Carlton Reid on QR safety

Discussion in 'Mountain Bikes' started by James Annan, Feb 4, 2006.

  1. Andy H wrote:
    >
    > Life sucks and shit happens, our (my anyway) pastime is rife with risk. If
    > the design is inherently flawed why have we not all been maimed by our
    > disk/qr problems? (As MV would no doubt wish :).


    Who is "MV"?

    --
    Tom Sherman - Fox River Valley

    "They [hominids] ARE acceptable prey, ESPECIALLY mountain bikers."
    - M.V.

    "We are discussing whether humans as prey are 'natural'. Clearly,
    they are, or that mountain lion wouldn't have been trying to eat a
    human." - M.V.

    "Abnormal would be a mountain lion speaking English." - M.V.

    "Mountain lions have always eaten humans, throughout our evolutionary
    history." - M.V.
     


  2. In article <[email protected]>,
    "Andy H" <[email protected]> wrote:

    > "David Martin" <[email protected]> wrote in message
    > news:[email protected]
    > >
    > > Werehatrack wrote:
    > >> Those of us who have seen your prior postings about the issue of disc
    > >> brake ejections are fully aware of your position on the matter. Is it
    > >> possible for you to accept the fact that for the majority of the
    > >> readers, the evidence thus far published is not persuasive that there
    > >> is a serious problem here which is not related to user error?

    > >
    > > Why do you claim to speak for the majority of readers, most of whom
    > > have expressed no public opinion on the matter?
    > >
    > > ..d
    > >

    > Does the fact that the majority of people have expressed no public opinion
    > (read; interest) speak volumes as to the severity of the problem? Do YOU
    > know the relevant statistics to say that this is a major problem or design
    > flaw?
    >
    > Life is inherently risky and I for one would rather check my qr's before a
    > ride and have disk brakes than try to do what I do with rim brakes.


    I draw inferences from the fact that those who claim there
    is no problem refuse to comment upon the force diagram.

    --
    Michael Press
     
  3. Shawn

    Shawn Guest

    Johnny Sunset wrote:
    > Andy H wrote:
    >
    >>Life sucks and shit happens, our (my anyway) pastime is rife with risk. If
    >>the design is inherently flawed why have we not all been maimed by our
    >>disk/qr problems? (As MV would no doubt wish :).

    >
    >
    > Who is "MV"?


    He who must not be named.
     
  4. > While promoting this new mechanism as "safer" than the existing system, he
    > also insists that "industry experts say QRs are safe, when used
    > correctly".
    >
    > This assertion is backed up with a quote from "industry expert" Bob Burns
    > (actually Trek's *lawyer*), which is nothing more than a boilerplate
    > denial dating to a few years ago when the QR/disk issue first surfaced.

    =======================
    "In 2003, Bob Burns, Trek's US-based General Counsel, told BikeBiz.com:

    "Virtually all 'defective quick release' claims that I have seen relate to
    an improperly used quick release. Either the consumer has ridden with the QR
    open; ridden with the QR closed like a wing nut (rather than closing it over
    the cam); or ridden with insufficient tightness to the adjusting nut to
    engage the cam."
    =======================

    Where, exactly, does the quote from Bob Burns say anything whatsoever about
    your QR/disk issue? He's addressing only one thing in the quote given- quick
    releases. Nothing about disk brakes.

    For that matter, not one place in the article is anything said about brakes.
    Just quick releases. And the timing and development w/regards Pacific
    Bicycles implementing a new quick release design probably has everything to
    do with the lawsuit they got hit with (quick releases supposedly failing in
    the field on low-end kids bikes) and nothing to do with disk brakes.

