Clicking square taper cranks - fixable?

I have a friend who brought his bike to me to look at (because he's too
cheap for the LBS and most days I can work out which end of the wrench to
hold)

His square taper cranks are clicking, and he says he has ridden about 50
miles since he first heard it (which I'd guess means he's done about 20).

Now, the bolt holding the cranks onto the BB wasn't very tight, so I
tightened it with an 8mm alan key in a bit of pipe. The noise has gone
away, but I had to tighten it a lot so it seems the cranks have been pushed
up the taper. The chainline may have been reduced a little, but probably in
itself this isn't such a bad thing since it was a tad outboard before.

In this situation, is it a case of tighten it up really good once and it'll
be fixed forever, or is it just going to need retightening over and over
and eventually ride up the taper far enough to crack the cranks?

I'm not a pro mechanic, but I don't want my friend to be injured. At the
same time, I don't want to tell him to spend money he doesn't have to.

Quoth Jim Higson:
...square taper cranks are clicking, and he says he has ridden about 50
miles since he first heard it (which I'd guess means he's done about 20).

Now, the bolt holding the cranks onto the BB wasn't very tight, so I
tightened it with an 8mm alan key in a bit of pipe. The noise has gone
away, but I had to tighten it a lot so it seems the cranks have been pushed
up the taper. The chainline may have been reduced a little, but probably in
itself this isn't such a bad thing since it was a tad outboard before.

In this situation, is it a case of tighten it up really good once and it'll
be fixed forever, or is it just going to need retightening over and over
and eventually ride up the taper far enough to crack the cranks?

Depends how much it was ridden while loose.

I would remove the crank, grease the spindle, grease the bolt threads,
grease the underside of the bolt head, then tighten the bejasus out of
it. If it isn't wrecked, this will do the trick.

I'm not a pro mechanic, but I don't want my friend to be injured. At the
same time, I don't want to tell him to spend money he doesn't have to.

There's not a major risk of injury here. If it doesn't work, the
symptom will be that the crank will loosen up again, nothing is likely
to snap off.

Sheldon "Unnnnnnngggh!" Brown
+---------------------------------------------------------------+
| There are 10 kinds of people in this world: |
| Those who understand the binary system, and those who don't |
+---------------------------------------------------------------+
Harris Cyclery, West Newton, Massachusetts
Phone 617-244-9772 FAX 617-244-1041
http://harriscyclery.com
Hard-to-find parts shipped Worldwide
http://captainbike.com http://sheldonbrown.com

Sheldon Brown advised:

...square taper cranks are clicking, and he says he has ridden about 50
miles since he first heard it (which I'd guess means he's done about 20).

Now, the bolt holding the cranks onto the BB wasn't very tight, so I
tightened it with an 8mm alan key in a bit of pipe. The noise has gone
away, but I had to tighten it a lot so it seems the cranks have been
pushed up the taper. The chainline may have been reduced a little, but
probably in itself this isn't such a bad thing since it was a tad
outboard before.

In this situation, is it a case of tighten it up really good once and
it'll be fixed forever, or is it just going to need retightening over and
over and eventually ride up the taper far enough to crack the cranks?

Depends how much it was ridden while loose.

I would remove the crank, grease the spindle, grease the bolt threads,
grease the underside of the bolt head, then tighten the bejasus out of
it. If it isn't wrecked, this will do the trick.

Ok, when I need a really big lever I use a bolt cutter with a good strong
hollow 90cm handle to put the key inside. Should be able to get it very
tight indeed. Normally I use it to undo stuck bolts.

The look on people's faces when I get the large bolt cutters out to get
something off their bike, by the way, is priceless :-)

Square taper Campag BBs and chainsets are going for silly money here at the
moment so if it is a write-off, at least it can be cheaply replaced. One
place has Mirage BBs for £2.50.

I'm not a pro mechanic, but I don't want my friend to be injured. At the
same time, I don't want to tell him to spend money he doesn't have to.

There's not a major risk of injury here. If it doesn't work, the
symptom will be that the crank will loosen up again, nothing is likely
to snap off.

Heh, in that case this actually seems like quite a good way of getting a
slightly shorter effective BB spindle length when finetuning the chainline.

Thanks.
--
Jim

On Feb 7, 1:35 pm, Jim Higson wrote:
Sheldon Brown advised:





...square taper cranks are clicking, and he says he has ridden about 50
miles since he first heard it (which I'd guess means he's done about 20).

