Help. My self-extracting crank bolts spontaneously self-extract

In article <[email hidden]>, [email hidden] says...

Quoted message said:

Hi:

I have a travel bike with S+S couplers and self-extracting crank bolts. Recently, perhaps because
of the cold weather, I have found that the cranks keep loosening up. I tighten the bolts as much
as I can using a 6 mm hex wrench but the cranks start "clunking" after less than 10 miles of
riding. Can anybody suggest a way to stop the bolts from loosening themselves?

Torque them to ~ 30 lb-ft, but it may already be too late. Riding loose cranks often distorts the
square hole that mates to the crank axle and makes it impossible to prevent slop. My 20 year-old
nephew tightened his cranks repeatedly with a hex wrench for several months, and was lucky that they
weren't ruined from the frequent loosening. Six months after torquing them on properly the cranks
are still tight and don't squirm on the crank axle.

Rick

Michael Tordoff said:

Hi:

I have a travel bike with S+S couplers and self-extracting crank bolts. Recently, perhaps because
of the cold weather, I have found that the cranks keep loosening up. I tighten the bolts as much
as I can using a 6 mm hex wrench but the cranks start "clunking" after less than 10 miles of
riding. Can anybody suggest a way to stop the bolts from loosening themselves?

Sorry, Mike, but this is not good news. I don't know whether it is due to the self-extracting bolts
or not (probably not), but it sounds like the cranks are shot. Square-taper cranks can easily be
damaged by riding them while they are loose. Once the tapers get rounded they will never be right
again. Repeated loosening is a sign of that.

Try one more time. Grease the tapers (you will see disagreement over this, but I always do it this
way), torque as another poster said (30 ft-lbs seems like a lot to me, though). If they loosen
again, look for new cranks.

You don't have to remove these to pack the bike up, do you?

--

David L. Johnson

__o | A mathematician is a machine for turning coffee into theorems. _`\(,_ | -- Paul Erdos
(_)/ (_) |

David L. Johnson <[email hidden]> wrote:
: You don't have to remove these to pack the bike up, do you?

it depends mostly on the size of the bike. with mine you do and mine is a fairly large bike (i'm
186cm, 6'1.5"😉 and a pretty tight fit. you get them in any way you can.
--
david reuteler [email hidden]

"David L. Johnson" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

Michael Tordoff said:

Hi:

I have a travel bike with S+S couplers and self-extracting crank

bolts.

Quoted message said:

Quoted message said:

Recently, perhaps because of the cold weather, I have found that the cranks keep loosening up. I
tighten the bolts as much as I can

using a 6

Quoted message said:

Quoted message said:

mm hex wrench but the cranks start "clunking" after less than 10

miles of

Quoted message said:

Quoted message said:

riding. Can anybody suggest a way to stop the bolts from loosening themselves?

Sorry, Mike, but this is not good news. I don't know whether it is

due to

Quoted message said:

the self-extracting bolts or not (probably not), but it sounds like

the

Quoted message said:

cranks are shot. Square-taper cranks can easily be damaged by riding

them

Quoted message said:

while they are loose. Once the tapers get rounded they will never be right again. Repeated
loosening is a sign of that.

And the same is true if they are splined cranks. People are not accustomed to paying attention when
mounting splined cranks because the old square-tapered cranks did not require any attention -- other
than to make sure the arms were going in opposite directions. It is not hard to mismount a Shimano
splined crank and ruin it. -- Jay Beattie.

David Reuteler said:

David L. Johnson <[email hidden]> wrote:
: You don't have to remove these to pack the bike up, do you?

it depends mostly on the size of the bike. with mine you do and mine is a fairly large bike (i'm
186cm, 6'1.5"😉 and a pretty tight fit. you get them in any way you can.

Mike's about that same size, so this may be a contributing factor. I wouldn't want to remove/replace
cranks all that often simply because of the concern that what seems to have happened to his cranks
would happen.

Oh, one more question for you, Mike. Is it the left crank arm that gets loose? That is usually the
one that goes bad. If so, you can probably just replace the left side.

--

David L. Johnson

__o | There is always an easy solution to every human problem - neat, _`\(,_ | plausible, and
wrong. --H.L. Mencken (_)/ (_) |

Quoted message said:

And the same is true if they are splined cranks. People are not accustomed to paying attention
when mounting splined cranks because the old square-tapered cranks did not require any attention
-- other than to make sure the arms were going in opposite directions. It is not hard to mismount
a Shimano splined crank and ruin it. -- Jay Beattie.

