Disk brakes and wheel ejection - Manitou's answer?

Quoted post said:

Originally posted by Mark McMaster
There have been several recent discussions regarding wheel
ejection forces caused by front disk brakes. In the
discussions, several possible design changes have been
suggested to mitigate the potential for wheel ejection. One
of the suggested changes was to re-orient the dropout axle
slot to face forward, so the slot would be perpendicular to
the wheel ejection force. Manitou, a prominent maker of
disk brake compatible suspension forks, appears to have
done just that.

In the May and June editions of "Mountain Bike Action"
magazine there is an advertisement by Manitou for their new
fork, the 2005 Nixon Platinum. The photograph of the fork
shows that the axle slot is oriented at an angle of about 45
degrees forward of the steering axis, which is just about at
the same angle as the line between the disk brake and the
axle. With a typical mountain bike head angle of about 70
degrees, the axle slot on this fork would be at angle of
about 65 degrees forward from the vertical.

It is unlikely that Manitou will admit that the new drop-out
design is in response to disk brake safety issues posed by
their previous designs, but I can't see what other reason
there could be for this new design.

Mark McMaster [email hidden]

Sturdy fork design with huge " lawyer lips" and a strong well secured QR will also help. I suspect we will see others who want to follow the trend towards disc brakes to make similar design changes.
It will also be interesting to see if the industry will adopt a wider spacing to provide for a front wheel that has better spoke support angles.

why do people want to wail & beat their breasts over mere
conjecture, yet have absolutely _no_ interest in
confronting fact?

my own posting showing _zero_ evidence of any slippage over
a considerable period of use elicited only one response;
that of carl fogel wondering why no one had bothered to
comment in view of previous 500# threads on the same
subject!!!

groups.google.comgroupsOpen ↗
fork%2Bgroup:rec.bicycles.tech%26hl%3Den%26lr%3D%26ie%3DUTF-
8%26oe%3DUTF-
8%26scoring%3Dr%26selm%3DPErbc.45543%2524UD3.38107%2540news-
svr25.news.prodigy.com%26rnum%3D5

carl, if you're reading this, perhaps you have some thoughts
on the perversity of human nature.

jb

Mark McMaster said:

There have been several recent discussions regarding wheel
ejection forces caused by front disk brakes. In the
discussions, several possible design changes have been
suggested to mitigate the potential for wheel ejection.
One of the suggested changes was to re-orient the dropout
axle slot to face forward, so the slot would be
perpendicular to the wheel ejection force. Manitou, a
prominent maker of disk brake compatible suspension forks,
appears to have done just that.

In the May and June editions of "Mountain Bike Action"
magazine there is an advertisement by Manitou for their
new fork, the 2005 Nixon Platinum. The photograph of the
fork shows that the axle slot is oriented at an angle of
about 45 degrees forward of the steering axis, which is
just about at the same angle as the line between the disk
brake and the axle. With a typical mountain bike head
angle of about 70 degrees, the axle slot on this fork
would be at angle of about 65 degrees forward from the
vertical.

It is unlikely that Manitou will admit that the new drop-
out design is in response to disk brake safety issues
posed by their previous designs, but I can't see what
other reason there could be for this new design.

Mark McMaster [email hidden]

jim beam said:

why do people want to wail & beat their breasts over mere
conjecture, yet have absolutely _no_ interest in
confronting fact?

my own posting showing _zero_ evidence of any slippage over
a considerable period of use elicited only one response;
that of carl fogel wondering why no one had bothered to
comment in view of previous 500# threads on the same
subject!!!

groups.google.comgroupsOpen ↗
ork%2Bgroup:rec.bicycles.tech%26hl%3Den%26lr%3D%26ie%3DUTF-
8%26oe%3DUTF-
8%26scoring%3Dr%26selm%3DPErbc.45543%2524UD3.38107%2540new-
ssvr25.news.prodigy.com%26rnum%3D5

carl, if you're reading this, perhaps you have some
thoughts on the perversity of human nature.

jb

Mark McMaster said:

There have been several recent discussions regarding
wheel ejection forces caused by front disk brakes. In the
discussions, several possible design changes have been
suggested to mitigate the potential for wheel ejection.
One of the suggested changes was to re-orient the dropout
axle slot to face forward, so the slot would be
perpendicular to the wheel ejection force. Manitou, a
prominent maker of disk brake compatible suspension
forks, appears to have done just that.

