RoadBikeReview.com's Forum Archives - General


Archive Home >> General(1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 )


How the #^%*& did this happen?(34 posts)

How the #^%*& did this happen?MrCelloBoy
Dec 16, 2001 11:33 PM
Sweetie and I were cruising the Calfee Tandem today in light rain and cold with our local clubsters when her left pedal (Performance Forte Road) came right off while going along at a nice clip.
Bizarre! As pedals are designed to tighten in normal use I'm mystified. If we were spies I'd suspect sabotage, but???
Anyone else had this happen?
re: How the #^%*& did this happen?Bruno S
Dec 17, 2001 1:04 AM
I think it was the Calfee rejecting those cheap Performance pedals. Buy Look and they will get along.

Other answer is that she was pedaling backwards. In Spring you will thank her.
she is a hammer.nmC-mond
Dec 17, 2001 5:20 AM
This question really weeds out the idiots.Bernie
Dec 17, 2001 12:05 PM
For those who think that a pedal is supposed to tighten by itself, they are WRONG!. Why do you think pedal wrenches are so large and can provide so much torque? So you can put a pedal on loosely and let it tighten up by itself? Pedals do not tighten by themselves. A pedal will loosen and come off it not installed properly. Pedals are similar to "English" bottom brackets. Both will loosen if not installed to the proper torque. If a pedal did tighten by itself it could be extremely hard to remove (engineers did not make pedal wrenches large for this purpose). Some here have found out for themselves that pedals will loosen if not installed properly. Finally, with a pedal wrench, you don't have to bust a nut installing a pedal (pedal wrenches can provide a tremendous amount of torque), just make sure they are on good and snug.
Actually,speed-chump
Dec 17, 2001 5:27 AM
they tend to loosen as you pedal. thread one in halfway, then hold the pedal spindle and use it to rotate the cranks
like you're pedalling, and it'll come out.
If it does, you have your pedals on the wrong sides! nmWrenched
Dec 17, 2001 7:48 AM
Sheldon Brown on the topic....speed-chump
Dec 17, 2001 8:07 AM
http://www.sheldonbrown.com/gloss_p.html#pedal
Which just goes to show...muncher.
Dec 17, 2001 8:52 AM
That not everything on the internet is true and accurate...
Which just goes to show...speed-chump
Dec 17, 2001 9:34 AM
fill your pedal bearings with epoxy or otherwise seize
the body to the spindle, and try to pedal. if they don't
unscrew from the crank, i'll buy you a new set of pedals of
your choice.
That's a kind offer, but....muncher.
Dec 17, 2001 10:20 AM
think it through - if the pedal body and spindle are fused, it can't do anything under pedaling, but tighten, unless the pedals are on the wrong sides. Sheldon's "pencil theory" doesn't work, because the "pencil" (spindle in our example) has to be free to rotate. In your scenario, it isn't, 'cos there's a fat foot/pedal preventing it.

I am too nice, which is a shame really, as I fancy a new pair of carbon Attacks for the XC bike, what with it being Christmas 'n' all....
This is an amazing topic.speed-chump
Dec 17, 2001 10:32 AM
loosen up a pedal so that you can turn the spindle
by hand. put your bike in a stand, grasp the spindle, and
turn the cranks forward. the pedal will unscrew.
it's not subject to interpretation, that's just the way it
is.

not only did i think it through, i just went and tried it
to make sure i'm not full of hot air.
speedy.... you're up against the inet phenom with thisCT1
Dec 17, 2001 7:11 PM
One thing I learned long ago was to NEVER "argue" a simple physical principal with a inet post. It is NOT possible.... as you have just learned.

ride on
JohnG
Read your post againmuncher.
Dec 18, 2001 1:46 AM
"seize body to spindle". That's a different situation entirely.

2nd - all I said was if the pedal comes undone, you have them on the wrong sides. Do your experiment with the other pedal - there you go. Why does everyone on this site go straight for the throat the whole time?

I do this all the time - I use different pedals on the trainer than I do on the road - I never tighten them up more than finger - there is no need - they don't come undone.
had it happen on a look pp296Js Haiku Shop
Dec 17, 2001 5:30 AM
but the pedal body came off the spindle. luckily, it was at the start of the ride, turning circles in the parking lot. glad it wasn't out of the saddle cresting a hill with a dog in tow!
had it happen on a look pp296mickey-mac
Dec 17, 2001 5:50 AM
The same thing happened to me on a set of Look pedals about 6 months ago. It was a bit confusing for a split-second. I knew the pedal was attached to the cleat, but then I looked down and saw the spindle sticking out of the crank. Unfortunately I wasn't close to home and had to stop about every mile to hand-tighten it.
Me too.look271
Dec 17, 2001 6:16 AM
Fortunately, it happened in the shop when they were doing a fitting for me!
Me threeterry brownell
Dec 17, 2001 8:37 AM
With Look 247. In my case I happened to look down and notice a lot of thread showing between the pedal body and the crank arm. I stopped to investigate and found I had about 3 threads left before the pedal separated from the spindle (which was still seated snugly in the crankarm.) Tightening that thing up was a stretch use for my multi-tool.
I've heard of itDog
Dec 17, 2001 6:26 AM
A friend who hastily reassembled his bike the night before after flying in to do the Death Ride had a pedal come off.

I did think they were supposed to self tighten, though. Maybe a stupid question, but is the tandem crankset threaded backwards for the stoker? The main chainrings are still on the right... but the sync chain (right term?) on the left...

Do you use a "real" poedal wrench? A good one will get'em nice and tight, and still be able to loosen. I use anti-seize on the threads, and never have a problem.

