brake failure

Tom Kunich said:

Quoted message said:

Quoted message said:

> 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.

Quoted message said:

Quoted message said:

Quoted message said:

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?

Quoted message said:

Quoted message said:

This is getting more wishy-washy with each response and is similar
to the claims to which I referred about center pull and cantilever
brakes in times gone by. No measurements were made, just
conjecture.

Quoted message said:

No Jobst, I actually MEASURED the distances from the fulcrum and it
was about 2.5:1. I say about because of the adjustments for the shoe
placement.

I didn't notice that anyone mentioned dimensions in this thread or
that measurements were made and how. I just find the language used
for brakes is misleading and asked what is "linear" and what the MA of
the brake mentioned is. Just because the cable moves farther doesn't
prove that this difference isn't canceled by the caliper leverage.

Quoted message said:

I can't quite understand what you're arguing - that V-brakes don't
have the mechanical advantage claimed or that there's something
wrong with that idea.

I feel the word "arguing" is inappropriate. I asked what the
effective MA of the brake is from hand lever to brake pad amd what
made it "linear". This problem is made clear by the dual pivot that
reduced pad clearance to accommodate the higher overall MA, human hand
stroke remaining constant.

--
Jobst Brandt

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

Quoted message said:

Tom Kunich said:

No Jobst, I actually MEASURED the distances from the fulcrum and it
was about 2.5:1. I say about because of the adjustments for the shoe
placement.

I didn't notice that anyone mentions dimensions in this thread or that
measurements were made and how. I just fine the language used for
brakes is misleading and asked what is linear and what the MA is in
the brake mentioned. Just because the cable moves farther doesn't
prove that this difference is canceled by the caliper leverage.

After all these years you should be more than prepared for the inaccurate
language used by most people when talking about mechanical things.

I used a metric tape measure to measure the distance to the brake shoe
center and to the cable attachment point. The leverage of the (Shimano XT)
unit was approximately 2.5:1. We don't need precision here.

Quoted message said:

I asked what the effective MA of the brake is from hand lever to brake pad
amd what
brake pad amd what made it "linear".

OK, we know that since they are rotating that they cannot be "linear" if
you're using the pure definition. But this world is full of misnamed things.

Quoted message said:

This problem is made clear by the dual pivot that
reduced pad clearance to accommodate the higher overall MA, human hand
stroke remaining constant.

The other problems are that the the pads wear to the unusable point a great
deal faster since they move a lot less. It is far too possible to lock the
front wheel with all that MA.

In the dirt that's not much of a problem but at the moment I'm recovering
from a rather nasty fall because one of these modern clipless pedals
released my foot in a high speed turn and it stuck in the front wheel spokes
breaking the carbon fork off and laying me into the emergency hospital. I'm
recovering rapidly and thank heavens that I didn't get any serious injuries,
but plainly there is a possibility of putting too much braking force on a
wheel.

Quoted message said:

This is getting more wishy-washy with each response and is similar to
the claims to which I referred about center pull and cantilever brakes
in times gone by. No measurements were made, just conjecture.

Measurements, part one:
On the bike I rode in today with a Weinmann type 500 sidepull*, the
cable stop to centerbolt center is 61mm. Centerbolt to center of pad is
55mm.

On a new V equipped bike near me now, cable stop to brake pivot is
111mm. Brake pivot to center of pad is 36mm.

SP- 61:55 or 90.1%
V- 111:36 or 32.4%

they differ overall by 35+%

Measurements, part two:
On a dual mode lever the pivot to cable mount is
Standard mode 28mm
'Linear' mode 37mm
or a difference of 25% in cable movement.

My conclusion is that you measured in a different era (when virtually
all bicycle brakes were nicely standardized within a narrow band) and
that you don't get out much to see modern low-end bikes with today's
linear brakes. Measuring carefully but ignoring another group is still
not complete comprehensive data of the whole!

Is there no one in your neighborhood with a $199 'hybrid' bicycle? There
are probably more new bikes sold in 2008 with "V" brakes than with dual
pivot calipers, at least in the USA.

*Fashionably equipped with Kool Stop "Vans Shoe" shoes!
--
Andrew Muzi
<www.yellowjersey.org/>
Open every day since 1 April, 1971
** Posted from http://www.teranews.com **

Quoted message said:

<[email hidden]> wrote in message

Quoted message said:

I asked what the effective MA of the brake is from hand lever to brake
pad amd what
brake pad amd what made it "linear".

Tom Kunich said:

OK, we know that since they are rotating that they cannot be "linear" if
you're using the pure definition. But this world is full of misnamed
things.

