Brakes: changing from nutted to recessed?

[jim beam]

[email protected] wrote:
> jim beam wrote:
>
>>[email protected] wrote:
>>
>>
>>>And it's amazing to me that on the matter of disk brakes and quick
>>>release mechanisms, mulitiple reports of failure were of no value to
>>>you. In this matter of brake bolt threads, a complete absence of
>>>failure likewise means nothing to you.
>>
>>that's /such/ flawed logic. ... you're trying to
>>argue that both instances are the same - and they're plainly not. if
>>someone doesn't bother to read the instruction manual and doesn't fasten
>>the skewer properly, that's only going to injure them. if it's a flaw
>>in the design it's going to injure everyone, myself included.
>
>
> Fine! Produce at least _one_ example of someone injured because a
> cut-thread brake mounting bolt failed in normal service.

show me any mainstream oem bolt that's not rolled! _one_ example will do.

>
> If you can't prove it injured _anyone_, it's damned silly of you to
> talk about injuring _everyone_!
>
> - Frank Krygowski
>

 

[Jasper Janssen]

On Wed, 30 Nov 2005 06:28:23 -0800, jim beam <[email protected]> wrote:

>really? don't you think it interesting that we've not been overwealmed
>with pics of brake bolts with cut threads? i know i've never seen one -
>not in the last 30 years at any rate. could that /possibly/ be related
>to actual failure rates?

People have stated in this thread that the strength difference between cut
and rolled threads is 30%. Can you produce (and preferably prove) a
significantly higher figure for the fatigue strength difference?

Incidentally, just how many cycles does a brake bolt typically go through?
I mean, it's sure as hell not as many as spokes, cranks, frames, or
seatposts.

Jasper

 

[Jasper Janssen]

On Thu, 01 Dec 2005 05:58:21 -0800, jim beam <[email protected]> wrote:
>Dave Larrington wrote:
>> jim beam <[email protected]> wrote:
>>
>>
>>>thanks! actually, that illustrates the difference very well and that
>>>second does indeed appear to be a cut thread. but that drop
>>>attachment [a hideous concept in the first place] is not suntour -
>>>it's a retrofit, and clearly made by someone that doesn't know their
>>>business.
>>
>> Maybe so, but as far as can be determined by careful study of the
>> photograph, it isn't broken...
>
>indeed. but can you say it's not fatigued?

Can you say it is?

Jasper

 

[jim beam]

Jasper Janssen wrote:
> On Thu, 01 Dec 2005 05:58:21 -0800, jim beam <[email protected]> wrote:
>
>>Dave Larrington wrote:
>>
>>>jim beam <[email protected]> wrote:
>>>
>>>
>>>
>>>>thanks! actually, that illustrates the difference very well and that
>>>>second does indeed appear to be a cut thread. but that drop
>>>>attachment [a hideous concept in the first place] is not suntour -
>>>>it's a retrofit, and clearly made by someone that doesn't know their
>>>>business.
>>>
>>>Maybe so, but as far as can be determined by careful study of the
>>>photograph, it isn't broken...
>>
>>indeed. but can you say it's not fatigued?
>
>
> Can you say it is?
>
> Jasper

that's my point jasper - you can not say anything without expensive
testing. it's not a situation like a frame where you can see cracking
at a weld - here, cracking is at a thread root - it's invisible.

if it's both in a hidden location /and/ invisible, /and/ in the worst
possible fatigue location [front of a fork vs. the rear], /and/ the most
critical safety component on the bike, then you simply cannot make
cavalier assumptions! where do you think all the crack detection
technologies came from? certainly not because they're all easily
visible to the naked eye.

 

[jim beam]

Jasper Janssen wrote:
> On Wed, 30 Nov 2005 06:28:23 -0800, jim beam <[email protected]> wrote:
>
>
>>really? don't you think it interesting that we've not been overwealmed
>>with pics of brake bolts with cut threads? i know i've never seen one -
>>not in the last 30 years at any rate. could that /possibly/ be related
>>to actual failure rates?
>
>
> People have stated in this thread that the strength difference between cut
> and rolled threads is 30%. Can you produce (and preferably prove) a
> significantly higher figure for the fatigue strength difference?

google was invented for questions like that jasper.

