Problems with mechanical disc brake

On Thu, 22 Jul 2004 09:34:32 +0200, Benno Pütz <[email hidden]>

Quoted message said:

I am currently building my new bike and have decided on mechanical disc
brakes (road version) from Avid with Ultegra STI levers.

My problem now is that after doing all the adjustments the brakes felt
rather soft (spongy?) - I could pull both levers all the way to the
handle bar with only relatively weak effects.

Seeing a lot of flexing in the brake cables, we replaced the housing (so
far only for the rear brake) with housing from a shifting cable and
found a marked improvement in performance. The brake acts much more
directly and blocking the wheel was no problem (as I would have expected
from the reviews I have seen).

I checked back with AVID's web site and found they have a
"compressionless Flak Jacket cable housing", however their (former)
German distributor did not even know about this housing and expected any
"normal" brake vable housing to work ...

So my question would be if others had similar experiences and what kind
of housing do you use?

Thank you in advance for any help or suggestions

Shifter cable housing is not safe to use for brake cable; it can
collapse under that much tension. It sounds like the first cable
housing was merely a very poorly made type; there are many good ones
available, and you can probably trust what is used by the people at
your local bike shop. It's also possible that the calipers are
improperly adjusted. Check the clearance between the fixed pad and
the disc; if it's too large, the brakes will not fully engage despite
large amounts of lever travel.
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Werehatrack said:

On Thu, 22 Jul 2004 09:34:32 +0200, Benno Pütz <[email hidden]>

Quoted message said:

I am currently building my new bike and have decided on mechanical disc
brakes (road version) from Avid with Ultegra STI levers.

My problem now is that after doing all the adjustments the brakes felt
rather soft (spongy?) - I could pull both levers all the way to the
handle bar with only relatively weak effects.

Seeing a lot of flexing in the brake cables, we replaced the housing (so
far only for the rear brake) with housing from a shifting cable and
found a marked improvement in performance. The brake acts much more
directly and blocking the wheel was no problem (as I would have expected

Quoted message said:

from the reviews I have seen).

Quoted message said:

I checked back with AVID's web site and found they have a
"compressionless Flak Jacket cable housing", however their (former)
German distributor did not even know about this housing and expected any
"normal" brake vable housing to work ...

So my question would be if others had similar experiences and what kind
of housing do you use?

Thank you in advance for any help or suggestions

Shifter cable housing is not safe to use for brake cable; it can
collapse under that much tension.

I should have added that this was only done to allow a quick check of
the suspicion mentioned, not as a long-term solution.

Quoted message said:

It sounds like the first cable
housing was merely a very poorly made type; there are many good ones
available, and you can probably trust what is used by the people at
your local bike shop.

I actually build it at my LBS so I would not have questioned their
choice of housing. It was the mechanic who suggested swapping the
housing to see if anything would improve ...

Quoted message said:

It's also possible that the calipers are
improperly adjusted. Check the clearance between the fixed pad and
the disc; if it's too large, the brakes will not fully engage despite
large amounts of lever travel.

I think I did that ... But I'll make sure to check it during my next
visit, probably tomorrow.

Benno P=FCtz said:

I am currently building my new bike and have decided on mechanical disc=

=20

Quoted message said:

brakes (road version) from Avid with Ultegra STI levers.
=20
My problem now is that after doing all the adjustments the brakes felt =

Quoted message said:

rather soft (spongy?) - I could pull both levers all the way to the=20
handle bar with only relatively weak effects.
=20
Seeing a lot of flexing in the brake cables, we replaced the housing (s=

o=20

Quoted message said:

far only for the rear brake) with housing from a shifting cable and=20
found a marked improvement in performance. The brake acts much more=20
directly and blocking the wheel was no problem (as I would have expecte=

d=20

Quoted message said:

from the reviews I have seen).

This is potentially quite dangerous. Most modern shift housing uses=20
longitudinal wires, which makes it stiff, but not as strong as the=20
spiral-wound wire of traditional ("brake"😉 housing.