"V" is a trademarked name, the generic term is "linear" (c.f. 'Kleenex',
'tissue'😉.
--
Andrew Muzi
<www.yellowjersey.org/>
Open every day since 1 April, 1971
** Posted from http://www.teranews.com **

On Tue, 20 May 2008 11:43:20 -0500, A Muzi <[email hidden]>

Quoted message said:

Quoted message said:

This is getting more wishy-washy with each response and is similar to
the claims to which I referred about center pull and cantilever brakes
in times gone by. No measurements were made, just conjecture.

Measurements, part one:
On the bike I rode in today with a Weinmann type 500 sidepull*, the
cable stop to centerbolt center is 61mm. Centerbolt to center of pad is
55mm.

On a new V equipped bike near me now, cable stop to brake pivot is
111mm. Brake pivot to center of pad is 36mm.

SP- 61:55 or 90.1%
V- 111:36 or 32.4%

they differ overall by 35+%

Measurements, part two:
On a dual mode lever the pivot to cable mount is
Standard mode 28mm
'Linear' mode 37mm
or a difference of 25% in cable movement.

My conclusion is that you measured in a different era (when virtually
all bicycle brakes were nicely standardized within a narrow band) and
that you don't get out much to see modern low-end bikes with today's
linear brakes. Measuring carefully but ignoring another group is still
not complete comprehensive data of the whole!

Is there no one in your neighborhood with a $199 'hybrid' bicycle? There
are probably more new bikes sold in 2008 with "V" brakes than with dual
pivot calipers, at least in the USA.

*Fashionably equipped with Kool Stop "Vans Shoe" shoes!

Dear Andrew,

Thanks for the measurements--I was beginning to wonder if Sheldon and
the rest of the world had missed something.

Cheers,

Carl Fogel

In article <[email hidden]>,

Tom Kunich' cyclintom@yahoo. com said:

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

Quoted message said:

Tom Kunich said:

No Jobst, I actually MEASURED the distances from the fulcrum and it
was about 2.5:1. I say about because of the adjustments for the shoe
placement.

I didn't notice that anyone mentions dimensions in this thread or that
measurements were made and how. I just fine the language used for
brakes is misleading and asked what is linear and what the MA is in
the brake mentioned. Just because the cable moves farther doesn't
prove that this difference is canceled by the caliper leverage.

After all these years you should be more than prepared for the inaccurate
language used by most people when talking about mechanical things.

I used a metric tape measure to measure the distance to the brake shoe
center and to the cable attachment point. The leverage of the (Shimano XT)
unit was approximately 2.5:1. We don't need precision here.

We do need accuracy of language, and accuracy is what you
are talking about here where you misuse the word `precision.'
They are not synonyms. Precision measures the repeatability
of a measuring technique.

Accuracy in a clock is how closely it reads to the `real' time.
Precision of a clock is the variability of the intervals between ticks.

--
Michael Press

Quoted message said:

Andrew Muzi said:

Quoted message said:

> 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.

[snip]

Quoted message said:

Jobst Brandt

Dear Jobst,

This may be what you're looking for:

http://sheldonbrown.com/cantilever-geometry.html

Cheers,

Carl Fogel

On Tue, 20 May 2008 09:35:59 -0700, "Tom Kunich" <cyclintom@yahoo.

com said:

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

Quoted message said:

Quoted message said:

I asked what the effective MA of the brake is from hand lever to brake pad
amd what
brake pad amd what made it "linear".

What makes it linear?
The mechanical advantage does not change with either the position of
the brake handle, or the position of the pad. Moving the handle the
first 1/16" moves the pads the same distance as the last 1/16" (within
a VERY small variance - so small as to be inconsequential)
This is NOT true of a center-pull or a cantilever because the angle of
the pull changes in an "arc" both at the handle end and at the
"caliper" end. Worse yet, the non-linearity ADDS instead of
cancelling.
The dual pivot "linear pull" handles pull straight - as does the "V"
brake "caliper".

Really quite a simple concept.
** Posted from http://www.teranews.com **

<clare at snyder dot ontario dot canada> wrote in message
news:[email hidden]...

Quoted message said:

The mechanical advantage does not change with either the position of
the brake handle, or the position of the pad. Moving the handle the
first 1/16" moves the pads the same distance as the last 1/16" (within
a VERY small variance - so small as to be inconsequential)

We agree, but I'm dotting the "i" for Jobst who could argue the stripes off
of a zebra. Technically the distance between the fulcrum and the cable
attachment points changes by a tiny amount as you squeeze the brake lever.

Carl Fogel said:

Quoted message said:

Quoted message said:

>> 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.

Quoted message said:

Quoted message said:

Quoted message said:

> 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.

