brake failure

Andrew Price

On Sun, 18 May 2008 13:01:55 -0700, "Tom Kunich" <cyclintom@yahoo.
com> wrote:

[---]

>For what it's worth, I've found the Dutch and Belgians seem able to speak
>more languages with less accent than even the Swiss.

"Even the Swiss"? You've never heard the Swiss speaking German or
French? They have an accent you can spot a mile away.

Martin Borsje

Tom Kunich expressed precisely :
>
> For what it's worth, I've found the Dutch and Belgians seem able to speak
> more languages with less accent than even the Swiss.

The Swiss have one common language: "money".

Tom Kunich

"Nate Nagel" <njnagel@roosters.net> wrote in message
news:g0q3bt02pds@news2.newsguy.com...
>
> The "noodle" is the little curved tube of metal that goes on the end of
> the brake cable housing. That's the only one-word name I've heard for it.
> Otherwise, it's "that little curved metal tube."

Ahh, that's what happens when you come in the middle of a conversation and
don't catch the fact that we're talking about V-brakes. Sorry about that.
Now it makes sense.

Tom Kunich

"Andrew Price" <ajprice@free.fr> wrote in message
news:7a41345i7ifpob0et2pm9gcpqvegifekoq@4ax.com...
> On Sun, 18 May 2008 13:01:55 -0700, "Tom Kunich" <cyclintom@yahoo.
> com> wrote:
>
>>For what it's worth, I've found the Dutch and Belgians seem able to speak
>>more languages with less accent than even the Swiss.
>
> "Even the Swiss"? You've never heard the Swiss speaking German or
> French? They have an accent you can spot a mile away.

In my experience they have an accent on purpose so that you don't mistake
them for a German or French..... I suppose that might be insulting if they
didn't have local dialects so that they can't be mistaken for someone from
10 km away from their birthplace.

Tom Kunich

"A Muzi" <am@yellowjersey.org> wrote in message
news:2561d$48309322$7670@news.teranews.com...
>
> Oh, I wasn't going anywhere with the humor, but linear brakes do have
> noodles and and, when the pad spacing is screwed up, the noodle really
> does hit the cable clamping bolt before braking. On your Campagnolo
> calipers this is not a problem!

I'm in the process of selling down my collection at the moment. But I may
have had as many personal bikes as you have in your store.... Yeh, I know -
really dumb. Now I'm down to about 10 and shrinking. By the way, some of
those were mountain bikes with V-brakes. Now I intend to keep just the one
cyclocross bike for offroad.

Brian Huntley

On May 18, 2:37 pm, A Muzi <a...@yellowjersey.org> wrote:
> I already suggested cantilevers rather than liner brakes to her weeks
> ago but those weren't readily available to her. Linear ("V") brakes are
> more prone to crud embedding and have rapid pad and rim wear. That goes
> double in dirt and rain.

Are you blaming the pads or the mechanics of the linear brake?

My current touring/commuting bike has cantilever brakes that use "V"
type pad (lots of surface area but thin.) For what it's worth, I do
find the pads wear quickly. Given that I ride in rain, snow, salt,
etc, that's to be expected, and at $4 a pair, I'm not too broken up
about it. What I really love is that I can change them out without
having to reset the brakes, something I never liked about traditional
cantilever brakes with smooth stud shoes.

A Muzi

> A Muzi <a...@yellowjersey.org> wrote:
>> I already suggested cantilevers rather than liner brakes to her weeks
>> ago but those weren't readily available to her. Linear ("V") brakes are
>> more prone to crud embedding and have rapid pad and rim wear. That goes
>> double in dirt and rain.

Brian Huntley wrote:
> Are you blaming the pads or the mechanics of the linear brake?
>
> My current touring/commuting bike has cantilever brakes that use "V"
> type pad (lots of surface area but thin.) For what it's worth, I do
> find the pads wear quickly. Given that I ride in rain, snow, salt,
> etc, that's to be expected, and at $4 a pair, I'm not too broken up
> about it. What I really love is that I can change them out without
> having to reset the brakes, something I never liked about traditional
> cantilever brakes with smooth stud shoes.

Although Kool Stop pads are better than oem (also not readily available
to Marian), linear systems promote rapid rim wear and seem to be more
prone to crud in the pads - whether it jams in faster or just scrapes
rim chunks into the pad faster I can't say.
--
Andrew Muzi
<www.yellowjersey.org/>
Open every day since 1 April, 1971
** Posted from http://www.teranews.com **

jobst.brandt@stanfordalumni.org

Andrew Muzi wrote:

>>> I already suggested cantilevers rather than liner brakes to her
>>> weeks ago but those weren't readily available to her. Linear
>>> ("V") brakes are more prone to crud embedding and have rapid pad
>>> and rim wear. That goes double in dirt and rain.