>
> Incidentally, just how many cycles does a brake bolt typically go through?
> I mean, it's sure as hell not as many as spokes, cranks, frames, or
> seatposts.

i don't know jasper, but look at an s/n graph. there's load, cycles to
failure, and the log relationship between the two. high cycles at low
load will achieve the same as low cycles at high load. you figure out
the number of application cycles, including modulation caused by
squealing [if present], grit, dents, etc., then let's figure out
together what the ballpark fatigue loading might be.

>
> Jasper

 

[jtaylor]

"jim beam" <[email protected]> wrote in message
news:[email protected]...
> >>>
> >>>Maybe so, but as far as can be determined by careful study of the
> >>>photograph, it isn't broken...
> >>
> >>indeed. but can you say it's not fatigued?
> >
> >
> > Can you say it is?
> >
> > Jasper
>
> that's my point jasper - you can not say anything without expensive
> testing. it's not a situation like a frame where you can see cracking
> at a weld - here, cracking is at a thread root - it's invisible.
>

For a single bolt, yes, expensive testing would be required.

But for say, 100 million, if none of them have failed, then it is
_extremely_ unlikely that fatigue is an issue.

So, how many BROKEN brake bolts have you seen, jim beam?

 

[jtaylor]

"jim beam" <[email protected]> wrote in message
news:[email protected]...
> >>>
> >>>Maybe so, but as far as can be determined by careful study of the
> >>>photograph, it isn't broken...
> >>
> >>indeed. but can you say it's not fatigued?
> >
> >
> > Can you say it is?
> >
> > Jasper
>
> that's my point jasper - you can not say anything without expensive
> testing. it's not a situation like a frame where you can see cracking
> at a weld - here, cracking is at a thread root - it's invisible.
>

For a single bolt, yes, expensive testing would be required.

But for say, 100 million, if none of them have failed, then it is
_extremely_ unlikely that fatigue is an issue.

So, how many BROKEN brake bolts have you seen, jim beam?

 

[jtaylor]

"jim beam" <[email protected]> wrote in message
news:[email protected]...
> >
> >
> > Fine! Produce at least _one_ example of someone injured because a
> > cut-thread brake mounting bolt failed in normal service.
>
> show me any mainstream oem bolt that's not rolled! _one_ example will do.
>
> >

And how do we know you won't dismiss bolts that have cut threads as not
"mainstream" because they, well, have cut threads?

And as we know there are brake bolts out there, that, while you would not
brand them "mainstream", nevertheless hold brakes to frames; and that they
have no history of failure.

Why then tell someone that running a die down his brake bolt to convert it
from nutted to recessed will result in a disaster waiting to happen?

 

[jtaylor]

"jim beam" <[email protected]> wrote in message
news:[email protected]...
> >
> >
> > Fine! Produce at least _one_ example of someone injured because a
> > cut-thread brake mounting bolt failed in normal service.
>
> show me any mainstream oem bolt that's not rolled! _one_ example will do.
>
> >

And how do we know you won't dismiss bolts that have cut threads as not
"mainstream" because they, well, have cut threads?

And as we know there are brake bolts out there, that, while you would not
brand them "mainstream", nevertheless hold brakes to frames; and that they
have no history of failure.

Why then tell someone that running a die down his brake bolt to convert it
from nutted to recessed will result in a disaster waiting to happen?

 

[Sandy]

Dans le message de news:[email protected]!nnrp1.uunet.ca,
jtaylor <[email protected]> a réfléchi, et puis a déclaré :
> "jim beam" <[email protected]> wrote in message
> news:[email protected]...
>>>>>
>>>>> Maybe so, but as far as can be determined by careful study of the
>>>>> photograph, it isn't broken...
>>>>
>>>> indeed. but can you say it's not fatigued?
>>>
>>>
>>> Can you say it is?
>>>
>>> Jasper
>>
>> that's my point jasper - you can not say anything without expensive
>> testing. it's not a situation like a frame where you can see
>> cracking at a weld - here, cracking is at a thread root - it's
>> invisible.
>>
>
> For a single bolt, yes, expensive testing would be required.
>
> But for say, 100 million, if none of them have failed, then it is
> _extremely_ unlikely that fatigue is an issue.
>
> So, how many BROKEN brake bolts have you seen, [jim beam?]

