I made a bit of a discovery recently, well i think it is…Has anyone els discoverd it??
Anywhom, what i have grown to believe is the reason that pedals have a reverse thread on one of them is so that the resistance caused by the bearing in the pedal does not un-screw the pedal off the crank arm…right??
So here’s an experiment that sort of proves this wrong:
Take a pedal wrench and put it on the pedal as if to take it off.
Now, hold the wrench tight against the pedal and wheel your uni forward, keeping the peda wrench and pedal paralell with the ground.
This is to reproduce the forces of riding.
Now, if you continue doing this, the pedal will fall off.
Try this with all your unicycles and bikes if you want. I have.
Is this not strange?
Am i making sense?
It sort of goes against how i thought it should work.
It has left me quite destressed actually!
If someone could explain to me if im wrong or how im wrong, that would be great.
Or just tell me the results of your test.
Re: World-Wide pedal reverse-thread theory cospiracy!!!
If you are holding the pedal and wrench still whilst rotating the wheel
forwards, this is just the same as holding the wheel still and rotating
the the wrench and pedal backwards… which, as you explained, is
exactly how they should come off.
All you’ve done is find another way of removing the pedals rather than
keeping the wheel still, not proven that the threads are the wrong way
Kind’ve weird to think about, you have to remember that the effective
directions change depending on what part you keep still.
If you’d ever ridden a unicycle backwards for a long distance, or put the seat on the wrong way round(*), you’d know that the pedals fall off surprisingly quickly.
Joe
(*) obviously I’m not stupid enough to have done this, it was ‘a friend of a friend’ who did this and then went for a ride with no tools and no way of tightening up the pedals leaving him walking home a couple of miles. Honest.
When I first arrived at Southampton & went to the Circus Society I did my usual checkover of the clubs unicycles, and saw to my horror that they had been riding it reversed for a considerable period of time. Asking the President at the time, apparently they stripped the threads from 2 crank arms, and thought this was due to learners being tough on equipment… I quickly put it right again, although I have 2 new crank arms to fit still.
What you could have done is, put the pedals back on finger-tight and then turn the saddle round so that they tighten the rest of the way whilst you rode.
Didn’t work. These particular pedals need to be quite tight like slightly tighter than finger tight to be not wobbly in the threads of a crank. It felt like I’d be too likely to strip the threads riding on them. It’s odd, some pedals are fine with being finger tight, some pedals you need a spanner, it doesn’t seem obvious why.
Probably just variations in machining; some sets of threads match up better (or worse) than others.
I don’t know why I’m posting to this thread. For Will: If you haven’t read the linked article from Sheldon Brown, please consider millions of people riding bicycles for over 100 years. The question is not whether the threading is backwards, it’s whether your theory is backwards. The key word is precession.
Thanks joemarshall for the link. That is really interesting.
Before i posted this thread, i asked at two local bike shops.
The first one said “I dont know how it works on your crazy bike” refering to my uni, and then walked off. The tech at the other shop said that it was so that the pedal didnt get stuck on too tight!
I wasn’t doubting hundreds of years of cycle technology, as i too have gad my pedals comming loose from riding backwards!
Re: World-Wide pedal reverse-thread theory cospiracy!!!
Will, your ‘conspiracy theory’ has been set straight, so I won’t add
to that.
But I’ll say, I appreciate how you put your question. This issue comes
up every so many months in this group, and is often phrased like “The
world has done it all wrong all the time”.
A few months ago, i wanted to unscrew my pedals and didn’t remember the good direction.
I tried to think to the stresses involved in pedaling as i knew there were something particular with pedals threads. I noticed the thing of the pedals getting loose when going backwards for a while. So i had the same thought as you, … and at first tightened my pedal.
I realized quickly that i was doing a mistake but didn’t understand why.
Thank you for your question, i read the page of sheldon brown and i have my so needed explanation.
Doing some tire testing I accidentally put the wheel on backwards. only got in about 5 minutes of riding when the pedals started to feel loose. Turned the seat around (too lazy to turn the wheel around) and the pedals tightened themselves again.
The conspiracy of unintuitive physics is real!
I was surprised how fast they loosened. I think if I was planning (and able) to do a lot of backwards riding I would use some blue loctite on the threads.
I understand where you are coming from - some time back I found that using my head to work out the way to unscrew the pedal always got the wrong answer. The reason dawned on me eventually.
If you turn the pedal, the situation is as it should be. It tightens the spindle as you ride.
But putting the torque on the spindle is not the same thing as putting it on the pedal. There is a single layer of ball bearings connecting the two. This reverses the direction of the torque that you apply to the pedal.
For example, putting a backward spin on the pedal, as y ou do when riding forward, will result in a forward torque onto the spindle.
I hope this makes sense. Does it?
btw I didn a quick tube repair on the road once and didn’t pay enough attention to reassembly. The pedal came off less than a kilometer later, to my embarrassment.