    --Mike-- Chain Reaction Bicycles
    www.ChainReactionBicycles.com


    "James Annan" <[email protected]> wrote in message
    news:[email protected]
    > Carlton Reid has a puff piece about a new "Secure QR system" on bikebiz:
    > <http://www.bikebiz.co.uk/daily-news/article.php?id=6427>
    >
    > While promoting this new mechanism as "safer" than the existing system, he
    > also insists that "industry experts say QRs are safe, when used
    > correctly".
    >
    > This assertion is backed up with a quote from "industry expert" Bob Burns
    > (actually Trek's *lawyer*), which is nothing more than a boilerplate
    > denial dating to a few years ago when the QR/disk issue first surfaced.
    >
    > Strangely, alongside this there is no space in his article for these
    > quotes from people who actually have some relevant engineering and
    > technical experience:
    >
    > ---
    > Chris Juden, Technical officer, CTC:
    > "It's not just scaremongering, but all hangs together and makes perfect
    > sense. In fact I'm kicking myself for not thinking of it before."
    >
    > "changes must be made to the way disk brakes and front wheels are attached
    > to forks"
    >
    > Jobst Brandt, author, "The Bicycle Wheel":
    > "The more I see on this the more I find the defense of the status quo
    > stranger than fiction. Why are writers trying to say that it can't
    > happen? What motivates writers to claim that disc brakes as currently
    > offered are not a hazard?
    >
    > The mechanism has been clearly stated, the forces have been identified in
    > magnitude and direction, and credible descriptions of failures have been
    > presented. What's going on here! There is no easter bunny. Believe it!"
    >
    > John Forester, author, "Effective Cycling":
    > "All that I can say is gross negligence."
    >
    > Unnamed Marzocchi Tech Support:
    > "It is recommended that an 8" rotor is not used on a standard axle fork
    > because the forces exerted on the wheel can potentially pull the axle out
    > of the dropouts."
    >
    > Brant Richards, On-One:
    > "From the next batch, our rigid forks will have dropouts which are angled
    > forward at 45degrees or thereabouts.
    >
    > This is because when I was coming home, and pulling a stoppy outside my
    > driveway, I kept finding the front wheel shifted in the dropout."
    >
    > Dave Gray, Surly:
    > "You are correct. I've noticed the problem on my Karate Monkey fork."
    >
    > Ben Cooper, Kinetics, describing his experiment:
    > "Conclusion: From the above, there seems to be an effect from the disc
    > brake which causes the quick release to loosen."
    > ---
    >
    >
    > And even more strangely, although he mentions the ongoing Walmart case
    > concerning children's bikes, and refers repeatedly to user error, he also
    > didn't find space to mention the recent out of court settlement in which a
    > manufacturer paid off an (experienced adult) rider who was seriously
    > injured by a front wheel ejection on a disk+QR fork.
    >
    >
    > James
    > --
    > James Annan
    > see web pages for email
    > http://www.ne.jp/asahi/julesandjames/home/
    > http://julesandjames.blogspot.com/
     
  5. Simon Brooke

    Simon Brooke Guest

    in message <[email protected]>, Richard
    ('[email protected]') wrote:

    > Andy H wrote:
    >> Does the fact that the majority of people have expressed no public
    >> opinion (read; interest)

    >
    > Why do you read that? I have hitherto expressed no public opinion.
    > I've read James' webpages on the subject and found his hypothesis
    > interesting and convincing


    I've read James' web pages on the subject, and I've listened to other
    people (Darth Ben for example) who have empirically verified James'
    hypothesis. I ride a lefty off road. I did before I knew about this
    problem, it has to be admitted. But if I did now convert back to a
    conventional fork, it would have a through axle.

    --
    [email protected] (Simon Brooke) http://www.jasmine.org.uk/~simon/

    ;; All in all you're just another hick in the mall
    -- Drink C'lloid
     
  6. Shawn wrote:

    >> Who is "MV"?

    >
    >
    > He who must not be named.


    If you've never encountered worse on Usenet,
    you've led a sheltered life.

    --
    Mike de Van Man
     
  7. "Andy H" <[email protected]>typed

    > Does the fact that the majority of people have expressed no public opinion
    > (read; interest) speak volumes as to the severity of the problem? Do YOU
    > know the relevant statistics to say that this is a major problem or design
    > flaw?


    I have expressed nothing on the subject as I have no relevant knowledge.

    This does NOT mean I have no interest; I just try not to post if I have
    nothing useful to add.

    --
    Helen D. Vecht: [email protected]
    Edgware.
     
  8. Richard <[email protected]>typed


    > Andy H wrote:
    > > Does the fact that the majority of people have expressed no public
    > > opinion
    > > (read; interest)


    > Why do you read that? I have hitherto expressed no public opinion.
    > I've read James' webpages on the subject and found his hypothesis
    > interesting and convincing; I would have liked to investigate the QR
    > vibrational loosening in more detail, but as I neither sell, use,
    > maintain, nor have any access to disk brakes or QR axles, I could add
    > nothing useful to the debate.


    YAM & IAY...

    --
    Helen D. Vecht: [email protected]
    Edgware.
     