For my part, the only one I can recall is the one YOU POSTED in another
thread minutes earlier. Did you figure no one read that ?

 

[[email protected]]

jim beam wrote:
> Jasper Janssen wrote:
> > On Thu, 01 Dec 2005 05:58:21 -0800, jim beam <[email protected]> wrote:
> >
> >>indeed. but can you say it's not fatigued?
> >
> > Can you say it is?
>
> that's my point jasper - you can not say anything without expensive
> testing.

False! Without expensive testing, you can say "We have seen no reports
of fatigue failures of brake bolts, except one which was blatantly,
stupidly loose."

> it's not a situation like a frame where you can see cracking
> at a weld - here, cracking is at a thread root - it's invisible.
>
> if it's both in a hidden location /and/ invisible, /and/ in the worst
> possible fatigue location [front of a fork vs. the rear], /and/ the most
> critical safety component on the bike,

Is _that_ the most critical safety component of the bike? I'd
have thought the mechanism that holds the front axle in place was more
critical!

Ah well, matter of judgement, I suppose. But it would be good to be
consistent!

- Frank Krygowski

 

[Chalo]

[email protected] wrote:
>
> Brake bolts, properly installed, don't break. Even RBT's own
> tester to destruction, Chalo Colina, has only reported maybe
> bending a few chintzy centerbolts.

True. It is the stiffness, and not the ultimate strength of the brake,
that suffers most in a centerbolt-mounted design. The couple I have
bent were probably attributable more to crooked mounting surfaces than
to the hardships of bringing me to a stop.

> IIRC, he usually bends the fork first.

Although I have bent many forks by means of braking forces, that trick
requires more braking power than a centerbolt-mounted brake can
provide. I concede that I have little experience with short-reach
brakes, since they restrict tire choice to smaller sizes than I can
live with. But the standard-reach (>50mm) and longer caliper brakes
that I have used won't bend anybody's forks.

Chalo Colina

 

[Phil, Squid-in-Training]

jtaylor wrote:
> "jim beam" <[email protected]> wrote in message
> news:[email protected]...
>
>
>>> But the second point is not how many bake bolts with cut threads jb
>>> has seen, it is instead what he has been asked many times in this
>>> thread, and so far refused to answer:
>>>
>>> "How many BROKEN brake bolts have you seen, jim beam?"
>>>
>>
>> you wonder why i don't respond to you posts? it's because you don't
>> understand the concepts of /fatigue strength/ vs. /static load
>> strength/. and you've just illustrated that yet again. until you
>> can demonstrate comprehension of that fundamental distinction,
>> there's no exchange we can have that will have any meaning.
>
> Sure, you and I know fatigue _can_ be a design consideration, but if
> failures do not occur with bolts that have either type of thread,
> then in such a case it is not an issue.
>
> So, have you ever seen ANY broken brake bolts?

I think you're missing the point here. JB is attacking the tenets of BAD
DESIGN. Why would anybody in their right mind go about designing things
with internal 90-degree angles, factors of safety of 1.1, and cut threads?
Bad design means that the designer will continue designing products that may
not break in that one product, but if the methods are utilized in a future
product that doesn't hold, it could cause "personal injury or even death."

Imagine us using aluminum pedal spindles. Bad design? Well, let's just
beef it up by 50%! That doesn't change the fact that it's still a bad
design. Think about it. Who wants shitty engineers designing their next
car hurtling down the road at 70mph? You design parts using the best, most
cost-effective, yet safe methods you have at the time.

