Carlton Reid on QR safety

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

  1. jim beam

    jim beam Guest

    James Annan wrote:
    > Tony Raven wrote:
    >
    >
    >> No one has yet commented on how the QR gets over the lawyers lips
    >> without anyone noticing how loose the wheel has become in the forks
    >> and the disc rubbing on the pads as the wheel flops from side to side.

    >
    >
    > By Jove, Tony, I think you've got it! In 3 years of this "debate",
    > no-one has yet mentioned this critical and obvious point! What were we
    > all thinking of?
    >
    > Sheesh. That's a truly lame attempt at denial, even by your own standards.
    >
    > James


    by jove, james, that's a really weak and pathetic denial of a pertinent
    and obvious point! truly lame, even by your own standards.
     


  2. jim beam

    jim beam Guest

    Michael Press wrote:
    > In article <[email protected]>,
    > Tony Raven <[email protected]> wrote:
    >
    >
    >>Mike Causer wrote:
    >>
    >>>On Mon, 06 Feb 2006 04:12:58 +0000, Michael Press wrote:
    >>>
    >>>
    >>>>You owe it to yourself to see for yourself. Jobst Brandt has already
    >>>>posted a clear word picture of what is going on. The braking force of the
    >>>>disk caliper on the disk generates a force. At the fork tips the braking
    >>>>force translates into a force on the axle in the direction out of the fork
    >>>>tips,
    >>>
    >>>This is correct if the caliper is behind the fork and the fork slots
    >>>are vertical.
    >>>

    >>
    >>Wrong. Provided the caliper is not mounted in line with the centre line
    >>of the fork slot there will be a component of the force along the centre
    >>line of the slot. If the caliper is behind the centre line the force
    >>component will be out of the slot, in front and its into the slot.
    >>
    >>No one has yet commented on how the QR gets over the lawyers lips
    >>without anyone noticing how loose the wheel has become in the forks and
    >>the disc rubbing on the pads as the wheel flops from side to side.

    >
    >
    > Loosening of the quick release nut from brake forces and
    > rough terrain vibration. The quick release clamp is not
    > designed for these conditions.
    >

    it's nylocked /and/ serrated, therefore it /is/ designed to resist
    vibration.
     
  3. jim beam

    jim beam Guest

    Tim McNamara wrote:
    > Or you could just mount the caliper on the leading side of the fork
    > and eliminate the need for the discussion entirely.


    no tim, it's bad deployment of both fork material and caliper material.
    compressive force [rear mounting] is much safer. which is why it's done.
     
  4. jim beam

    jim beam Guest

    Mike Causer wrote:
    > On Mon, 06 Feb 2006 19:32:45 +0000, jobst.brandt wrote:
    >
    >
    >>>If you open your copy of Bicycling Science 3rd Ed to page 244, you will
    >>>see that DGW shows the calculation of the maximum retardation possible
    >>>for any bicycle configuration and that it depends on the position of the
    >>>Centre of Mass. As the ejection force depends on the actual
    >>>retardation, it should be clear that the maximum ejection force
    >>>generated is directly dependent on the maximum retardation possible
    >>>which is directly dependent on the rider position.

    >>
    >>That is for retardation of the bicycle and rider. It has nothing to do
    >>with what is essential to the force on the dropout.

    >
    >
    > So are you saying that this ejection force exists even if there is no
    > braking? Or if it only exists under braking, that it does not vary with
    > the amount of braking effort?
    >
    >
    >
    > Mike


    heretic.
     
  5. jim beam

    jim beam Guest

    Werehatrack wrote:
    > On 06 Feb 2006 15:22:28 +0000 (GMT), David Damerell
    > <[email protected]> wrote:
    >
    >
    >>Quoting Andy H <[email protected]>:
    >>
    >>>If
    >>>the design is inherently flawed why have we not all been maimed by our
    >>>disk/qr problems?

    >>
    >>Hyperbole. A design can be unsafe relative to other designs without the
    >>failure rate being such as to injure every user.

    >
    >
    > The stated attitude, however, is at the root of the problem. To
    > convince someone of a risk, it must be presented to them in terms that
    > they can understand, and it must look like something that could
    > actually be a problem *for them*. Thus far, I have to say that the
    > evidence for wheel ejection as a problem for the average rider is much
    > too thin to be compelling. One good, repeatable demo could change
    > that. I doubt that anything else will.


    indeed.
     
