Carlton Reid on QR safety



Benjamin Lewis wrote:
> jim beam wrote:
>
>
>>Benjamin Lewis wrote:
>>
>>>jim beam wrote:
>>>
>>>
>>>>Tim McNamara wrote:
>>>><snip drivel>
>>>>
>>>>>I see. And that situation is insurmountable? The designers are
>>>>>incompetent to deal with that? Good heavens. Might as well go back
>>>>>to V-brakes, dude. Oh wait, those are mounted on the front too- no
>>>>>doubt there are millions of them being ripped off of forks even as we
>>>>>speak.
>>>>
>>>>oh dear. sorry tim, zero points. do the math on the force at the
>>>>brake bosses compared to a disk tab. look at the comparative size
>>>>differences too and use that to estimate stress.
>>>
>>>How can we "look at the size differences" on a non-existent design?

>>
>>eh? disk tabs and brake bosses exist. do we have a communication
>>problem?

>
>
> Disk tabs on front mounted calipers do not exist. If they did, an
> intelligent designer would make them larger.


that's only considering the tabs - the calipers have the same problems
as well.

>
>
>>>That stress is greater on rear mounted disk brake tabs than on
>>>cantilever bosses is true, but irrelevant.

>>
>>it's /highly/ relevant in fatigue!

>
>
> The stress on rear-mounted disk tabs is irrelevant in a discussion of
> front-mounted disk tabs.
>


not when front mounted calipers are subject to unfavorable fatigue
loading...
 
jim beam wrote:
> Tim McNamara wrote:
> > jim beam <[email protected]> writes:
> >
> >
> >>James Annan wrote:
> >>
> >>>Ed Pirrero wrote:
> >>>
> >>>
> >>>>James Annan wrote:
> >>>>
> >>>>
> >>>>>Ed Pirrero wrote:
> >>>>>
> >>>>>
> >>>>>>Zero
> >>>>>>credibility.
> >>>>>
> >>>>>Yes, that seems a fair summary of your scientific background.
> >>>>
> >>>>And here we have a concise summary of James Annan. Takes the data
> >>>>that fits his view, and rejects the rest.
> >>>>
> >>>>To real scientists, this is called "junk science".
> >>>>
> >>>
> >>>How would you know what a "real scientist" would think? Have you
> >>>ever met one? James
> >>>
> >>
> >>he is one annan. he's all over the web if you know who you're
> >>looking for.

> >
> >
> > He's all over Usenet, anyway, but that's only proof of an Internet
> > connection. I find nothing by him that is scientific or scholarly,
> > certainly not in this newsgroup. Is he just another sock puppet of
> > yours, perhaps?

>
> the chickens taking up too much of the intellectual resources tim? "ed"
> is not his real name. there, that was hard to figure out, wasn't it.


Is "Pirrero" a made-up name too, like "jim beam"?

http://scholar.google.com/scholar?hl=en&lr=&c2coff=1&q=pirrero&btnG=Search

James
 
[email protected] wrote:
> Old Crow writes:
>
>
>>>>>>no, the over-center was not an original feature - the old
>>>>>>straight lever campy qr's tighten all the way to the stop.

>
>
>>>>>You should take one of those apart. The original design clearly
>>>>>goes 'over center' to lock.

>
>
>>>>i did. it functioned as i described. i wouldn't use it because
>>>>of that.

>
>
>>>That's too bad, because even without taking it apart the over
>>>center feature is detectable both by inspection and manual action.
>>>I wouldn't be riding those original QR's if that were not the case.
>>>You are trying hard to avoid any credibility, if there was any.

>
>
>>just like your assertion that the traction cable on san francisco cable
>>cars are wound with longitudinal strands rather than helical strands,
>>you're wrong on this one jobst. regrettably, i've sold the hub so i
>>can't prove it to you, but i would if it still had it.

