Knackered crank?

Nate Knutson said:

NickD said:

Cheers for the replies fellas (and ladies?). Found a website that
does Shimano spares, so will try loctite for now. If that doesn't
fix the issue satisfactorily, I'll get a new non-drive crank. I'm in
the process of speccing a new hardtail frame anyway - I'll just make
sure I use a different BB and crankset in future...

Any recommendations? ISIS is made of playdoh, by all accounts. Back
to square taper?

Thanks
Nick

I'll warn you that to contradict what most of your replies said, I've
definitely seen splines on an ISIS BB spindle get messed up from being
ridden with the crank loose, even though the spindle is made of much
harder stuff than the crank. It wasn't dramatic in appearance but it
was certainly damage to a part that needs to be precise, and was
enough to make putting a new crank on that BB questionable at best. I
don't know if the same thing could happen with Octalink but I would
assume so unless I had reason to think otherwise.

I have heard of bent (twisted) ISIS bb spindles from jumps to flat impacts.
160lb riders, nothing crazy.
--
Phil, Squid-in-Training

NickD said:

Cheers for the replies fellas (and ladies?). Found a website that does
Shimano spares, so will try loctite for now. If that doesn't fix the
issue satisfactorily, I'll get a new non-drive crank. I'm in the
process of speccing a new hardtail frame anyway - I'll just make sure I
use a different BB and crankset in future...

Any recommendations? ISIS is made of playdoh, by all accounts. Back to
square taper?

Thanks
Nick

Well, Octalink and ISIS answered no questions, solved no problems with
regards to square taper. Many ST BBs out there includiung SKF, very
high quality. many square taper cranks as well, TA, Stronglight for
MTB. Outboard bearings are another option, These DO fix the
Octalink/ISIS problems.

Can't argue with that. I mean, after years of square taper, some bright
spark at Shimano decided splined was the way forward. After not too
long, they decided to change it - the main reason has to be because
they're guff. As for outboard bearings, they may solve the problems of
Octalink, but do they do anything square taper didn't? Other than wear
expensively, I mean.

Nick

Llatikcuf said:

NickD said:

Any recommendations? ISIS is made of playdoh, by all accounts. Back to
square taper?

I went back to square on both my bikes, seems to be the best option
IMO. Honestly I don't notice any of that "flex" marketing people talk
about.

That's because it's mostly BS.

Quoted message said:

Just simple and reliable.

NickD said:

Can't argue with that. I mean, after years of square taper, some bright
spark at Shimano decided splined was the way forward.

The question is, was the "bright spark" that thought a neww BB standard
was needed working in engineering or in marketing?

Quoted message said:

From a business standpoint, a propietary BB standard (e.g., Octalink)

has all sorts of advantages. Everyone who has your cranks (as in all
those new bikes sold each year), *must* buy their replacement BBs from
you. And, when you "walk away" from that standard, alot of folks are
going to have to buy new cranks as well as new BBs.

Quoted message said:

After not too
long, they decided to change it - the main reason has to be because
they're guff. As for outboard bearings, they may solve the problems of
Octalink, but do they do anything square taper didn't? Other than wear
expensively, I mean.

Nick

Nick Drew said:

Can't argue with that. I mean, after years of square taper, some
bright spark at Shimano decided splined was the way forward. After
not too long, they decided to change it - the main reason has to be
because they're guff. As for outboard bearings, they may solve the
problems of Octalink, but do they do anything square taper didn't?
Other than wear expensively, I mean.

What is less obvious is that the square taper is not as strong as we
would like it to be, the square end being no larger than the last
joint of your little finger. I have broken a couple of these and seen
others. Approaching failure cannot be anticipated or inspected for.
Because it is a catastrophic failure, manufacturers have been looking
for a clean solution. As you see, it isn't easy.

The spindle breaks off in torsion, just inside the press fit of the
aluminum crank where stress is greatest. The fractures I had
initiated in the center of the flats leaving a spiral four toothed
face, the corners being the ends of the "teeth".

Jobst Brandt

Quoted message said:

Nick Drew said:

Can't argue with that. I mean, after years of square taper, some
bright spark at Shimano decided splined was the way forward. After
not too long, they decided to change it - the main reason has to be
because they're guff. As for outboard bearings, they may solve the
problems of Octalink, but do they do anything square taper didn't?
Other than wear expensively, I mean.

What is less obvious is that the square taper is not as strong as we
would like it to be, the square end being no larger than the last
joint of your little finger. I have broken a couple of these and seen
others.

