RBR on crank failures

Matt O'Toole said:

Today's Road Bike Rider newsletter had a piece on crank failures. I don't
find RBR's writers to be particularly insightful, but they do have a large
audience. Maybe this is a good opportunity to educate these folks, so
they can pass this wisdom along to their readers. Drop 'em a note.
Article below.

Matt O.

--
3. UNCLE AL: When Parts Fail

RBR got wind of a nasty crash in North Carolina involving a rider we'll
call RJ to protect the injured.

Seems that RJ, all 140 pounds of him, was just riding along on his
Litespeed when the right crankarm snapped off about two inches above the
pedal. He came out of the ensuing tangle with scrapes, bruises and a
damaged wrist but no missing teeth.

The crankset in question is a Shimano Dura-Ace triple, four years old with
about 24,000 miles on it. We're told this was the bike's first crash and
that RJ is known for keeping the machine in immaculate condition.

In an e-mail, RJ posed a key question: "Should we replace parts after a
certain number of miles as a precaution? Hey maybe this would be a good
time to explain to Sue why I need a whole new bike -- just to be on the
safe side. I've been drooling over the Scott Addict -- only thirteen
pounds. . . ."

I think there should be a standard for longevity of components and the
factors that affect their life. But can you imagine the hue and cry if
Shimano or Campagnolo said," This is our most expensive crank. It'll last
for two seasons. If you go beyond that it could fail and you might crash
your brains out." Not a good marketing concept.

But in the quest for lightness -- RJ apparently hasn't learned and now
wants a 13-pound Scott with a frame you can "oil can" with your thumb --
strength is compromised. Not a single Euro pro rides any frame or
component long enough for it to fail from age, although failures do happen
(ask Tom Boonen about Time carbon stems).

That's part of a pro's job -- testing lightweight [censored] for the rest of us.
If we followed their lead, however, we wouldn't ride the stuff forever . .
. or until it breaks.

I personally know of four broken crankarms in the last 42 years. Three
were the old-style Campy Nuovo/Super Record arms and now this Dura-Ace.
The Campy arms (drive side) failed from poor design combined with too many
miles of hard use.

I remember telling a local guy he should put a new crankset on his old
Columbine bike before he got back into riding. He thought I was trying to
sell him something. He ignored my advice and wouldn't you know, the right
crankarm broke when he was sprinting out of a corner. Result: concussion,
65 stitches in his forehead, and a destroyed bike.

If I had to guess at what happened to RJ's crankarm, I'd say his shoe
rubbed it often enough during pedaling to create a stress riser. This is
not as much a problem with arms that are cold-forged and solid, but it's
certainly something to watch for with hollow alloy arms like on his crank.

I've seen arms with enough rubbing to create a groove -- a perfect spot
for a catastrophic failure. Would you take a file to a crankarm and think
it wouldn't be weakened?
--

the other thing to look into is whether, since this rider was "known for
keeping the machine in immaculate condition", there were any chemicals
used in maintenance that could have been a factor.

the comment alleging "poor design", presumably a barb aimed at the
hollow arm structure, is underinformed supposition. the failure record
of the shimano hollowtech is exemplary.

jim beam said:

Matt O'Toole said:

Today's Road Bike Rider newsletter had a piece on crank failures. I don't
find RBR's writers to be particularly insightful, but they do have a large
audience. Maybe this is a good opportunity to educate these folks, so
they can pass this wisdom along to their readers. Drop 'em a note.
Article below.

Quoted message said:

Matt O.

Quoted message said:

--
3. UNCLE AL: When Parts Fail

Quoted message said:

RBR got wind of a nasty crash in North Carolina involving a rider we'll
call RJ to protect the injured.

Quoted message said:

Seems that RJ, all 140 pounds of him, was just riding along on his
Litespeed when the right crankarm snapped off about two inches above the
pedal. He came out of the ensuing tangle with scrapes, bruises and a
damaged wrist but no missing teeth.

Quoted message said:

The crankset in question is a Shimano Dura-Ace triple, four years old with
about 24,000 miles on it. We're told this was the bike's first crash and
that RJ is known for keeping the machine in immaculate condition.

