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Old 10-07-04, 08:37 AM   #1
quemazon
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Full cable housing + rollamajig = bliss

Why do most bike manufacturers still insist on bare cables everywhere? Every time a cable goes in and out of a housing there is a point of entry for dirt and moisture. Then to compensate, they came up with "sealed" ferrules and "rain jackets" all of which add friction. Why all the complexity? It's especially ridiculous on top routed rear deraileur cables. One of the cable stops on the rear triangle actually faces upward, just waiting to swallow any moisture that comes in contact with your cable.

Why do frame builders still go crazy with the cable stops? I don't understand. A cable stop must be more difficult and costly to make than a simple cable stay, and it adds a point of weakness to the frame.

So anyway, I have decided to take a stand. I drilled out all of the cable stops on my commuter and ran full housing. Then I installed a rollamajig on the rear derailleur, and now I'm in bliss. Shifting is smooth and effortless and there's practically no way water can get into the housing to mess things up. I'll admit, this is only on my commuter (old junker frame). I still don't have the nerve to put the drill on my $2K Gary Fisher. But, every day of smooth shifting on my commuter takes me one step closer.
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Old 10-07-04, 08:44 AM   #2
bnet1
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Wow, I wonder if that would work on recumbents with their LONG cable runs?

'bent Brian
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Old 10-07-04, 09:27 AM   #3
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What's a rollamajig?
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Old 10-07-04, 09:40 AM   #4
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Originally Posted by Sloth
What's a rollamajig?
The bend that cable housing has to make to get to the rear derailleur causes a lot of friction and premature failure of the housing. The rollamajig solves this problem very nicely. It costs less than $10 and will make and immediate improvement in your shifting (that's been my experience, anyway).
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Old 10-07-04, 10:34 AM   #5
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When you pull on the cables a compression force is put on the housing. This force shortens the housing in proportion to its length. The frame of the bike can resist this compressive force much better than the housing. So bike manufacturers keep the lengths of housings as short as possible, to achieve the most precision in trahsferring movement from the brakes levers and shifters to the business end. All your improvement comes from the rollamajig and not from the superlong housings.

Good point about water entry when the cable is vertical. This is particularly bad with the cable for the rear brake on 'ladies' bikes. If I work on one of them, I split that housing in two at the lowest point so there is a place for the water to drain out.
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Old 10-07-04, 10:57 AM   #6
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On lots of nice road frames they have internal cable routes.
My mtb has 2 x-posed wires, I think they look o.k.

Thanks about giving me the idea to cut cable stops off. Thats all I need to worry about today. I got a saw and files right in the bike room...hmmmmm..what to do...?
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Old 10-07-04, 11:25 AM   #7
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So bike manufacturers keep the lengths of housings as short as possible, to achieve the most precision in trahsferring movement from the brakes levers and shifters to the business end.
That's understandable for the rear brake, but the shifters/derailleurs apply very little force on the cable housing so there is effectively no compression. Plus, those housings are made to be compressionless.

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All your improvement comes from the rollamajig and not from the superlong housings.
Mostly, but not completely. On a standard rear derailleur routing there are 4 cable stops (plus the ends at the sifter and derailleur). Each one of them causes extra friction on the cable, especially if the end hasn't been properly opened up after cutting. Further, if you want to add sealed ferrules and boots you increase the friction even more. On top of that, if your housing isn't cut VERY perpendicularly, it will either a.) not meet flush with the cable stop, and act as a sping in your housing or b.) skew slightly in the cable stop causing friction with the cable. In the even that you actually get all of the housing cut and installed perfectly, the best you could possibly do is get it as good as a full run of housing, with the disadvantage that you now have 4 more places for nasties to get inside your housing. The overall effect is that a full housing will have less friction and last longer.