In the past, speaking of square taper spindles, you yourself said:
"there are not many crank failures". And another very experienced
observer (Andrew Muzi) said, in the same thread: "do you mean a spindle
snapped in half? I've seen 2 or 3 in my lifetime".

http://tinyurl.com/rexel

But now, you make it sound a commonplace hazard in dire need of fixing.
What's up?

Quoted message said:

Approaching failure cannot be anticipated or inspected for.
Because it is a catastrophic failure, manufacturers have been looking
for a clean solution. As you see, it isn't easy.

The spindle breaks off in torsion, just inside the press fit of the
aluminum crank where stress is greatest. The fractures I had
initiated in the center of the flats leaving a spiral four toothed
face, the corners being the ends of the "teeth".

Jobst Brandt

You're talking about a guy who uses the phrase 'most of the dozens of
cranks that I broke' - essentially, Evel Knievel on a mountain bike.

Ozark Bicycle said:

Quoted message said:

Nick Drew said:

Can't argue with that. I mean, after years of square taper, some
bright spark at Shimano decided splined was the way forward. After
not too long, they decided to change it - the main reason has to be
because they're guff. As for outboard bearings, they may solve the
problems of Octalink, but do they do anything square taper didn't?
Other than wear expensively, I mean.

What is less obvious is that the square taper is not as strong as we
would like it to be, the square end being no larger than the last
joint of your little finger. I have broken a couple of these and seen
others.

In the past, speaking of square taper spindles, you yourself said:
"there are not many crank failures". And another very experienced
observer (Andrew Muzi) said, in the same thread: "do you mean a spindle
snapped in half? I've seen 2 or 3 in my lifetime".

http://tinyurl.com/rexel

But now, you make it sound a commonplace hazard in dire need of fixing.
What's up?

Quoted message said:

Approaching failure cannot be anticipated or inspected for.
Because it is a catastrophic failure, manufacturers have been looking
for a clean solution. As you see, it isn't easy.

The spindle breaks off in torsion, just inside the press fit of the
aluminum crank where stress is greatest. The fractures I had
initiated in the center of the flats leaving a spiral four toothed
face, the corners being the ends of the "teeth".

Jobst Brandt

I've seen it 3 times in 21 years. Not common, certainly not a reason
for octalink or outboard bearings.

Peter Chisholm said:

Quoted message said:

Quoted message said:

> Can't argue with that. I mean, after years of square taper, some
> bright spark at Shimano decided splined was the way forward.
> After not too long, they decided to change it - the main reason
> has to be because they're guff. As for outboard bearings, they
> may solve the problems of Octalink, but do they do anything
> square taper didn't? Other than wear expensively, I mean.

Quoted message said:

Quoted message said:

Quoted message said:

What is less obvious is that the square taper is not as strong as
we would like it to be, the square end being no larger than the
last joint of your little finger. I have broken a couple of these
and seen others.

Quoted message said:

Quoted message said:

In the past, speaking of square taper spindles, you yourself said:
"there are not many crank failures". And another very experienced
observer (Andrew Muzi) said, in the same thread: "do you mean a
spindle snapped in half? I've seen 2 or 3 in my lifetime".

http://tinyurl.com/rexel

Quoted message said:

Quoted message said:

But now, you make it sound a commonplace hazard in dire need of
fixing. What's up?

Quoted message said:

Quoted message said:

Quoted message said:

Approaching failure cannot be anticipated or inspected for.
Because it is a catastrophic failure, manufacturers have been
looking for a clean solution. As you see, it isn't easy.

Quoted message said:

Quoted message said:

Quoted message said:

The spindle breaks off in torsion, just inside the press fit of
the aluminum crank where stress is greatest. The fractures I had
initiated in the center of the flats leaving a spiral four toothed
face, the corners being the ends of the "teeth".

Quoted message said:

I've seen it 3 times in 21 years. Not common, certainly not a
reason for Octalink or outboard bearings.

Well, I've experienced it twice on my bicycle. Looking at the last
joint of one's little finger, visualize pushing hard on a pedal that
is in effect a 5" lever (pedal load from the spindle) bending it while
a 7" lever (the crank) is twisting it. That isn't reasonable to me.

Octalink definitely solved the spindle breaking and assembly problems,
but did so while violating other design criteria, such as bearing
durability, and above all the backlash problem that loosens retaining
bolts causing spline failure.

Jobst Brandt

Quoted message said:

Peter Chisholm said:

Quoted message said:

>> Can't argue with that. I mean, after years of square taper, some
>> bright spark at Shimano decided splined was the way forward.
>> After not too long, they decided to change it - the main reason
>> has to be because they're guff. As for outboard bearings, they
>> may solve the problems of Octalink, but do they do anything
>> square taper didn't? Other than wear expensively, I mean.