He's not dodging the issue. You're bringing up an irrelevant one.
--
Phil, Squid-in-Training

 

[jim beam]

[email protected] wrote:
> jim beam wrote:
>
>>Jasper Janssen wrote:
>>
>>>On Thu, 01 Dec 2005 05:58:21 -0800, jim beam <[email protected]> wrote:
>>>
>>>
>>>>indeed. but can you say it's not fatigued?
>>>
>>>Can you say it is?
>>
>>that's my point jasper - you can not say anything without expensive
>>testing.
>
>
> False! Without expensive testing, you can say "We have seen no reports
> of fatigue failures of brake bolts, except one which was blatantly,
> stupidly loose."

hmmm. what that citation actually reads is: "Poor maintenance had
allowed the brake bolt to loosen and allow the assembly to 'chatter'
when braking imposing cyclic loads instead of steady stress on the
fastening bolt."

there's a bit of a gap between this not unlikely scenario and
krygowski's being "blatantly stupidly loose" methinks. but even then,
this is still a red herring because the issue of fatigue detection is
still not being addressed.

>
>
>>it's not a situation like a frame where you can see cracking
>>at a weld - here, cracking is at a thread root - it's invisible.
>>
>>if it's both in a hidden location /and/ invisible, /and/ in the worst
>>possible fatigue location [front of a fork vs. the rear], /and/ the most
>>critical safety component on the bike,
>
>
> Is _that_ the most critical safety component of the bike? I'd
> have thought the mechanism that holds the front axle in place was more
> critical!
>
> Ah well, matter of judgement, I suppose. But it would be good to be
> consistent!
>
> - Frank Krygowski
>

 

[[email protected]]

jim beam wrote:
> [email protected] wrote:
> > False! Without expensive testing, you can say "We have seen no reports
> > of fatigue failures of brake bolts, except one which was blatantly,
> > stupidly loose."
>
> hmmm. what that citation actually reads is: "Poor maintenance had
> allowed the brake bolt to loosen and allow the assembly to 'chatter'
> when braking imposing cyclic loads instead of steady stress on the
> fastening bolt."
>
> there's a bit of a gap between this not unlikely scenario and
> krygowski's being "blatantly stupidly loose" methinks. but even then,
> this is still a red herring because the issue of fatigue detection is
> still not being addressed.

The issue of fatigue detection _is_ being addressed, as many people
have pointed out. Specifically, (except for one example of non-typical
use), no fatigue has been detected.

If fatigue isn't detected, we're concluding that there isn't a fatigue
problem. Seems simple enough!

- Frank Krygowski

 

[[email protected]]

Phil, Squid-in-Training wrote:
> jtaylor wrote:
> >
> >
> > So, have you ever seen ANY broken brake bolts?
>
> I think you're missing the point here. JB is attacking the tenets of BAD
> DESIGN. Why would anybody in their right mind go about designing things
> with internal 90-degree angles, factors of safety of 1.1, and cut threads?
> Bad design means that the designer will continue designing products that may
> not break in that one product, but if the methods are utilized in a future
> product that doesn't hold, it could cause "personal injury or even death."
>
> Imagine us using aluminum pedal spindles. Bad design? Well, let's just
> beef it up by 50%! That doesn't change the fact that it's still a bad
> design.

You seem to have no knowledge of what design is, Phil.

How do you tell a design is "bad"? If you're referring to inadequate
strength (whether fatigue strength or static strength or some other
variety) the lack of failure is a damned good criterion.

You may feel aluminum pedal spindles are bad - but why? I assume it's
because you feel they would break. If aluminum pedal spindles had been
on the market for thirty years and there were no reports of breakage,
it would prove you wrong.

And speaking of aluminum, it's worth noting that we have many other
parts just as critical as pedal spindles that _are_ aluminum, and that
some of them have been known to break. The obvious example is crank
arms. Do you therefore declare all aluminum crank arms "bad designs"?


My bet is, you don't. My bet is you regularly ride aluminum crank
arms, and perhaps recommend them to others. My bet is you're aware
that some fail catastrophically, but you feel the incidence of such
failure is low enough the design merits your approval.

What we have with the brake bolt is a design that seems to _never_
fail. It apparently fails far, far less often than, say, a downward
facing dropout trying to retain a disk brake hub and axle.

If it _never_ fails, it's not a _very_ bad design, is it?