In the May and June editions of "Mountain Bike Action"
magazine there is an advertisement by Manitou for their
new fork, the 2005 Nixon Platinum. The photograph of the
fork shows that the axle slot is oriented at an angle of
about 45 degrees forward of the steering axis, which is
just about at the same angle as the line between the disk
brake and the axle. With a typical mountain bike head
angle of about 70 degrees, the axle slot on this fork
would be at angle of about 65 degrees forward from the
vertical.

It is unlikely that Manitou will admit that the new drop-
out design is in response to disk brake safety issues
posed by their previous designs, but I can't see what
other reason there could be for this new design.

Mark McMaster [email hidden]

Dear Jim,

My thoughts on human nature are too perverse for
publication.

Here are those two pictures that you took of your disk-brake
and fork. Judging by the tooth-marks of the quick-reelase
washers in the front axle slot, no ejection force was great
enough to even begin to drag the teeth out of position:

home.comcast.netImg 3199.jpgOpen ↗

home.comcast.netImg 3196.jpgOpen ↗

If I followed your theory in that thread, the flaw in the
notion that the disk brake would lever a quick-release and
its wheel out of a fork was that most calculations failed to
consider the tremendously greater resistance provided when
normal serrated washers bite even a tiny bit into the fork.

Here's the tinyurl version of your post:

tinyurl.comyutgyOpen ↗

or

groups.google.comgroupsOpen ↗
8&selm=PErbc.45543%24UD3.38107%40newssvr25.news.prodigy.com

If anyone has pictures of disk-brake forks that show marks
of such serrated washers being dragged out of position, I'd
be glad to host them.

Some people who posted in the ejection thread indicated that
they were going to mark quick-releases and watch for
movement, so if they have pictures of whatever happened, I
can host them, too.

Carl Fogel

jim beam said:

why do people want to wail & beat their breasts over mere
conjecture, yet have absolutely _no_ interest in
confronting fact?

What is conjecture and what is fact? That current (front)
disk brake designs generate very large forces tending to
pull the axle out of the dropout? Anyone who can construct a
free body diagram or conduct a simple experiment can see
that these forces exist. That Manitou has redesigned the
dropouts on their latest fork in a way which reduces the
chances that the disk brake forces pull the wheel out? The
photographic evidence of their redesign is in national
publications. While no explanation is given for the design
change, I doubt that it was for ease of use, as it will be
more difficult to insert a wheel into these forward facing
dropouts than fir traditional vertical dropouts. (Note:
Manitou probably knows better than many about the forces
exerted on dropouts, after having endured a costly product
recall of their Mach 5 forks due to the breakage of
improperly designed and manufactured dropouts.)

Quoted message said:

my own posting showing _zero_ evidence of any slippage
over a considerable period of use elicited only one
response; that of carl fogel wondering why no one had
bothered to comment in view of previous 500# threads on
the same subject!!!

groups.google.comgroupsOpen ↗
rk%2Bgroup:rec.bicycles.tech%26hl%3Den%26lr%3D%26ie%3DUTF-
8%26oe%3DUTF-
8%26scoring%3Dr%26selm%3DPErbc.45543%2524UD3.38107%2540ne-
wssvr25.news.prodigy.com%26rnum%3D5

