Newsgroups: rec.bicycles.tech
From: jbrandt@hpl.hp.com (Jobst Brandt)
Subject: Re: Brake Problem; help?
Date: Fri, 1 Sep 1995 20:04:03 GMT

Eugene Chu writes:

> I hope some of the expert techies can help me on this one.  I've been
> experiencing a brake problem on a couple of my mountain bikes which
> sound pretty bad.  When I have to brake moderately hard for any
> length of time, the pads start to dig up metal from the aluminum
> rims.  Then I get metal on metal scraping, which sound really
> sickening.  I found that if I "pumped" the brakes, I can eventually
> shake the metal bits off, and they'll be fine for a while, and then
> it starts over.

This is a common occurrence with brakes and it is primarily caused by
the pad material.  Old Mafac pads were notorious for this as were some
early Campagnolo pads, however there is help if you are willing to
buy pads that don't get a lot of bike rag exposure.  I have found that
KoolStop makes excellent friction material and offers it in several
types of pads.  I prefer their red standard pads and have never had
the galling problem nor streaked, gummy rims that some other pads have.

If you can clear the pads by short hard pumping of the brakes, you are
better off than some where only a sharp instrument will dislodge the
metal debris.

Jobst Brandt      <jbrandt@hpl.hp.com> 

Newsgroups: rec.bicycles.tech
From: jbrandt@hpl.hp.com (Jobst Brandt)
Subject: Re: recovering original braking ability: how?
Date: Tue, 7 Feb 1995 19:04:18 GMT

Tom Nakashima writes:

> How about if you change wheels, say from the Mavic MA-2's to the
> Open-4's?  One of the wheels I use for touring and commuting, the
> other for weekend rides and hill climbing.  I noticed the Open-4's
> wear the brake pads differently than the MA-2's.  Is it better to
> stick to one type of rim?

I don't think the brake pads give a damn.  In fact I can't imagine any
difference between pad wear from one aluminum rim to the next, assuming
it isn't one with ceramic or heavy hard anodizing in comparison to a
bare aluminum rim.  Using Cool Stop 'reds', I don't notice much pad wear
unless I'm in the mud like last sunday on Gazos Creek Road where it's
steep with plenty of slop.  

Some guy on an MTB asked us how we planned to get back with our skinny
tired bikes.  I told him we weren't going back, that we had been on
the way home since we started and that we didn't have a pickup truck
at park HQ...  disbelief as we rode on out to the coast.

Jobst Brandt      <jbrandt@hpl.hp.com> 

Newsgroups: rec.bicycles.tech
From: jbrandt@hpl.hp.com (Jobst Brandt)
Subject: Re: grinding brakes
Date: Tue, 23 Jan 1996 17:53:50 GMT

Stephen Hill writes:

> I have a Cannondale H600 which I love to pieces except for this
> irritating problem.  Whenever I ride in wet weather, particularly if
> it is cold, I find that the brakes grind unnervingly.  When I open
> the brakes up top inspect the shoes I find what looks like little
> pieces of aluminium stuck in the pads.

You have poor brake pads.  Replace them with something like KoolStop
pads and this problem will go away.

> My rims, which are aluminium, don't look like they are being torn
> up, except for a few minor gouges from these chunks of metal.  

Your rims are being eaten alive, believe it, and when they get hollow
cheeks, make sure to replace them or you'll blow out a sidewall,
suddenly.  The cause of the debris pickup is that moisture makes road
grit stick to the rim and enter the brake action.  Some pads tend to
immobilize the grit and use it as a cutting tool.  You are observing
the material removal chips that are cut as on a lathe from your rims.

> Has anyone else had this problem, and if so, how did you solve it?  In
> particular, which brake pads has anyone tried on this bike that don't have
> this problem?  

KoolStop pads, among others work excellently.

Jobst Brandt      <jbrandt@hpl.hp.com> 

From: jbrandt@hpl.hp.com (Jobst Brandt)
Newsgroups: rec.bicycles.tech
Subject: Re: wheel lifetime
Date: 30 Apr 1998 21:38:20 GMT

Andrew Thorne writes:

>> Probably, but I just put on new ones whenever they wear down to the
>> holder.  I don't keep track of that other than to throw them in a
>> pile of worn out pads.


