Safety of splicing brake housing with electrical tape

[Gary Young]

This question has come up at a community bike shop where I volunteer:

When a long piece of brake housing is not available, is it safe to use
two smaller pieces end-to-end, with a wrapping of electrical tape around
the joint?

I have my own opinion on the issue, but I was hoping to get a more
authoritative reaction -- for instance, from engineers or bike shop
owners. Better still if you can point to some kind of authoritative
documentation on this question.

[AMuzi]

There's a cute little Shimano ferrule made just for that
(goes at the end of the tape so you can service damaged
cables without re-wrapping). Works well but costs more than
a complete double-ended wire with teflon lined casing, which
is probably what you seek. Those are dirt cheap.


Electrical tape? Really?
--
Andrew Muzi
<www.yellowjersey.org/>
Open every day since 1 April, 1971

[datakoll]

JEEEEEZ yawl get meals outta a dumpster or what ?

[John B.]

On Thu, 22 Mar 2012 21:59:31 -0400, Gary Young <garyy...@gmail.com>
wrote:

Well the "electrical tape" is a bit tatty but essentially there is no
difference then butting the cable into a cable stop somewhere.

--
Cheers,

John B.

[datakoll]

and he said "GOD MAKE IT A DREAM.."

electrical tape may not prevent a debutting with one cable end passing over the other....like the stuff was made to stick to itself in a pliable and yielding, conforming way

there just no telling what it'll do !!

[datakoll]

which is on second thought duhduhduhduh an answer. Place buttees next to tubing then wrap buttees to tubing and tape over tape, pulling tightly as wound over tube, fastening housing to tube and wollaaah you got it 1!!!

eeyeyehahahhahahahh....

so what's for breakfast ? any nused pizza ?

[Frank Krygowski]

I doubt you'll ever find an authoritative document on that. You won't
find one on using electrical tape to repair your car's brake lines,
either.

Although bike brakes are usually applied gently, they occasionally get
squeezed hard, even if just for a stationary test. So a bike's brake
cable needs to support a tension of perhaps 200 pounds (50 pounds grip
strength, 4:1 force multiplication). The housing needs to support
that same force in compression. Any slight misalignment of the two
ends will cause it to buckle at the splice, or at least shift out of
alignment to the point that the housing will be trying to saw the
cable in two.

If I were forced to try such a thing, I'd at least scrounge a close-
fitting metal tube to reinforce the joint. But it's so much simpler
to spend a buck or two on a new piece of housing, and just do the job
right.

- Frank Krygowski

[Chalo]

To directly address your question: As long as the housing ends that
are butted together are treated such that the cut surfaces sit flat
against each other and the cable remains taut at all times, there
would be no significant safety implications of using brake housing
that way. However, if the brake cable goes slack for whatever reason
(e.g. very loose adjustment, or brakes that fail to fully return due
to friction), movement and vibration could overwork and eventually
break the cable at the location of the housing joint.

My shop gets basic brake housing, with various colored jackets and
plastic liner, for $0.15 per foot. Other cable housings can be *much*
more expensive, but generic brake housing is cheap. If your community
bike shop has a wholesale account somewhere (and it should, for basic
consumables at least), then someone should pony up the few bucks for a
roll of the stuff.

I'll reuse housing if the jacket is in good shape, there are no kinks,
and the damaged ends are trimmed away. But if reused housing isn't
long enough to do the job, you should just use a piece that is.

Chalo

[m-gineering]

> Gary Young wrote:
>>
>> This question has come up at a community bike shop where I volunteer:
>>
>> When a long piece of brake housing is not available, is it safe to use
>> two smaller pieces end-to-end, with a wrapping of electrical tape around
>> the joint?
>>

the only reason to do this is to save a bar tape wrap. You can get
double sided cable caps (Shimano used to include them with some old
Ultegra stuff) or you can hide the joint with an inline cable adjuster.

Tape is just silly

--
/Marten

info(apestaartje)m-gineering(punt)nl

[DirtRoadie]

Provided that the respective ends of the cable housing are squared and
smooth (think dremel tool, file or grinding wheel) to butt against one
another solidly, this should work with little issue.
Look at the right figure here:
http://sheldonbrown.com/images/cable-cuts.gif

from
http://sheldonbrown.com/cables.html

However it would probably be desirable to avoid having such a butted
joint on any tightly curved section of cable.
The cable itself helps insure that housing alignment is maintained,
especially if it is not dramatically undersized with respect to the
inner diameter of the housing.

Note: This is not remotely akin to repairing a car's hydraulic brake
lines with electrical tape. That would be utterly foolish.