Here is where the larger conjecture lay. You seem to
contend that just because you have not seen evidence of
wheel pull-out in a sample of one (and not a particularly
well controlled sample at that), that it can't exist with
any combination of axle/dropout/skewer. How do you account
for others who have experienced dropout axle movement with
disk brake equipped bikes? There have been several reports
in the press about occurrences of axle slippage with quick
release brakes. For example, Lennerd Zinn (frame builder,
technical editor, and author of several books on bicycle
repair and maintenance) reports having seen this phenomenon
on several bikes:

velonews.com5432.0.htmlOpen ↗

Here is an account of Missy Giove (professional mountain
bike racer and former world champion) having her front
quick release inexplicably loosen up on a disk brake
equipped bike.

cyclingforums.comt25255 15 1.htmlOpen ↗

There have been several others that have been in the
national press as well. It is difficult to chalk these
occurrences up simply to improper usage of quick releases
skewers - if anyone should know how to tighten a quick
release, you would expect at least Zinn should (and his
experiences with axle slippage appears to be repeatable).

Of course, I am not asserting that there will be axle
slippage with all (front) disk brakes equipped wheel, or
even the majority of them. But it can not be denied that the
potential exists for slippage or ejection with some
axle/dropout/skewer combinations, and that skewer tightness
becomes far more critical with the current disk brake
mounting design.

The present configuration of vertical dropout and disk brake
caliper mounted behind the fork leg is a poor design, or at
least much less than ideal. I don't think that this
particular design was consciously thought out, it simply
metamorphosed by the addition of disk brakes to traditional
bicycles. It can only be seen as a sign of good engineering
if Manitou or other fork manufacturers choose to further
evolve their fork/dropout designs to mitigate the increased
possibility of wheel ejection with disk brakes. (Note: there
is a reference in the Zinn/Velonews web page cited about
Kelly Bicycles also redesigning the dropouts of their disk
brake forks, orienting the dropout slots to face forward.)

Mark McMaster [email hidden]

Mark McMaster said:

The present configuration of vertical dropout and disk
brake caliper mounted behind the fork leg is a poor design,
or at least much less than ideal. I don't think that this
particular design was consciously thought out, it simply
metamorphosed by the addition of disk brakes to traditional
bicycles. It can only be seen as a sign of good engineering
if Manitou or other fork manufacturers choose to further
evolve their fork/dropout designs to mitigate the increased
possibility of wheel ejection with disk brakes.

I doubt that anybody here argues this point. Surely, let
good engineering, design and technology evolve and make
bicycles better and safer for all.

The issue discussed ad nauseam in this n.g. over the past
year or two was whether or not the sky was falling and
whether a REVOLUTION was required. The answer is that is
was NOT. As Zinn says, although the issue is real, it is
"perhaps overstated in bicycle chat rooms." The CPSC was
advised and decided not to pursue it. No flood of injuries
or lawsuits have appeared. The number of injuries which
have appeared
- assuming they were actually caused by this problem - are
miniscule as compared to the number of disc brake equipped
bicycles in use. A good QR that is inspected frequently
solves the problem. Eventually, design and engineering
will evolve and there will be no problem.

End of Story. --dt

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

Quoted message said:

Mark McMaster said:

The present configuration of vertical dropout and disk
brake caliper mounted behind the fork leg is a poor
design, or at least much less than ideal. I don't think
that this particular design was consciously thought out,
it simply metamorphosed by the addition of disk brakes to
traditional bicycles. It can only be seen as a sign of
good engineering if Manitou or other fork manufacturers
choose to further evolve their fork/dropout designs to
mitigate the increased possibility of wheel ejection with
disk brakes.

I doubt that anybody here argues this point. Surely, let
good engineering, design and technology evolve and make
bicycles better and safer for all.

The issue discussed ad nauseam in this n.g. over the past
year or two was whether or not the sky was falling and
whether a REVOLUTION was required. The answer is that is
was NOT. As Zinn says, although the issue is real, it is
"perhaps overstated in bicycle chat rooms." The CPSC was
advised and decided not to pursue it. No flood of injuries
or lawsuits have appeared.