Now, the bolt holding the cranks onto the BB wasn't very tight, so I
tightened it with an 8mm alan key in a bit of pipe. The noise has gone
away, but I had to tighten it a lot so it seems the cranks have been
pushed up the taper. The chainline may have been reduced a little, but
probably in itself this isn't such a bad thing since it was a tad
outboard before.

In this situation, is it a case of tighten it up really good once and
it'll be fixed forever, or is it just going to need retightening over and
over and eventually ride up the taper far enough to crack the cranks?

Depends how much it was ridden while loose.

I would remove the crank, grease the spindle, grease the bolt threads,
grease the underside of the bolt head, then tighten the bejasus out of
it. If it isn't wrecked, this will do the trick.

Ok, when I need a really big lever I use a bolt cutter with a good strong
hollow 90cm handle to put the key inside. Should be able to get it very
tight indeed. Normally I use it to undo stuck bolts.

Careful.....you do not want to get carried away and damage the bolt,
especially in a way that would make it hard to remove (I once snapped
the head off a crank bolt in a moment of ham fisted madness).

The look on people's faces when I get the large bolt cutters out to get
something off their bike, by the way, is priceless :-)

Square taper Campag BBs and chainsets are going for silly money here at the
moment so if it is a write-off, at least it can be cheaply replaced. One
place has Mirage BBs for £2.50.

I'm not a pro mechanic, but I don't want my friend to be injured. At the
same time, I don't want to tell him to spend money he doesn't have to.

There's not a major risk of injury here. If it doesn't work, the
symptom will be that the crank will loosen up again, nothing is likely
to snap off.

Heh, in that case this actually seems like quite a good way of getting a
slightly shorter effective BB spindle length when finetuning the chainline.

Thanks.
--
Jim- Hide quoted text -

- Show quoted text -

Ozark Bicycle wrote:

In this situation, is it a case of tighten it up really good once and
it'll be fixed forever, or is it just going to need retightening over
and over and eventually ride up the taper far enough to crack the
cranks?

Depends how much it was ridden while loose.

I would remove the crank, grease the spindle, grease the bolt threads,
grease the underside of the bolt head, then tighten the bejasus out of
it. If it isn't wrecked, this will do the trick.

Ok, when I need a really big lever I use a bolt cutter with a good strong
hollow 90cm handle to put the key inside. Should be able to get it very
tight indeed. Normally I use it to undo stuck bolts.

Careful.....you do not want to get carried away and damage the bolt,
especially in a way that would make it hard to remove (I once snapped
the head off a crank bolt in a moment of ham fisted madness).

Well, I wasn't going to put my full weight on the end of the 90cm lever,
just enough torque for all residual bejasus to be removed.

On Feb 7, 2:01 pm, Jim Higson wrote:
Ozark Bicycle wrote:
In this situation, is it a case of tighten it up really good once and
it'll be fixed forever, or is it just going to need retightening over
and over and eventually ride up the taper far enough to crack the
cranks?

Depends how much it was ridden while loose.

I would remove the crank, grease the spindle, grease the bolt threads,
grease the underside of the bolt head, then tighten the bejasus out of
it. If it isn't wrecked, this will do the trick.

Ok, when I need a really big lever I use a bolt cutter with a good strong
hollow 90cm handle to put the key inside. Should be able to get it very
tight indeed. Normally I use it to undo stuck bolts.

Careful.....you do not want to get carried away and damage the bolt,
especially in a way that would make it hard to remove (I once snapped
the head off a crank bolt in a moment of ham fisted madness).

Well, I wasn't going to put my full weight on the end of the 90cm lever,
just enough torque for all residual bejasus to be removed.


My snapped-the-head-off misadventure was done using a regular 3/8"
socket drive, and I was just trying to get it 'really tight', not any
more than that.

"Ozark Bicycle" wrote in message
ups.com...
On Feb 7, 2:01 pm, Jim Higson wrote:
Ozark Bicycle wrote:
In this situation, is it a case of tighten it up really good
once and
it'll be fixed forever, or is it just going to need retightening
over
and over and eventually ride up the taper far enough to crack
the
cranks?

Depends how much it was ridden while loose.

I would remove the crank, grease the spindle, grease the bolt
threads,
grease the underside of the bolt head, then tighten the bejasus
out of
it. If it isn't wrecked, this will do the trick.

Ok, when I need a really big lever I use a bolt cutter with a good
strong
hollow 90cm handle to put the key inside. Should be able to get it
very
tight indeed. Normally I use it to undo stuck bolts.

Careful.....you do not want to get carried away and damage the bolt,
especially in a way that would make it hard to remove (I once
snapped
the head off a crank bolt in a moment of ham fisted madness).