>
>
> Well I still ride on those hubs and they are in hand and they have an
> eccentric circular cam whose position is over-center when closed.
> They are the same as the later ones with curved lever except that the
> lever is straight.
>
> About cable cars, you must have misinterpreted what was said. I know
> how cables are made and that they cannot be bent around corners unless
> they are helically wound.


misinterpretation indeed - i'm not talking about bendability. of course
they're wound, but as your pic shows, the strands are oriented to be
angled as far from cable axis as possible. conventional rope has the
external strands axial the cable.

> I have explained that often on this forum
> and for cable cars, I posted pictures:
>
> http://www.gmerch.net/cablecar/stand_large.jpg
>
> Jobst Brandt
 
jim beam wrote:

> Benjamin Lewis wrote:
>
>>>> That stress is greater on rear mounted disk brake tabs than on
>>>> cantilever bosses is true, but irrelevant.
>>>
>>> it's /highly/ relevant in fatigue!

>> The stress on rear-mounted disk tabs is irrelevant in a discussion of
>> front-mounted disk tabs.

>
> not when front mounted calipers are subject to unfavorable fatigue
> loading...


If you design the attachments with only twice as much material as rear
mounted tabs they'll experience half the stress, which should amply take
care of the fatigue loading, and the maximum ejection force will be roughly
two orders of magnitude smaller -- probably even less, but nobody has
provided an upper bound.

--
Benjamin Lewis

Now is the time for all good men to come to.
-- Walt Kelly
 
Benjamin Lewis wrote:
> jim beam wrote:
>
>
>>Benjamin Lewis wrote:
>>
>>
>>>>>That stress is greater on rear mounted disk brake tabs than on
>>>>>cantilever bosses is true, but irrelevant.
>>>>
>>>>it's /highly/ relevant in fatigue!
>>>
>>>The stress on rear-mounted disk tabs is irrelevant in a discussion of
>>>front-mounted disk tabs.

>>
>>not when front mounted calipers are subject to unfavorable fatigue
>>loading...

>
>
> If you design the attachments with only twice as much material as rear
> mounted tabs they'll experience half the stress,


and weigh twice as much.

> which should amply take
> care of the fatigue loading,


it depends. you may need a larger safety factor - depends on the alloy
and casting quality.

> and the maximum ejection force will be roughly
> two orders of magnitude smaller -- probably even less, but nobody has
> provided an upper bound.
>
 
Marvin wrote:
>
> So my actual, experimental evidence suggests that on new bikes you
> don't have a metal to metal interface no matter what you do to the QR.
> This substantially lowers the required pullout force.
>
> Now if you've got a larger sample size, I'd love to hear it. Until
> then I think I'm one of the only people who's even attempted actual,
> unbiased experiments on this topic...


FWIW, I also checked for evidence of embossing on my 1972 commuting
bike.

IIRC, the only place I saw embossing to any appreciable degree is on
the right rear dropout, and Jobst explained that in terms of the
constant flexing from chain tension. The forks ends were quite smooth,
despite the serrated surfaces of the Shimano QRs.

Of course, that fork's only 34 years old. And I didn't acquire it
until 1976, when it had only a few miles on it. Perhaps the
indentations will appear some day. ;-)

- Frank Krygowski
 
"A Muzi" <[email protected]> wrote:

> I hadn't thought about it before but Jobst makes a good
> point about diameters and arm clearances. The present cut
> thread brake bolt is the cheapest way to adequately solve
> the problem. And with no change in scores of years without
> problems they are indeed adequate, from LeeChi to Record.


I've followed the various discussions about this issue, though not
diligently. Without ever having consciously considered the matter before,
it's always struck me that brake bolts are made as Jim Beam suggests: a
rolled thread on a necked-down section of shaft, exactly as the threads of
a quick release skewer are formed.

I don't have a camera capable of taking sufficiently detailed pictures to
illuminate the differences, but the examples I have lying around (Shimano
600 6208, Shimano 105 1050, Suntour Superbe Pro BRS) all seem to exhibit
the qualities of rolled threads. The 6208 is particularly clear as the
thread doesn't run all the way to the shoulder of the stepped-down section.

What seems telltale to me is that the first thread, adjacent to the
shoulder, has both a lower maximum diameter and a higher minimum diameter
than the subsequent threads. That is, it has both a lower peak and a higher
trough. Cut threads show a first peak that is equal in height to the
others, with a trough that descends from the maximum diameter of the piece.