> Just out of curiosity, why would one keep a pile of worn out pads
> instead of simply throwing them away? Are they good for anything?
> Can they be melted down and molded into new pads? ;)

Interesting that you should ask.  Like some of the discontents here on
wreck.bike, who cite old legends in response to my effort at debunking
them, they exist in real life, some of whom are active in the bicycle
business.  They claim that brake pads are worn out when the fine
detail on their faces wears off and that one cannot ride them any more
once they are beyond that.  They claim that adjusting pad position is
a constant necessity even with good brakes and that setting the toe-in
is a regular task.  So in the past few years I just tossed the KoolStop
red pads in a heap and have them available as evidence when pseudo
brake experts begin to repeat their "mantra".

On old Campagnolo (single pivot) brakes, pads can be worn from new
down to the metal without repositioning the pads.  The cable length
adjuster is all it takes.

Jobst Brandt      <jbrandt@hpl.hp.com>

From: jbrandt@hpl.hp.com (Jobst Brandt)
Newsgroups: rec.bicycles.tech
Subject: Re: Rough braking surface...
Date: 5 Feb 1999 00:45:02 GMT

Sheldon Brown writes:

>>> I thought it was the salmon pads rather than the red pads.

>> Salmon IS red.  Salmon is just a product specific "red".

> That's not correct.  "Salmon" is actually an orange color.  The
> distinction is not about cosmetics, however.

Actually it is because there was no red,green,yellow, etc colors
before colors became important as matching a ladies shoe to her purse.

> The "salmon" formulation is the same as the no-longer-available
> Scott Mathauser recipe.  The salmon color comes from the iron oxide
> which is one of the ingredients.

There is an odd quirk here.  The original Matthauser pads had a
compound that melted and became dangerously gummy before failing
entirely.  I had some scary moments on these because they were
insertable in Campagnolo holders and I had been told how good they
were.  I still have samples of these pads with obvious molten material
on them.  Subsequently Matthauser used KoolStop salmon compound that
had previously been available but only in the Continental model, that
did not have the wheel insertion ears of the Campagnolo brakes.
That's when I changed to KoolStop and have not regretted it.

> Kool Stop actually made the Mathauser pads; with Scott's retirement,
> they have bought the rights to use this superior mix for their own
> shoes (which are a superior mechanical design to the old Mathauser
> models.)

Talking to the KoolStop people at the annual bicycle trade show, I
learned that it is a KoolStop formulation and that they make pads for
most of the smaller brand brakes, including Matthauser.  You might
recall that the Matthauser brake pads had cooling fins on the rear.
This was as scientifically incorrect as the compound.  Effectively no
heat passes through the brake pad that is an insulator.  The heat must
go into the rim to be dissipated.

> Unfortunately, Kool Stop has done a very poor job of marketing these
> shoes; they mostly just say "here's another color"...but it's such
> an ugly color that nobody but an Ulsterman would buy them on that
> basis.  Nevertheless, they really are superior, both in durability
> and stopping power.

I don't understand their method but it may be that selling brake pads
to the after-market is less interesting than to OEM people, where I
believe their business is.


Jobst Brandt      <jbrandt@hpl.hp.com>

From: jbrandt@hpl.hp.com (Jobst Brandt)
Newsgroups: rec.bicycles.tech
Subject: Re: KoolStop Road Pads
Date: 3 Nov 2000 00:59:15 GMT

lemonade continues anonymously:

> http://bittburg.ethz.ch/LSST/Tribology/nanotribology.html

> There is no particular reason I chose this except that it says
> basically the above, i.e. I searched on AltaVista for some selection
> of those words.

The title of "Nanotribology and Macrotribology" tells me much about
this effort.  These are buzzwords for folks who don't understand
roughness with respect to material granularity, crystallography and
finally atomic structure.  Much of the advances in this business have
been made in the computer disk science, where carbon coatings a few
nanometers thick are used to prevent wear debris and data loss,
commonly known as a disk crash.