Quoted message said:

In an e-mail, RJ posed a key question: "Should we replace parts after a
certain number of miles as a precaution? Hey maybe this would be a good
time to explain to Sue why I need a whole new bike -- just to be on the
safe side. I've been drooling over the Scott Addict -- only thirteen
pounds. . . ."

Quoted message said:

I think there should be a standard for longevity of components and the
factors that affect their life. But can you imagine the hue and cry if
Shimano or Campagnolo said," This is our most expensive crank. It'll last
for two seasons. If you go beyond that it could fail and you might crash
your brains out." Not a good marketing concept.

Quoted message said:

But in the quest for lightness -- RJ apparently hasn't learned and now
wants a 13-pound Scott with a frame you can "oil can" with your thumb --
strength is compromised. Not a single Euro pro rides any frame or
component long enough for it to fail from age, although failures do happen
(ask Tom Boonen about Time carbon stems).

Quoted message said:

That's part of a pro's job -- testing lightweight [censored] for the rest of us.
If we followed their lead, however, we wouldn't ride the stuff forever . .
. or until it breaks.

Quoted message said:

I personally know of four broken crankarms in the last 42 years. Three
were the old-style Campy Nuovo/Super Record arms and now this Dura-Ace.
The Campy arms (drive side) failed from poor design combined with too many
miles of hard use.

Quoted message said:

I remember telling a local guy he should put a new crankset on his old
Columbine bike before he got back into riding. He thought I was trying to
sell him something. He ignored my advice and wouldn't you know, the right
crankarm broke when he was sprinting out of a corner. Result: concussion,
65 stitches in his forehead, and a destroyed bike.

Quoted message said:

If I had to guess at what happened to RJ's crankarm, I'd say his shoe
rubbed it often enough during pedaling to create a stress riser. This is
not as much a problem with arms that are cold-forged and solid, but it's
certainly something to watch for with hollow alloy arms like on his crank.

Quoted message said:

I've seen arms with enough rubbing to create a groove -- a perfect spot
for a catastrophic failure. Would you take a file to a crankarm and think
it wouldn't be weakened?
--

the other thing to look into is whether, since this rider was "known for
keeping the machine in immaculate condition", there were any chemicals
used in maintenance that could have been a factor.

the comment alleging "poor design", presumably a barb aimed at the
hollow arm structure, is underinformed supposition. the failure record
of the shimano hollowtech is exemplary

The "poor design" comment was in regard to the old Campy NR/SR cranks,
which made up 75% of the crank failures seen by the writer ("Uncle
Al"😉, over a period of 42 years. Those Campy cranks *were* prone to
failure, despite the lofty Campy reputaion of the time.

In article <[email hidden]>,

jim beam said:

Matt O'Toole said:

Today's Road Bike Rider newsletter had a piece on crank failures.
I don't find RBR's writers to be particularly insightful, but they
do have a large audience. Maybe this is a good opportunity to
educate these folks, so they can pass this wisdom along to their
readers. Drop 'em a note. Article below.

-- 3. UNCLE AL: When Parts Fail

<snip>

Quoted message said:

Quoted message said:

I personally know of four broken crankarms in the last 42 years.
Three were the old-style Campy Nuovo/Super Record arms and now this
Dura-Ace. The Campy arms (drive side) failed from poor design
combined with too many miles of hard use.

<snip>

Quoted message said:

the comment alleging "poor design", presumably a barb aimed at the
hollow arm structure, is underinformed supposition. the failure
record of the shimano hollowtech is exemplary.

It looks to me like the "poor design" comment was aimed at the Campy
cranks. The Nuovo/Super Record cranks had known problems where the
spider met the crank, and there are plenty of examples of failures. A
few:

http://pardo.net/bike/pic/fail-001/000.html

And a hollow Shimano crank, courtesy of Andrew Muzi:

http://pardo.net/bike/pic/fail-001/FAIL-029.html

Quoted message said:

Matt O'Toole said:

Today's Road Bike Rider newsletter had a piece on crank failures. I
don't
find RBR's writers to be particularly insightful, but they do have a
large
audience. Maybe this is a good opportunity to educate these folks, so
they can pass this wisdom along to their readers. Drop 'em a note.
Article below.
--
3. UNCLE AL: When Parts Fail
RBR got wind of a nasty crash in North Carolina involving a rider we'll
call RJ to protect the injured.
Seems that RJ, all 140 pounds of him, was just riding along on his
Litespeed when the right crankarm snapped off about two inches above the
pedal. He came out of the ensuing tangle with scrapes, bruises and a
damaged wrist but no missing teeth.
The crankset in question is a Shimano Dura-Ace triple, four years old
with
about 24,000 miles on it. We're told this was the bike's first crash and
that RJ is known for keeping the machine in immaculate condition.
In an e-mail, RJ posed a key question: "Should we replace parts after a
certain number of miles as a precaution? Hey maybe this would be a good
time to explain to Sue why I need a whole new bike -- just to be on the
safe side. I've been drooling over the Scott Addict -- only thirteen
pounds. . . ."
I think there should be a standard for longevity of components and the
factors that affect their life. But can you imagine the hue and cry if
Shimano or Campagnolo said," This is our most expensive crank. It'll last
for two seasons. If you go beyond that it could fail and you might crash
your brains out." Not a good marketing concept.

But in the quest for lightness -- RJ apparently hasn't learned and now
wants a 13-pound Scott with a frame you can "oil can" with your thumb --
strength is compromised. Not a single Euro pro rides any frame or
component long enough for it to fail from age, although failures do
happen
(ask Tom Boonen about Time carbon stems).

That's part of a pro's job -- testing lightweight [censored] for the rest of
us.
If we followed their lead, however, we wouldn't ride the stuff forever
. . . or until it breaks.
I personally know of four broken crankarms in the last 42 years. Three
were the old-style Campy Nuovo/Super Record arms and now this Dura-Ace.
The Campy arms (drive side) failed from poor design combined with too
many
miles of hard use.
I remember telling a local guy he should put a new crankset on his old
Columbine bike before he got back into riding. He thought I was trying to
sell him something. He ignored my advice and wouldn't you know, the right
crankarm broke when he was sprinting out of a corner. Result: concussion,
65 stitches in his forehead, and a destroyed bike.

If I had to guess at what happened to RJ's crankarm, I'd say his shoe
rubbed it often enough during pedaling to create a stress riser. This is
not as much a problem with arms that are cold-forged and solid, but it's
certainly something to watch for with hollow alloy arms like on his
crank.

I've seen arms with enough rubbing to create a groove -- a perfect spot
for a catastrophic failure. Would you take a file to a crankarm and think
it wouldn't be weakened?

jim beam said:

the other thing to look into is whether, since this rider was "known for
keeping the machine in immaculate condition", there were any chemicals
used in maintenance that could have been a factor.

the comment alleging "poor design", presumably a barb aimed at the
hollow arm structure, is underinformed supposition. the failure record
of the shimano hollowtech is exemplary.

I agree, alleging a design deficiency is strong. Most modern aluminum
cranks have very low failure rates. It's doubly unfortunate riders
continue to ride fatally cracked arms after Cassandra mechanics point
them out. I doubt the hollow design is different enough to be a hazard
in itself. Every cracked crank I've seen exhibited the telltale dark
area that was long-failed before the last bit gave way:
http://www.yellowjersey.org/jayscranks.html
--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971

A Muzi said:

Quoted message said:

Matt O'Toole said:

Today's Road Bike Rider newsletter had a piece on crank failures. I
don't
find RBR's writers to be particularly insightful, but they do have a
large
audience. Maybe this is a good opportunity to educate these folks, so
they can pass this wisdom along to their readers. Drop 'em a note.
Article below.
--
3. UNCLE AL: When Parts Fail
RBR got wind of a nasty crash in North Carolina involving a rider we'll
call RJ to protect the injured.
Seems that RJ, all 140 pounds of him, was just riding along on his
Litespeed when the right crankarm snapped off about two inches above the
pedal. He came out of the ensuing tangle with scrapes, bruises and a
damaged wrist but no missing teeth.
The crankset in question is a Shimano Dura-Ace triple, four years old
with
about 24,000 miles on it. We're told this was the bike's first crash and
that RJ is known for keeping the machine in immaculate condition.
In an e-mail, RJ posed a key question: "Should we replace parts after a
certain number of miles as a precaution? Hey maybe this would be a good
time to explain to Sue why I need a whole new bike -- just to be on the
safe side. I've been drooling over the Scott Addict -- only thirteen
pounds. . . ."
I think there should be a standard for longevity of components and the
factors that affect their life. But can you imagine the hue and cry if
Shimano or Campagnolo said," This is our most expensive crank. It'll
last
for two seasons. If you go beyond that it could fail and you might crash
your brains out." Not a good marketing concept.