If you use indexed shift housing for a brake application, it will likely =

work very well until it suddenly ruptures and the brake fails completely.=

Check out my article on cables and cable prep:

http://sheldonbrown.com/cables

Sheldon "Sometimes You Need To Follow The Rules" Brown
+----------------------------------------------------------+
| And what are all these mysteries to me, |
| Whose life is full of indices and surds? |
| x^2 + 7x + 53 |
| =3D 11/3 --Lewis Carroll |
+----------------------------------------------------------+
Harris Cyclery, West Newton, Massachusetts
Phone 617-244-9772 FAX 617-244-1041
http://harriscyclery.com
Hard-to-find parts shipped Worldwide
http://captainbike.com http://sheldonbrown.com

I have the avid for road on my bike. They work fantastically (very
strong). If you're having sponginess it sounds like the brake pads are not
optimally aligned, if you can't get them close enough without rub on the
pads, it could be that the rotor is warped (both of mine were warped from
the manufacturer), they can be easily straightened with a set of pliers.

Initial set up is not for the casual user or for a low quality LBS, these
are precision parts and require expertise. I use stock (off the roll)
housing for front and back, and I can lock the wheels like their glued to
cement with one finger on each lever.

"Benno Pütz" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

I am currently building my new bike and have decided on mechanical disc
brakes (road version) from Avid with Ultegra STI levers.

My problem now is that after doing all the adjustments the brakes felt
rather soft (spongy?) - I could pull both levers all the way to the
handle bar with only relatively weak effects.

Seeing a lot of flexing in the brake cables, we replaced the housing (so
far only for the rear brake) with housing from a shifting cable and
found a marked improvement in performance. The brake acts much more
directly and blocking the wheel was no problem (as I would have expected
from the reviews I have seen).

I checked back with AVID's web site and found they have a
"compressionless Flak Jacket cable housing", however their (former)
German distributor did not even know about this housing and expected any
"normal" brake vable housing to work ...

So my question would be if others had similar experiences and what kind
of housing do you use?

Thank you in advance for any help or suggestions

Benno

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Benno Pütz said:

I am currently building my new bike and have decided on mechanical disc
brakes (road version) from Avid with Ultegra STI levers.

My problem now is that after doing all the adjustments the brakes felt
rather soft (spongy?) - I could pull both levers all the way to the
handle bar with only relatively weak effects.

Make sure that you are using V-brake levers to pull these brakes;
cantilever brake levers or drop bar levers will not work (unless you
have the type of Avid brakes designed for drop bar levers.)

Use regular brake cable housing, but make sure it is of good quality
and that the ends are filed flat for a good fit inside the ferrules.
Use smooth-drawn 19 strand brake cable and avoid the 49 strand kind,
which stretches more.

Chalo Colina

Benno Pütz said:

Seeing a lot of flexing in the brake cables, we replaced the housing
(so far only for the rear brake) with housing from a shifting cable
and found a marked improvement in performance. The brake acts much
more directly and blocking the wheel was no problem (as I would have
expected from the reviews I have seen).

Umm. Locking wheel is easy with dual pivots (one finger pressure is
enough) and single pivots (might take two fingers). For that matter
centerpulls, cantilevers and V-brakes can all lock of the rear wheel
easily.

Sheldon Brown <[email hidden]> wrote in message news:<[email hidden]>...
<snip>

Quoted message said:

Quoted message said:

Seeing a lot of flexing in the brake cables, we replaced the housing (s

o

Quoted message said:

far only for the rear brake) with housing from a shifting cable and
found a marked improvement in performance. The brake acts much more
directly and blocking the wheel was no problem (as I would have expecte

d

Quoted message said:

from the reviews I have seen).

This is potentially quite dangerous. Most modern shift housing uses
longitudinal wires, which makes it stiff, but not as strong as the
spiral-wound wire of traditional ("brake"😉 housing.