It is in this field that I have experience and made a seminal
discovery that the wear debris of carbon is CO2 and that it is
therefore an ideal friction material.  When I first proposed this on
the basis of relatively crude experiments, it was greeted by similar
criticism as what you have offered in this exchange.  Subsequently two
researchers used my test equipment with enhancements to complete their
PhD theses on the benign sliding friction of carbon that produces CO2,
at melting temperatures that occur at asperity contacts.  This concept
was developed on the theory that, in the absence of a lubriucant, all
material deformation causes local melting, consistent with material
removal in the machine tool industry and friction pairings such as
automotive drum and disk brakes.

> And if I am approaching this from an unconventional perspective-
> hmm- I am not the only one: for example, your statement that all
> frictional wear is adhesive. Youch.

As I said previously, your approach is mainly by default, exposing
neither your identity nor what you believe.  Anonymity and
argumentation by leading questions is a subtle ploy that exposes no
vulnerability, having not made any statements of where you stand on
the issues.

> There are many details in our last exchanges that I think you will
> agree are not really worth going on about, although we could each
> get some satisfaction out of pounding the other with them, I
> imagine, and even if perhaps some useful clarification might result.
> I remind myself that such exchanges, even with zero rancor, are not
> the reason that I have been in this newsgroup.

I see no parallel between what you have put forth in this thread and
what I have said and to characterize it as agreement is a stretch of
the term.  In fact, I don't see that you have stated anything about
the subject except to question all aspects of what I have written.

> In fact, if I hadn't interpreted your "and" to mean "and", and thus
> that you were saying heat could only be generated if bonds were
> ultimately broken, I doubt I would have posted anything on the
> subject at all- you will recall I said something like, that all
> seems plausible up until the part about the bond breakage.

I did not say that and your saying so doesn't make it so, nor does it
have much to do with bicycle brakes.

> I appreciate that perhaps they may be one of your reasons though,
> whether to chase pseudoscientists into a hole or to elaborate on an
> interesting technical point, whichever the case you feel this may
> be.  Well then, let me instead just ask you to explain one point of
> your argument which I find particularly difficult to understand:

These are long paragraphs but they contain no information about the
nature of friction or its effects.  Is this the way you do business in
real life?

> You say, to cite you more precisely this time, that grit wears down
> rims.  But since the grit is mostly what, sand, then in this case it
> is the rim that is the softer of the pair, and so there must in fact
> be some heat generated in the rim, according to the mechanism you
> describe.

There are two ways of removing material, by molecular interaction with
thermal and adhesive removal, and mechanical removal as with a cutting
tool.  Grit in a brake pad is bimodal but primarily a cutting tool as
one can see by the pile of aluminum shavings that become embedded in
the pad with most brake pads that harbor such grit.  This is what
makes Kool-Stop pads superior to others.  They resist retaining grit
and in the event of such an inclusion, the material can be purged by
repeated pumping the brake.  Grinding with abrasive slurry is a
machining operation not a friction operation such as is classic in an
automotive brake on a shiny smooth surface, one that shows friction
heating and melting with the microscopic appearance of a dry lake bed.

> How about a calculation then?  Perhaps you could use your expertise
> to fill in or modify a few of the rough spots here.  It might still
> be too rough to be useful, or perhaps you may even laugh at this,
> but if so, perhaps you could suggest an alternative, one suitable
> for r.b.t:

> 1. About how many sets of pads does it take to wear out a rim?  Of
> course it depends on the conditions, i.e. the grit- but that is
> irrelevant for the discussion of how much heat might be produced in
> a rim, as compared to the pad, under this mechanism.  Would you say
> somewhere between about 50 and 500?  Rather extraordinarily on the
> high side, I'd venture.

That depends on how much wet weather and where.  I have used up a pair
of rims with one set of Kool-Stop pads in which nearly every major
descent in the alps on a 3000km ride was in the rain.  That removed
more than 1mm of wall thickness from MA-2 rims.  In contrast, I have
ridden several tours in the Alps with the same rims on essentially the
same route.  I think you'll see that your request is unanswerable.

> By the way I guess you never would have come into contact with
> anything so barbaric as a Modolo sinterized brake pad.  I would
> never dare actually mount one on a working bicycle- my set is to
> look at only- but I think there are several in this forum who could
> say something about how fast they wear down rims.  That is, if there
> is anybody besides us who is reading these posts.

There are many experiments that I do not need to do, being a subset of
something I have already tried.  The only drawback in this is that
there is always a possibility that there is a hidden effect that I had
not anticipated, but by now, I think I have seen and experienced most
of what is reasonable and have written about it.