As for the rear brake, you can now get compressionless brake housing that has a kevlar jacket. The only real advantage that I can see with cable stops is that you can save a few grams of weight.
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Old 10-07-04, 11:31 AM   #8
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Originally Posted by jeff williams
Thanks about giving me the idea to cut cable stops off. Thats all I need to worry about today. I got a saw and files right in the bike room...hmmmmm..what to do...?
I'd suggest drilling them out instead of cutting them off. They work as great stays to run the housing through.
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Old 10-07-04, 11:39 AM   #9
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Originally Posted by quemazon
I'd suggest drilling them out instead of cutting them off. They work as great stays to run the housing through.
Ah...I can chop one tho- I run a mono-ring front, no der.
Good idea though, will consider the full cable housing\ drilling.

Last edited by jeff williams; 10-07-04 at 08:30 PM.
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Old 10-07-04, 12:57 PM   #10
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The stops dont increase friction, since there is no side force on them. They increase dimensional stability - however since the change-over from spiral wound housing to longitudinal reinforced housing, this is less of an issue. Manufacturers may just be doing this from force of habit.
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Old 10-07-04, 01:17 PM   #11
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The stops dont increase friction, since there is no side force on them.
No, but cable housing that isn't cut and prepared properly (not necissarily trivial, BTW) certainly does have higher friction. Plus, any sealed ferrules and such will increase friction. The bottom line is that a full run of housing will almost always have less friction than one with multiple cable stops.

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Manufacturers may just be doing this from force of habit.
I suspect you're right.
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Old 10-08-04, 07:43 AM   #12
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Why not just run your cable housing and use zip ties,leave the cable stops,at least till your sure you like the full length housing, no since ruining a frame,once the cable stops are gone you have real problems if you ever want them back
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Old 10-08-04, 07:50 AM   #13
Michel Gagnon
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Quote:
Originally Posted by quemazon
[About Keeping housing runs short to avoid compression:]
That's understandable for the rear brake, but the shifters/derailleurs apply very little force on the cable housing so there is effectively no compression. Plus, those housings are made to be compressionless.

... On a standard rear derailleur routing there are 4 cable stops... Each one of them causes extra friction on the cable, especially if the end hasn't been properly opened up after cutting...

I'll throw in a few observations:

1. "Compressionless housing" or SIS housing used for derailleur cables is not totally compressionless. The brake housing with a spiral cable within has actually much better compression resistance, which is why SIS housing should never be used for the brakes. The problem with spiral wounding is that the housing lenghtens when it is bent around, which explains why brake pads move by 1-2 mm when one turns the handlebars, but also why brake housing doesn't work too well with indexed shifting.

2. As far as full cable housing vs limited housing, I don't think it makes too much of a difference with good cable and good housing. Good housing costs money too; I don't know how 3 ft of housing compares to 2 extra brazeons plus a bottom bracket guide, but it's probably equivalent. Besides, if one uses housing, one needs clips, tie wraps or brazed on guides for the housing.

3. Bare cables always travel in a straight line. Housed cable doesn't. My 1980 commuter has a housed brake cable, which follows a sinuous line on the top of the top tube. Not as nice. Besides, housing is now sold in black, sometimes in white and in fluo colours, so it's hard to conceal housing on a beige frame (which had beige housing 20 years ago). However, if you don't have the doughnuts, the bare cable may flap in the wind (especially with v-brakes set at a fairly low tension), but housing flapping in heavy wind is even noisier (though it doesn't happen often).

4. Housed cables can travel where you want them to go. Don't like the bend near the chainstay? Make a more gracious curve.

5. In terms of rain or grit accumulation, there was a problem with derailleur cables when they used housing for the bend near the bottom bracket. Not as much a problem with open metal or plastic guides. Fenders and mudflaps help keep the road grit away.

6. You are right about the importance of good cuts, especially with regard to added friction point.

7. In winter, I find that less housing is better. Less to grease, less to maintain.
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Old 10-08-04, 07:54 AM   #14
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and can you get them in China?
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Old 10-08-04, 09:56 AM   #15
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I'm not such a big fan of full housing, because I had a bad experience with it.

