Disk brakes and wheel ejection - Manitou's answer?

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

Mark McMaster wrote:
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


Sturdy fork design with huge " lawyer lips" and a strong well secured Q
will also help. I suspect we will see others who want to follow th
trend towards disc brakes to make similar design changes. It will als
be interesting to see if the industry will adopt a wider spacing t
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!!!

http://groups.google.com/groups?hl=e...com%26rnum%3D5

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

jb


Mark McMaster wrote:
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

On Sun, 09 May 2004 04:42:29 GMT, jim beam wrote:

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!!!

http://groups.google.com/groups?hl=e...com%26rnum%3D5

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

jb


Mark McMaster wrote:
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



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:

http://home.comcast.net/~carlfogel/d...d/Img_3199.jpg

http://home.comcast.net/~carlfogel/d...d/Img_3196.jpg

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:

http://tinyurl.com/yutgy

or

http://groups.google.com/groups?hl=e....pr odigy.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 wrote:
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.)


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!!!

http://groups.google.com/groups?hl=e...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:

http://www.velonews.com/tech/report/...es/5432.0.html

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.

http://www.cyclingforums.com/t25255-15-1.html

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

Mark McMaster wrote:

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" wrote in message
...
Mark McMaster wrote:

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 !!

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

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) wrote:

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.

An ex disc user

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

--dt

On Tue, 11 May 2004 09:41:48 -0400, Doug Taylor
wrote:

(Ex Disc User) wrote:

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.

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

wrote in message . ..

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.

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