  6. jim beam

    jim beam Guest

    James Annan wrote:
    > Werehatrack wrote:
    >
    >>On 5 Feb 2006 22:47:12 -0800, "James Annan"
    >><[email protected]> wrote:
    >>
    >>
    >>>Werehatrack wrote:
    >>>
    >>>
    >>>>It is very hard to convince people that a problem is both real *and
    >>>>serious* when you don't have anything but math and a few isolated
    >>>>phenomena to offer as evidence. That the problem is real they may
    >>>>accept if they are math-literate, but since nearly everything has risk
    >>>>of one sort or another, it's also necessary to convince them that the
    >>>>problem is serious enough (not just in terms of potential harm should
    >>>>it occur, but more specifically in terms of the potential for the harm
    >>>>to come *to them* at all) before they will be persuaded that action is
    >>>>warranted or necessary. The paucity of demonstrated failures speaks
    >>>>volumes to the masses.
    >>>
    >>>Do you think that Shimano were wrong to recall their brake cables?
    >>>
    >>>http://www.bikebiz.com/daily-news/article.php?id=4933
    >>>
    >>>----
    >>>A statement from Shimano said:
    >>>
    >>>"It is possible that the tensile strength of the joint between the
    >>>cable and the cable end (nipple) may not meet Shimano's usual standards
    >>>and that therefore the nipple, when under stress during application of
    >>>the brake, could pull loose or detach from the cable. This could lead
    >>>to brake failure.
    >>>
    >>>"Shimano is not aware of any case in which the nipple has separated

    >>
    >>>from one of these cables during use on a bicycle."

    >>
    >>>----
    >>>
    >>>Note that not only was there not a single injury as a result of this
    >>>fault, there wasn't even a single failure in use. Numerous recalls are
    >>>made on a similar basis - this was just the first I googled. I question
    >>>whether you are aware of the relevant laws on the matter.

    >>
    >>This was an example of a readily replicatable and demonstrated
    >>shortcoming in a product. Shimano acted correctly even though no
    >>in-service failures were on record.

    >
    >
    > Why would they do any testing? There were no reported failures, right?
    >
    > Just like in the case of disk brakes - except in this case there
    > actually are several reported cases, which have all been brushed off by
    > the manufacturers - except for the ones who paid off a plaintiff.
    >
    >
    > James
    >


    so james, are you able to differentiate between someone that doesn't
    operate their qr correctly [user error] and design flaw? no? are you
    going to keep on ignoring the FACT that correctly fastened qr's retain
    wheels with a significant safety margin? [also ignoring the efficacy of
    lawyer lips of course.] until you can, you're simply the lunatic the
    industry is going to ignore.
     
  7. Benjamin Lewis writes:

    >>>> 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 don't see why. All that is required is what I stated, the ratio
    >>> of disk diameter to tire OD and the position of the caliper. The
    >>> fore that the caliper puts on the fork relative to the wheel is as
    >>> I stated, only caliper location is the matter at hand.


    >> Except that there is a maximum force that be generated in this way,
    >> and to find the maximum we need to consider the factors I've
    >> mentioned.


    >> Assuming a conventional upright bike, with wheelbase a little over
    >> 1 metre, the maximum braking effort is found when the back wheel
    >> lifts, at which point the retardation will be about 0.65g.


    > You don't think you can momentarily spike the braking force above
    > that without doing an endo?


    Use your imagination. The rider is descending a bumpy trail, causing
    intermittent lift-off. When he lands, the wheel skids and he bounces
    again. Anyone who has some trail experience has heard and seen this
    effect. It does not involve and end-over.

    > (I don't know if you can, or by how much, but the point seems to
    > have been neglected).


    If you stop averaging for the bicycle, you'll see that fairly high
    forces are absorbed. This is just like the people who cannot
    visualize that a spoked wheel regularly gets peak loads that are as
    much as four time the average load. That's why crummy wheels need
    spoke prep.

    Jobst Brandt
     
  8. jim beam

    jim beam Guest

    [email protected] wrote:
    > Benjamin Lewis writes:
    >
    >
    >>>>>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 don't see why. All that is required is what I stated, the ratio
    >>>>of disk diameter to tire OD and the position of the caliper. The
    >>>>fore that the caliper puts on the fork relative to the wheel is as
    >>>>I stated, only caliper location is the matter at hand.

    >
    >
    >>>Except that there is a maximum force that be generated in this way,
    >>>and to find the maximum we need to consider the factors I've
    >>>mentioned.

    >
    >
    >>>Assuming a conventional upright bike, with wheelbase a little over
    >>>1 metre, the maximum braking effort is found when the back wheel
    >>>lifts, at which point the retardation will be about 0.65g.