I used to have a bike with full cable housing. It was fine until it went through a winter, when the shifting got gummy. It turns out that salt and water that had entered through the back end of the housing and had no way to leave, so it caused about a foot of cable to rust. I ended up replacing the whole housing, but since none of the few-foot sections I had lying around were long enough, I had to go spend $24 on a 6-foot run of housing at the shop. With shorter segments, replacing just a part would have cost a lot less money.

From then on, I decided to use stainless cables, but given enough salt and water, even stainless can corrode. Even without corrosion, the housing can get gummy if dirt gets inside. Then you have to replace the whole thing.

Even if you use sealed ferrules on the back end, water can still get in from the front end, where the housing meets the shift lever. And once water and dirt gets in there, it stays there, so it seems to me that you'd have to replace the housing periodically anyway.

You may be able to go longer between replacements with full housing (plus a sealed ferrule at the rear) but when you do, you'll have to replace a lot more of it, so it seems like a wash to me. If you could seal up both ends, that's a different story. Then maybe you could use a cable+housing set forever.
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Old 10-08-04, 10:04 AM   #16
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i thought the whole point to using a rollamajig is to get away with using a *shorter* rear cable housing!! isn't that like using fork boots on a rigid fork?
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Old 10-08-04, 10:54 AM   #17
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till now I have never disagreed with anything Michel Gagnon has said, and I have profound respect for his wisdom on bicycles, but here goes. The reason for not using SIS housing for brakes is that derailler cables are smaller diameter, so brake cables are liable to jam in SIS housings.
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Old 10-08-04, 12:08 PM   #18
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Quote:
Originally Posted by AndrewP
till now I have never disagreed with anything Michel Gagnon has said, and I have profound respect for his wisdom on bicycles, but here goes. The reason for not using SIS housing for brakes is that derailler cables are smaller diameter, so brake cables are liable to jam in SIS housings.
Wrong.

Quote:
Compressionless "Index-compatible" Housing

With the advent of indexed shifting combined with handlebar mounted shift levers, it developed that conventional housing was a source of imprecise shifting. This is because the effective length of the housing changes as it is bent. This is not a problem with brakes: Although sometimes it will be noted that rear brakes may drag slightly when the handlebars are turned all the way to one side, you can't turn the bars that far when the bike is actually in motion.

This small variation in housing length was too much for reliable indexed shifting, however, so Shimano introduced "S.I.S." housing, now widely copied by other manufacturers. This type of housing does not consist of a single spiral-wound wire, but a bundle of wires running pretty much straight along parallel to the housing. They are held in place by the fact that they are sandwiched between the plastic housing liner and the plastic outer covering.

"Compressionless" housing doesn't change length significantly as it is flexed, so the indexed shifter is able to communicate the correct setting to the derailer, even as the handlebars are turned, and the loops of cable housing bounce up and down due to bumps.
Quote:
Warning: Since compressionless housing relies on plastic to hold it together, it is not as strong as conventional spiral housing, and should never be used for brakes! The loads applied to brake cables can easily cause compressionless housing to rupture and burst, causing a complete and sudden loss of brake function.
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Old 10-08-04, 02:22 PM   #19
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Thanks for the explanation
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Old 10-08-04, 02:25 PM   #20
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Originally Posted by AndrewP
Thanks for the explanation
Don't thank me, thank Sheldon Brown. Most of the stuff I've learned over the years about bikes has roots in what he's written.
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Old 10-08-04, 07:25 PM   #21
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Quote:
Originally Posted by AndrewP
till now I have never disagreed with anything Michel Gagnon has said, and I have profound respect for his wisdom on bicycles, but here goes. The reason for not using SIS housing for brakes is that derailler cables are smaller diameter, so brake cables are liable to jam in SIS housings.

True. That's another very obvious reason. However, some derailleur cable housings have a fairly large diametre, and I suspect one could physically insert a brake cable into them. I haven't tried, though.

P.S. Thanks Raiyn for stating more clearly what I had in mind.
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