- Frank Krygowski

 

[jim beam]

[email protected] wrote:
> jim beam wrote:
>
>>[email protected] wrote:
>>
>>>False! Without expensive testing, you can say "We have seen no reports
>>>of fatigue failures of brake bolts, except one which was blatantly,
>>>stupidly loose."
>>
>>hmmm. what that citation actually reads is: "Poor maintenance had
>>allowed the brake bolt to loosen and allow the assembly to 'chatter'
>>when braking imposing cyclic loads instead of steady stress on the
>>fastening bolt."
>>
>>there's a bit of a gap between this not unlikely scenario and
>>krygowski's being "blatantly stupidly loose" methinks. but even then,
>>this is still a red herring because the issue of fatigue detection is
>>still not being addressed.
>
>
> The issue of fatigue detection _is_ being addressed, as many people
> have pointed out. Specifically, (except for one example of non-typical
> use), no fatigue has been detected.

you're priceless. you clutch straws with singular examples when talking
disk brakes, something of which you have no direct experience and for
which you've still shown no direct causation, but you can dismiss cited
direct causation for fatigue?

>
> If fatigue isn't detected, we're concluding that there isn't a fatigue
> problem. Seems simple enough!

frank, show me /one/ oem cut thread bolt? please? if not, don't
lecture me on how cut threads are such a non-issue.

>
> - Frank Krygowski
>

 

[Phil, Squid-in-Training]

<[email protected]> wrote in message
news:[email protected]...
>
> Phil, Squid-in-Training wrote:
>> jtaylor wrote:
>> >
>> >
>> > So, have you ever seen ANY broken brake bolts?
>>
>> I think you're missing the point here. JB is attacking the tenets of BAD
>> DESIGN. Why would anybody in their right mind go about designing things
>> with internal 90-degree angles, factors of safety of 1.1, and cut
>> threads?
>> Bad design means that the designer will continue designing products that
>> may
>> not break in that one product, but if the methods are utilized in a
>> future
>> product that doesn't hold, it could cause "personal injury or even
>> death."
>>
>> Imagine us using aluminum pedal spindles. Bad design? Well, let's just
>> beef it up by 50%! That doesn't change the fact that it's still a bad
>> design.
>
> You seem to have no knowledge of what design is, Phil.
>
> How do you tell a design is "bad"? If you're referring to inadequate
> strength (whether fatigue strength or static strength or some other
> variety) the lack of failure is a damned good criterion.

We don't have enough data.

> You may feel aluminum pedal spindles are bad - but why? I assume it's
> because you feel they would break. If aluminum pedal spindles had been
> on the market for thirty years and there were no reports of breakage,
> it would prove you wrong.

The benefits of an alu spindle don't outweigh the potentially catastrophic
costs.

> And speaking of aluminum, it's worth noting that we have many other
> parts just as critical as pedal spindles that _are_ aluminum, and that
> some of them have been known to break. The obvious example is crank
> arms. Do you therefore declare all aluminum crank arms "bad designs"?

The benefits outweigh the costs, and the bending moment stress is far lower
on a crank than a pedal spindle.

> My bet is, you don't. My bet is you regularly ride aluminum crank
> arms, and perhaps recommend them to others. My bet is you're aware
> that some fail catastrophically, but you feel the incidence of such
> failure is low enough the design merits your approval.

Hehe... where's Chalo when you need him? Just kidding. I think that the
benefits outweigh the costs for most riders. Most crankarms see far less
miles than the ones the people on this newsgroup put them through.

> What we have with the brake bolt is a design that seems to _never_
> fail. It apparently fails far, far less often than, say, a downward
> facing dropout trying to retain a disk brake hub and axle.

We've seen one picture so far, posted by jtaylor. We've seen one picture of
disc brake failure, posted by an alarmist. With no lawyer lips to boot.

> If it _never_ fails, it's not a _very_ bad design, is it?

No it's not. But it's still bad design. If the engineer specs a set of
brake caliper bolts on a car that are undersized, cut, or whatever, the
results could be grave. How can a low-cost modification that, according to
the principles of physics, not be recommended? Hint: forward-facing
dropouts.