  9. "Andy H" <[email protected]>typed



    > "Richard" <[email protected]> wrote in message
    > news:[email protected]
    > Snip -
    > >......but as I neither sell, use, maintain, nor have any access to disk
    > >brakes or QR axles, I could add nothing useful to the debate.
    > >
    > > R.

    > Then do just that, you have no potential problems do you? Do you have the
    > statistics to hand?


    > Andy H



    The problem is not statistical.

    The problem is anecdotal.

    Many here in the UK will know of a single catastrophic event that might
    have been the result of wheel ejection.

    A single catastrophe does not a statistic make but it does not mean
    there is not a problem.

    That IS the problem.

    --
    Helen D. Vecht: [email protected]
    Edgware.
     
  10. Shawn

    Shawn Guest

    Mike de Van Man wrote:
    > Shawn wrote:
    >
    >
    >>>Who is "MV"?

    >>
    >>
    >>He who must not be named.

    >
    >
    > If you've never encountered worse on Usenet,
    > you've led a sheltered life.
    >

    Sure, but he's still a dick.
     
  11. In article <[email protected]>,
    Helen Deborah Vecht <[email protected]> wrote:

    > "Andy H" <[email protected]>typed
    >
    >
    >
    > > "Richard" <[email protected]> wrote in message
    > > news:[email protected]
    > > Snip -
    > > >......but as I neither sell, use, maintain, nor have any access to disk
    > > >brakes or QR axles, I could add nothing useful to the debate.
    > > >
    > > > R.

    > > Then do just that, you have no potential problems do you? Do you have the
    > > statistics to hand?

    >
    > > Andy H

    >
    >
    > The problem is not statistical.
    >
    > The problem is anecdotal.
    >
    > Many here in the UK will know of a single catastrophic event that might
    > have been the result of wheel ejection.
    >
    > A single catastrophe does not a statistic make but it does not mean
    > there is not a problem.
    >
    > That IS the problem.


    Please comment upon the force diagram for front disc brakes.

    --
    Michael Press
     
  12. jim beam

    jim beam Guest

    James Annan wrote:
    > Carlton Reid has a puff piece about a new "Secure QR system" on bikebiz:
    > <http://www.bikebiz.co.uk/daily-news/article.php?id=6427>
    >
    > While promoting this new mechanism as "safer" than the existing system,
    > he also insists that "industry experts say QRs are safe, when used
    > correctly".
    >
    > This assertion is backed up with a quote from "industry expert" Bob
    > Burns (actually Trek's *lawyer*), which is nothing more than a
    > boilerplate denial dating to a few years ago when the QR/disk issue
    > first surfaced.
    >
    > Strangely, alongside this there is no space in his article for these
    > quotes from people who actually have some relevant engineering and
    > technical experience:


    to which the response may as well be: "strangely, there's no space in
    this article for any evidence of this supposed disaster ever being
    attributable to anything other than inability to use a q.r."

    >
    > ---
    > Chris Juden, Technical officer, CTC:
    > "It's not just scaremongering, but all hangs together and makes perfect
    > sense. In fact I'm kicking myself for not thinking of it before."


    strange how he hadn't noticed disk brakes ejecting /before/ reading
    chicken littles tale of doom...

    >
    > "changes must be made to the way disk brakes and front wheels are
    > attached to forks"
    >
    > Jobst Brandt, author, "The Bicycle Wheel":
    > "The more I see on this the more I find the defense of the status quo
    > stranger than fiction. Why are writers trying to say that it can't
    > happen? What motivates writers to claim that disc brakes as currently
    > offered are not a hazard?


    as above, how are we not swamped with reports of ejected disks here on
    r.b.t? the chicken littles, would /LOVE/ to jump aboard if ejection was
    actually an occurrence.

    >
    > The mechanism has been clearly stated, the forces have been identified
    > in magnitude and direction, and credible descriptions of failures have
    > been presented. What's going on here! There is no easter bunny.
    > Believe it!"


    i'll believe it when i see it. i've been riding disk 3 years - never
    any slippage or ejection. and i still ask among others i meet with
    negative results. strange how reality seems to be so easily discounted
    around here.

    >
    > John Forester, author, "Effective Cycling":
    > "All that I can say is gross negligence."


    another one suckered into the hysteria.

    >
    > Unnamed Marzocchi Tech Support:
    > "It is recommended that an 8" rotor is not used on a standard axle fork
    > because the forces exerted on the wheel can potentially pull the axle
    > out of the dropouts."


    un named? that's credible james. especially when force is /less/ for
    an 8" disk compared to 6".