But in the quest for lightness -- RJ apparently hasn't learned and now
wants a 13-pound Scott with a frame you can "oil can" with your thumb --
strength is compromised. Not a single Euro pro rides any frame or
component long enough for it to fail from age, although failures do
happen
(ask Tom Boonen about Time carbon stems).

That's part of a pro's job -- testing lightweight [censored] for the rest
of us.
If we followed their lead, however, we wouldn't ride the stuff
forever . . . or until it breaks.
I personally know of four broken crankarms in the last 42 years. Three
were the old-style Campy Nuovo/Super Record arms and now this Dura-Ace.
The Campy arms (drive side) failed from poor design combined with too
many
miles of hard use.
I remember telling a local guy he should put a new crankset on his old
Columbine bike before he got back into riding. He thought I was
trying to
sell him something. He ignored my advice and wouldn't you know, the
right
crankarm broke when he was sprinting out of a corner. Result:
concussion,
65 stitches in his forehead, and a destroyed bike.

If I had to guess at what happened to RJ's crankarm, I'd say his shoe
rubbed it often enough during pedaling to create a stress riser. This is
not as much a problem with arms that are cold-forged and solid, but it's
certainly something to watch for with hollow alloy arms like on his
crank.

I've seen arms with enough rubbing to create a groove -- a perfect spot
for a catastrophic failure. Would you take a file to a crankarm and
think
it wouldn't be weakened?

jim beam said:

the other thing to look into is whether, since this rider was "known
for keeping the machine in immaculate condition", there were any
chemicals used in maintenance that could have been a factor.

the comment alleging "poor design", presumably a barb aimed at the
hollow arm structure, is underinformed supposition. the failure
record of the shimano hollowtech is exemplary.

I agree, alleging a design deficiency is strong. Most modern aluminum
cranks have very low failure rates. It's doubly unfortunate riders
continue to ride fatally cracked arms after Cassandra mechanics point
them out. I doubt the hollow design is different enough to be a hazard
in itself. Every cracked crank I've seen exhibited the telltale dark
area that was long-failed before the last bit gave way:
http://www.yellowjersey.org/jayscranks.html

indeed.

i misread the "design" point - it was aimed at campy. when i go to a
swap meet, i see campy cranks of that era offered for sale, and with
only one exception, every single one i've seen has been cracked to some
degree. the one that wasn't was new in box.

I'm kinda surprised just how 'un'hollow these cranks are. I hadn't
seen a cross section before.

Robert

Robert said:

I'm kinda surprised just how 'un'hollow these cranks are. I hadn't
seen a cross section before.

Robert

Just another hollow promise.

Quoted message said:

Just another hollow promise.

Are the failure rate of carbon cranks better or worse?

Quoted message said:

Quoted message said:

Just another hollow promise.

Are the failure rate of carbon cranks better or worse?

It was just a comment about the marketing aspects of "Hollowtech", not
a comment regarding reliability.

In article <[email hidden]>,

Robert said:

I'm kinda surprised just how 'un'hollow these cranks are. I hadn't
seen a cross section before.

Me, too, actually. I expected the cranks to look more tubular, but I
suppose that the properties of aluminum are such that the walls of the
"tube" have to be pretty thick. The question for me would be whether
there is any actual benefit to this design.

Tim McNamara said:

In article <[email hidden]>,

Robert said:

I'm kinda surprised just how 'un'hollow these cranks are. I hadn't
seen a cross section before.

Me, too, actually. I expected the cranks to look more tubular, but I
suppose that the properties of aluminum are such that the walls of the
"tube" have to be pretty thick. The question for me would be whether
there is any actual benefit to this design.

Quoted message said:

From other pictures that have been posted here in the

past, they are more hollow near the center of the arm.
That one is broken near the end where the void is
small. The void has to end well before the pedal eye
and BB mounting hole. An industrious person might
be able to compute the volume of the interior void
by measuring both the weight and the volume displacement
of a crank (by submerging in water).