If you use indexed shift housing for a brake application, it will likely

work very well until it suddenly ruptures and the brake fails completely.

There is "compressionless" housing made specifically for brake
systems:
http://www.biketoolsetc.com/index.cgi?id=25125659884&d=single&c=Repair%20Parts&sc=Cable%20and%20Housing&tc=Casing-Brake&item_id=JW-BCHKEB99
or
http://tinyurl.com/5ljjw

Manufacturer's site: http://www.jagwire.com.tw/frame.htm

Jeff

Werehatrack <[email hidden]> wrote in message news:<[email hidden]>...

Quoted message said:

On Thu, 22 Jul 2004 09:34:32 +0200, Benno Pütz <[email hidden]>

Quoted message said:

I am currently building my new bike and have decided on mechanical disc
brakes (road version) from Avid with Ultegra STI levers.

My problem now is that after doing all the adjustments the brakes felt
rather soft (spongy?) - I could pull both levers all the way to the
handle bar with only relatively weak effects.

Seeing a lot of flexing in the brake cables, we replaced the housing (so
far only for the rear brake) with housing from a shifting cable and
found a marked improvement in performance. The brake acts much more
directly and blocking the wheel was no problem (as I would have expected
from the reviews I have seen).

I checked back with AVID's web site and found they have a
"compressionless Flak Jacket cable housing", however their (former)
German distributor did not even know about this housing and expected any
"normal" brake vable housing to work ...

So my question would be if others had similar experiences and what kind
of housing do you use?

Thank you in advance for any help or suggestions

Shifter cable housing is not safe to use for brake cable; it can
collapse under that much tension. It sounds like the first cable
housing was merely a very poorly made type; there are many good ones
available, and you can probably trust what is used by the people at
your local bike shop. It's also possible that the calipers are
improperly adjusted. Check the clearance between the fixed pad and
the disc; if it's too large, the brakes will not fully engage despite
large amounts of lever travel.

Derailleur housing works just fine if you use the types designed for
brake use such as Avid's Flack Jacket system. Jagwire makes a linear
housings & cable stop ferrules that are suitable for brake usage.
These are JW-Kevlar94 housing & JW-CC182 cable stop ferrules as shown
pages 32 & 33 of Bike Tools etc. catalog #2. www.biketoolsetc.com
(someday I've got to learn how to make a link)
John

Thanks for all your contributions - I'll give the Jagwire housing a try
first. Have to order it, though.

Benno

Thanks for all your contributions - I'll give the Jagwire housing a try
first. Have to order it, though.

Benno

Jeff Wills said:

Sheldon Brown <[email hidden]> wrote in message news:<[email hidden]>...
<snip>

Quoted message said:

Quoted message said:

Seeing a lot of flexing in the brake cables, we replaced the housing (s

o

Quoted message said:

far only for the rear brake) with housing from a shifting cable and
found a marked improvement in performance. The brake acts much more
directly and blocking the wheel was no problem (as I would have expecte

d

Quoted message said:

from the reviews I have seen).

This is potentially quite dangerous. Most modern shift housing uses
longitudinal wires, which makes it stiff, but not as strong as the
spiral-wound wire of traditional ("brake"😉 housing.

If you use indexed shift housing for a brake application, it will likely

work very well until it suddenly ruptures and the brake fails completely.

There is "compressionless" housing made specifically for brake
systems:
http://www.biketoolsetc.com/index.cgi?id=25125659884&d=single&c=Repair%20Parts&sc=Cable%20and%20Housing&tc=Casing-Brake&item_id=JW-BCHKEB99
or
http://tinyurl.com/5ljjw

Manufacturer's site: http://www.jagwire.com.tw/frame.htm

Jeff

Thanks for the suggestion.
I got the brake set yesterday and had it put in. Now the brake is great.
Even though I have not yet relly broken it in ...

Benno