Quoted message said:

Quoted message said:

> What is less obvious is that the square taper is not as strong as
> we would like it to be, the square end being no larger than the
> last joint of your little finger. I have broken a couple of these
> and seen others.

Quoted message said:

Quoted message said:

In the past, speaking of square taper spindles, you yourself said:
"there are not many crank failures". And another very experienced
observer (Andrew Muzi) said, in the same thread: "do you mean a
spindle snapped in half? I've seen 2 or 3 in my lifetime".

http://tinyurl.com/rexel

Quoted message said:

Quoted message said:

But now, you make it sound a commonplace hazard in dire need of
fixing. What's up?

Quoted message said:

Quoted message said:

> Approaching failure cannot be anticipated or inspected for.
> Because it is a catastrophic failure, manufacturers have been
> looking for a clean solution. As you see, it isn't easy.

Quoted message said:

Quoted message said:

> The spindle breaks off in torsion, just inside the press fit of
> the aluminum crank where stress is greatest. The fractures I had
> initiated in the center of the flats leaving a spiral four toothed
> face, the corners being the ends of the "teeth".

Quoted message said:

I've seen it 3 times in 21 years. Not common, certainly not a
reason for Octalink or outboard bearings.

Well, I've experienced it twice on my bicycle.

Twice in how many total miles? And, remind us of your size, please.

Quoted message said:

Looking at the last
joint of one's little finger, visualize pushing hard on a pedal that
is in effect a 5" lever (pedal load from the spindle) bending it while
a 7" lever (the crank) is twisting it. That isn't reasonable to me.

So, in the end, it seems more of a *theoretical problem* (just look at
that poor 'lil spindle, it looks ready to break at any minute) than a
practical one (the spindle *actually* broke twice over many, many miles
under a large, powerful rider).

Quoted message said:

Octalink definitely solved the spindle breaking

Which didn't happen very often.....

Quoted message said:

and assembly problems,
but did so while violating other design criteria, such as bearing
durability, and above all the backlash problem that loosens retaining
bolts causing spline failure.

So, Octalink obviated a very infrequent problem and replaced it with a
much more frequent failure mode. This is progress??

And now, Octalink is another (about to be) abandoned Shimano standard,
joining Dyna-Drive pedals, etc., in the Shimano Hall of Shame.

Quoted message said:

Peter Chisholm said:

Quoted message said:

>> Can't argue with that. I mean, after years of square taper, some
>> bright spark at Shimano decided splined was the way forward.
>> After not too long, they decided to change it - the main reason
>> has to be because they're guff. As for outboard bearings, they
>> may solve the problems of Octalink, but do they do anything
>> square taper didn't? Other than wear expensively, I mean.

Quoted message said:

Quoted message said:

> What is less obvious is that the square taper is not as strong as
> we would like it to be, the square end being no larger than the
> last joint of your little finger. I have broken a couple of these
> and seen others.

Quoted message said:

Quoted message said:

In the past, speaking of square taper spindles, you yourself said:
"there are not many crank failures". And another very experienced
observer (Andrew Muzi) said, in the same thread: "do you mean a
spindle snapped in half? I've seen 2 or 3 in my lifetime".

http://tinyurl.com/rexel

Quoted message said:

Quoted message said:

But now, you make it sound a commonplace hazard in dire need of
fixing. What's up?

Quoted message said:

Quoted message said:

> Approaching failure cannot be anticipated or inspected for.
> Because it is a catastrophic failure, manufacturers have been
> looking for a clean solution. As you see, it isn't easy.

Quoted message said:

Quoted message said:

> The spindle breaks off in torsion, just inside the press fit of
> the aluminum crank where stress is greatest. The fractures I had
> initiated in the center of the flats leaving a spiral four toothed
> face, the corners being the ends of the "teeth".

Quoted message said:

I've seen it 3 times in 21 years. Not common, certainly not a
reason for Octalink or outboard bearings.

Well, I've experienced it twice on my bicycle. Looking at the last
joint of one's little finger, visualize pushing hard on a pedal that
is in effect a 5" lever (pedal load from the spindle) bending it while
a 7" lever (the crank) is twisting it. That isn't reasonable to me.

Octalink definitely solved the spindle breaking and assembly problems,
but did so while violating other design criteria, such as bearing
durability, and above all the backlash problem that loosens retaining
bolts causing spline failure.

Jobst Brandt

Thanks Jobst, but I didn't write most of that above BUT, it may be
unreasonable but when I saw a pic of your bike, with the knackered
chainrings, it was a 7410 crank-no? with a 103mm square taper BB-