> 2. A pad is considered worn out after what, about a 1/4" of wear?
> Shall we say 5mm?  And is say, an inch and a half long, say 40mm?
> Multiplying the total of 250 to 2500 linear mm of wear, by the 40mm,
> gives say a factor of 10000 to 100000.

A pad is worn out when the backing plate makes contact with the rim.
I take along spare brake pads on longer trips and ride until I hear a
scrape.  Some people insist this doesn't work so a few years ago I
began saving the worn out pads and have a bag full of pads that have
either metal showing or are worn so far that one wonders why the metal
isn't showing.  I also have a stack of worn out rims but they die from
dents as much as thin walls.

> 3. A rim is considered worn out after how much wear?  1mm?  If we
> assume the wear track is the same width as the pad, we need not
> consider either; multiplying by the circumference, say 311mm^2*pi,
> gives a ratio of the volume of material lost of between 3 and 30 to
> 1, in favour of the rim.  That is rather surprising, so please
> supply the relevant correction.  500 to 5000 sets of pads? I don't
> think so.  Perhaps something with the amount of wear, there not
> being much else to play with.  But I don't think those numbers could
> be changed by a factor of 10.

What are you getting at?  This has all been done.  Get on your bicycle
and put on some distance so you can stop hypothesizing.  Dry clean
Kool-Stop pads practically do not wear.  As I said, I have taken a
tour in the Alps with a couple of mm material left and came back with
no apparent loss.  I recall clearly how my friend at the bike shop
near Zurich laughed when he saw my brake pads before the trip.  He was
astounded when I returned with the same pads.

> 4. The ratio of the energy/heat produced in the relevant
> molecule-by-molecule wear processes in the aluminum (oxides) and pad
> materials?  Not so easy to determine- besides the material properties
> of the brake pads, which I don't know even where to look up, or the
> aluminum and aluminum oxides, there are other factors to consider,
> such as the fact that the wear does not consist in a molecule by
> molecule stripping of the material.  But it seems to me that the
> ratio is again in favor of the rim, it, even the oxides, being that
> much harder.  5 to 1?  Just to have a number.

> 5. Combined with #3, that would make the energy ratio somewhere
> between around 15 and 125 to one, in favor of the rim.

I think you need to ride more bike besides studying tribology.

> This all is only one mechanism anyway.  I saw in another of your
> posts that you were mentioning melting of the pad, and also in the
> above, water on the rim.  Depending on the thickness of the layer-
> only at most a few molecules are necessary- and other factors, then
> heat could be produced by, in addition to bond stretching or
> breaking, cavitation.  And then there are components of the heat
> budget from phase changes.  Etc.  Is r.b.t. the place to tally it
> all up?

So how about it.  Who are you, what is your name and what do you do in
life as we know it.  I notice in all the text you have composed, that
you don't answer any questions but pose endless series of specious
arguments, rhetorical and leading questions.  Are you a trial lawyer?

Jobst Brandt      <jbrandt@hpl.hp.com>

From: jbrandt@hpl.hp.com (Jobst Brandt)
Newsgroups: rec.bicycles.tech
Subject: Re: KoolStop Road Pads
Date: 3 Nov 2000 22:40:59 GMT

Tim McNamara writes:

>> There are two ways of removing material, by molecular interaction with
>> thermal and adhesive removal, and mechanical removal as with a cutting
>> tool.

> You lost me on this part, maybe I missed a post where these concepts
> were introduced.  What are thermal and adhesive removal?

When two materials slide in contact with one another in the absence of
a lubricant, one or both of them experiences temperatures sufficient
to cause melting at asperity contacts on a molecular level.  These are
commonly called adhesive friction because one material leaves
particles adhering to the other such as a skid mark on pavement, an
example that is on a scale that is visible.

In most interfaces, enough contaminants or adsorbed moisture and other
vapors are enough to offer lubrication.  People who work with high
vacuum are aware of cleaning processes for such contaminants and the
difficulty of removing water from surfaces.  Anodized aluminum doesn't
clean up, being a vast sponge filled with aerosols.

Jobst Brandt      <jbrandt@hpl.hp.com>