More on disk brakes and wheel ejection

wrote in message ...
It isn't a "theory." It is a straight forward measurable fact and is
obvious by inspection, geometrically knowing that forces have actions
and reactions.

Let's not forget that Newtonian physics is only a theory...

Seriously though, here's my A$0.03. The two sides of this argument are
proposing, respectively, redesigning the system to be infallible under
design loads, and redesigning the system to fail safely.

I am very much in favour of the second approach - especially as a
first-response solution.

Especially on a mountain bike, "design loads" mean nothing. People
will, and do, ride to the limits of their equipment.

Even if we only consider manufacturing variability, there _will_ be
failures in the field. It's a statistical certainty. Whether the QR
skewers are as thick as your finger and located in recessed conical
seats as Jobst proposes...there will be a defective part, and it will
fail.

WHEN that one-in-a-billion part fails, if the caliper is behind a
vertical dropout, the axle WILL tend to be ejected under brakes. It is
an unacceptable failure mode.

The system needs to be re-designed so that if/when an axle slips,
breaks, whatever, the wheel will not be ejected by braking forces.
That means either re-directing the force (eg. caliper in front of fork
leg) or providing support for the force as it is currently directed
(eg. forward-facing dropouts, QR20/Tullio closed retention systems).

I can only imagine one direction from here. Fork/brake manufacturers
can't afford the legal implications of admitting that there's a
problem. The lawsuits would break them. But the next design iteration
of all fork models will either have closed retention systems, or no
disc brake mounts.

The reason given will be that the XC race forks are so light and
cutting-edge that they can't handle disc brake loads without
compromising performance; and the
freeride/all-mountain/whatever-the-buzzword-is-this-week will be all
Tullio or QR20 for increased stiffness.

Dropout forks with disc brake mounts will be quietly dropped from the
lineup. The axle-eject issue will be sidestepped.

In any case, my next bike will have discs and clamped axles. I've just
started using discs on my current dropout fork - mindful of the
shortcomings in the design. I'd like it to be otherwise, but it's not
going to happen with my budget.

fs

In my experience, the QR is much easier to undo at the end of a long ride.
(Yes, this is on a bike with a front disc brake.) When I first noticed
this, I assumed it was because they were off-brand skewers.

I have yet to find the QR completely loose, but it definitely takes less
effort to open it than to close it.

-Dion

wrote in message
...

We are not talking about "extreme cases" but rather reasonably
predictable failures among normal distributions of users. Why wheels
do not separate more often has been explained. The greatest number of
riders assemble their bicycles after arriving by car at the trailhead.
This assures a tight QR at the beginning of each ride. Of those that
do not do that, only a small number experience any loosening and don't
question that the wheel was rattling in the retention ridges and
tighten it. This is not a reasonable way to offer a product to users.
CA

In article ,
James Annan wrote:

|James, it seems that, at least in the US 'operator error' has been the
|prominent call from the legal world.
That's Rockshox speaking. Do you really believe they will do it?

Do you really believe that ultimately they will have a choice? Just

I'm not sure they can *afford* it. It is true that a lot of forks are
sold as OEM parts so they can refuse to recall them unless the bike
mounted disks right out of the factory, but there's still a hell of a
lot of forks to update. And they have to pay for labour too, not only
the parts that for them may be relatively cheap to produce.
Popular pressure (i.e. people refusing to buy disk brakes, but I don't
see it happen) can lead them to use better solutions in the future, but
I'm not optimistic about existing stuff.
I hope I'm wrong, but I think the scenario painted by Fakhina Sohl is
the more realistic I've seen.

because they have money, does not mean that they can prove black is
white, even in a US court. IMO a few unequivocal statements from
independent testing labs (such as the German one that is investigating
the problem) will put intolerable pressure on them. At some point they
may have to start worrying about the unlimited punitive damages rather
than merely compensation - this is the fault with the 'cheaper to
compensate' line of thought.

Read Pace arguments to see their defense line. For them it's always
someone else's fault, their product is ISO compliant.

--
Fact of life #15: Heads bleed, walls don't.

In article ,
Rick Onanian wrote:

Why are you still calling me that way? You look really childish.

Somehow, I get the idea that he's not sitting there typing
out "Maki Tartamillo writes:" on his keyboard.

Unfortunately he probably does since it doesn't happen with other people.
Or at least he changed the settings in his newsreader so that it does
the job for him. That's not the default for Tin, which is, I'm told, an
excellent newsreder.

--
Fact of life #15: Heads bleed, walls don't.

On Fri, 15 Aug 2003 19:29:02 GMT, Maki wrote:
In article ,
Rick Onanian wrote:
Somehow, I get the idea that he's not sitting there typing
out "Maki Tartamillo writes:" on his keyboard.

Unfortunately he probably does since it doesn't happen with other people.
Or at least he changed the settings in his newsreader so that it does the
job for him. That's not the default for Tin, which is, I'm told, an
excellent newsreder.

Tin is a very excellent newsreader, but can come
in a very wide variety of configurations. It's
nowhere near unreasonable to expect that the
default configuration that he has will do that.

Granted, it is possible that he has changed the
settings himself; this may have been to alleviate
some other problem.

I just don't believe that _anybody_ would make an
effort to type out "So and so writes..."; and
I especially don't believe that anybody would do
that _and_ continuously do it wrong.

Gah. I find myself in the middle of somebody else's
argument again. Now I'm even _guessing_ what other
people are doing and thinking! When will I learn?

Jobst? Care to comment?
--
Rick Onanian