    >
    > Brant Richards, On-One:
    > "From the next batch, our rigid forks will have dropouts which are
    > angled forward at 45degrees or thereabouts.
    >
    > This is because when I was coming home, and pulling a stoppy outside my
    > driveway, I kept finding the front wheel shifted in the dropout."


    and his axle faces were serrated? and his dropouts were made of what?

    >
    > Dave Gray, Surly:
    > "You are correct. I've noticed the problem on my Karate Monkey fork."


    as above, steel fork.

    >
    > Ben Cooper, Kinetics, describing his experiment:
    > "Conclusion: From the above, there seems to be an effect from the disc
    > brake which causes the quick release to loosen."
    > ---


    eh? "loosening" is not slippage or ejection.

    >
    >
    > And even more strangely, although he mentions the ongoing Walmart case
    > concerning children's bikes, and refers repeatedly to user error, he
    > also didn't find space to mention the recent out of court settlement in
    > which a manufacturer paid off an (experienced adult) rider who was
    > seriously injured by a front wheel ejection on a disk+QR fork.
    >
    >
    > James


    bottom line, we still have yet to see any disk brake ejection. james,
    you get 10 points for effort in trying to create this storm, but alas,
    your teacup of evidence is bone dry. stick to climatology if you want
    to keep your name in the headlines - this is a q.r. user competency
    issue, not a disk brake design issue. what's next? the crusade against
    fundamentally unstable two-wheelers?
     
  13. Ed Pirrero

    Ed Pirrero Guest

    jim beam wrote:
    >
    >
    > bottom line, we still have yet to see any disk brake ejection. james,
    > you get 10 points for effort in trying to create this storm, but alas,
    > your teacup of evidence is bone dry. stick to climatology if you want
    > to keep your name in the headlines - this is a q.r. user competency
    > issue, not a disk brake design issue. what's next? the crusade against
    > fundamentally unstable two-wheelers?


    Fundementally, it's all about James' ego. That's why he busts out his
    yawn-inducing troll every four months or so.

    Funny thing - no movement at all in my Shimano XT QR on Marzocchi
    Flylight 80. Commuter with slicks - lots of hard, high-g braking.
    Lever got closed at about 80 degrees, which is a little less than
    normal for me.

    His chatter, along with the sycophantic "me toos", seems to have no
    effect on the ability of the QR to do its basic function. Heh.

    E.P.
     
  14. G.T.

    G.T. Guest

    jim beam wrote:
    >
    > i'll believe it when i see it. i've been riding disk 3 years -


    Clearly you're one of the many who don't need disks riding nothing
    off-road but the wimpier trails of Marin.

    >
    > bottom line, we still have yet to see any disk brake ejection.


    So what happened to Russ Pinder, someone who knows how to tighten a QR
    and checked his before his fateful ride? You're really offensive with
    your adamant refusal to acknowledge the failures that have happened.

    Greg
    --
    "All my time I spent in heaven
    Revelries of dance and wine
    Waking to the sound of laughter
    Up I'd rise and kiss the sky" - The Mekons
     
  15. jim beam wrote:

    > James Annan wrote:
    >
    >> Brant Richards, On-One: "From the next batch, our rigid forks will have
    >> dropouts which are angled forward at 45degrees or thereabouts. This is
    >> because when I was coming home, and pulling a stoppy outside my
    >> driveway, I kept finding the front wheel shifted in the dropout."

    >
    > and his axle faces were serrated? and his dropouts were made of what?


    What clamping force did he apply to the QR? Was it perhaps less than it
    should have been due to poor lubrication? What was the geometry and centre
    of mass of the bike+rider+panniers? What is the maximum instantaneous
    braking force it is possible to apply for this configuration?

    No thanks, I'll stick to a design that doesn't rely so heavily on so many
    unknowns and variables. Adding serrations to directly resist pullout of a
    critical component is not good design, it's a kludge required to make a
    fundamentally flawed design work most of the time. See if you can find a
    qualified mechanical engineer who disagrees.

    --
    Benjamin Lewis

    Now is the time for all good men to come to.
    -- Walt Kelly
     
  16. Michael Press <[email protected]>typed

    > >
    > >
    > > The problem is not statistical.
    > >
    > > The problem is anecdotal.
    > >
    > > Many here in the UK will know of a single catastrophic event that might
    > > have been the result of wheel ejection.
    > >
    > > A single catastrophe does not a statistic make but it does not mean
    > > there is not a problem.
    > >
    > > That IS the problem.


