Author Topic: Cables?  (Read 2934 times)

Thomas777

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Cables?
« on: February 05, 2017, 11:33:40 PM »
As a new Rohloff owner, well actually my wife's bike!, I have question. Are the cables that used just regular derailleur cables?
 

bobs

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Re: Cables?
« Reply #1 on: February 05, 2017, 11:40:00 PM »
The cables are 1.1mm dia for the inner cable.

Bob

rualexander

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Re: Cables?
« Reply #2 on: February 06, 2017, 12:20:45 AM »
Or standard 1.2mm gear cable, doesn't really matter.

Dave Whittle Thorn Workshop

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Re: Cables?
« Reply #3 on: February 06, 2017, 09:49:52 AM »
Quote
Or standard 1.2mm gear cable, doesn't really matter.

The important thing is the head diameter, only 1.1mm Rohloff, Fibrax and Sram cables have the correct diameter head. 1.2mm cable heads unless filled down tend to damage plastic cable drum in the shifter. Rohloff cables are also ground wire so tend to flow better round the pulley in the shifter and EX Box so do give a smoother shifter feel.

rualexander

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Re: Cables?
« Reply #4 on: February 06, 2017, 04:34:58 PM »
Ok fair enough, you're the expert Dave.
I've never had any problems using standard cables though.

RST Scout

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Re: Cables?
« Reply #5 on: February 25, 2017, 01:04:52 AM »
Out of interest, do you need to leave the bike in a particular gear if you're not going to use it for a few days (or longer). I was advised many moons ago to leave my Brompton with it SRAM hub in a gear that prevents chain stretch. Does the same apply to a Rohloff?

Janet
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rualexander

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Re: Cables?
« Reply #6 on: February 25, 2017, 01:29:17 AM »
Out of interest, do you need to leave the bike in a particular gear if you're not going to use it for a few days (or longer). I was advised many moons ago to leave my Brompton with it SRAM hub in a gear that prevents chain stretch. Does the same apply to a Rohloff?

Janet

No

Matt2matt2002

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Re: Cables?
« Reply #7 on: February 25, 2017, 08:52:03 PM »
Am i correct in thinking that the cables are not under any tension when at rest? And so no need for any special position.
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bobs

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Re: Cables?
« Reply #8 on: February 25, 2017, 08:55:56 PM »
The cables are not under tension at all.

David Simpson

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Re: Cables?
« Reply #9 on: February 25, 2017, 09:50:52 PM »
I don't know about the Rohloff with the internal shifter, but I just replaced the cables on my Nomad, which has the Ext Box shifter, so I know how the Ext Box cables work.

There are two cables that go from the shifter on the handlebar to the Ext Box at the rear wheel. On the handlebar shifter, one cable winds around the shifter clockwise, and the other cable winds around counter-clockwise. So when you twist the shifter, you are winding in one cable and winding out the other cable.

At the other end of the cables (in the Ext Box), there is a pulley, and the cables also wind around the pulley in opposite directions. When one cable is winding in, the other cable is winding out.

It is just like the chain on your bike. When you pedal forwards, the top part of the chain is pulling (winding in) and the bottom part is releasing (winding out). When you pedal backwards, it is the opposite. Now imagine that instead of a single chain in a loop, you cut the chain horizontally at the front of the chainring and the back of the sprocket, so that the two halves of the loop (the top half and the bottom half) are separate lengths of chain, not a single loop. When you pedal slightly forward, the top length of chain is pulling and the bottom length is being released. When you pedal slightly backward, the bottom length is pulling. I say "slightly" because you could only pedal for about half a turn, since the place where you cut the chain cannot go past the top or bottom position. (It's hard to describe, but easy to see if you draw it out.) The Rohloff twist shifter is the same, using cables instead of lengths of chain. When you turn (twist) the shifter, you are turning the pulley in the Ext Box.

The only time there is tension in the cables is when you are twisting the shifter and moving the cables. When the shifter is not being twisted, neither cable has tension, just as there is no tension in your chain unless you are pedalling.