Quoted message said:

Quoted message said:

Quoted message said:

"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

Quoted message said:

Quoted message said:

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. Â

Quoted message said:

This may be what you're looking for:

http://sheldonbrown.com/cantilever-geometry.html

It is NOT. The combination of cable yoke angles and brake lever
angles is highly confusing to most people. For that reason, measuring
hand lever stroke and combined pad(s) stroke is the only unambiguous
measure of MA. The article by Sheldon is as vague as claims by brake
manufacturers.
--
Jobst Brandt

clare who? said:

Quoted message said:

Quoted message said:

I asked what the effective MA of the brake is from hand lever to
brake pad and what brake pad and what made it "linear".

OK, how much more linear and how about a graph of had lever motion vs
pad motion comparing the most common brakes.

Quoted message said:

What makes it linear?

Quoted message said:

The mechanical advantage does not change with either the position of
the brake handle, or the position of the pad. Moving the handle the
first 1/16" moves the pads the same distance as the last 1/16"
(within a VERY small variance - so small as to be inconsequential)
This is NOT true of a center-pull or a cantilever because the angle
of the pull changes in an "arc" both at the handle end and at the
"caliper" end. Worse yet, the non-linearity ADDS instead of
canceling. The dual pivot "linear pull" handles pull straight - as
does the "V" brake "caliper".

Show how much this is on a graph.

Quoted message said:

Really quite a simple concept.

Not simple at all. Just recall how long it took the concept of the
Dual Pivot brake to be even partly understood and why two pivots.

We aren't getting any closer to the answer of MA or linearity.

Jobst Brandt

Quoted message said:

clare who? said:

Quoted message said:

> I asked what the effective MA of the brake is from hand lever to
> brake pad and what brake pad and what made it "linear".

OK, how much more linear and how about a graph of had lever motion vs
pad motion comparing the most common brakes.

ok, how about NOT having 1/sin theta affecting the mechanical advantage
of the straddle cable?????

Quoted message said:

Quoted message said:

What makes it linear?

Quoted message said:

The mechanical advantage does not change with either the position of
the brake handle, or the position of the pad. Moving the handle the
first 1/16" moves the pads the same distance as the last 1/16"
(within a VERY small variance - so small as to be inconsequential)
This is NOT true of a center-pull or a cantilever because the angle
of the pull changes in an "arc" both at the handle end and at the
"caliper" end. Worse yet, the non-linearity ADDS instead of
canceling. The dual pivot "linear pull" handles pull straight - as
does the "V" brake "caliper".

Show how much this is on a graph.

Quoted message said:

Really quite a simple concept.

Not simple at all. Just recall how long it took the concept of the
Dual Pivot brake to be even partly understood and why two pivots.

We aren't getting any closer to the answer of MA or linearity.

and you aren't getting any closer to you ever being able to pay any
freakin' attention to anything you didn't read before age 30. and
precious little of /that/ seems to have sunk in properly.

from: http://sheldonbrown.com/cantilever-geometry.html [thanks carl]

Yoke Angle Mechanical
(Degrees) Advantage
90° 1
80° 1.015
70° 1.063
60° 1.15
50° 1.31
40° 1.55
30° 2
20° 2.92
10° 5.76
5° 11.47
0° Infinity!

Quoted message said:

Carl Fogel said:

Quoted message said:

>>> 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.

Quoted message said:

Quoted message said:

>> 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.

Quoted message said:

Quoted message said:

> "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

Quoted message said:

Quoted message said:

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.

Quoted message said:

This may be what you're looking for:

http://sheldonbrown.com/cantilever-geometry.html

It is NOT. The combination of cable yoke angles and brake lever
angles is highly confusing to most people.

"some people" = you.

Quoted message said:

For that reason, measuring
hand lever stroke and combined pad(s) stroke is the only unambiguous
measure of MA. The article by Sheldon is as vague as claims by brake
manufacturers.

rubbish jobst. the math is clear and unambiguous.

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

Quoted message said:

We aren't getting any closer to the answer of MA or linearity.

Not helped by you deliberately ignoring what's going on. The cable pull for
a V/linear brake system is more than for others, thus the MA of the brake
end is different. However this is compensated for in the lever, thus the MA
for the total system returns to being the same.

There are _two_ different MAs to consider - the one you're going on about,
for the whole system, is useful for some things, and the one everybody else
is going on about, that of cable travel to pad travel, is useful for people
who wish to know how to make components work together.

Clive George said:

Quoted message said:

We aren't getting any closer to the answer of MA or linearity.

Quoted message said:

Not helped by you deliberately ignoring what's going on. The cable
pull for a V/linear brake system is more than for others, thus the
MA of the brake end is different. However this is compensated for
in the lever, thus the MA for the total system returns to being the
same.

