brake failure

jim beam

Tom Kunich wrote:
> "jim beam" <spamvortex@bad.example.net> wrote in message
> news:9cWdnQLiw4PEsqPVnZ2dnUVZ_srinZ2d@speakeasy.net...
>>
>> then you didn't read what i said!!! identical calipers, pads, levers,
>> different cables, front and rear. the rear lever /always/ get more
>> displacement, and that is /entirely/ due to the greater elasticity of
>> the longer cable. jobst says observed elasticity is only "elastomeric
>> brake pads". it's not, and the above proves it! sheesh.
>
> Invention again?


eh?

jobst.brandt@stanfordalumni.org

clare who? wrote:

>>>> As was mentioned, caliper arms act in bending against
>>>> elastomeric brake pads, causing elasticity in brake response.

>>> actually jobst, you know how the rear brake system is more elastic
>>> than the front? well, that's 100% because of cable/cable run
>>> elasticity. the pads cancel out of that equation.

>> Jim. if you don't understand what Jobst is talking about why are
>> you making such stupid statements? Remove a flexible cable that
>> stretches x. Replace it with a stiffer cable that doesn't flex and
>> now the pads compress. How do you tell the difference?

>>> typical ill-considered presumptive jobstian nonsense. the pads,
>>> because of low force per area, won't deflect much. a nice long
>>> cable run otoh most definitely will. as will calipers, levers,
>>> and even frames where the brakes are cantilever.

>> Have you ever bothered to actually LOOK at the braking system on a
>> bicycle? The entire mechanism is flexible because it's being made
>> as light as possible.

>>> again, check lever displacement per unit force comparison between
>>> front and rear. with caliper brakes, that easily determined
>>> differential is simply cable elasticity.

>> When did you developed the ability to tell the difference between
>> 15 ft/lbs and 17 ft/lbs of force manually?

> Not hard to tell if a cable is stretching (or cable sheath
> compressing). Particularly on a "V" brake.

> Measure the distance between the tops of the brake "caliper" arms
> with the brake handle pulled just past firm contact, then squeeze
> the handle hard and see if the measurement changes. If the handles
> get closer to the bar without that measurement changing it IS the
> cables - not the brake "caliper" arms or pads, or anything else.

Forget about that. The test is whether the exposed end of the cable,
attached to the anchor bolt at the caliper, Is moving with respect to
the cable housing where it becomes exposed. All the other dimensions
are elasticity in caliper arms and brake pads. This us so simple and
requires no measuring devices.

Jobst Brandt

jobst.brandt@stanfordalumni.org

someone wrote:

>> I don't see how cable stretch can be determined from hand lever
>> motion.

> If "nothing" else changes in either set-up or riding conditions
> other than a switch from cable A to cable B, then what other reasons
> are there for not getting wheel lock prior to bottoming out with one
> cable when it turns out to be consistently possible with another?

Without some background and measurements, this is the same old story
that lets riders believe in cable stretch. I have not seen it in many
years of bicycling, only keep hearing claims.

> An amazing amount of cable housing seating occurring during the
> first half mile of the 2nd ride that for some reason just didn't
> happen during the 3 miles of the 1st ride?

Amazing story!