    >
    >
    >>You don't think you can momentarily spike the braking force above
    >>that without doing an endo?

    >
    >
    > Use your imagination. The rider is descending a bumpy trail, causing
    > intermittent lift-off. When he lands, the wheel skids and he bounces
    > again. Anyone who has some trail experience has heard and seen this
    > effect. It does not involve and end-over.


    so jobst, on my ride this sunday, i descended three sections of rocky
    trail that were so steep, even hard braking at the skid threshold could
    not prevent rapid acceleration. these were hard rock bumpy rock, no
    loose surface to reduce tire friction. now, given that my qr was
    exactly as tight after this ride as it was before, with not even
    slippage evident, can you please explain to me how exactly ejection
    force is spiking beyond retention force "descending a bumpy trail"? how
    about the fact that i've never experienced slippage or ejection in the 3
    years i've ridden disk brakes? you can answer from your own extensive
    experience actually riding disk braked mountain bikes, right?

    >
    >
    >>(I don't know if you can, or by how much, but the point seems to
    >>have been neglected).

    >
    >
    > If you stop averaging for the bicycle, you'll see that fairly high
    > forces are absorbed. This is just like the people who cannot
    > visualize that a spoked wheel regularly gets peak loads that are as
    > much as four time the average load. That's why crummy wheels need
    > spoke prep.


    red herring.

    >
    > Jobst Brandt
     
  9. G.T.

    G.T. Guest

    jim beam wrote:
    > [email protected] wrote:
    >
    >> Benjamin Lewis writes:
    >>
    >>
    >>>>>> 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 don't see why. All that is required is what I stated, the ratio
    >>>>> of disk diameter to tire OD and the position of the caliper. The
    >>>>> fore that the caliper puts on the fork relative to the wheel is as
    >>>>> I stated, only caliper location is the matter at hand.

    >>
    >>
    >>
    >>>> Except that there is a maximum force that be generated in this way,
    >>>> and to find the maximum we need to consider the factors I've
    >>>> mentioned.

    >>
    >>
    >>
    >>>> Assuming a conventional upright bike, with wheelbase a little over
    >>>> 1 metre, the maximum braking effort is found when the back wheel
    >>>> lifts, at which point the retardation will be about 0.65g.

    >>
    >>
    >>
    >>> You don't think you can momentarily spike the braking force above
    >>> that without doing an endo?

    >>
    >>
    >>
    >> Use your imagination. The rider is descending a bumpy trail, causing
    >> intermittent lift-off. When he lands, the wheel skids and he bounces
    >> again. Anyone who has some trail experience has heard and seen this
    >> effect. It does not involve and end-over.

    >
    >
    > so jobst, on my ride this sunday, i descended three sections of rocky
    > trail that were so steep,


    Get back to us when you descend something for more than 30 seconds.

    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
     
  10. James Annan

    James Annan Guest

    jim beam wrote:

    > until you can, you're simply the lunatic the
    > industry is going to ignore.


    It's not me they have to worry about, it's the injured riders seeking
    compensation. But if they are happy to pay anyone off who gets as far
    as serving a writ, this could go on a long time. Especially since the
    journalists have apparently decided that their readers don't need to
    hear about it.

    James
     
  11. Luns Tee

    Luns Tee Guest

    In article <[email protected]>,
    jim beam <[email protected]> wrote:
    >Tim McNamara wrote:
    >> Or you could just mount the caliper on the leading side of the fork
    >> and eliminate the need for the discussion entirely.

    >
    >no tim, it's bad deployment of both fork material and caliper material.
    > compressive force [rear mounting] is much safer. which is why it's done.


    Two questions.
    1) What is the distance between the brake disc and the caliper mount
    2) How thick is the caliper mount on an MTB fork?

    Then, from the answers, answer these questions:

    1) What turning moment does the force of braking generate as
    it's transmitted across this distance
    2) What forces must be present in the caliper mount to support
    this moment

    -Luns
     
  12. Clive George

    Clive George Guest

    "Michael Press" <[email protected]> wrote in message
    news:[email protected]
    > In article
    > <[email protected]>,
    > "Clive George" <[email protected]> wrote:
    >
    >> "Michael Press" <[email protected]> wrote in message
    >> news:[email protected]
    >>
    >> >> > 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.
    >> >
    >> > You owe it to yourself to see for yourself.