View the following in a fixed-width font:



(a) a rolled thread on a constant diameter shaft
_ _ _ _
___________ /\ / \ / \ / \ /
\/ \ / \ / \ / \ /
\/ \_/ \_/ \_/


(b) a cut thread on a constant diameter shaft
___________ __ __ _ _ _
\/ \ / \ / \ / \ /
\/ \ / \ / \ /
\_/ \_/ \_/


(c) a rolled thread on a stepped diameter shaft
______ _ _ _ _
\____ /\ / \ / \ / \ /
\/ \ / \ / \ / \ /
\/ \_/ \_/ \_/



What looks like a very clear example of a cut thread that happens to be on
my desk is a titanium SRP M15 self-extracting crank bolt for a Shimano
Hollwtech crank, and what looks like a very clear example of a rolled
thread that happens to be on my desk is a Wheels Manufacturing 9mm x 1mm
titanium QR axle.

I don't think the pictures you posted yesterday of a modern Chorus brake
are sufficiently detailed to distinguish between (b) and (c), but to my
eye, the shaft looks stepped, and the thread rolled.

http://www.yellowjersey.org/photosfromthepast/CHRCALIP.JPG

Reducing the distance from the shoulder of the shaft to the root of the
thread can make it hard to tell the difference:


(d) a rolled thread on a stepped diameter shaft
______ _ _ _ _
\_ /\ / \ / \ / \ /
\/ \ / \ / \ / \ /
\/ \_/ \_/ \_/


Let me stress that these are the uneducated musings of a layman, but I do
own a magnifying glass and a Vernier caliper. I'd be happy to learn where
I'm in error.


James Thomson
 
On Mon, 13 Feb 2006 20:28:17 -0800, jim beam <[email protected]>
wrote:

>
>hold the phone indeed.
>
>1. we get rid of the qr /if/ it's not retaining the axle with sufficient
>force, which it clearly is.
>
>2. caliper ahead of the fork has been abandoned by engineers that
>fortunately know more about materials than you do! your comprehension
>of fatigue is abysmal jobst.


So, there is never enough force from braking to move the wheel held by
friction alone in the dropouts but if the caliper is mounted ahead the
same forces will destroy the bike? You can not have your cake and eat
it.
 
In article <[email protected]>, Tim McNamara
<[email protected]> wrote:

> "Marvin" <[email protected]> writes:
>
> > But you haven't actually *given* a magnitude for this force. All
> > you've done is show a relationship to another force (which you can't
> > measure either). If you can put a number to any of these forces,
> > that would indeed be a step forward.

>
> Those numbers have already been given, they are available on James
> Annan's Web page. Numbers from Cannondale have also been given:
>

<snip>

A clear and objective assessment of the hazard. Thank you.

Luke
 
Quoting Ed Pirrero <[email protected]>:
>David Damerell wrote:
>>Quoting Ed Pirrero <[email protected]>:
>>>David Damerell wrote:
>>>>Quoting Ed Pirrero <[email protected]>:
>>>>>I understand that. In a world filled with emotional rhetoric and
>>>>>name-calling, I seek facts.
>>>>It must have been some other <[email protected]> who explicitly stated
>>>>they help with the name-calling, I suppose?
>>>Don't throw stones when your abode is made of glass.

>>I'm not lying about the name-calling. You are.

>Hmm, I don't recall denying that I have done it.


Weasel successfully predicted. Shock.

>>>>In some way carefully hidden from Google. Of course. Funny how most of the
>>>>scientists I know are pretty keen to be visible on the Web...
>>>Logical fallacy: ad hominem.

>>Er, no. An ad hominem would be suggesting your argument is invalid because
>>there is no evidence to support your claim to be a scientist.

>That's exactly what you're suggesting.