Well, I wasn't going to put my full weight on the end of the 90cm
lever,
just enough torque for all residual bejasus to be removed.


My snapped-the-head-off misadventure was done using a regular 3/8"
socket drive, and I was just trying to get it 'really tight', not any
more than that.


You can overtighten the crank bolts which can cause the square taper to
stretch a little thus reducing the contact area of the small end of the
taper. This happens frequently on machinery that runs on hardened steel
taper drives.

Chas.

In this situation, is it a case of tighten it up really good
once and
it'll be fixed forever, or is it just going to need retightening
over
and over and eventually ride up the taper far enough to crack
the
cranks?
Depends how much it was ridden while loose.
I would remove the crank, grease the spindle, grease the bolt
threads,
grease the underside of the bolt head, then tighten the bejasus
out of
it. If it isn't wrecked, this will do the trick.
Ok, when I need a really big lever I use a bolt cutter with a good
strong
hollow 90cm handle to put the key inside. Should be able to get it
very
tight indeed. Normally I use it to undo stuck bolts.

Ozark Bicycle wrote:
Careful.....you do not want to get carried away and damage the bolt,
especially in a way that would make it hard to remove (I once
snapped
the head off a crank bolt in a moment of ham fisted madness).

Jim Higson wrote:
Well, I wasn't going to put my full weight on the end of the 90cm
lever,
just enough torque for all residual bejasus to be removed.

"Ozark Bicycle" wrote:
My snapped-the-head-off misadventure was done using a regular 3/8"
socket drive, and I was just trying to get it 'really tight', not any
more than that.

* * Chas wrote:
You can overtighten the crank bolts which can cause the square taper to
stretch a little thus reducing the contact area of the small end of the
taper. This happens frequently on machinery that runs on hardened steel
taper drives.

Yes with repeated torque but not at one time. I used to have a big-bicep
employee who routinely snapped off crank bolts before we got her to
use a torque wrench. The bolt head breaks before you damage the crank.
--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971

"A Muzi" wrote in message
...
In this situation, is it a case of tighten it up really good
once and
it'll be fixed forever, or is it just going to need retightening
over
and over and eventually ride up the taper far enough to crack
the
cranks?
Depends how much it was ridden while loose.
I would remove the crank, grease the spindle, grease the bolt
threads,
grease the underside of the bolt head, then tighten the bejasus
out of
it. If it isn't wrecked, this will do the trick.
Ok, when I need a really big lever I use a bolt cutter with a good
strong
hollow 90cm handle to put the key inside. Should be able to get it
very
tight indeed. Normally I use it to undo stuck bolts.

Ozark Bicycle wrote:
Careful.....you do not want to get carried away and damage the
bolt,
especially in a way that would make it hard to remove (I once
snapped
the head off a crank bolt in a moment of ham fisted madness).

Jim Higson wrote:
Well, I wasn't going to put my full weight on the end of the 90cm
lever,
just enough torque for all residual bejasus to be removed.

"Ozark Bicycle" wrote:
My snapped-the-head-off misadventure was done using a regular 3/8"
socket drive, and I was just trying to get it 'really tight', not any
more than that.

* * Chas wrote:
You can overtighten the crank bolts which can cause the square taper
to
stretch a little thus reducing the contact area of the small end of
the
taper. This happens frequently on machinery that runs on hardened
steel
taper drives.

Yes with repeated torque but not at one time. I used to have a big-bicep
employee who routinely snapped off crank bolts before we got her to
use a torque wrench. The bolt head breaks before you damage the crank.
--
Andrew Muzi
www.yellowjersey.org

I've only broken 1crank bolt from over tightening in 35+ years. I have a
torque wrench, I should use it. What torque specs do you use for M8 x 1.0
crank bolts?

Chas.

On Feb 8, 8:28 am, "* * Chas" wrote:
I've only broken 1crank bolt from over tightening in 35+ years. I have a
torque wrench, I should use it. What torque specs do you use for M8 x 1.0
crank bolts?

Though the question was not addressed to me, never mind my far poorer
experience than you guys have, I feel like jumping in and giving my
own answer.
Around here I have never seen any (expert) mechanic use a dynanometric
wrench while tightening such bolts. My way of approaching such a
problem is quite pragmatic, in fact.

Given that God Tullio has made a wrench that long, rather short in
fact, for my arms to use, and that all Goddesses recommend everything
be clean and lubricated, I do clean, lube and turn by feel.
No failure, so far.

Sergio
Pisa