I'm afraid I don't understand.

Michael Tordoff said:

Recently, perhaps because of the cold weather, I have found that the cranks keep loosening up. I
tighten the bolts as much as I can using a 6 mm hex wrench but the cranks start "clunking" after
less than 10 miles of riding.

They're probably ruined. There is no way you can get enough torque using a 6 mm allen key. You need
to use a torque wrench or ratchet wrench with a 6 mm bit.

Art Harris

David L. Johnson said:

On Mon, 17 Nov 2003 12:45:48 +0000, Michael Tordoff wrote:

Quoted message said:

Quoted message said:

I have a travel bike with S+S couplers and self-extracting crank bolts. Recently, perhaps because
of the cold weather, I have found that the cranks keep loosening up. I tighten the bolts as much
as I can using a 6 mm hex wrench but the cranks start "clunking" after less than 10 miles of
riding. Can anybody suggest a way to stop the bolts from loosening themselves?

Quoted message said:

Try one more time. Grease the tapers (you will see disagreement over this, but I always do it this
way), torque as another poster said (30 ft-lbs seems like a lot to me, though). If they loosen
again, look for new cranks.

30 foot/pounds IS a lot of torque, but it's what crank bolts are supposed to be tightened to.
That's almost impossible with a normal hex wrench or T-handle tool. I really do advocate the use
of a torque wrench, at least once - so you can get an idea of just how tight those bolts are
supposed to be.

But David's right - grease the taper, crank down on the bolt and hope for the best. If (as I
suspect) you have to remove the cranks to pack the bike, you should probably just budget in a new
crank ever few dozen "packings", as the crank will squirm slightly further onto the spindle after
each installation. Maybe this would be a good bike to consider a splined BB/crank (which come with
their own baggage, but are immune to "multiple installation problems".

Mark Hickey Habanero Cycles habcycles.comhabcycles.comOpen ↗ Home of the $695 ti frame

"David L. Johnson" <[email hidden]> wrote in message
news:<[email hidden]>...

Quoted message said:

Michael Tordoff said:

Hi:

I have a travel bike with S+S couplers and self-extracting crank bolts. Recently, perhaps
because of the cold weather, I have found that the cranks keep loosening up. I tighten the bolts
as much as I can using a 6 mm hex wrench but the cranks start "clunking" after less than 10
miles of riding. Can anybody suggest a way to stop the bolts from loosening themselves?

Sorry, Mike, but this is not good news. I don't know whether it is due to the self-extracting
bolts or not (probably not), but it sounds like the cranks are shot. Square-taper cranks can
easily be damaged by riding them while they are loose. Once the tapers get rounded they will never
be right again. Repeated loosening is a sign of that.

Or maybe not a problem at all. On my first good bike I did a novice's job of tightening the crank
bolts on my Record crank and had several occurences of loose crank arms happening a long way from a
wrench. Eventually I did get them tightened down properly and got many years of use out of them.

I frankly don't see how riding cranks with loose bolts is going to round the tapers, unless they are
so loose that you spin them on the spindle. I also think it would take a lot of effort to compress
the alloy in such a way that you could not get them to tighten square on the spindle. I think the
issue is the surface area of the crank that could be damaged by banging around a loose crank, versus
the surface area of the crank that contacts the spindle when it is properly torqued. One thing I
can't visualize at all is how this could lead to making it impossible to keep the bolts tight.

I'm not saying it is impossible to ruin a crank by riding it with a loose crank arm, I'm saying that
I think it is a lot more difficult than the impression you get from the experts here, and I'd guess
that a lot of people have been convinced that their cranks were ruined when all they needed to do
was torque them down properly. (Don't know about splined cranks, though.)

JP

Art Harris said:

They're probably ruined. There is no way you can get enough torque using a 6 mm allen key.

I don't see why not.

Practical observation; I've installed cranks with a 6mm allen key on which I've then ridden thousand
of miles without anything bad happening.

Theoretical basis; Mark Hickey says 30 foot-pounds. My 6mm allen key is about 4" long, and I reckon
I can lean on it with about half my body weight.
--
David Damerell <[email hidden]> Kill the tomato!

Mark Hickey said:

30 foot/pounds IS a lot of torque, but it's what crank bolts are supposed to be tightened to.
That's almost impossible with a normal hex wrench or T-handle tool.

That's a relief, actually; I'd always wondered if I was overtightening them.
--
David Damerell <[email hidden]> Kill the tomato!