Jobst Brandt

jim beam

jobst.brandt@stanfordalumni.org wrote:
> clare who? wrote:
>
>>>>> As was mentioned, caliper arms act in bending against
>>>>> elastomeric brake pads, causing elasticity in brake response.
>
>>>> actually jobst, you know how the rear brake system is more elastic
>>>> than the front? well, that's 100% because of cable/cable run
>>>> elasticity. the pads cancel out of that equation.
>
>>> Jim. if you don't understand what Jobst is talking about why are
>>> you making such stupid statements? Remove a flexible cable that
>>> stretches x. Replace it with a stiffer cable that doesn't flex and
>>> now the pads compress. How do you tell the difference?
>
>>>> typical ill-considered presumptive jobstian nonsense. the pads,
>>>> because of low force per area, won't deflect much. a nice long
>>>> cable run otoh most definitely will. as will calipers, levers,
>>>> and even frames where the brakes are cantilever.
>
>>> Have you ever bothered to actually LOOK at the braking system on a
>>> bicycle? The entire mechanism is flexible because it's being made
>>> as light as possible.
>
>>>> again, check lever displacement per unit force comparison between
>>>> front and rear. with caliper brakes, that easily determined
>>>> differential is simply cable elasticity.
>
>>> When did you developed the ability to tell the difference between
>>> 15 ft/lbs and 17 ft/lbs of force manually?
>
>> Not hard to tell if a cable is stretching (or cable sheath
>> compressing). Particularly on a "V" brake.
>
>> Measure the distance between the tops of the brake "caliper" arms
>> with the brake handle pulled just past firm contact, then squeeze
>> the handle hard and see if the measurement changes. If the handles
>> get closer to the bar without that measurement changing it IS the
>> cables - not the brake "caliper" arms or pads, or anything else.
>
> Forget about that. The test is whether the exposed end of the cable,
> attached to the anchor bolt at the caliper, Is moving with respect to
> the cable housing where it becomes exposed.

no, it's measured at the tip of the brake lever - the point at which
/all/ system elasticity combined manifests.


> All the other dimensions
> are elasticity in caliper arms and brake pads. This us so simple and
> requires no measuring devices.

i wish there were measuring devices for ego and self delusion.

JG

There's a lot of talk about measurements, but the dimensions are
pretty small. A one percent change in cable/housing translates into
4mm+ slop in a standard brake lever.

JG

jobst.brandt@stanfordalumni.org

someone wrote:

> There's a lot of talk about measurements, but the dimensions are
> pretty small. A one percent change in cable/housing translates into
> 4mm+ slop in a standard brake lever.

I take it you are trying to support the cable stretch adherents from
what you say. In contrast, I am proposing a simpler test, that of
noting whether there is any relative motion at the operating end of
the control cable. Once the pads have made contact with the rim (I am
assume these are worn-in pads that make full contact), seeing whether
motion at the hand lever is producing movement at the exit of the
cable is a simple matter and one that resolves the stretch theory.

Do it and you'll see that the cable is not stretching but in fact
transmitting force and motion.

Jobst Brandt

JG

Whoops, that should have been, "a one tenth of one percent change in a
meter of cable/housing translates into 4mm+ of slop"...

Jobst, why would you "take" something I haven't said? is it what you
want to hear? What I wrote was "cable/housing". Whether its housing
compression, or housing seating, or cable unkinking, or cable
stretching, the point is simply that it takes a rather small amount to
have a noticable effect because of the 4:1 multiplier.

To tell the truth, I haven't paid much attention to what the two of
you are babbling about. It's just not as interesting as it was a
generation ago. I "take" cable stretch to usually mean non-elastic
elongation - and accept that it is a real result of a number of
factors not including meaningful physical elongation of the cable
itself, which are a product of industry bike setup practices. As for
the cable's contribution to the overall elasticity of the braking
system, it's all bs until someone pulls out the micrometer...

JG

Tom Kunich

"JG" <jchg@cox.net> wrote in message
news:25cda13c-afe0-4c49-9280-91aa4dbe8787@d77g2000hsb.googlegroups.com...
> Whoops, that should have been, "a one tenth of one percent change in a
> meter of cable/housing translates into 4mm+ of slop"...
>
> Jobst, why would you "take" something I haven't said? is it what you
> want to hear? What I wrote was "cable/housing". Whether its housing
> compression, or housing seating, or cable unkinking, or cable
> stretching, the point is simply that it takes a rather small amount to
> have a noticable effect because of the 4:1 multiplier.

Jobst is trying to be exact I suppose but that's what tends to irritate
normal people who assume that there are normal errors in descriptions.

> I "take" cable stretch to usually mean non-elastic
> elongation - and accept that it is a real result of a number of
> factors not including meaningful physical elongation of the cable
> itself, which are a product of industry bike setup practices. As for
> the cable's contribution to the overall elasticity of the braking
> system, it's all bs until someone pulls out the micrometer...