That's not actually the case. Your argument is invalid either way;
demanding measurements merely exposes your inability to understand the
mechanics. Of course, your claim that your argument is valid because you
are a scientist is the logical fallacy you claim I am making (I notice you
neatly excised that observation, so let's have it again); the fact that
the claim to be a scientist also seems to be fantasy is just icing on the
cake.
--
David Damerell <[email protected]> flcl?
Today is Second Monday, February.
 
< [email protected] > wrote:

> I don't see where that proves the thread on these bolts is rolled.
> The ones I have for inspection do not have the classic bolt end,
> have a thread whose major diameter is exactly the same as the
> bearing surface of the shaft


[snip]

> The problem with that is the thread and shaft are the same diameter
> within less than 0.01mm, something that is not readily repeatable with
> a rolled thread.


I've just measured the threads and shafts of the three caliper brakes I
have lying around. The figures are each the mean of five readings, shaft
first, then thread, then the diameter of the shaft adjacent to the root of
the thread:

Shimano 6208: 5.90mm , 5.83mm , 5.28mm

Suntour Superbe Pro: 5.96mm , 5.76mm, 5.38mm

and here's the interesting one:

Shimano 1050: 5.80mm, 5.90mm, 5.37mm

In other words, the diameter of the thread of the 1050 is greater than the
maximum diameter of the plain section of the shaft.

James Thomson
 
On Mon, 13 Feb 2006 18:38:37 -0600, Tim McNamara wrote:


> every action...). ;-) Let me try using more common units of measurement.
> I am sure that my math and my assumptions will be adequately scrutinized
> by both sides of the discussion.


Excellent summary Tim.



Mike
 
James Thomson wrote:
> "A Muzi" <[email protected]> wrote:
>
>
>>I hadn't thought about it before but Jobst makes a good
>>point about diameters and arm clearances. The present cut
>>thread brake bolt is the cheapest way to adequately solve
>>the problem. And with no change in scores of years without
>>problems they are indeed adequate, from LeeChi to Record.

>
>
> I've followed the various discussions about this issue, though not
> diligently. Without ever having consciously considered the matter before,
> it's always struck me that brake bolts are made as Jim Beam suggests: a
> rolled thread on a necked-down section of shaft, exactly as the threads of
> a quick release skewer are formed.
>
> I don't have a camera capable of taking sufficiently detailed pictures to
> illuminate the differences, but the examples I have lying around (Shimano
> 600 6208, Shimano 105 1050, Suntour Superbe Pro BRS) all seem to exhibit
> the qualities of rolled threads. The 6208 is particularly clear as the
> thread doesn't run all the way to the shoulder of the stepped-down section.
>
> What seems telltale to me is that the first thread, adjacent to the
> shoulder, has both a lower maximum diameter and a higher minimum diameter
> than the subsequent threads. That is, it has both a lower peak and a higher
> trough. Cut threads show a first peak that is equal in height to the
> others, with a trough that descends from the maximum diameter of the piece.
>
> View the following in a fixed-width font:
>
>
>
> (a) a rolled thread on a constant diameter shaft
> _ _ _ _
> ___________ /\ / \ / \ / \ /
> \/ \ / \ / \ / \ /
> \/ \_/ \_/ \_/
>
>
> (b) a cut thread on a constant diameter shaft
> ___________ __ __ _ _ _
> \/ \ / \ / \ / \ /
> \/ \ / \ / \ /
> \_/ \_/ \_/
>
>
> (c) a rolled thread on a stepped diameter shaft
> ______ _ _ _ _
> \____ /\ / \ / \ / \ /
> \/ \ / \ / \ / \ /
> \/ \_/ \_/ \_/
>
>
>
> What looks like a very clear example of a cut thread that happens to be on
> my desk is a titanium SRP M15 self-extracting crank bolt for a Shimano
> Hollwtech crank, and what looks like a very clear example of a rolled
> thread that happens to be on my desk is a Wheels Manufacturing 9mm x 1mm
> titanium QR axle.
>
> I don't think the pictures you posted yesterday of a modern Chorus brake
> are sufficiently detailed to distinguish between (b) and (c), but to my
> eye, the shaft looks stepped, and the thread rolled.
>
> http://www.yellowjersey.org/photosfromthepast/CHRCALIP.JPG
>
> Reducing the distance from the shoulder of the shaft to the root of the
> thread can make it hard to tell the difference:
>
>
> (d) a rolled thread on a stepped diameter shaft
> ______ _ _ _ _
> \_ /\ / \ / \ / \ /
> \/ \ / \ / \ / \ /
> \/ \_/ \_/ \_/
>
>
> Let me stress that these are the uneducated musings of a layman, but I do
> own a magnifying glass and a Vernier caliper. I'd be happy to learn where
> I'm in error.
>
>
> James Thomson
>
>

you're right on the money james. great ascii.
 
