency and warming. I recon these hubs are pretty efficient.

Maybe the cable route on this bike has one or more up-turned casing ends? If so, I'd set about re-arranging things. For whereas it's usually best to minimise the amount of outer casing - since that's where friction happens - outer all the way is a less bad alternative to water traps!

I learnt this years ago when front derailleur mechs used to have a short length of outer casing from the mech, under the bottom-bracket to a stop on the down-tube. This little U-tube of casing was ideally located to collect water, which rusted the casing and sometimes froze, so that operation of the front mech soon became sticky and it ceased to shift at all in really cold weather. I soon spotted the problem and after a few attempts to fill this U-tube with grease, simply ran a bare wire under the bottom-bracket shell. It wore the paint, but the mech worked better! Nowadays that routing is standard of course, and catered for by a piece of plastic.

Then in the 1990s some ignorant MTB designer thought the rear cable would work better routed higher above the mud, resulting in an up-ended casing on the seatstay. Many attempts have been made to seal those obvious water traps. Few of them really work - but that's okay because in mountain-biking it goes with the territory that the rider will have to spend almost as much time cleaning fettling their bike as riding it.

Actually there is one sealing system that works reasonably well. I use it on bikes where the cable cannot be re-routed. It's made by Transfil and comprises ferrules with teats that fit inside a plastic "straw" to cover the intervening bare cable.

CJ wrote:I learnt this years ago when front derailleur mechs used to have a short length of outer casing from the mech, under the bottom-bracket to a stop on the down-tube. This little U-tube of casing was ideally located to collect water, which rusted the casing and sometimes froze, so that operation of the front mech soon became sticky and it ceased to shift at all in really cold weather. I soon spotted the problem and after a few attempts to fill this U-tube with grease, simply ran a bare wire under the bottom-bracket shell. It wore the paint, but the mech worked better! Nowadays that routing is standard of course, and catered for by a piece of plastic.

I had the same trouble; campy used to do 'bare' stainless outer housing which at least let the water drain. I used 4mm nylon or PTFE compressed air hose and made a small hole in it to let the water out. This worked fine (better than a bare wire) and saves the paint; no good for a front mech where the outer stop is the bit that moves though!

CJ wrote:Actually there is one sealing system that works reasonably well. I use it on bikes where the cable cannot be re-routed. It's made by Transfil and comprises ferrules with teats that fit inside a plastic "straw" to cover the intervening bare cable.

On MTBs the seat stay cable route is preferable to the chainstay route provided it is sealed as you suggest. Even a simple underbracket guide gets clagged up eventually and of course 'enthusiastic' offroading involves bashing the BB on all sorts of peculiar things.... Shimano SP41 ferrules are available separately and do the business eg.

http://bike-x-perts.com/fahrradteile/bowdenzuege/ferrule-for-derailleur-housing-sp41-sealed-with-rubber-shield.html?___store=en&___from_store=de

I got mine (after the usual LBS-blank-look routine) from the 'woolly hat shop' -top blokes. Not sure the transfil ones can be had separately....?

Good to use these on an all-weather roadbike too if the cable runs down the seat stay.

cheers