Lawsuits take some time to prepare and then even longer to
process and may well be setled complete with gagging order.
Just because you haven't heard about them don't assume
they're not happening. They are !!

Quoted message said:

The number of injuries which have appeared
- assuming they were actually caused by this problem - are
miniscule as compared to the number of disc brake
equipped bicycles in use. A good QR that is inspected
frequently solves the problem.

Nope - it may mitigate the problem it doesn't solve it

Quoted message said:

Eventually, design and engineering will evolve and there
will be no problem.

Ah yes - at last you're talking real sense. The revolution
is happening - albeit rather an evolution - but without all
the talk "perhaps overstated in bicycle chat rooms."
there'd be no evolution and the danger of the poor design
would continue.

Or maybe it's the very real fear of the
lawsuits...............

Or maybe the fear follows the knowledge

Who knows - at least the change is starting though.

An ex disc user

(Ex Disc User) said:

Quoted message said:

good QR that is inspected frequently solves the problem.

Nope - it may mitigate the problem it doesn't solve it

If "solve" means that the wheel does not eject under braking
force, then a good QR that is inspected frequently
absolutely solves the problem. At least for me, Leonard
Zinn, Carl Fogel and the vast majority of countless other
cyclists using discs.

Quoted message said:

An ex disc user

"Most likely you'll go your way and I'll go mine" -
Robert Zimmerman

--dt

Doug Taylor said:

(Ex Disc User) said:

Quoted message said:

good QR that is inspected frequently solves the problem.

Nope - it may mitigate the problem it doesn't solve it

If "solve" means that the wheel does not eject under
braking force, then a good QR that is inspected frequently
absolutely solves the problem. At least for me, Leonard
Zinn, Carl Fogel and the vast majority of countless other
cyclists using discs.

Quoted message said:

An ex disc user

"Most likely you'll go your way and I'll go mine" - Robert
Zimmerman

--dt

Dear Doug,

Alas, I remain agnostic about it all (and cannot imagine
my opinion counting for much--I ride on pavement and use
rim brakes).

From what I've read, a trailing arm disk brake does indeed
produce a force that would tend to eject an unsecured front
wheel, but something seems to keep the vast majority of
front wheels in place.

Jim Beam has suggested that the calculations of the
ejection forces have overlooked the massive frictional
resistance of typical serrated axle washers that actually
dent the surface of the fork. His pictures show the tiny
dents from the serrated washers, which seem to have
remained frimly in place instead of dragging grooves
through the metal of the fork.

If all that it takes to resist a trailing disk brake is a
firmly clamped quick-release and serrated washers, then the
problem and its solution are about the same as preventing
wheel nuts from coming loose on car wheels by using conical
instead of flat lug nuts.

So far, no one has posted a follow-up about marking their
front axles,

Carl Fogel

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

Quoted message said:

If anyone has pictures of disk-brake forks that show marks
of such serrated washers being dragged out of position,
I'd be glad to host them.

Both of my forks have discrete indentations where the
knurling of the steel QR faces and axle nut faces have
bitten into the soft aluminum dropout faces. No tearing or
drag marks at all.

Quoted message said:

Some people who posted in the ejection thread indicated
that they were going to mark quick-releases and watch for
movement, so if they have pictures of whatever happened, I
can host them, too.

Unfortunately my camera does not do well in macro mode, so
the pictures are disappointingly unclear. The QR/DO
interface has been doped with yellow fingernail polish, and
I inspect the interface twice per ride - before I go, and
after I'm done. I have zero cracking of the material at the
interface, which leads me to believe that there is no
movement. If there comes a time that I must change a tube, I
will remove and reapply the polish. But so far, I have been
lucky WRT flats.

The QRs are not done up "stupid-tight", I go just beyond 90
degrees with the lever (93-96, IMO), and close the thing
down with my palm. It leaves a mark on my palm, which
quickly goes away. I close up my rear QRs the same way. And
have done it exactly this way for as long as I've been
riding QR-equipped bikes. Never had a hassle with bearings -
could be luck, I guess.