    > Please comment upon the force diagram for front disc brakes.


    I am neither a physicist nor engineer; many here are.

    I will leave comments to those more qualified.

    --
    Helen D. Vecht: [email protected]
    Edgware.
     
  17. Mike Causer

    Mike Causer Guest

    On Sun, 05 Feb 2006 20:31:15 +0000, Michael Press wrote:


    > Please comment upon the force diagram for front disc brakes.


    Are there any besides Annan's hand-drawn on a photo?

    That one omits the vertical load the forks put on the spindle, which at
    maximum braking effort will be weight of the rider plus ( bicycle minus
    front-wheel) .


    To eject the spindle the force trying to do so from the geometry of the
    brakes will need to be greater than that vertical load _plus_ the
    frictional force from the clamping of the spindle -- be it QR or hex
    nut. To do the calculations you need to know the coefficient of friction
    between tyre & road, and the location of the Centre of Gravity of the
    rider+bike combination as well as the location of the brake pads,
    the front wheel & brake diameters, and the wheelbase.

    Because the CoG of recumbents is somewhat lower than an upright, the
    braking forces can be greater (10-15% -- not as much better as some
    believe) so I would expect a genuine problem to turn up first on
    disk-braked 'bents. I've been reading the HPVA mailing lists and
    alt.rec.bicycles.recumbents for many years and don't remember seeing this
    problem mentioned. OTOH, maybe 'bent riders know how to do up a QR
    properly.



    Mike
     
  18. Mike Causer writes:

    >> Please comment upon the force diagram for front disc brakes.


    > Are there any besides Annan's hand-drawn on a photo?


    > That one omits the vertical load the forks put on the spindle, which
    > at maximum braking effort will be weight of the rider plus ( bicycle
    > minus front-wheel) .


    > To eject the spindle the force trying to do so from the geometry of
    > the brakes will need to be greater than that vertical load _plus_
    > the frictional force from the clamping of the spindle -- be it QR or
    > hex nut. To do the calculations you need to know the coefficient of
    > friction between tyre & road, and the location of the Centre of
    > Gravity of the rider+bike combination as well as the location of the
    > brake pads, the front wheel & brake diameters, and the wheelbase.


    You can isolate the forces of interest more simply by noting the ratio
    of wheel OD to brake disk diameter and from that assess forces
    (assuming a traction coefficient of one, which is appropriate for
    knobby tires on stiff clay or road tires on dry pavement). The rear
    portion of the disk rotates upward through the brake caliper that
    stops the wheel and thereby receives an upward force of wheel:disk
    ratio times the load on the wheel, even tough the downward force on
    the dropout is only half the wheel load, each dropout carrying half
    that load.

    I think that calculation accurately states the problem and should make
    apparent why this is a bad design. Forget about GC and other
    calculations that muddy the straight forward relationship between
    downward and upward forces on the dropout in question. I think
    caliper position is an obvious main item for discussion.

    Jobst Brandt
     
  19. Jay Beattie

    Jay Beattie Guest

    Werehatrack wrote:
    > On Sat, 04 Feb 2006 13:24:51 -0800, "G.T." <[email protected]>
    > wrote:
    >
    > >David wrote:
    > >> James Annan wrote:
    > >>
    > >>> Werehatrack wrote:
    > >>>
    > >>>> Those of us who have seen your prior postings about the issue of disc
    > >>>> brake ejections are fully aware of your position on the matter.
    > >>>
    > >>>
    > >>>
    > >>> However, those who read Carlton's article on Bikebiz might think it
    > >>> safe to draw the conclusion that "industry experts say QRs are safe,
    > >>> when used correctly", even though numerous industry experts have quite
    > >>> clearly expressed the contrary view.
    > >>>
    > >>> They will also not know that one case was recently settled in favour
    > >>> of the rider.
    > >>>
    > >>> James
    > >>
    > >>
    > >> Out of court settlements almost always include a statement that the
    > >> plantiff is not admitting liability. It is often less costly to pay a
    > >> small settlement than it is to defend the claim, particularly if the
    > >> jurisdiction is known to be plaintiff-favorable.

    > >
    > >That first plantiff should be defendant.