    >>
    >> Micheal, you seem to be confusing comment with understanding.
    >> Understanding
    >> the force diagram is easy enough. Being able to comment on it in a useful
    >> manner, especially without repeating what has already been said, is
    >> entirely
    >> different.
    >>
    >> Or do you feel "me too" is an acceptably useful post?

    >
    > Some folks are adamant that there is not a problem; but
    > never address the force diagram, and its consequences.


    You might want to read what Helen wrote a little more carefully then, rather
    than just leaping in in the manner in which you did.

    > Being able to comment upon it in a useful manner is a
    > prerequisite to productively entering this discussion.


    Bollocks. Maybe the physics is all you're interested in, but there are other
    ramifications - eg user interface, legal, and the one which Helen raised,
    which is the perception of the problem.

    cheers,
    clive
     
  13. Tony Raven

    Tony Raven Guest

    [email protected] wrote:
    >
    > I've seen several beginning bicyclists misuse a quick release and
    > showed them the correct method of fastening the wheel. So I think
    > that bicyclists should welcome a simplification of the current design.
    >


    Not just beginners. I put the following page up two years ago
    http://www.cycling.raven-family.com/Dropouts/QR.htm

    --
    Tony

    "The best way I know of to win an argument is to start by being in the
    right."
    - Lord Hailsham
     
  14. Tony Raven

    Tony Raven Guest

    Michael Press wrote:
    > In article <[email protected]>,
    > Tony Raven <[email protected]> wrote:
    >>
    >> No one has yet commented on how the QR gets over the lawyers lips
    >> without anyone noticing how loose the wheel has become in the forks and
    >> the disc rubbing on the pads as the wheel flops from side to side.

    >
    > Loosening of the quick release nut from brake forces and
    > rough terrain vibration. The quick release clamp is not
    > designed for these conditions.
    >


    Try it. Undo your quick release until it just releases over the lawyers
    lips and then do it up just enough to marginally retain the axle. Go
    test ride the bike carefully. Then tell me that it is not very obvious
    that the QR is undone. I know, I've forgotten to do up the QR on
    occasions when setting off and I have never got more than a few yard
    before it is very obvious something is wrong.

    --
    Tony

    "The best way I know of to win an argument is to start by being in the
    right."
    - Lord Hailsham
     
  15. Tony Raven

    Tony Raven Guest

    jim beam wrote:
    >
    > it's nylocked /and/ serrated, therefore it /is/ designed to resist
    > vibration.


    As recommended as two of the three ways to prevent vibration loosening
    in the Bolt Science website that JA uses as the basis for his vibration
    loosening theory. That bit always seems to be glossed over for some reason.

    --
    Tony

    "The best way I know of to win an argument is to start by being in the
    right."
    - Lord Hailsham
     
  16. James Annan

    James Annan Guest

    Tony Raven wrote:

    > Michael Press wrote:
    >
    >> In article <[email protected]>,
    >> Tony Raven <[email protected]> wrote:
    >>
    >>>
    >>> No one has yet commented on how the QR gets over the lawyers lips
    >>> without anyone noticing how loose the wheel has become in the forks
    >>> and the disc rubbing on the pads as the wheel flops from side to side.

    >>
    >>
    >> Loosening of the quick release nut from brake forces and rough terrain
    >> vibration. The quick release clamp is not designed for these conditions.
    >>

    >
    > Try it. Undo your quick release until it just releases over the lawyers
    > lips and then do it up just enough to marginally retain the axle. Go
    > test ride the bike carefully. Then tell me that it is not very obvious
    > that the QR is undone. I know, I've forgotten to do up the QR on
    > occasions when setting off and I have never got more than a few yard
    > before it is very obvious something is wrong.


    So what? Even you can't deny that this wheel loss actually happens. Some
    of the people have noticed their front wheel coming loose. Some of them
    lost the wheel before they could stop. So what's your point?

    James
    --
    James Annan
    see web pages for email
    http://www.ne.jp/asahi/julesandjames/home/
    http://julesandjames.blogspot.com/
     
  17. Quoting Tony Raven <[email protected]>:
    >Try it. Undo your quick release until it just releases over the lawyers
    >lips and then do it up just enough to marginally retain the axle. Go
    >test ride the bike carefully. Then tell me that it is not very obvious
    >that the QR is undone.


    OK, I will; the local chavs periodically undo front QRs, so - back when I
    had a front QR hub - I've found myself riding with a loose one once or
    twice (lucky me, I don't have a disc brake). No, it's not necessarily
    obvious; and that's on smooth flat pavement, not rattling about like crazy
    down a hill offroad. The axle is retained in its normal position in the
    dropouts by the weight of the rider.
    --
    David Damerell <[email protected]> Kill the tomato!
    Today is First Monday, February.
     