There's your early-season report.
--
R.F. Jones

"Ex Disc User" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

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

<snip>

Quoted message said:

Quoted message said:

The issue discussed ad nauseam in this n.g. over
the past

year or two

Quoted message said:

Quoted message said:

was whether or not the sky was falling and whether a

REVOLUTION was

Quoted message said:

Quoted message said:

required. The answer is that is was NOT. As Zinn says,

although the

Quoted message said:

Quoted message said:

issue is real, it is "perhaps overstated in bicycle chat

rooms." The

Quoted message said:

Quoted message said:

CPSC was advised and decided not to pursue it. No
flood of

injuries

Quoted message said:

Quoted message said:

or lawsuits have appeared.

Lawsuits take some time to prepare and then even longer to

process and may

Quoted message said:

well be setled complete with gagging order. Just
because you

haven't heard

Quoted message said:

about them don't assume they're not happening. They are !!

They are? How do you know? I represent several large
manufacturers in Oregon and have not seen a disk brake case
-- either as a claim or a filed lawsuit. Perhaps there is a
problem that needs to be addressed, but it is not one that
has resulted in a lot of claims, or any claims as far as I
know. One possible reason for the lack of claims is that the
ejection forces do not materialize on soft ground due to
traction losses or that the rider is ejected by the braking
forces in any event. Remember that there are no seatbelts on
bikes and that riders are often go OTB regardless of whether
something breaks. -- Jay Beattie.

Carl Fogel said:

From what I've read, a trailing arm disk brake does indeed
produce a force that would tend to eject an unsecured
front wheel, but something seems to keep the vast majority
of front wheels in place.

Can't we just get along with the "majority" without the
hyperbole of "vast" or "overwhelming". I'm overwhelmed by
these words that merely mean "most".

Quoted message said:

So far, no one has posted a follow-up about marking their
front axles,

My front axles don't even have knurling on their lock
nuts, being ancient Campagnolo Record hubs from the
1960's... as in:

tinyurl.com2gbsjOpen ↗

Jobst Brandt [email hidden]

On Tue, 11 May 2004 18:24:49 GMT, [email hidden]

Quoted message said:

Carl Fogel said:

From what I've read, a trailing arm disk brake does
indeed produce a force that would tend to eject an
unsecured front wheel, but something seems to keep the
vast majority of front wheels in place.

Can't we just get along with the "majority" without the
hyperbole of "vast" or "overwhelming". I'm overwhelmed by
these words that merely mean "most".

Quoted message said:

So far, no one has posted a follow-up about marking their
front axles,

My front axles don't even have knurling on their lock
nuts, being ancient Campagnolo Record hubs from the
1960's... as in:

tinyurl.com2gbsjOpen ↗

Jobst Brandt [email hidden]

Dear Jobst,

A bare majority is 51%.

A vast majority in the case of non-ejected wheels appears to
be something like 99.999%.

The overwhelming majority of us can follow this idea.

A tiny minority quibbles.

Cheers,

Carl Fogel

How is a bike stopped by a disc brake any different than a
bike stopped by a rim brake?? they both have to generate the
same force. Both bikes stop in the same amount of time. What
a load of $^^^T&*(*(.

Carl Fogel said:

Quoted message said:

Quoted message said:

From what I've read, a trailing arm disk brake does
indeed produce a force that would tend to eject an
unsecured front wheel, but something seems to keep the
vast majority of front wheels in place.

Quoted message said:

Quoted message said:

Can't we just get along with the "majority" without the
hyperbole of "vast" or "overwhelming". I'm overwhelmed by
these words that merely mean "most".