>> Are you blaming the pads or the mechanics of the linear brake?

>> My current touring/commuting bike has cantilever brakes that use
>> "V" type pad (lots of surface area but thin.) For what it's worth,
>> I do find the pads wear quickly. Given that I ride in rain, snow,
>> salt, etc, that's to be expected, and at $4 a pair, I'm not too
>> broken up about it. What I really love is that I can change them
>> out without having to reset the brakes, something I never liked
>> about traditional cantilever brakes with smooth stud shoes.

> Although Kool Stop pads are better than OEM (also not readily
> available to Marian), linear systems promote rapid rim wear and seem
> to be more prone to crud in the pads - whether it jams in faster or
> just scrapes rim chunks into the pad faster I can't say.

Having had many years to research brakes, starting with Universal,
pre-Campagnolo brakes, Weinmann, and various centerpull calipers, I
searched for several effects: 1) Embedded grit in pads, 2) Hand lever
braking force required and 3) brake pad wear rate. In that pursuit I
also measured mechanical advantage of various brakes and discovered
that contrary to he bicycling press, all calipers had a 1:1 ratio and
hand levers had 4:1. That is, the mechanical advantage was the same
for all brakes (Including Campagnolo when they took over the high
quality end of the business and having an excellent QR.

What I found was that Kool-Stop Salmon pads were the best, Campagnolo
a distant second, and Mafac, horrible in that they always chewed up
rims. Universal didn't come off well either. The most striking
feature of Kool-Stop pads was that even when riding through wet dirt
and picking up road mud and grit, the pads would clear themselves once
back on pavement by merely pumping the brake hard.

Not being one to worry about fashion and having a line of
practicality, I chose the Continental model because, unlike inserts
(typically in Campagnolo and Universal brakes) these pads could not be
accidentally knocked out of the pad holder when inserting a wheel,
something I observed happening a few times to the surprise of a rider
after a wheel change.

High pitch squeal is mainly caused by contamination on the braking
surface, mainly humidity, but also from soft drink splash or even
urine from roadside relief while standing astride the bicycle. Squeal
can be cleared up by heavy braking on a steep descent that gets rims
hot. It is not a matter of pad toe-in as is often claimed.

Just the same, toe-in occurs naturally because when braking hard
caliper arms bend forward in a way that makes the rear of the pad wear
faster than the forward end. I suppose someone noticed that well worn
pads seldom squealed AND that they had toe-in, which led to brutal
deformation of brake calipers. If this were a manually added feature,
then it should be added by running a rasp lengthwise across the brake
pad, not by bending brake calipers.

http://www.koolstop.com/brakes/index.php
--
Jobst Brandt

jobst.brandt@stanfordalumni.org

Andrew Muzi wrote:

> That's all generally helpful but the specific bike here has linear
> ("V") brakes, which not only have a ratio with greater cable travel
> and greater pressure at the rim for a given effort at the lever, but
> are notorious for chewing rims and pads.

Maybe you can tell me what is "linear" about these brakes and what the
MA (mechanical advantage) is. Appearances can deceive. It was once
believed that centerpull brakes had twice the MA of sidepull calipers
based on the length of caliper input levers on which the straddle
cable acts. This ignored that there are two of these, which divides
that apparent MA in two.

Other than these considerations, more pad force does not affect
whether they develop grit or not.

Jobst Brandt

A Muzi

> Andrew Muzi wrote:
>> That's all generally helpful but the specific bike here has linear
>> ("V") brakes, which not only have a ratio with greater cable travel
>> and greater pressure at the rim for a given effort at the lever, but
>> are notorious for chewing rims and pads.

jobst.brandt@stanfordalumni.org wrote:
> Maybe you can tell me what is "linear" about these brakes and what the
> MA (mechanical advantage) is. Appearances can deceive. It was once
> believed that centerpull brakes had twice the MA of sidepull calipers
> based on the length of caliper input levers on which the straddle
> cable acts. This ignored that there are two of these, which divides
> that apparent MA in two.
>
> Other than these considerations, more pad force does not affect
> whether they develop grit or not.

