L/H R/H threads on pedals

[Bob]

Hi Im still new to cycling, so im sorry if this has been covered before but im confused.

I removed the pedals from my bike today for cleaning and lubing, the right hand (as you sit on the
bike) pedal has a normal right hand thread and the left has a left hand thread, correct?

Surely that should be the other way around? I thought the idea of L/H and R/H threads was to keep
the rotating shaft turning in a direction that always tightens them, but it doesn't.

If you put a spanner on the R/H pedal shaft as if you were about to undo it, and turn the crank in a
forward direction as if pedalling forward, keeping the spanner in a horizontal manner (like your
foot) the pedal would unscrew, same on the left side. Or am I missing the point?

BoB

[Pete Biggs]

bob wrote:
> I removed the pedals from my bike today for cleaning and lubing, the right hand (as you sit on the
> bike) pedal has a normal right hand thread and the left has a left hand thread, correct?

That's right.

> Surely that should be the other way around? I thought the idea of L/H and R/H threads was to keep
> the rotating shaft turning in a direction that always tightens them, but it doesn't.

It's done for good reason. Look up "precession" here:
http://www.sheldonbrown.com/gloss_p.html - Pedal

~PB

[Bob]

> It's done for good reason. Look up "precession" here:
> http://www.sheldonbrown.com/gloss_p.html - Pedal
>
> ~PB
>
OK, thanks for that, I wouldn't have thought there would have been that much reverse force from the
bearings, I just thought that if the bearing partially seized, it would unscrew its self. At least I
can sleep tonight :)

BoB

[Anonymous]

"bob" <sorry@spamboys.com> wrote in message
news:buf03e$sc5$1@newsg3.svr.pol.co.uk...

> OK, thanks for that, I wouldn't have thought there would have been that much reverse force from
> the bearings, I just thought that if the bearing partially seized, it would unscrew its self.

Yup, you were right - fortunately as you now know this isn't the failure mode.

cheers, clive

[Martinm]

> "bob" <sorry@spamboys.com> wrote in message
> news:buf03e$sc5$1@newsg3.svr.pol.co.uk...
>
> > OK, thanks for that, I wouldn't have thought there would have been that much reverse force from
> > the bearings, I just thought that if the bearing partially seized, it would unscrew its self.
>
> Yup, you were right - fortunately as you now know this isn't the failure mode.
>
> cheers, clive

On a slight tangent, why is there a British and Italian convention for BB's, which swap over the
thread direction AIUI, and how are we supposed to know if we have eg a Ribble frame made in Italy?

[Nora Lenderby]

"Martinm" writes:

> On a slight tangent, why is there a British and Italian
> convention for BB's,

This is in the nature of things.

> which swap over the thread direction AIUI,

It would be a courtesy to all your readers if you were kind enough not to use obscure achronisms in your posting.

> and how are we supposed to know if we have eg a
> Ribble frame made in Italy?

If you examine your frame closely, you will probably find markings of the form "Ribble Cycles" and "Made in Italy".

I hope this helps.

N. Lenderby (Mrs)

[Pete Biggs]

MartinM wrote:

> On a slight tangent, why is there a British and Italian convention for BB's, which swap over the
> thread direction AIUI

I can't remember why the Italian standard is different. Maybe they just never got round to changing
after the rest of us discoved the alternative direction prevents unscrewing.

> and how are we supposed to know if we have eg a Ribble frame made in Italy?

Italian shell would be 70mm wide instead of 68mm.

See: http://www.sheldonbrown.com/gloss_i-l.html#italian http://www.sheldonbrown.com/gloss_bo-z.html

~PB