LH threads...urban legend?

John Foss wrote,
>It sounds like you may have your wheel on backwards. Like a bicycle, the pedal
>on your right foot should be the one with right hand threads. The left pedal
>has reverse threads, to keep it from unscrewing.

I’ve always felt that the reverse threads thing on the left pedal was a little
fishy. I can’t believe that a standard-thread left pedal would unscrew if it is
properly torqued on - unless the bearings were really shot, which should alert
you to replace the pedal anyway.

If the left pedal requires reverse threads to stay on, why don’t unicyclists and
trick bicyclists find that their right pedals are unscrewing from riding
backwards and mounting? Or do they?

As far as finding a spiderless righthand crank, I’d be tempted to try a left
hand crank on the right side, with some Loc-tite anti-vibration thread-coating
on the pedal threads, and see what happens…check the torque periodically.

~Rick Bissell

Re: LH threads…urban legend?

Rick, A few weeks ago someone sent me this URL which explains why the LH threads
are necessary. Check it out.

 <a href="http://www.sheldonbrown.com/gloss_p.html#pedal">http://www.sheldonbrown.com/gloss_p.html#pedal</a>

Regards,

John Drummond, Writer IBM Product Communications Support 3200 Windy Hill Road,
Atlanta, GA 30339 770-835-6691 voice, 770-835-8627 fax, T/L 445

Rick Bissell <rick@tridelta.com> on 04/28/99 04:34:43 AM

Please respond to Rick Bissell <rick@tridelta.com>

To: “John Foss” <jfoss@unicycling.com>, unicycling@winternet.com
cc: (bcc: John Drummond/Atlanta/IBM) Subject: LH threads…urban legend?

John Foss wrote,
>It sounds like you may have your wheel on backwards. Like a bicycle, the pedal
>on your right foot should be the one with right hand threads. The left pedal
>has reverse threads, to keep it from unscrewing.

I’ve always felt that the reverse threads thing on the left pedal was a little
fishy. I can’t believe that a standard-thread left pedal would unscrew if it is
properly torqued on - unless the bearings were really shot, which should alert
you to replace the pedal anyway.

If the left pedal requires reverse threads to stay on, why don’t unicyclists and
trick bicyclists find that their right pedals are unscrewing from riding
backwards and mounting? Or do they?

As far as finding a spiderless righthand crank, I’d be tempted to try a left
hand crank on the right side, with some Loc-tite anti-vibration thread-coating
on the pedal threads, and see what happens…check the torque periodically.

~Rick Bissell

RE: LH threads…urban legend?

> If the left pedal requires reverse threads to stay on, why don’t unicyclists
> and trick bicyclists find that their right pedals are unscrewing from riding
> backwards and mounting? Or do they?

They do if you ride backwards enough. But for the most part, your forward riding
will far outweigh anything you do backwards. To test the theory, turn your seat
around and see how long it takes before you find your crank threads
“disintegrating”. How long will depend on two main factors, how tight they’re
screwed on, and the type of riding you do. But 100 years and millions of bikes
with left-threaded left pedals should be enough evidence to convince anyone that
the threads are on the right (correct?) sides…

I use a purpose-made pedal wrench, which has a nice long handle and can get the
pedals really tight. Friends of mine have had a problem removing pedals I put on
for them, when they try to use short handled adjustable wrenches or the
palm-slicing Miyata tool.

Stay on top,

John Foss, the Uni-Cyclone http://www.unicycling.com

RE: LH threads…urban legend?

We see pedals coming unscrewed when the seat is on backwards or twisted.

RE: LH threads…urban legend?

Foss, JohnX writes:
> > If the left pedal requires reverse threads to stay on, why don’t
> > unicyclists and trick bicyclists find that their right pedals are
> > unscrewing from riding backwards and mounting? Or do they?
>
> They do if you ride backwards enough. But for the most part, your forward
> riding will far outweigh anything you do backwards. To test the theory, turn
> your seat around and see how long it takes before you find your crank threads
> “disintegrating”. How long will depend on two main factors, how tight they’re
> screwed on, and the type of riding you do. But 100 years and millions of
> bikes with left-threaded left pedals should be enough evidence to convince
> anyone that the threads are on the right (correct?) sides…

To provide a data point at the other end of the experience spectrum: I have
never bothered with using right-hand cranks or pedals on my unicycle (I don’t
want to pay a premium for non-standard bike parts unless I need to). I ride my
cycle reasonably hard (mountain unicycling, uni hockey, etc) and basically the
pedals don’t come loose (maybe once ever two or three years). I don’t do
anything more than tighten them as hard as I can with a 6" adjustable wrench.

I have even got to that dangerous point of arrogance where I no longer carry a
toolkit with me when I ride!

Cheers,

James Gifford


<James.Gifford@anu.edu.au

RE: LH threads…urban legend?

>From memory from cycling with James, he actually rides his unicycle
backwards all of the time. (by that I mean he rides forwards but the unicycle
seat is on backwards) or something like that.

nic

On Thu, 29 Apr 1999 James.Gifford@anu.edu.au wrote:

> To provide a data point at the other end of the experience spectrum: I have
> never bothered with using right-hand cranks or pedals on my unicycle (I don’t
> want to pay a premium for non-standard bike parts unless I need to). I ride my
> cycle reasonably hard (mountain unicycling, uni hockey, etc) and basically the
> pedals don’t come loose (maybe once ever two or three years). I don’t do
> anything more than tighten them as hard as I can with a 6" adjustable wrench.
>
> I have even got to that dangerous point of arrogance where I no longer carry a
> toolkit with me when I ride!
>
> Cheers,
>
> James Gifford
>
> –
> <James.Gifford@anu.edu.au>

RE: LH threads…Sheldon’s response

I wrote to Sheldon Brown, the “Great and Powerful Oz” of bicycle wisdom (he has
one of the best cycling web pages on the Net ~ www.sheldonbrown.com) and he
directed me to an entry that he has on this subject. I’ve copied it below. It’s
interesting.

He also said though, “I had some experience with wrong-way threading on my
early home-built tandems. It worked OK as long as the pedals were tightened
REALLY tight”

Here is the entry copied from Sheldon’s page:


Pedal Threading Direction

The right pedal has a normal thread, but the left pedal has a left
(reverse) thread.

The reason for this is not obvious. The force from bearing friction would, in
fact, tend to unscrew pedals threaded in this manner. The fact is, however, that
it is not the bearing friction that makes pedals unscrew themselves, but a
phenomenon called “precession”.

You can demonstrate this to yourself by performing a simple experiment. Hold a
pencil loosely in one fist, and move the end of it in a circle. You will see
that the pencil, as it rubs against the inside of your fist, rotates in the
opposite direction.

Ignorant people outside the bike industry sometimes make the astonishing
discovery that the way it has been done for 100 years is “wrong.” “Look at these
fools, they go to the trouble of using a left thread on one pedal, then the
bozos go and put the left thread on the wrong side! Shows that bicycle designers
have no idea what they are doing…”

Another popular theory of armchair engineers is that the threads are done this
way so that, if the pedal bearing locks up, the pedal will unscrew itself
instead of breaking the rider’s ankle.

The left threaded left pedal was not the result of armchair theorizing, it was a
solution to a real problem: people’s left pedals kept unscrewing!

I have read that this was invented by the Wright brothers, but I am not
sure of this.