That is what I was trying to resolve. The way it was first stated,
one would believe that the overall mechanical advantage was greater
than with other brakes, therefore greater stopping force, something
that is not reasonably possible, so thanks for "the same" statement.

Quoted message said:

There are _two_ different MAs to consider - the one you're going on
about, for the whole system, is useful for some things, and the one
everybody else is going on about, that of cable travel to pad
travel, is useful for people who wish to know how to make components
work together.

To me it was a method by which the V-brake caliper could be made to
work without running out of hand reach. Meanwhile much hay has been
made of its supposed greater MA and linearity for better performance.

Jobst Brandt

"Clive George" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

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

Quoted message said:

We aren't getting any closer to the answer of MA or linearity.

Not helped by you deliberately ignoring what's going on. The cable pull
for a V/linear brake system is more than for others, thus the MA of the
brake end is different. However this is compensated for in the lever, thus
the MA for the total system returns to being the same.

A lot of people simply install the linear brake onto a normal touring bike
and retain the original levers. You need to set the brakes very close to the
rims and you need to have very straight rims but they work fine.

Quoted message said:

There are _two_ different MAs to consider - the one you're going on about,
for the whole system, is useful for some things, and the one everybody
else is going on about, that of cable travel to pad travel, is useful for
people who wish to know how to make components work together.

I think that you have the correct idea of reality Clive, but that, perhaps,
isn't the subject here.

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

Quoted message said:

To me it was a method by which the V-brake caliper could be made to
work without running out of hand reach. Meanwhile much hay has been
made of its supposed greater MA and linearity for better performance.

Ahh, now I understand what you were getting at. I wish you'd just come out
and say that in the first place.

But as I pointed out to Clive, some people simply install the linear brakes
onto their original street bike retaining the levers (whether they are
shifters or old-style brake levers) and just keep them in adjustment.

"Tom Kunich" <cyclintom@yahoo. com> wrote in message
news:[email hidden]...

Quoted message said:

"Clive George" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

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

Quoted message said:

We aren't getting any closer to the answer of MA or linearity.

Not helped by you deliberately ignoring what's going on. The cable pull
for a V/linear brake system is more than for others, thus the MA of the
brake end is different. However this is compensated for in the lever,
thus the MA for the total system returns to being the same.

A lot of people simply install the linear brake onto a normal touring bike
and retain the original levers. You need to set the brakes very close to
the rims and you need to have very straight rims but they work fine.

I suspect in that instance they actually work very well :-) But you'd need
to keep them in adjustment and everything straight etc.

cheers,
clive

"jim beam" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

Quoted message said:

For that reason, measuring
hand lever stroke and combined pad(s) stroke is the only unambiguous
measure of MA. The article by Sheldon is as vague as claims by brake
manufacturers.

rubbish jobst. the math is clear and unambiguous.

Jim, because of your dislike of Jobst's style you're failing to understand
what he's saying. In truth he is correct that in order to get the same BRAKE
PAD TRAVEL you need to have the same overall ratios. There is a small
problem in that idea though - in order to make the brake lever forces
smaller, they set the system up to use SHORTER TRAVEL. The results of this
is that linear brakes have to have very straight wheels and the pads are set
much closer to the rims.

So in truth the linear braking system does use a higher MA but at the cost
of higher maintenance.

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

Quoted message said:

Clive George said:

Quoted message said:

We aren't getting any closer to the answer of MA or linearity.

Quoted message said:

Not helped by you deliberately ignoring what's going on. The cable
pull for a V/linear brake system is more than for others, thus the
MA of the brake end is different. However this is compensated for
in the lever, thus the MA for the total system returns to being the
same.

That is what I was trying to resolve. The way it was first stated,
one would believe that the overall mechanical advantage was greater
than with other brakes, therefore greater stopping force, something
that is not reasonably possible, so thanks for "the same" statement.

Quoted message said:

There are _two_ different MAs to consider - the one you're going on
about, for the whole system, is useful for some things, and the one
everybody else is going on about, that of cable travel to pad
travel, is useful for people who wish to know how to make components
work together.

To me it was a method by which the V-brake caliper could be made to
work without running out of hand reach. Meanwhile much hay has been
made of its supposed greater MA and linearity for better performance.

Ah, that's a different problem :-)

AIUI one reason they're better than conventional cantis because the MA is
closer to linear - doesn't the geometry of conventional cantis work against
them in that regard? OTOH they also had thinner pads, which gives an
improvement at the expense of durability.
But I mustn't forget the pads - I hate conventional canti pads, cos they're
too darn hard to set up :-)

On a tandem, Vs should be better for the back, because the cable stretch
would be less of an issue with the travel being doubled and hence the force
halved.

cheers,
clive