left handed left pedals

I've been riding for a long time, mostly for commuting, never racing.
Recently, I replaced the pedals on my daughters bike and noticed that
the left hand pedal has a left hand thread. (all 3 kids have bikes).

Now, I have a problem understanding this because, if the pedal
seizes, it will unscrew. Same for the other side. In getting the
spanner ready to unscrew the old pedal axle, I figured the right side
would be lefthanded and was stymied to find it was not.

Over many years I've broken pedal axles, (I grew up before the time
of the ATB and simply rode my 10 speed racer everywhere, including
the MX track and the abandoned clay mine and.... yes, I broke at
least one frame in half :-) or had the pedal come off the axle, but
never had one unscrew unless it wasn't properly tightened in the
first place. This tells me that it is not necessary to lefthand
thread one of them at all.

So, can some guru explain why this is like it is please?
(btw, if you visit my web pages you'll find that I'm am more than
averagly technically adept so technical discussions of this issue are
just fine).

Thanks

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DejaVU wrote in message ...
I've been riding for a long time, mostly for commuting, never racing.
Recently, I replaced the pedals on my daughters bike and noticed that
the left hand pedal has a left hand thread. (all 3 kids have bikes).

Now, I have a problem understanding this because, if the pedal
seizes, it will unscrew. Same for the other side. In getting the
spanner ready to unscrew the old pedal axle, I figured the right side
would be lefthanded and was stymied to find it was not.

Over many years I've broken pedal axles, (I grew up before the time
of the ATB and simply rode my 10 speed racer everywhere, including
the MX track and the abandoned clay mine and.... yes, I broke at
least one frame in half :-) or had the pedal come off the axle, but
never had one unscrew unless it wasn't properly tightened in the
first place. This tells me that it is not necessary to lefthand
thread one of them at all.

So, can some guru explain why this is like it is please?

I believe it is so that the direction you turn the spanner (wrench to
us Yanks) is the same for both sides. Rather than try to remember
which pedal turns which to take it off it is easier to remember turn
the spanner towards the rear of the bike. That is the way I was taught
and it is easy to remember.

Andy

On 1 Oct 2003 10:41:05 GMT, DejaVU
wrote:

I've been riding for a long time, mostly for commuting, never racing.
Recently, I replaced the pedals on my daughters bike and noticed that
the left hand pedal has a left hand thread. (all 3 kids have bikes).

Now, I have a problem understanding this because, if the pedal
seizes, it will unscrew.

So, can some guru explain why this is like it is please?

There was a discussion of this on rec.bicycles.tech in the last couple
of months which includes some of the tech gurus. If you want the tech
talk, you might find that thread.

What I remember- Most (all?) bicycles in the late 1800s/ early 1900s
were fixed gear, not freewheeled. Like modern track bikes. If you are
strapped in tightly, like a track rider would be, you *want* the pedal
to unthread if it seizes. If it didn't unthread... well, I don't know
the physics involved, the forces and vectors and stuff, but I do know
that something is going to have to change and change quickly

On 1 Oct 2003 10:41:05 GMT, DejaVU
wrote:

I've been riding for a long time, mostly for commuting, never racing.
Recently, I replaced the pedals on my daughters bike and noticed that
the left hand pedal has a left hand thread. (all 3 kids have bikes).

Now, I have a problem understanding this because, if the pedal
seizes, it will unscrew. Same for the other side. In getting the
spanner ready to unscrew the old pedal axle, I figured the right side
would be lefthanded and was stymied to find it was not.

Over many years I've broken pedal axles, (I grew up before the time
of the ATB and simply rode my 10 speed racer everywhere, including
the MX track and the abandoned clay mine and.... yes, I broke at
least one frame in half :-) or had the pedal come off the axle, but
never had one unscrew unless it wasn't properly tightened in the
first place. This tells me that it is not necessary to lefthand
thread one of them at all.

So, can some guru explain why this is like it is please?
(btw, if you visit my web pages you'll find that I'm am more than
averagly technically adept so technical discussions of this issue are
just fine).

http://sheldonbrown.com/gloss_p.html#pedal


jeverett3ATearthlinkDOTnet http://home.earthlink.net/~jeverett3

AMH wrote:

I believe it is so that the direction you turn the spanner (wrench to
us Yanks) is the same for both sides. Rather than try to remember
which pedal turns which to take it off it is easier to remember turn
the spanner towards the rear of the bike. That is the way I was taught
and it is easy to remember.