Ian Blake wrote:
> On Mon, 13 Feb 2006 20:28:17 -0800, jim beam <[email protected]>
> wrote:
>
>
>>hold the phone indeed.
>>
>>1. we get rid of the qr /if/ it's not retaining the axle with sufficient
>>force, which it clearly is.
>>
>>2. caliper ahead of the fork has been abandoned by engineers that
>>fortunately know more about materials than you do! your comprehension
>>of fatigue is abysmal jobst.

>
>
> So, there is never enough force from braking to move the wheel held by
> friction alone in the dropouts but if the caliper is mounted ahead the
> same forces will destroy the bike? You can not have your cake and eat
> it.


the cake is called "fatigue". check it out some time.
 
jim beam wrote:
> Ian Blake wrote:
> > On Mon, 13 Feb 2006 20:28:17 -0800, jim beam <[email protected]>
> > wrote:
> >
> >
> >>hold the phone indeed.
> >>
> >>1. we get rid of the qr /if/ it's not retaining the axle with sufficient
> >>force, which it clearly is.
> >>
> >>2. caliper ahead of the fork has been abandoned by engineers that
> >>fortunately know more about materials than you do! your comprehension
> >>of fatigue is abysmal jobst.


> the cake is called "fatigue". check it out some time.


Can you demonstrate this *EVER* occuring in a front mounted disc
caliper on a bicycle? Or is it the same kind of wild speculation that
you accuse Annan of (ie a theoretical possibility with no verifiable
evidence of practical occurence)?

Any experimental data? Any calculations at all?

I am interested to see whether this is such a significant problem as
you make out or whether it is tradition and looks that govern the
market.

...d
 
On Tue, 14 Feb 2006 09:51:50 +0100, "James Thomson"
<[email protected]> wrote:


>View the following in a fixed-width font:
>

[snip]
>(b) a cut thread on a constant diameter shaft
>___________ __ __ _ _ _
> \/ \ / \ / \ / \ /
> \/ \ / \ / \ /
> \_/ \_/ \_/
>


It depends on the threading method used. While a screw machine can
make something like what you indicated (though your pitch was off), a
thread cutting die will not produce that pattern. This is the result
that is obtained with a typical die:

___________ _ _ _ _ _
\_____/ \ / \ / \ / \ /
\___/ \ / \ / \ /
\_/ \_/ \_/


This is still an approximation, of course; the bottoms of the troughs
would be angled, not flat. Die-cut threads are easily spotted by the
observation of the multiple points around the circumference where the
cut stopped. Lathe-cut threads will not show this characteristic.

I have seen clearly identifiable die-cut threads on the mounting studs
of inexpensive brake calipers in the past. I haven't looked lately.
--
Typoes are a feature, not a bug.
Some gardening required to reply via email.
Words processed in a facility that contains nuts.
 
[email protected] wrote:

> I don't see where that proves the thread on these bolts is rolled.


I wasn't replying to whether the actual piece in your hand is a cut or
rolled thread. Without a picture or the part in my hand, I couldn't
tell anyway. I _am_ replying to your assertions that:

1. A rolled thread is weaker
2. A rolled thread cannot be on the same shaft where another diameter
is used as a bushing.

Both of those assumptions scream BS.

Here's how a rolled thread is done:

A rod is ground, drawn, rolled, turned, forged to the blank diameter

The thread-area diameter of the blank is more than the minor diameter of
the thread, but less than the major diameter to let the metal flow into
the valleys of the die. There are charts for this, and I am not going
to post them here. They are in Machinery's Handbook and other places.