You and I have more or less the same take on it. Absolute precision in
writing and meaning isn't really part of the internet experience.

catzz66

JG wrote:
>...
>
> To tell the truth, I haven't paid much attention to what the two of
> you are babbling about. It's just not as interesting as it was a
> generation ago. I "take" cable stretch to usually mean non-elastic
> elongation - and accept that it is a real result of a number of
> factors not including meaningful physical elongation of the cable
> itself, which are a product of industry bike setup practices. As for
> the cable's contribution to the overall elasticity of the braking
> system, it's all bs until someone pulls out the micrometer...
>
>

I may have missed it, but this thread rather quickly evolved into
something quite far the original post. It is no surprise, considering
everything that has been written since, but unless I just missed it, the
original poster hasn't been back!

catzz66

JG wrote:
>...
>
> To tell the truth, I haven't paid much attention to what the two of
> you are babbling about. It's just not as interesting as it was a
> generation ago. I "take" cable stretch to usually mean non-elastic
> elongation - and accept that it is a real result of a number of
> factors not including meaningful physical elongation of the cable
> itself, which are a product of industry bike setup practices. As for
> the cable's contribution to the overall elasticity of the braking
> system, it's all bs until someone pulls out the micrometer...
>
>

This thread rather quickly evolved into something quite far the original
post. It is no surprise, considering everything that has been written
since, but unless I just missed it, the original poster hasn't been back!

Tim McNamara

In article <aLydnZ-7SbpMw93VnZ2dnUVZ_rfinZ2d@earthlink.com>,
"Tom Kunich" <cyclintom@yahoo. com> wrote:

> "JG" <jchg@cox.net> wrote in message
> news:25cda13c-afe0-4c49-9280-91aa4dbe8787@d77g2000hsb.googlegroups.com
> ...
> > Whoops, that should have been, "a one tenth of one percent change
> > in a meter of cable/housing translates into 4mm+ of slop"...
> >
> > Jobst, why would you "take" something I haven't said? is it what
> > you want to hear? What I wrote was "cable/housing". Whether its
> > housing compression, or housing seating, or cable unkinking, or
> > cable stretching, the point is simply that it takes a rather small
> > amount to have a noticable effect because of the 4:1 multiplier.
>
> Jobst is trying to be exact I suppose but that's what tends to
> irritate normal people who assume that there are normal errors in
> descriptions.
>
> > I "take" cable stretch to usually mean non-elastic elongation - and
> > accept that it is a real result of a number of factors not
> > including meaningful physical elongation of the cable itself, which
> > are a product of industry bike setup practices. As for the cable's
> > contribution to the overall elasticity of the braking system, it's
> > all bs until someone pulls out the micrometer...
>
> You and I have more or less the same take on it. Absolute precision
> in writing and meaning isn't really part of the internet experience.

This is, however, a tech newsgroup and therefore there are some
expectations of accuracy and precision.

JG

> This is, however, a tech newsgroup and therefore there are some
> expectations of accuracy and precision.- Hide quoted text -

To be precise and accurate, "some" means more than zero. There are
probably some expectations of accuracy and precision on
alt.garden.gnomes...

JG

Tim McNamara

In article
<942c3a7a-bd1b-42ea-b972-b9646faaf1e1@27g2000hsf.googlegroups.com>,
JG <jchg@cox.net> wrote:

> > This is, however, a tech newsgroup and therefore there are some
> > expectations of accuracy and precision.
>
> To be precise and accurate, "some" means more than zero.

Indeed. Unfortunately in the context of my statement the degree of
accuracy and precision to be expected is not quantifiable. Nor was that
necessary for my intent, which simply to contradict Tom Kunich's
suggestion that accuracy and precision are alien to the Internet or to
Usenet. In this case your comment was directed more to precision than
accuracy.

Brian Huntley

On May 30, 4:31 pm, catzz66 <nos...@nospam.com> wrote:

> This thread rather quickly evolved into something quite far the original
> post. It is no surprise, considering everything that has been written
> since, but unless I just missed it, the original poster hasn't been back!

No, Marian has been back - check May 23rd, for example. And she's been
updating her journal on Crazyguyonabike.com too. It's a great story so
far. She doubled back to a bike shop to get repairs, then got new
brake shoes, eventually. She's also met and socialized with a half
dozen bike clubs so far.