  18. jim beam

    jim beam Guest

    James Annan wrote:
    > Tony Raven wrote:
    >
    >> Michael Press wrote:
    >>
    >>> In article <[email protected]>,
    >>> Tony Raven <[email protected]> wrote:
    >>>
    >>>>
    >>>> No one has yet commented on how the QR gets over the lawyers lips
    >>>> without anyone noticing how loose the wheel has become in the forks
    >>>> and the disc rubbing on the pads as the wheel flops from side to side.
    >>>
    >>>
    >>>
    >>> Loosening of the quick release nut from brake forces and rough
    >>> terrain vibration. The quick release clamp is not designed for these
    >>> conditions.
    >>>

    >>
    >> Try it. Undo your quick release until it just releases over the
    >> lawyers lips and then do it up just enough to marginally retain the
    >> axle. Go test ride the bike carefully. Then tell me that it is not
    >> very obvious that the QR is undone. I know, I've forgotten to do up
    >> the QR on occasions when setting off and I have never got more than a
    >> few yard before it is very obvious something is wrong.

    >
    >
    > So what? Even you can't deny that this wheel loss actually happens.


    i'll deny it for you james. wheel loss CANNOT happen on a fork with
    lawyer lips. sorry to point out something so fundamentally obvious and
    painful for you, but reality has to slap you in the face some day.

    > Some
    > of the people have noticed their front wheel coming loose. Some of them
    > lost the wheel before they could stop. So what's your point?
    >
    > James
     
  19. jim beam

    jim beam Guest

    G.T. wrote:
    > jim beam wrote:
    >
    >> [email protected] wrote:
    >>
    >>> Benjamin Lewis writes:
    >>>
    >>>
    >>>>>>> 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 don't see why. All that is required is what I stated, the ratio
    >>>>>> of disk diameter to tire OD and the position of the caliper. The
    >>>>>> fore that the caliper puts on the fork relative to the wheel is as
    >>>>>> I stated, only caliper location is the matter at hand.
    >>>
    >>>
    >>>
    >>>
    >>>>> Except that there is a maximum force that be generated in this way,
    >>>>> and to find the maximum we need to consider the factors I've
    >>>>> mentioned.
    >>>
    >>>
    >>>
    >>>
    >>>>> Assuming a conventional upright bike, with wheelbase a little over
    >>>>> 1 metre, the maximum braking effort is found when the back wheel
    >>>>> lifts, at which point the retardation will be about 0.65g.
    >>>
    >>>
    >>>
    >>>
    >>>> You don't think you can momentarily spike the braking force above
    >>>> that without doing an endo?
    >>>
    >>>
    >>>
    >>>
    >>> Use your imagination. The rider is descending a bumpy trail, causing
    >>> intermittent lift-off. When he lands, the wheel skids and he bounces
    >>> again. Anyone who has some trail experience has heard and seen this
    >>> effect. It does not involve and end-over.

    >>
    >>
    >>
    >> so jobst, on my ride this sunday, i descended three sections of rocky
    >> trail that were so steep,

    >
    >
    > Get back to us when you descend something for more than 30 seconds.
    >
    > Greg
    >

    eh? how does that effect grade or braking magnitude???
     
  20. jim beam

    jim beam Guest

    Luns Tee wrote:
    > In article <[email protected]>,
    > jim beam <[email protected]> wrote:
    >
    >>Tim McNamara wrote:
    >>
    >>>Or you could just mount the caliper on the leading side of the fork
    >>>and eliminate the need for the discussion entirely.

    >>
    >>no tim, it's bad deployment of both fork material and caliper material.
    >> compressive force [rear mounting] is much safer. which is why it's done.

    >
    >
    > Two questions.
    > 1) What is the distance between the brake disc and the caliper mount
    > 2) How thick is the caliper mount on an MTB fork?
    >
    > Then, from the answers, answer these questions:
    >
    > 1) What turning moment does the force of braking generate as
    > it's transmitted across this distance
    > 2) What forces must be present in the caliper mount to support
    > this moment
    >
    > -Luns


    aha! logic!!! excellent!

    i started going down that road in the carbon seat post thread recently,
    but no one seemed interested in talking sense...

    in brief,

    1. the disk tab is roughly 1/3rd the distance from the axle of the brake
    bosses.
    2. there is one primary tab, which is thiner than one brake boss.

    numbers are back in that thread.
     
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