Quoted message said:

Quoted message said:

Quoted message said:

So far, no one has posted a follow-up about marking
their front axles,

Quoted message said:

Quoted message said:

My front axles don't even have knurling on their lock
nuts, being ancient Campagnolo Record hubs from the
1960's... as in:

Quoted message said:

Quoted message said:

tinyurl.com2gbsjOpen ↗

Quoted message said:

A bare majority is 51%.

I don't see where I mentioned bare. Is this a colored
herring?

Quoted message said:

A vast majority in the case of non-ejected wheels appears
to be something like 99.999%.

Appears to be? Well what then is "most"? You might observe
that neither vast nor overwhelming are much used in English
except to sound impressive when making an argument that
something is wide spread, in the absence of supporting
evidence. It's a red flag for the observant reader.

Quoted message said:

The overwhelming majority of us can follow this idea.

Quoted message said:

A tiny minority quibbles.

Don't use majority unless you mean that. Overwhelming
majority is just another flourish of enhanced speech.

Jobst Brandt [email hidden]

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

Quoted message said:

How is a bike stopped by a disc brake any different than a
bike stopped by a rim brake?? they both have to generate
the same force. Both bikes stop in the same amount of
time. What a load of $^^^T&*(*(.

Ummm..to be blunt..you're incorrect. You're a latecomer to
this argument so you should google this up and see the
background. Once you understand both sides of the argument,
THEN you can come back and say it's a load of $^^^T&*(*(.

Scott..

On 11 May 2004 12:40:21 -0700, [email hidden] (Evan Evans)

Quoted message said:

How is a bike stopped by a disc brake any different than a
bike stopped by a rim brake?? they both have to generate
the same force. Both bikes stop in the same amount of time.
What a load of $^^^T&*(*(.

Dear Evan,

It's not a matter of braking power or stopping distance, but
of how the different leverage of the brake arm on the wheel
shoves the axle.

Briefly, a front caliper brake applied to the disk or to a
rim forces the axle up into the fork, but a rear caliper
brake produces an ejection force.

A normal, old-fashioned front-wheel rim brake is just barely
in front of the fork and as far as possible from the axle.
It has very little leverage and stuffs the axle feebly up
into the fork.

A disk brake, on the other hand, is much closer to the axle
and is offset much further from the fork, giving it
considerably more leverage. If it's a rear (or trailing)
design, a considerable ejection force is produced by normal
braking. (Converting it to a front or leading disk brake
would turn it into a considerable retention force.)

The overwhelming majority of disk brake users have not
noticed their front wheels popping out. Wheels that have
popped out may well have been lost because the quick-release
skewers were defective or not properly tightened.

A reasonably clear pro-ejection explanation with diagrams
and calculations of the forces can be found at:

ne.jpdisk and quick reOpen ↗
lease/index.html

or

tinyurl.combt7eOpen ↗

However, Jim Beam has suggested that these calculations are
fatally flawed because they do not include the tremendous
resistance of serrated axle washers (or knurled skewer
faces or whatever we decide to call them) biting into the
fork metal:

tinyurl.comyutgyOpen ↗

or

groups.google.comgroupsOpen ↗
8&selm=PErbc.45543%24UD3.38107%40newssvr25.news.prodigy.com

I hosted some pictures of his disk-brake fork that show the
clear imprint of the serrations, but no sign of braking
forces dragging the skewers across the bare metal:

home.comcast.netImg 3199.jpgOpen ↗

home.comcast.netImg 3196.jpgOpen ↗

The recent 500+ post disk-brake-ejection thread can still be
browsed through google groups:

tinyurl.com2263xOpen ↗

or

s.google.com/groups?q=g:thl2792415317d&dq=&hl=en&lr=&ie=UTF-
8&oe=UTF-
axy=2004&selm=405aed81%240%2423537%2444c9b20d%40news3.asahi-
net.or.jp

Again, it's nothing to do with stopping distance, just how
likely a behind-the-fork disk-brake is to eject an axle.

