Safety of splicing brake housing with electrical tape

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.

John B. writes:

On Thu, 22 Mar 2012 21:59:31 -0400, 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?

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.

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

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

On Mar 22, 9:59*pm, 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?

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 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

On Mar 23, 7:53*pm, Gary Young wrote:
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.

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

Op 24-3-2012 3:55, Sir Ridesalot schreef:
On Mar 22, 9:59 pm, Gary 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 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


All this trouble to avoid spending a couple of dollars?

Lou

On Mar 24, 4:27*am, Lou Holtman wrote:
Op 24-3-2012 3:55, Sir Ridesalot schreef:





On Mar 22, 9:59 pm, Gary *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 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

All this trouble to avoid spending a couple of dollars?

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