David Damerell said:

Art Harris said:

They're probably ruined. There is no way you can get enough torque using a 6 mm allen key.

I don't see why not.

Practical observation; I've installed cranks with a 6mm allen key on which I've then ridden
thousand of miles without anything bad happening.

Theoretical basis; Mark Hickey says 30 foot-pounds. My 6mm allen key is about 4" long, and I
reckon I can lean on it with about half my body weight.

I haven't found it to be a problem either. I have a folding bike that requires removal of the cranks
for packing and it also uses the self-extracting allen-head bolts. I've had them off a few dozen
times for trips without any problems getting sufficient torque with the supplied allen wrench (mine
is about 8" long to make it easier).

"Adam Rush" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

Quoted message said:

And the same is true if they are splined cranks. People are not accustomed to paying attention
when mounting splined cranks because

the

Quoted message said:

Quoted message said:

old square-tapered cranks did not require any attention -- other

than to

Quoted message said:

Quoted message said:

make sure the arms were going in opposite directions. It is not

hard

Quoted message said:

Quoted message said:

to mismount a Shimano splined crank and ruin it. -- Jay Beattie.

I'm afraid I don't understand.

With a square taper BB, the crank arm has only one way of going on -- square peg into square hole.
There is no chance of ruining the interface during installation, assuming you do not torque to a
million foot-pounds or the parts do not match in the first place. With the Shimano splined BB, there
is a "pseudo-fit place" -- a place where the splines on the BB do not match up with the channels on
the inside of the crank arm, but they feel like they do. The crank arms are basically in the right
orientation, and there is no giant red flag to tell you that there is a problem. If you torque the
crank bolts when the arm and BB are in this place, you end up squashing the splines, and you get
that permanent loose fit thing going. You really have to look at the interface to make sure you have
the proper spline alignment before installing and tightening the bolts. Because there is less of an
interference fit on a splined BB (hardly any) you also have to be scrupulous about getting the bolts
up to torque, which means making the investment in the right hex socket for your torque wrench. --
Jay Beattie.

In article <[email hidden]>, [email hidden] says...

Quoted message said:

Hi: I have a travel bike with S+S couplers and self-extracting crank bolts. Recently, perhaps
because of the cold weather, I have found that the cranks keep loosening up. I tighten the bolts as
much as I can using a 6 mm hex wrench but the cranks start "clunking" after less than 10 miles of
riding. Can anybody suggest a way to stop the bolts from loosening themselves?

If your cranks aren't ruined, which is a distinct possibility, then the fix is to _PROPERLY_ tighten
the cranks. Using your average 6mm hex wrench is not the right way to do it. Best way is to get a
3/8 drive 6mm hex bit and use a torque wrench to tighten the bolt to approx. 30ft/lb. Then leave it
alone. Oops, almost forgot. Don't froget to grease the tapers before you mount the cranks. 🙂
--------------
Alex

In article <[email hidden]>, [email hidden] says...

Quoted message said:

That's a relief, actually; I'd always wondered if I was overtightening them.

It's hadr to overtighten them. A while back someone on this newsgroup did an experiment with an old
set of cranks to see if they could break the cranks by overtightening them. He ended up breaking the
bolt head before the cranks were damaged.
-------------
Alex

Alex Rodriguez said:

In article <[email hidden]>, [email hidden] says...

Quoted message said:

Hi: I have a travel bike with S+S couplers and self-extracting crank bolts. Recently, perhaps
because of the cold weather, I have found that the cranks keep loosening up. I tighten the bolts
as much as I can using a 6 mm hex wrench but the cranks start "clunking" after less than 10 miles
of riding. Can anybody suggest a way to stop the bolts from loosening themselves?

If your cranks aren't ruined, which is a distinct possibility, then the fix is to _PROPERLY_
tighten the cranks. Using your average 6mm hex wrench is not the right way to do it. Best way is
to get a 3/8 drive 6mm hex bit and use a torque wrench to tighten the bolt to approx. 30ft/lb.
Then leave it alone. Oops, almost forgot. Don't froget to grease the tapers before you mount the
cranks. 🙂
--------------
Alex

An even better way is to use an 8mm hex bit, which fits the bolts on modern Shimano and Campagnolo
cranks much better than a 6mm bit. Maybe the OP had some unusual crank that took a 6mm bit, but I
don't think that's big enough for the torque required.

Dave Lehnen

David Damerell said:

Art Harris said:

They're probably ruined. There is no way you can get enough torque using a 6 mm allen key.