The benefits outweigh the costs. Although I don't have any data backing up
costs of rolling versus cutting, I'm betting that with the vast majority of
bolts in general being rolled, the additional cost is almost nothing.

--
Phil, Squid-in-Training

 

[[email protected]]

Phil Lee writes:

>> You may feel aluminum pedal spindles are bad - but why? I assume
>> it's because you feel they would break. If aluminum pedal spindles
>> had been on the market for thirty years and there were no reports
>> of breakage, it would prove you wrong.

> The benefits of an alu spindle don't outweigh the potentially
> catastrophic costs.

Not only that but steel pedal spindles with inappropriate radiused
diameter transitions of various brands have failed. I had an early
Campagnolo steel spindle break. Since this is a place where pedal
height and bearing diameters need to be small, the larger diameter of
aluminum spindles would be functionally impractical. It's not a good
example of material choice. Axles are generally steel for that
reason.

>> And speaking of aluminum, it's worth noting that we have many other
>> parts just as critical as pedal spindles that _are_ aluminum, and
>> that some of them have been known to break. The obvious example is
>> crank arms. Do you therefore declare all aluminum crank arms "bad
>> designs"?

> The benefits outweigh the costs, and the bending moment stress is
> far lower on a crank than a pedal spindle.

>> My bet is, you don't. My bet is you regularly ride aluminum crank
>> arms, and perhaps recommend them to others. My bet is you're aware
>> that some fail catastrophically, but you feel the incidence of such
>> failure is low enough the design merits your approval.

The first aluminum Campagnolo cranks broke for me in 1959 so I
switched back to steel for th next three years until the failure
reports got small. Even then, because no good steel cranks or their
chainwheels were available anymore, I continued to break more than two
dozen aluminum cranks in the following years.

> Hehe... where's Chalo when you need him? Just kidding. I think
> that the benefits outweigh the costs for most riders. Most
> crankarms see far less miles than the ones the people on this
> newsgroup put them through.

We came from steel cranks and the change to aluminum has demonstrated
that failure rates are low enough that many right here on wreck.bike
don't believe that they can break unless the rider misused them.

>> What we have with the brake bolt is a design that seems to _never_
>> fail. It apparently fails far, far less often than, say, a downward
>> facing dropout trying to retain a disk brake hub and axle.

> We've seen one picture so far, posted by jtaylor. We've seen one
> picture of disc brake failure, posted by an alarmist. With no
> lawyer lips to boot.

>> If it _never_ fails, it's not a _very_ bad design, is it?

It could be over designed but then there are parts that should never
fail because they are vital to the life of the rider.

> No it's not. But it's still bad design. If the engineer specs a
> set of brake caliper bolts on a car that are undersized, cut, or
> whatever, the results could be grave. How can a low-cost
> modification that, according to the principles of physics, not be
> recommended? Hint: forward-facing dropouts.

> The benefits outweigh the costs. Although I don't have any data
> backing up costs of rolling versus cutting, I'm betting that with
> the vast majority of bolts in general being rolled, the additional
> cost is almost nothing.



Jobst Brandt

 

[[email protected]]

Phil, Squid-in-Training wrote:

> No it's not. But it's still bad design. If the engineer specs a set of
> brake caliper bolts on a car that are undersized, cut, or whatever, the
> results could be grave. How can a low-cost modification that, according to
> the principles of physics, not be recommended? Hint: forward-facing
> dropouts.
>
> The benefits outweigh the costs. Although I don't have any data backing up
> costs of rolling versus cutting, I'm betting that with the vast majority of
> bolts in general being rolled, the additional cost is almost nothing.

Dude,

You and jim beam are changing the subject. Read the original post.
The question was not, Should bike designers design brake bolts
that are rolled or cut-thread? Nobody really disputes that rolled
is better, the only disagreement was about how much. The original
question was, Can an individual rider use a die to cut 5mm more of
threads on a rare, trick-part, long out-of-production brake so that
it is usable? jim's answer was that the sky will fall if you do that.
The dispute is over whether the sky is falling.