DR

[Sir Ridesalot]

Ask them if they are willing to risk a lawsuit if the housing join
fails when if the rider attempts and emergency panic stop and the
housing ends shift and the inner cable jams. I wouldn't do such a join
nor would I allow anyone to do it on any bike repair I had anything to
do with. In fact if I ever saw a bicycle co-op volunteer make such a
repair and the co-op allowed it I stopped volunteering there as I'd
never know what other potentially dangerous shortcuts they're possible
doing. Remember that a lot of the brakes on co-op bicycles are
marginal at best. Many people who buy co-op repared bicycles would not
recognize a potential failure of a brake cable join. Saving a little
bit on new brake housing is not worth the risk of falure in my
opinion.

Cheers

[Kerry Montgomery]

Gary Young,
I'm with the folks who say to not do this. But, if you must, it'd be safer
(less unsafe?) if you were able to make the join where the housing runs
along a frame tube, and securely tape the join to the tube.
Kerry

[thirty-six]

Soft electrical tape will do next to sod-all. Grind the ends exactly
perpendicular and if the sheath is adequate, it will hold the spiral
just as if it was continuous. As long as it isn't in a bend it
doesn't matter. If it is in a bend a short length of adhesive cable
sheathing such as Scotchtite will do the job of joining the outers
admirably.

[thirty-six]

On Mar 23, 5:18 pm, m-gineering <ikmotgeens...@m-gineering.nl> wrote:
> > Gary Young wrote:
>
> >> This question has come up at a community bike shop where I volunteer:
>
> >> When a long piece of brake housing is not available, is it safe to use
> >> two smaller pieces end-to-end, with a wrapping of electrical tape around
> >> the joint?
>
> the only reason to do this is to save a bar tape wrap. You can get
> double sided cable caps (Shimano used to include them with some old
> Ultegra stuff) or you can hide the joint with an inline cable adjuster.

Obvious choice if you have calipers and levers without adjusters and a
possible alternative to caliper adjusters on a racing bike, in fact
I'd say it may be a preferable position of adjustment particularly for
a cyclocross bike.

[thirty-six]

IME it's better to join quality housing with a good binding sheath
than it is to replace with a length of economy housing. I regretted
throwing away my Campagnolo housing the first time I did that. The
second time I had Campag' housing I kept it and spliced in a disposed
length from another rider's machine to make a good complete rear
cable. Extended experience shows joining not to be a problem with
good quality cables. It is also using equipment of proven
reliability.

[thirty-six]

On Mar 23, 3:41 pm, Frank Krygowski <frkry...@gmail.com> wrote:
> On Mar 22, 9:59 pm, Gary Young <garyyou...@gmail.com> wrote:
>
> > This question has come up at a community bike shop where I volunteer:
>
> > When a long piece of brake housing is not available, is it safe to use
> > two smaller pieces end-to-end, with a wrapping of electrical tape around
> > the joint?
>
> > I have my own opinion on the issue, but I was hoping to get a more
> > authoritative reaction -- for instance, from engineers or bike shop
> > owners. Better still if you can point to some kind of authoritative
> > documentation on this question.
>
> I doubt you'll ever find an authoritative document on that. You won't
> find one on using electrical tape to repair your car's brake lines,
> either.
>
> Although bike brakes are usually applied gently, they occasionally get
> squeezed hard, even if just for a stationary test.  So a bike's brake
> cable needs to support a tension of perhaps 200 pounds (50 pounds grip
> strength, 4:1 force multiplication).  The housing needs to support
> that same force in compression.  Any slight misalignment of the two
> ends will cause it to buckle at the splice, or at least shift out of
> alignment to the point that the housing will be trying to saw the
> cable in two.

Doesn't happen.

[Sir Ridesalot]

TheOP is talking about cable housing being used by a bicycle co-op. Do
you really think that they are putting Campy quality brake housing on
what is most likely going to be a beater bike? The inexpensive stuff
can compress and shift around at the best of times. For safety sake I
really feel that skimping on brake cable housing is penny wisebut
pound foolish.

Cheers

[thirty-six]

A splice is not going to stop a poor cable from squirming and neither
will it make matters worse. If the outers are buckling they are
unsuitabe and a better off the reel cable should be sought.

[Chalo]

Sir Ridesalot wrote:
>
> TheOP is talking about cable housing being used by a bicycle co-op. Do
> you really think that they are putting Campy quality brake housing on
> what is most likely going to be a beater bike? The inexpensive stuff
> can compress and shift around at the best of times. For safety sake I
> really feel that skimping on brake cable housing is penny wisebut
> pound foolish.

