"Streched' Gear Cables

[Li Mu Bai]

dont lube the cable, this just helps dust etc stick to it and foul the housing.

as for a cable snapping, this does happen. My partner suffered this occurrence on his rear deraileur at last years Sani - disaster as we had no spare.

[RiderX]

dont lube the cable, this just helps dust etc stick to it and foul the housing.

as for a cable snapping, this does happen. My partner suffered this occurrence on his rear deraileur at last years Sani - disaster as we had no spare.

 

Where exactly did the cable snap? The only place I can think of for this to happen is at the cable bolt where you clamp the cable. If this is done too often or the bolt is tightened too much, the derailleur cable can become worn here and possibly snap.

[RodTi]

Some posts were reported.

Nothing major - I've removed them and those related/quoted to keep the thread on track.

 

Nothing wrong with robust debate - but play the ball, not the man.

[Big H*]

Some posts were reported.

Nothing major - I've removed them and those related/quoted to keep the thread on track.

 

Nothing wrong with robust debate - but play the ball, not the man.

 

eish....

[Tumbleweed]

How are brakes cables made? I did a bit of a search and found articles about Bowden cables, etc, but want I want to know is how the wound steel in a cable is held together? The reason I ask is I thought about a huge brake failure I had at the Rhodes Challenege some years back. I had a fraying cable on my rear mechanical disk brake when I started the race. This died on the descent after Naudesnek. and I had to rely on my front brake after that. Towards the start of the last descent of the ride, I started losing feel of the front one too. Then the cable snapped on the concrete jeep track with rather scary results. I understand how heat affects fade in hydraulic systems, but this thread got me thinking. Could a transference of heat from the front brake pads to the cables have contributed to the failure? (I suppose this wouldn't happened in a rim-brake system because the rubber pads wouldn't conduct heat.) That the heat somehow affected the "elasticity" or "stretch" (sorry Minion) of the cable under stress? Or would the heat generated not be enough to affect this at all?

[RexFuzzle]

It is possible to heat treat steel to make it harder and thus also more brittle which I suppose is possible in mechanical discs but I doubt the heat transfer is enough to have any noticeable effects. In most cases I think it is strain hardening which is basically what causes a wire to break when you bend it back and forth repeatedly. Thus sharp corners are not good for cables.

[Minion]

How are brakes cables made? I did a bit of a search and found articles about Bowden cables, etc, but want I want to know is how the wound steel in a cable is held together? The reason I ask is I thought about a huge brake failure I had at the Rhodes Challenege some years back. I had a fraying cable on my rear mechanical disk brake when I started the race. This died on the descent after Naudesnek. and I had to rely on my front brake after that. Towards the start of the last descent of the ride, I started losing feel of the front one too. Then the cable snapped on the concrete jeep track with rather scary results. I understand how heat affects fade in hydraulic systems, but this thread got me thinking. Could a transference of heat from the front brake pads to the cables have contributed to the failure? (I suppose this wouldn't happened in a rim-brake system because the rubber pads wouldn't conduct heat.) That the heat somehow affected the "elasticity" or "stretch" (sorry Minion) of the cable under stress? Or would the heat generated not be enough to affect this at all?

 

Steel looses strength and stiffness with temperature, but it only starts becoming a major problem above 250°C or so. Up to that point, it still retains around 80-90% of its properties. I'm not sure if the brakes could generate enough heat for that. Of course, it might just have been enough to push it over the edge if there was some other defect already there.

 

Heat treating of steel occurs at temperatures above 600°C or so.

Edited May 8, 2012 by Minion

[Tumbleweed]

Steel looses strength and stiffness with temperature, but it only starts becoming a major problem above 250°C or so. Up to that point, it still retains around 80-90% of its properties. I'm not sure if the brakes could generate enough heat for that. Of course, it might just have been enough to push it over the edge if there was some other defect already there.

 

Heat treating of steel occurs at temperatures above 600°C or so.

 

Thanks for the answer.

 

And on the first part of my post, any idea of what holds the strands of a cable together?

[Minion]

Thanks for the answer.

 

And on the first part of my post, any idea of what holds the strands of a cable together?

Nothing much, aside from a bit of friction. The way they're wound means that if you pull on a cable, the strands want to get tighter together. If you push on it carefully, you can actually get the strands to separate (it's much easier to do this with string than wire, though). It also means that if a strand breaks, there's nothing really, aside from its own stiffness, stopping it from unravelling.

Edited May 8, 2012 by Minion