No offense to you or whoever told you that, but that's the most
ridiculous explanation I've ever heard for why the pedals are
threaded as they are. On bikes with bolt-on wheels, the nuts on the
left hand side reverse threaded, so why would they do it only for
pedals and not wheels then? Sorry, but that explanation doesn't
hold water.

I meant to say...

On bikes with bolt-on wheels, the nuts on the left hand side AREN'T
reverse threaded, so why would they do it only for the pedals and
not the wheels then?

On Wed, 01 Oct 2003 09:13:50 +0000, Dan Daniel wrote:

I've been riding for a long time, mostly for commuting, never racing.
Recently, I replaced the pedals on my daughters bike and noticed that the
left hand pedal has a left hand thread. (all 3 kids have bikes).

This is correct.

Now, I have a problem understanding this because, if the pedal seizes, it
will unscrew.

Well, chances are that will never happen. When a pedal fails, parts spew
out and it flops around. It just doesn't seize.

So, can some guru explain why this is like it is please?

What I remember- Most (all?) bicycles in the late 1800s/ early 1900s were
fixed gear, not freewheeled. Like modern track bikes. If you are strapped
in tightly, like a track rider would be, you *want* the pedal to unthread
if it seizes. If it didn't unthread... well, I don't know the physics
involved, the forces and vectors and stuff, but I do know that something
is going to have to change and change quickly

It has nothing to do with fixed gears, or seizing pedals. Very simply,
before the left pedal got left-hand threads, they tended to unscrew on
their own, no matter how tight they were. Because of the way the bearing
works, with balls rolling around their centers rolling against two
circluar races, one inside the other, the torsional forces tend to twist
the axle in the opposite way from what you would think.

It was, according to legend, the Wright brothers who first tried using
left-hand threads on the left pedal. Voila, no more pedals unscrewing.
These days, if a pedal unscrews, it was probably not properly tightened in
the first place.

--

David L. Johnson

__o | Do not worry about your difficulties in mathematics, I can
_`\(,_ | assure you that mine are all greater. -- A. Einstein
(_)/ (_) |

On Wed, 01 Oct 2003 21:31:22 -0400, "David L. Johnson"
wrote:



It has nothing to do with fixed gears, or seizing pedals. Very simply,
before the left pedal got left-hand threads, they tended to unscrew on
their own, no matter how tight they were. Because of the way the bearing
works, with balls rolling around their centers rolling against two
circluar races, one inside the other, the torsional forces tend to twist
the axle in the opposite way from what you would think.

It was, according to legend, the Wright brothers who first tried using
left-hand threads on the left pedal. Voila, no more pedals unscrewing.
These days, if a pedal unscrews, it was probably not properly tightened in
the first place.

Thanks for the correction and proper explanation.

David is the first one who got it right about reverse pedal threads
on the left side. To elaborate about the action of the bearings, the
pedals rotate backward to the direction of the crankarms and the
spindles of the pedals. The cups of the pedals push backward on the
bearings on the outside, so the bearngs turn forward on the inside,
where they ride on the cones on the spindles. If leftside pedals didn't
have reverse threads, the forward push of the bearings on the spindles
would tend to unscrew them.

The same principle applies to the use of reverse threads on
rightside bottom-bracket cups. The BB cups are pushed backward by the
bearings.

If there was a problem with the locking nuts of bolt-on wheel
spindles coming unscrewed on the left side, then reverse threads on that
side would be in order. But, the spindles are held so firmly to the
frame by the tightness of the nuts, that they can't rotate.

Steve McDonald

John Everett scribed in
:

On 1 Oct 2003 10:41:05 GMT, DejaVU
wrote:

I've been riding for a long time, mostly for commuting, never
racing. Recently, I replaced the pedals on my daughters bike and
noticed that the left hand pedal has a left hand thread. (all 3
kids have bikes).


http://sheldonbrown.com/gloss_p.html#pedal

thanks, it is making sense now
I'll look up the .tech discussion too, should be interesting

swarf, steam and wind

--
David Forsyth -:- the email address is real /"\
http://terrapin.ru.ac.za/~iwdf/welcome.html \ /
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