- DaveS

Javier

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Re: Cables?
« Reply #10 on: February 25, 2017, 10:58:20 PM »
Last time I changed the EX box shifter cables of my Rohloff I realised how tricky this can be if you do not have a very sharp pair of nipper pliers with you (I have them). If the pliers do not cut clean and fray the end of the wire then it will be very difficult, if not impossible, to put all the strands of the cable through the tiny hole of the pulley. Besides, it you tighten the no-head bolt of the pulley too much it will fray the end of the wire and you will be in trouble if in the future you want to take the cable out of the pulley, as it will be almost impossible to put back the cable through the wee hole of the pulley. And if you remove a frayed cable out of the housing then it will fray even more if you try to put it back through the housing.
I also tried to tape the cable, also glue it at the end (Loctite) but it does not help a lot, despite what many people say. The best, by far, is to cut the cable with a sharp pair of pliers and silver solder the end, so the cable will not fray no matter how many times you mess around with the cable. I have also silver solder the brake cable ends, and leave then without end caps.
I found out about all this by playing with the old cables that I was replacing. Now I have a great respect to a shifter cable replacement, and I know you can be in deep trouble if you make a mess when you have only one spare cable with you when touring.
Next time I tour I might take with me pre-cut cables with the ends silver solder, although I am not totally happy with this idea in case I damage the housing and then the cables are too short, as a pre-cut cable has to be, exactly, 200 mm longer than the housing (Rohloff manual).
So as a piece of advice, and basically when touring, do not underestimate how tricky to change the shifter cable can be, no matter how easy it looks in the manual or in the Rohloff official video. In my opinion the tiny hole of the pulley is the problem maker.
« Last Edit: February 26, 2017, 03:28:21 PM by Javier »

David Simpson

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Re: Cables?
« Reply #11 on: February 25, 2017, 11:19:37 PM »
Javier --

I completely agree. I bought a pair of cable cutters, and that makes all the difference for cutting the cables. On a cable cutter, then cutting blades are curved to hold the cable together as it cuts, so that the end of the cable doesn't separate and fray.

SJS sells them: https://www.sjscycles.co.uk/search/?term=cable%20cutters

However, there is still the problem of the cable ends being frayed by the small holding screws in the Ext Box pulley. I have made the mistake of inserting the cables into the wrong holes in the pulley, and needing to cut off the frayed end in order to insert them correctly. As you said, once the cable end becomes frayed, it is a hopeless nightmare to attempt to insert the cable into the pulley hole.

Here are the lessons that I have learned:
  • Use a proper cable cutter.
  • Cut the cable (and cable housing) 2 or 3 cm longer than you need. If you make a mistake and fray a cable end, then you will need to cut off about 1cm. Starting with 2 or 3 cm extra will allow you to make 2 or 3 mistakes. Remember that you can always cut a cable shorter. You can never make it longer. If you do need to start again, SJS will happily sell you a replacement cable/housing set, as they have done for me. ;)
  • Check very carefully about which cable to insert into which hole in the pulley.
  • Insert the cables into the pulley, but do not tighten the small holding screw yet. Check the cables again.
  • Only tighten the holding screws in the pulley after you are certain that the cables are correct.

If I was going on a longer tour, I would definitely pre-cut the cables and housing to the proper length (+ 2 or 3 cm) and solder the cable ends to prevent fraying.

I found that the Rohloff manual is very well written. However, the procedure is one of those things that is easy to show, but hard to describe. I found myself reading the relevant paragraphs several times before I figured it out. Once I figured it out, it was rather straightforward to do.

- DaveS

Edit: To clarify, when I say "2 or 3 cm longer", I mean the entire cable and housing, not the cable extending beyond the housing. The cable must be cut 200mm longer than the housing (see the Rohloff manual).
« Last Edit: February 25, 2017, 11:22:56 PM by David Simpson »

Thomas777

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Re: Cables?
« Reply #12 on: February 26, 2017, 12:05:14 AM »
Great few posts! I am building up my wife's bike with a Rohloff and will make up a set of cables with sodered ends. We will be riding across Canada this summer.

mickeg

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Re: Cables?
« Reply #13 on: February 26, 2017, 12:53:01 AM »
Great few posts! I am building up my wife's bike with a Rohloff and will make up a set of cables with sodered ends. We will be riding across Canada this summer.

I am not sure which hub you have, my comment is specific to the one with the EX box.  Solder might not work too well if the solder makes the cable too fat to fit in the hole and the cable has to wrap around a fitting so the solder should extend a very short distance up from the end.

I think I used standard Shimano type cables with that size head on the cable.  I had heard that a special size head was needed, but when I did the work I found that not to be the case.

I use Sram cable cutters, but have not used others enough to offer any insight as to which is best.  But the Sram ones have performed quite well for both inner and outer cable cutting.  It has a awl that can cleanup the cut end on the outer housing.