    >
    > True, as is the statement so amended.
    >
    > And in fact, in most such cases, getting an out-of-court settlement
    > also has two other beneficial results for the defendant; it ends the
    > case completely without any opening for it to continue through some
    > sort of appeal, and it precludes the possibility that the case can be
    > used as a precedent. Given the combination of cost of defense, the
    > possibility that the suit might initially be lost (and thereby often
    > bring on a spate of me-too suits), the hazard that the defense expense
    > might dwarf the actual settlement if an appeal is (or must be) filed,
    > and the hazard that the finding might be cited in other cases as a
    > precedent, there's lots of reason to shut down the process by making
    > an offer to settle even when the case isn't necessarily all that
    > strong for the plaintiff.


    The fact is that most cases settle -- except med mal, where the
    consequences of settlement are significant (doctor gets reported to
    national registry, premiums go through the roof), and the chances of
    winning generally are high. Notwithstanding what you read in the news,
    it is the rare case when a plaintiff wins a med-mal case. Products
    cases -- even big ones -- usually settle unless there is an
    exceptionally low chance of liability or the probable award is way
    lower than plaintiff's demand. Also, some companies just try
    everything, and some companies settle everything. Toro -- the lawmower
    company -- puts everything into mediation. Make a claim, go to
    mediation.

    > In some states, the impetus to settle is being reduced by
    > defendant-friendly changes to statute, often made under the guise of
    > "ending lawsuit abuse". Sometimes, what's billed as an abuse-control
    > measure turns out to be a PLI-defense attorney's nightmare...because
    > the defense lawyers don't get paid the big bucks for doing the
    > slam-dunk early dismissal filings, they only make the big bucks when
    > the case goes on long enough to rack up some worthwhile billable
    > hours.


    You have been reading too many Grisham novels. Every time some tort
    reform package is put together, it usually gets smushed like a bug. All
    I see are statutes creating new claims for relief and not ending them,
    particularly in the employment field.

    > Look for subtle and stealthy moves by PLI defense attorneys, and more
    > open ones by plaintiff lawyers, to get plaintiff-friendly changes made
    > if their billable hours drop too low. They both have a vested
    > interest in keeping the process alive.


    There is very, very little legislation proposed by defense lawyers, and
    most of that is "law improvement" legislation, e.g., clarificaiton of a
    poorly drafted statute or process-related changes like amending the
    rules of civil proceedure. Most all of that is done on a bi-partisan
    basis. Most of the defense-friendly tort reform legislation is proposed
    by industry or professional organizations including the AMA and the
    Chamber of Commerce. On the other hand, ATLA and some of the
    plaintiff's attorneys groups do propose or oppose legislation more
    vigorously -- which generally means a welter of Erin Brockovich
    commercials until the legislation passes or fails. -- Jay Beattie.
     
  20. Mike Causer

    Mike Causer Guest

    On Mon, 06 Feb 2006 01:23:22 +0000, jobst.brandt wrote:

    > I think that calculation accurately states the problem and should make
    > apparent why this is a bad design.


    The racing car design world went through this in the 1970s when the
    argument was that leading calipers loaded the hub bearings under braking
    but trailing calipers unloaded the hub. So the effect is there without
    doubt. For racing cars (and modern motorbikes) it turned out that brake
    cooling was more important than bearing loads.


    > Forget about GC and other calculations that muddy the straight forward
    > relationship between downward and upward forces on the dropout in
    > question.


    I am not questioning the direction of the load, what I _am_ questioning
    is its magnitude in relation to the other loads present. To find the
    value of the ejection force and the value of the retaining forces we
    need to know the geometry of the whole bike and rider.


    > I think caliper position is an obvious main item for discussion.


    If the caliper is forward of the axle it will not try to eject the
    spindle, but it will obstruct cooling of the disc. If the caliper is
    aft of the axle the cooling will improve, but it will try to eject the
    spindle. If the cooling _is_ needed are the ejection forces outweighed
    by the existing retention forces?

    As I have not yet seen a bicycle brake disk that looked as if any effort
    had been made to improve its cooling (funky slots don't do a lot [1]), I
    suppose that brake overheating is not a significant factor in bike
    brakes, so the short-duration loading on emergency stops should take
    precedence and the caliper would preferably be to the front. If I
    lived in the Alps instead of the Fens I might have a different view.



    [1] Slots and holes take the "fire-band" off the pad material. To get
    the pads that hot the disk will be glowing red. To have the slots
    doing anything to cool the disk there needs to be an airflow _though_
    them, which needs air ducts or some other method of moving air at right
    angles to the direction of travel.



    Mike
     
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