Carl Fogel

On Tue, 11 May 2004 19:07:26 GMT, [email hidden]

Quoted message said:

Carl Fogel said:

Quoted message said:

> From what I've read, a trailing arm disk brake does
> indeed produce a force that would tend to eject an
> unsecured front wheel, but something seems to keep the
> vast majority of front wheels in place.

Quoted message said:

Quoted message said:

Can't we just get along with the "majority" without the
hyperbole of "vast" or "overwhelming". I'm overwhelmed
by these words that merely mean "most".

Quoted message said:

Quoted message said:

> So far, no one has posted a follow-up about marking
> their front axles,

Quoted message said:

Quoted message said:

My front axles don't even have knurling on their lock
nuts, being ancient Campagnolo Record hubs from the
1960's... as in:

Quoted message said:

Quoted message said:

tinyurl.com2gbsjOpen ↗

Quoted message said:

A bare majority is 51%.

I don't see where I mentioned bare. Is this a colored
herring?

Quoted message said:

A vast majority in the case of non-ejected wheels appears
to be something like 99.999%.

Appears to be? Well what then is "most"? You might observe
that neither vast nor overwhelming are much used in English
except to sound impressive when making an argument that
something is wide spread, in the absence of supporting
evidence. It's a red flag for the observant reader.

Quoted message said:

The overwhelming majority of us can follow this idea.

Quoted message said:

A tiny minority quibbles.

Don't use majority unless you mean that. Overwhelming
majority is just another flourish of enhanced speech.

Jobst Brandt [email hidden]

Dear Jobst,

Ah, the familiar overwhelming dodge and bluster.

Enjoy!

Carl Fogel

[email hidden]:

Quoted message said:

However, Jim Beam has suggested that these calculations
are fatally flawed because they do not include the
tremendous resistance of serrated axle washers (or knurled
skewer faces or whatever we decide to call them) biting
into the fork metal:

You've misunderstood the implication of JB's proclamation,
who has at best also misunderstood the calculations.

The ejection force calculation, although based on a
simplified system than actual, is reasonable. The resistance
that the dropout/skewer knobs present to counter the
ejection force is IRRELEVANT to the calculation of the
ejection force.

What one can question is the ability of the dropout/skewer
knob interface to withstand the ejection force; this is
where the knobs biting into the dropout faces make a
difference.

Jose Rizal _@_._ said:

[email hidden]:

Quoted message said:

However, Jim Beam has suggested that these calculations
are fatally flawed because they do not include the
tremendous resistance of serrated axle washers (or
knurled skewer faces or whatever we decide to call them)
biting into the fork metal:

You've misunderstood the implication of JB's proclamation,
who has at best also misunderstood the calculations.

The ejection force calculation, although based on a
simplified system than actual, is reasonable. The
resistance that the dropout/skewer knobs present to counter
the ejection force is IRRELEVANT to the calculation of the
ejection force.

What one can question is the ability of the dropout/skewer
knob interface to withstand the ejection force; this is
where the knobs biting into the dropout faces make a
difference.

Dear Jose,

I'm sorry, but I don't see the misunderstanding.

The diagram and calculations of the ejection force do
seem to be correct, as far as they go, but they are
fatally flawed as an argument that the front wheel is in
danger of being ejected if serrated washers biting into
fork metal provide far more resistance than the ejection
force can overcome.

The diagram and its calculations use an ISO quick-release
resistance from 1996 that I assume are presented in good
faith, but which may well not include serrated washers.

So far, no one has mentioned any pictures of forks
showing marks of serrated washers being forced out by the
ejection force, gouging tiny grooves in the fork metal as
they're ejected.

Jim Beam pointed out a force or friction that was generally
overlooked and that seems to explain why front wheels aren't
ejecting left and right as the incomplete diagram would lead
us to expect.

I may have missed it, but I haven't seen any rebuttal to
Jim's point about properly closed serrated fasteners
offering far too much resistance for the calculated ejection
force to overcome.

Carl Fogel