"Linear" a.k.a. "Direct Pull" a.k.a. "V" type brakes really are
different from all other cable actuated bicycle brakes. Here are the
lurid details, provided by Sheldon from beyond the grave:

http://www.sheldonbrown.com/canti-direct.html
--
Andrew Muzi
<www.yellowjersey.org/>
Open every day since 1 April, 1971
** Posted from http://www.teranews.com **

jobst.brandt@stanfordalumni.org

Andrew Muzi wrote:

>>> That's all generally helpful but the specific bike here has linear
>>> ("V") brakes, which not only have a ratio with greater cable
>>> travel and greater pressure at the rim for a given effort at the
>>> lever, but are notorious for chewing rims and pads.

>> Maybe you can tell me what is "linear" about these brakes and what
>> the MA (mechanical advantage) is. Appearances can deceive. It was
>> once believed that centerpull brakes had twice the MA of sidepull
>> calipers based on the length of caliper input levers on which the
>> straddle cable acts. This ignored that there are two of these,
>> which divides that apparent MA in two.

>> Other than these considerations, more pad force does not affect
>> whether they develop grit or not.

> "Linear" a.k.a. "Direct Pull" a.k.a. "V" type brakes really are
> different from all other cable actuated bicycle brakes. Here are
> the lurid details, provided by Sheldon from beyond the grave:

http://www.sheldonbrown.com/canti-direct.html

Sheldon isn't able to explain that maze of words today, in the absence
of picture or reasonable proof that the mechanical advantage is
significantly higher or lower between one brake and another, nor how
these differences were measured or verified. It sounds like the
explanations of the centerpull days where Mafac Racer brakes were said
to have twice the MA of, for instance, a Universal side pull.
Although commonly believed, it was not fact. From the wording of
Sheldon's text, it seems to be left over from those days.

I am unsure whether readers here are familiar with the term "bell
crank", an important mechanical device that escaped the understanding
of most high school physics students in my day, and apparently is no
longer used as an example of a simple mechanisms with special use.

http://www.flying-pig.co.uk/mechani.../bellcrank.html

Note: The MA is constant throughout the stroke. Similarly bicycle
brake levers and calipers do the same to a large degree, a
characteristic not commonly recognized, judging from discussions I
read and hear.
--
Jobst Brandt

Clive George

<jobst.brandt@stanfordalumni.org> wrote in message
news:483210c5$0$34531$742ec2ed@news.sonic.net...

> Sheldon isn't able to explain that maze of words today, in the absence
> of picture or reasonable proof that the mechanical advantage is
> significantly higher or lower between one brake and another, nor how
> these differences were measured or verified. It sounds like the
> explanations of the centerpull days where Mafac Racer brakes were said
> to have twice the MA of, for instance, a Universal side pull.
> Although commonly believed, it was not fact. From the wording of
> Sheldon's text, it seems to be left over from those days.

Um, the MA of linear brakes _is_ different to calipers and conventionally
set up cantis. That's why they have different levers and why getting them to
work on a bike with drop bars is a PITA. See also tektro mini-Vs. Or are you
being deliberately obtuse, coz I thought this was ancient knowledge?

> I am unsure whether readers here are familiar with the term "bell
> crank", an important mechanical device that escaped the understanding
> of most high school physics students in my day, and apparently is no
> longer used as an example of a simple mechanisms with special use.
>
> http://www.flying-pig.co.uk/mechani.../bellcrank.html

BPB sidewinder?

Tom Kunich

<jobst.brandt@stanfordalumni.org> wrote in message
news:483210c5$0$34531$742ec2ed@news.sonic.net...
>
> Sheldon isn't able to explain that maze of words today, in the absence
> of picture or reasonable proof that the mechanical advantage is
> significantly higher or lower between one brake and another, nor how
> these differences were measured or verified.

Visually the V-Brake appears to have a MA of about 2.5:1. From the feel of
it I also think that it has a significantly higher MA than a standard
sidepull brake. Is there some question about this?

jim beam

jobst.brandt@stanfordalumni.org wrote:
> Andrew Muzi wrote:
>
>> That's all generally helpful but the specific bike here has linear
>> ("V") brakes, which not only have a ratio with greater cable travel
>> and greater pressure at the rim for a given effort at the lever, but
>> are notorious for chewing rims and pads.
>
> Maybe you can tell me what is "linear" about these brakes and what the
> MA (mechanical advantage) is. Appearances can deceive. It was once
> believed that centerpull brakes had twice the MA of sidepull calipers
> based on the length of caliper input levers on which the straddle
> cable acts. This ignored that there are two of these, which divides
> that apparent MA in two.

but jobst, the two lever arms have the above leverage ratio. the
straddle cable divides the force on each, but two lever arms do not per
se reduce the m.a. and the straddle cable math is governed by its pull
angles.


>
> Other than these considerations, more pad force does not affect
> whether they develop grit or not.

red herring.