left handed left pedals

DejaVU <[email hidden]> wrote in message news:<[email hidden]>...

Quoted message said:

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

DejaVU said:

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 🙂

DejaVU said:

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).

sheldonbrown.comgloss p.htmlOpen ↗

jeverett3<AT>earthlink<DOT>net home.earthlink.net~jeverett3Open ↗

AMH said:

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?

Dan Daniel said:

Quoted message said:

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.

Quoted message said:

Quoted message said:

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.

Quoted message said:

Quoted message said:

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

Quoted message said:

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 (_)/ (_) |

David L. Johnson said:

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.

John Everett <[email hidden]> scribed in
<[email hidden]>:

Quoted message said:

DejaVU said:

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).

sheldonbrown.comgloss p.htmlOpen ↗

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 /"\ terrapin.ru.ac.zawelcome.htmlOpen ↗ \
/ ASCII Ribbon campaign against HTML E-Mail > - - - - - - -> X If you receive email saying
"Send this to everyone you know," / \ PLEASE pretend you don't know me.

It doesn't have to do with bearings. Indeed that torque is not enough to do much of anything; but
the pedal would unscrew under zero torque in any case.

The hole the pedal is screwed into is bigger than the screw. The screw rolls around in the
larger hole. Since the circumference of the hole is bigger than the circumference of the screw,
there's a net rotation of the screw each pedal rotation. You want this rotation direction to
tighten the pedal.

What direction is this?

Consider the instant when the left pedal is at its top and you're pedalling forwards. The pedal
screw is at the bottom of the hole and you're forcing the pedal forwards, so the pedal screw rotates
counter-clockwise, which unscrews a RH thread. So they put LH threads on the LH pedal.

The RH pedal tightens already (same rotation but viewed from the other end; alternatively, the
tighten direction is reversed because the crank arm is on the other end of the screw).
--
Ron Hardin [email hidden]

On the internet, nobody knows you're a jerk.

Papayahed1 <[email hidden]> wrote:
:>
:>Well, chances are that will never happen. When a pedal fails, parts spew out and it flops around.
:>It just doesn't seize.

: Mine did...

Did it tear your foot off?

--------------------------------
Bob Masse' [email hidden]
--------------------------------

The C Man <[email hidden]> wrote in message
news:<[email hidden]>...

Quoted message said:

AMH said:

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.

Be that as it may it works for me.

On bikes with bolt-on wheels, the nuts on the

Quoted message said:

left hand side reverse threaded, so why would they do it only for pedals and not wheels then?

My opinion is that it is possible to see the threads on the axel and therefore easy to figure out
which way the nut turns.

Sorry, but that explanation doesn't

Quoted message said:

hold water.

Whatever has enough water to float your boat.

Andy