I've used a *lot* of Shimano, Campagnolo, Jagwire, and no-name brake
housing. Properly prepped and routed, all the plastic-lined stuff
works the same. I'll repeat myself if need be, but I hope that's not
necessary. I hope nobody here is dumb enough that they'll only do
proper prep and routing on cable housing they paid way too much for.

The real IQ test is that expensive long-lay cable housing with a
kevlar or other woven fiber jacket, which is supposed to make it
suitable for both brakes and index shifters. It may not burst when
used for brakes, but it's much squishier than normal helical wire
brake housing.

Chalo

[John B.]

Do you actually own a bicycle? That has cable operated brakes or
shifting?

How do you think that the cable ends, actually the cable housing ends,
are going to "debutt" ?

Of course they might assuming that the actual cable were to break, but
by then any movement of the housings has become immaterial.

--
Cheers,

John B.

[Gary Young]

Thanks to everyone who's responded. I have to admit that I thought --
and still think -- that this is a crazy idea. It seems to me that some
of those who think this is an acceptable practice believe that the
inner cable is enough to keep the walls of the two pieces of housing
lined up. However, I've been playing around with housing and cable and
that doesn't seem to be the case. Even with housing with a plastic
liner, there is still some play and I don't see why the two joining
faces wouldn't easily slip against each other, resulting in a
stairstep meeting of the cable walls. Wouldn't this narrowed opening
present a danger of fraying the cable over time? The problem would be
even more severe with unlined housing.

The other thing I've noticed is that it takes very little force to
create a v-shape bend at the juncture between the two pieces of
housing. I don't think it would take more force than might occur if
someone snagged the housing on a branch, for instance. By contrast,
unbroken housing, after being subjected to a similar amount of force,
returns to a nice smooth bend.

[Radey Shouman]

I vote for shrink wrap tubing, especially the red stuff.

[Sir Ridesalot]

On Mar 22, 9:59 pm, Gary Young <garyyou...@gmail.com> wrote:

I just went through my helfpful hints folder and found a blurb I
created on what to do if there isn't enough brake cable housing to
reach the rear brake. This method is almost as good as having brazed-
on rear brake cable housing stops. It allows you to use two shorter
pieces of housing to get enough housing for a rear brake.

Get two brake or rear derailleur cable housing adjustment bolts. Grind
or file (a flat on one side of each bolt where the housing would go.
Then cut off most of the bolt or you can skip that if looks don't
matter). Then insert one each of the so modified derailleur cable
housing bolts into the first and last cable guides on the bicycle. Now
you can attach two SHORT lengths of brake cable housing just as if the
bike had brazed-on cable shousing stops. You'll have an exposed run of
inner cable of about 12 inches between the two top tube cable guides.
This method looks most elegant if the bolts are cut so that they are
flush with the cable guides on the top tube - that is the bolts don't
protrude past the cable guide.

Hope this idea is of use to you.

Cheers

[DirtRoadie]

Are you making these observations with housing portions that have a
cable with tension on it inside? And with housing portions neatly
squared off to butt cleanly as has been suggested ?
What force is it that you think will make the housing sections slip
laterally? (it isn't coming from cable tension) If they slip laterally
so easily, how are they going to apply sufficient sideways force (so
as to cause abrasive wear to the cable?)
Sure you can "force" lateral displacement of the housing portions but
normal cable tensions are not going to cause it. And the tape will
maintain alignment against any minimal lateral forces. In fact, in
anything other than a perfectly straight run, the cable will tend to
lie against one side of the housing and keep the housing portions
aligned.
How many layers of tape are you using? More than one is probably
useful.

I don't think anyone has suggested that a cleanly butted and taped
junction will match intact housing in bending resistance, but you have
hypothesized an uncommon situation. And barring a kink of the inner
cable, once tension is reapplied the housing pieces will re-butt and
work essentially as originally configured.

Tape (or heat shrink tubing) has the advantage over metal tubing of
more positively sealing the housing against moisture or other
contaminants. But that could be reinforced with metal tubing if
desired. Small brass and aluminum tubing is readily available from
"hobbyist" sources. I know that the Ace hardware store here carries
this line:
http://www.ksmetals.com/products.html

While it is perfectly feasible, you needn't mate cable housings if you
choose not to.
DR

[Lou Holtman]

Op 24-3-2012 3:55, Sir Ridesalot schreef:

All this trouble to avoid spending a couple of dollars?

Lou

[Sir Ridesalot]

> Lou- Hide quoted text -
>
> - Show quoted text -

Sometimes the person doesn't have that couple of dollars at the
time.Some people are not that close to a bike shop. I have many brake
cable barrel adjusters from old brake calipers. A lot of times they
will slip under the cable guide without needing any modification. My
post upthread was given to allow someone to use short lengths of
housing in a safe manner.

Cheers