On a bolt, or other external thread, a roll-thread die is either turned
on to the blank or the blank is rotated into the die, most likely the
latter. As the die impinges on the metal of the blank, the metal flows
into the valleys of the die.

Voila. There is no magic or uncertainty. Since the major diameter is
controlled by the die, the major diameter cannot exceed the nominal
diameter (it's almost slightly always less than nominal in either cut or
threaded) of the die, as there is no more room for the metal to flow
into the valleys of the die.

The great thing about rolled threads, from a manufacturing POV, is that
the method is chipless and quick.

> The ones I have for inspection do not have the classic bolt end, have
> a thread whose major diameter is exactly the same as the bearing
> surface of the shaft and show no classic rolled thread form but rather
> has a single point thread runout at the transition to the shaft.


Almost all threads have a single point runout at the transition.
Exceptions to this are double, triple and quad lead threads (which leave
2, 3, and 4 single point ends, obviously) and undercut thread
transitions as in stripper screws and captivated screws.

Unless you're talking about a mangulated thread transition where the
single point sat there while the part turned. Since machining centers
are lightning fast and they can repeatedly cut a thread deeper and
deeper in multiple passes, you'll never see such a transition to a
mangled end of thread. A mangled transition is the result of manual
processes.

> That
> doesn't prove that they aren't rolled but it definitely suggests that.


Oh, look, Jobst shows a streak of honesty instead of bombastic
pompousity (which I'm currently using...you may have it back when I'm done)

> In response to your question above, I could also say that steel is
> stronger than titanium. So what. That doesn't make a certain part one
> metal or the other.


What?

> The problem with that is the thread and shaft are the same diameter
> within less than 0.01mm, something that is not readily repeatable with
> a rolled thread.


********. Jobst, please visit your neighborhood job shop for a field
trip before spouting this. Rolled threads are not inaccurate. Indeed,
failure to be within the same standards for a typical cut thread means
either a problem with the operator or the machine itself.

Rolled threads will be less accurate than, say, the ground thread of a
micrometer, but for the purposes of a _bicycle_ a rolled thread is just
dandy. And since a rolled thread is stronger than a cut thread, as this
newsgroup often revolves around catastrophic failure, then a rolled
thread should definitely recieve the approving nods of the talking heads
here, no?

One more thing, the most important part of a thread is the pitch
diameter. That's the bit that allows mating parts to be threaded. If
rolled threads are inaccurate, then we'd have problems with mating such
beasties, but we don't.

> I don't doubt that, but in some instances a rolled thread is
> inappropriate for the other functions of the screw...


Bicycle brake hardware is not rocket science and does not require class
A grade 8 screws (which can be and often _are_ rolled, btw) nor Starret
Micrometer ground thread accuracy.

> as in this case.
> You might do some measuring and micro-inspection of such bolts and
> report what you find. The parts I inspected had machining centers in
> both ends.


Centers in both ends means nothing WRT whether a screw is turned or
rolled. When turning a diameter prior to threading (roll or single
point), it's a good idea to drill a center in the end for the tailstock
to support the blank as it is, more often than not, sticking out of the
spindle more than 2.5 times the diameter (deflection issues).

> Just by the way, what moves you to use such an insulting tone when
> discussing bicycle parts?


Following your example.

I would not even pretend to be an expert in physics, but I would not
expect a physicist who has not been in my field to claim to be an expert
in machining or toolmaking, either.

--
BMO
 
Werehatrack wrote:

> It depends on the threading method used. While a screw machine can
> make something like what you indicated (though your pitch was off)


I thought he was singing on key...

, a
> thread cutting die will not produce that pattern. This is the result
> that is obtained with a typical die:
>
> ___________ _ _ _ _ _
> \_____/ \ / \ / \ / \ /
> \___/ \ / \ / \ /
> \_/ \_/ \_/
>
>
> This is still an approximation, of course; the bottoms of the troughs
> would be angled, not flat.


That's because a cutting die has a lead. You can see that plainly by
actually looking at a thread cutting die.