Ben

Tim McNamara said:

And a hollow Shimano crank, courtesy of Andrew Muzi:

http://pardo.net/bike/pic/fail-001/FAIL-029.html

These pictures illustrate perfectly how silly Hollowtech cranks really
are. Note how small the hollow is. It can't possibly be worth the extra
manufacturing expense to eliminate such a miniscule amount of metal.
What's worth it for Shimano is being able to say they're "hollow,"
conjuring up images of super-lightweight parts in buyers' minds. These
things are a joke.

Matt O.

In article <[email hidden]>, Tim

McNamara said:

In article <[email hidden]>,

Robert said:

I'm kinda surprised just how 'un'hollow these cranks are. I hadn't
seen a cross section before.

Me, too, actually. I expected the cranks to look more tubular, but I
suppose that the properties of aluminum are such that the walls of the
"tube" have to be pretty thick. The question for me would be whether
there is any actual benefit to this design.

Increased profits?

Luke

Luke said:

In article <[email hidden]>, Tim

McNamara said:

In article <[email hidden]>,
"Robert" <[email hidden]> wrote:

Quoted message said:

Quoted message said:

I'm kinda surprised just how 'un'hollow these cranks are. I hadn't
seen a cross section before.

Quoted message said:

Me, too, actually. I expected the cranks to look more tubular, but I
suppose that the properties of aluminum are such that the walls of the
"tube" have to be pretty thick. The question for me would be whether
there is any actual benefit to this design.

Increased profits?

At least increased marketability.

Luke said:

In article <[email hidden]>, Tim

McNamara said:

In article <[email hidden]>,

Robert said:

I'm kinda surprised just how 'un'hollow these cranks are. I hadn't
seen a cross section before.

Me, too, actually. I expected the cranks to look more tubular, but I
suppose that the properties of aluminum are such that the walls of the
"tube" have to be pretty thick. The question for me would be whether
there is any actual benefit to this design.

Increased profits?

Luke

quite the contrary.

now to understand, think about "traditional" cranks - the section is
akin to an "I" beam. that means material removed from the low load
areas for lightness. but, that profile is more susceptible to fatigue.
so, where's the most useful and safe area to remove material that's
not going to affect our handy-dandy researched fatigue resistant shimano
crank arm profile now?

Matt O'Toole said:

Tim McNamara said:

And a hollow Shimano crank, courtesy of Andrew Muzi:

http://pardo.net/bike/pic/fail-001/FAIL-029.html

These pictures illustrate perfectly how silly Hollowtech cranks really
are. Note how small the hollow is. It can't possibly be worth the extra
manufacturing expense to eliminate such a miniscule amount of metal.
What's worth it for Shimano is being able to say they're "hollow,"
conjuring up images of super-lightweight parts in buyers' minds. These
things are a joke.

Matt O.

negative. see my response to luke - there's very sound reasoning behind
shimano's engineering.

Matt O'Toole said:

These pictures illustrate perfectly how silly Hollowtech cranks really
are. Note how small the hollow is.

I agree that it looks pretty useless for that crank (though I think it
hollows out more in the middle of the arm), but the DA model is much
more hollow... and costly. It is one of the lightest cranks made, and
is more durable than most of the others in it's weight category.

Ron Ruff said:

Matt O'Toole said:

These pictures illustrate perfectly how silly Hollowtech cranks really
are. Note how small the hollow is.

I agree that it looks pretty useless for that crank (though I think it
hollows out more in the middle of the arm), but the DA model is much
more hollow... and costly. It is one of the lightest cranks made, and
is more durable than most of the others in it's weight category.

more durable /regardless/ of weight!

In article <[email hidden]>,

jim beam said:

Ron Ruff said:

Matt O'Toole said:

These pictures illustrate perfectly how silly Hollowtech cranks
really are. Note how small the hollow is.

I agree that it looks pretty useless for that crank (though I think
it hollows out more in the middle of the arm), but the DA model is
much more hollow... and costly. It is one of the lightest cranks
made, and is more durable than most of the others in it's weight
category.

more durable /regardless/ of weight!

Please cite your source for this claim.