Cracked crank

[Simon Mason]

My jinxed road bike continues to have problems. I noticed a creaking sound
from the cranks and was surprised to see this crack. The bottom bracket hex
nut was only "hand tight", so would this have caused this damage and does it
mean a new crank? TIA
http://www.simonmason.karoo.net/zcrank.htm

[Msa]

In article <hRWdnQtXEojcLCXdSa8jmw@karoo.co.uk>,
simon@simonmason.karoo.co.uk says...
> My jinxed road bike continues to have problems. I noticed
> a creaking sound from the cranks and was surprised to see
> this crack. The bottom bracket hex nut was only "hand
> tight", so would this have caused this damage

No, but it doesn't help matters.

> and does it mean a new crank? TIA

I wouldn't suggest you turn another revolution on those.

--
Mark (MSA) This post is packaged by intellectual weight, not
volume. Some settling of contents may have occurred during
transmission

[Simon D]

"Simon Mason" <simon@simonmason.karoo.co.uk> wrote in message
news:hRWdnQtXEojcLCXdSa8jmw@karoo.co.uk...
> The bottom bracket hex nut was only "hand tight", so would
> this have caused this damage

No - if anything, overtightening would be more likely to
cause it, or possibly greasing the interface between the
crank and the axle (since this facilitates
overtightening).The nut is only hand tight because the
square taper is now an irregular quadrilateral taper, if you
see what I mean!

> and does it mean a new crank?

Lets just say it's your teeth that will be biting tarmac
very shortly if you don't replace it! ;-)

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[Zog The Undenia]

Simon Mason wrote:
> My jinxed road bike continues to have problems. I noticed
> a creaking sound from the cranks and was surprised to see
> this crack. The bottom bracket hex nut was only "hand
> tight", so would this have caused this damage and does it
> mean a new crank? TIA
> http://www.simonmason.karoo.net/zcrank.htm
>
>
Did you check the tightness of the bolts regularly? You
shouldn't - a retighten after the first 50 miles or so is
fine, but then put the bolts in with threadlock and don't
touch them again (unless you need to get the cranks off for
some reason).

Crankbolts always come loose as the crank squirms up the
taper to relieve the pressure from the bolt. Retightening
them just starts the squirming process from a new point, and
eventually it cracks. Greasing has nothing to do with this,
but may stop your crank seizing to the spindle.

[A.Lee]

On Sat, 29 May 2004 16:50:17 +0100, Simon Mason wrote:

> My jinxed road bike continues to have problems. I noticed
> a creaking sound from the cranks and was surprised to see
> this crack. The bottom bracket hex nut was only "hand
> tight", so would this have caused this damage and does it
> mean a new crank? TIA
> http://www.simonmason.karoo.net/zcrank.htm

As has been said, tightening it up too much casues this.A
typical scenario would be put it on, ride a while, realise
the crank arm is slightly loose, then retighten.Trouble is,
the damage has already been done now, as the taper has worn
slightly inside, so you'll need to tighten it further to get
it tight, thus straining the ally, and then causing the
crack you have got. No choice but to get a new one. Parker
International are reasonably priced, or for a bargian get
Cycling Weekly, and check out all the ads, there are a
couple of places that sell excess Campy stuff at bargain
prices - Oldham Cycle Centre, and a place near
Hereford(Leominster?) IIRC, I've bought stuff off both of
them and can recommmend them, I got a Veloce cahinset
recently for £37. Alan.

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[Mark South]

"Simon D" <simondaw@NOSPAMmsn.com> wrote in message
news:c9adb8$bha$1@newsg3.svr.pol.co.uk...
>
> "Simon Mason" <simon@simonmason.karoo.co.uk> wrote in
> message news:hRWdnQtXEojcLCXdSa8jmw@karoo.co.uk...
> > The bottom bracket hex nut was only "hand tight", so
> > would this have caused this damage
>
> No - if anything, overtightening would be more likely to
> cause it, or possibly greasing the interface between the
> crank and the axle (since this facilitates
> overtightening).

I dare you to go over to rec.bicycles.tech and offer this
explanation there!

> The nut is only hand tight because the square taper is now
> an irregular quadrilateral taper, if you see what I mean!

The nut probably loosened originally because the crank
squirmed up the taper.

> > and does it mean a new crank?
>
> Lets just say it's your teeth that will be biting tarmac
> very shortly if you don't replace it! ;-)

To which I would add, is your top tube harder than your
family jewels?
--
Mark South: World Citizen, Net Denizen