They may not be if the crank taper is not damaged. If they are now torqued down properly they may
stay tight. Only way to find out is
(a) inspect the taper (b) try it. I've rescued cranks that came loose only once, many times is
probably worse.

Quoted message said:

I don't see why not. Practical observation; I've installed cranks with a 6mm allen key on which
I've then ridden thousand of miles without anything bad happening.

This happens, but it's also an example of the NASA theory of failure analysis: we did it before and
nothing broke, so we'll keep doing it. There is some margin for error for people who are light on
equipment. Heavy people, mashers, people who stand on the pedals a lot will have more failures.

Quoted message said:

Theoretical basis; Mark Hickey says 30 foot-pounds. My 6mm allen key is about 4" long, and I
reckon I can lean on it with about half my body weight.

NFW. 4" is way too short. You aren't actually applying the force at the very end of the allen key
handle, and you aren't really putting half your weight on it. I recommend borrowing a torque wrench
(or buy a cheap beam-type one) and trying it. The crank doesn't reach a hard stop like a nut and
bolt and it is really surprising how much you have to reef on a nominal 16" long torque wrench
handle to reach 30 foot pounds - I sometimes give up at 25 ft-lb, the lower end of the spec range.

(JP) said:

I'm not saying it is impossible to ruin a crank by riding it with a loose crank arm, I'm saying
that I think it is a lot more difficult than the impression you get from the experts here, and I'd
guess that a lot of people have been convinced that their cranks were ruined when all they needed
to do was torque them down properly. (Don't know about splined cranks, though.)

The problem is that the BB spindle is very hard, and the aluminum crank is very soft. If the crank
rotates on the spindle, the taper fit is no longer square, but very slightly "bowed" on each of the
flats. Once this happens to a large enough degree, there's nothing that keeps the crankarms from
squirming back and forth.

IF you catch and correct the loose bolt before the flats are sufficiently damaged, the aluminum will
deform enough to provide a "square fit", and all is well with the world.

However, like it or not, most cranks that have been ridden any real distance loose are ruined.
Heavier, stronger riders will damage them quicker, and will have less luck getting a marginal crank
to stay put once it's tightened. Lighter riders or those who spend very little time out of the
saddle will do much less damage to a loose crank, and will have a better chance of successfully
using a damaged crank.

Mark Hickey Habanero Cycles habcycles.comhabcycles.comOpen ↗ Home of the $695 ti frame

Benjamin Weiner said:

David Damerell <[email hidden]> wrote:

Quoted message said:

Quoted message said:

I don't see why not. Practical observation; I've installed cranks with a 6mm allen key on which
I've then ridden thousand of miles without anything bad happening.

This happens, but it's also an example of the NASA theory of failure analysis: we did it before and
nothing broke, so we'll keep doing it. There is some margin for error for people who are light on
equipment. Heavy people, mashers, people who stand on the pedals a lot will have more failures.

Quoted message said:

Theoretical basis; Mark Hickey says 30 foot-pounds. My 6mm allen key is about 4" long, and I
reckon I can lean on it with about half my body weight.

NFW. 4" is way too short. You aren't actually applying the force at the very end of the allen key
handle, and you aren't really putting half your weight on it. I recommend borrowing a torque wrench
(or buy a cheap beam-type one) and trying it. The crank doesn't reach a hard stop like a nut and
bolt and it is really surprising how much you have to reef on a nominal 16" long torque wrench
handle to reach 30 foot pounds - I sometimes give up at 25 ft-lb, the lower end of the spec range.

Ben's probably right - if you figure 3.5" as the center of your effort, you'd have to put over 100
pounds (45kg) of push on that skinny little wrench. I know it IS possible to do that, but it will be
VERY uncomfortable at best (and virtually impossible for most people). You can test the concept by
lifting 100 pounds of anything with a hard handle the width of that allen wrench - it will hurt. Or,
if you weigh about 200 pounds, put two allen wrenches on two horizontal surfaces and lift yourself
off the ground with only your thumbs, on top of the allen wrenches. That's how hard you have to push
to get to the required spec.

It IS amazing how far you have to turn the bolt to get the proper torque AFTER it gets up to about
20 ft/lbs - there are a lot of amazing molecular-level things going on in the interface between the
spindle and crank, and doing it with a torque wrench once will help you figure out how to do it
right even without a torque wrench.

Mark Hickey Habanero Cycles habcycles.comhabcycles.comOpen ↗ Home of the $695 ti frame