> Die-cut threads are easily spotted by the
> observation of the multiple points around the circumference where the
> cut stopped. Lathe-cut threads will not show this characteristic.


Nor will those made in a machining center.

> I have seen clearly identifiable die-cut threads on the mounting studs
> of inexpensive brake calipers in the past. I haven't looked lately.


There are dies and then there are dies. There are dies like what you
see in tap/die sets at Sears, and then there are those that fit in a
machining center, screw machine, or lathe, that have replacable carbide
or HSS cutters. Those are typically called "die heads".

BTW, I took a trip to Balzers in Agawam MA, yesterday.
Mmmm....coatings... One thing, if you're deciding whether to buy the
tap or die that's nitrided or the one that's plain HSS, get the nitrided
one. We're looking at coating thousands of punches. The most expensive
coating is 75 percent more than the cheapest one, and I must say that
even the cheapest (TiN) coating magically turns one punch into 5 or 7
(depending on material and whoever is sharpening).

--
BMO
 
Boyle M. Owl wrote:

> Rolled threads will be less accurate than, say, the ground thread of a
> micrometer, but for the purposes of a _bicycle_ a rolled thread is just
> dandy. And since a rolled thread is stronger than a cut thread, as this
> newsgroup often revolves around catastrophic failure, then a rolled
> thread should definitely recieve the approving nods of the talking heads
> here, no?


Not exactly. Briefly, rolled threads can be fine. Cut threads can be
fine.

We already know that, other things being equal, rolled threads have
advantages regarding strength. I don't think anyone's disputing that.


Those who say cut threads are adequate for brake mounting bolts are
simply pointing out that there have been NO reports of a brake mounting
bolt failing, save one that was ridden for a long time so loose that it
was literally rattling around. Rolled or cut, brake mounting bolts are
adequate for the job they do. (The original thread issue arose when
someone needed to extend the threading on his brake mounting bolt, and
proposed doing it with a thread die. Jim beam told him it would be
fatal, or words to that effect.)

This issue arises only because jim beam howls cut threads are deadly,
while having zero failures that prove his point...

.... yet he simultaneously howls that rear-mounted disk brakes with
quick release axles are perfectly safe, despite many reports of failure
that prove him wrong. It's the ludicrous inconsistency that draws
attention.

- Frank Krygowski
 
[email protected] wrote:

> Those who say cut threads are adequate for brake mounting bolts are
> simply pointing out that there have been NO reports of a brake mounting
> bolt failing, save one that was ridden for a long time so loose that it
> was literally rattling around. Rolled or cut, brake mounting bolts are
> adequate for the job they do.


That they are, because the yeild point of a screw is at least an order
of mangnitude more than the forces put upon it.

(The original thread issue arose when
> someone needed to extend the threading on his brake mounting bolt, and
> proposed doing it with a thread die. Jim beam told him it would be
> fatal, or words to that effect.)


I didn't see that.

Gawd. If the difference between a cut thread and a rolled thread meant
the difference between catastrophic failure and no failure, then the
cross section of the screw itself was too small in the first place. I
know of no engineer that will design a brake mounting screw so tiny that
it will break in that manner.

> This issue arises only because jim beam howls cut threads are deadly,
> while having zero failures that prove his point...


See above paragraph.

> ... yet he simultaneously howls that rear-mounted disk brakes with
> quick release axles are perfectly safe, despite many reports of failure
> that prove him wrong. It's the ludicrous inconsistency that draws
> attention.


I, myself, don't see the big deal about QR issue. If you're
experiencing pullout, replace the hollow axels with solid ones and nuts.
Problem solved. However, I can sit here, close my eyes, and be
confounded at how wheel pullout can happen if the skewers are properly
tightened in the first place. The braking force has to overcome the
clamping force of the properly tightened skewer _and_ make the skewer
jump over the lawyer lips. For that to happen, you have to make the
skewer _stretch_ by making it exceed its yeild point.

I just don't see it happening in either my head, nor in the experience
of my off-road buddies who see more of a hazard of boobytraps on the
trails in Lincoln Woods than anything else.

--
BMO