Dog
Actually...John-d
Dec 17, 2001 7:06 AM
they self-loosen, The left crank if memory serves me right has a left hand thread.

I have always thought that this was a 'safety'???? feature should the pedal seize.

OK I'm braced and well dug in.

John
hmm, easy enough to check outDog
Dec 17, 2001 7:41 AM
The safely feature makes sense. Never thought of it that way. But, I've never heard of a pedal seizing, either.

Unless you had a fixed gear hub, it wouldn't be an issue, though -- a pedal seizes, you just stop pedaling. Now, if both the pedal AND the hub froze, it would yank your ankle right off...

I'll check it out unless someone beats me to it.

Dog
hmm, easy enough to check outJohn-d
Dec 17, 2001 8:01 AM
Something you said made me think, hmmm well, when the crank and pedal systems were first designed, fixed gear riding was very common - if not the norm. Sometimes things just don't get changed and no one can remember why it's done like that.
Well, now that the answers are thoroughly confusing...MrCelloBoy
Dec 17, 2001 8:24 AM
It was the whole pedal (spindle included) that came off.
According to Sheldon, whom I tend to believe) the normal pedaling motion would actually tighten the pedal, so I guess it was sabotage. ; )
Well, now that the answers are thoroughly confusing...cyclaholic
Dec 17, 2001 9:53 AM
There's no need to get confused about this.

Go back and carefully read the Sheldon Brown article. Regardless of the physical force or forces exerted on the pedal, the problem that engineers had was that pedals kept unscrewing. In order to resolve that problem, the general cure was to thread the left crank backwards.

Obviously, that improved things but it didn't eliminate all cases of pedals becoming loose on the cranks. Simple observation tells us that pedals do indeed come loose and, as a result, you'd better check them from time to time. Pedals come loose. Cranks come loose. Headsets get loose. Chains break.

Since those things happen, you need to keep an eye on potential problems and carry the appropriate tools for an emergency situation.

Just because you had a really great mechanic put those pedals on your bike, there is no guarantee they will not get loose.
re: How the #^%*& did this happen?Shad
Dec 17, 2001 8:11 AM
This same thing happened to a good friend of mine while we were riding mountain bikes last winter in MN. He must not have tightened the pedal enough to begin with. Unfortunately, he didn't notice until the pedal popped off ruining the threading in his crank. Ooops! - one legged ride home, new crankset needed and late for work to boot. He bought a proper pedal wrench after that, having learned his leason, and now doesn't assume the pedal tightens as you ride.
By the way...MrCelloBoy
Dec 17, 2001 8:27 AM
After this happens we discovered that by threading the pedal from the BACK of the crankarm first, you can clear some of the stripped threads and then reattach the pedal. It's worked twice now. My sweetie thought of this! The biker babe of the year!
Thanks, good idea...Shad
Dec 17, 2001 10:12 AM
If only we would have known then! He kept trying to thread it back on and thus kept stripping more threads. That sweetie sounds very resourceful. That tip may come in handy in the future. Thanks!
This goes back to the days before freewheelsAlex-in-Evanston
Dec 17, 2001 8:45 AM
The tradition of reverse threading the non-drive-side pedal is to make sure it would loosen if the pedal were to seize about the spindle, as the conventionally threaded drive-side pedal would. If one is riding a fixed gear, a seized pedal would result in serious mayhem if it were theaded to tighten in the forward direction.

How a pedal could possibly seize about the spindle is a mystery to me.

Alex
who put your bike together?gtx
Dec 17, 2001 9:58 AM
There isn't really a good excuse for that happening, and it could have been dangerous. Maybe you should go through and make sure everything is tight and safe and to spec. Stem, bars, cranks, cassette, etc.
I put it back together!MrCelloBoy
Dec 17, 2001 1:02 PM
I'd been pissed when I couldn't loosen the pedals the last time the shop installed them so I'd put them on looser this time, assuming (wrongly) they were tightening themselves on.
It's always great to be reminded that we don't know everything the way we thought we did, after years and years of experience!
re: How the #^%*& did this happen?josh_putnam
Dec 17, 2001 11:06 AM
Sheldon's page is correct, once installed reasonably tight, pedals self-tighten in use. Precession is a well-documented phenomenon with bearings in general, not just bicycle pedals.

You can't just grab the pedal spindle, or seize up the bearings, to test the phenomenon, because both of those approaches eliminate the bearings, and it's the bearings that cause the phenomenon.

Reverse-threaded pedals were developed specifically to address the problem of pedals loosening in use, not as a safety measure in case the bearings seized -- the history of this is also well documented.

A similar situation is the bottom bracket cups on cup-and-cone bottom brackets. Before English BB threading became the near-universal standard, there were some national standards that had both cups threaded with right hand threads, and they constantly suffered from the cups loosening up in use. Reversed threading makes them self-tighten instead.

All this only applies to threaded joints that were reasonably tight to begin with. If you thread a pedal in only finger tight, the pedal wallowing around loosely will overwhelm the smaller forces from precession and the pedal will come loose.
AHHHH!speed-chump
Dec 17, 2001 11:25 AM
Now I understand what he was saying.

I maintain that IF (big if) the bearings were
to seize, the pedal would unscrew. I already
tested that.

But i also see what you guys are saying now about
precession. I was stuck on the idea that
the only forces being considered were bearing friction.

Good post, thanks.

I new a Josh Putnam in Tulsa, OK once. Your not him, are
you?
interesting; check this thread, too...Dog
Dec 17, 2001 11:39 AM
http://cycling.org/lists/hardcore-bicycle-science/hardcore-bicycle-science-archive-hyper/hardcore-bicycle-science.199906/0185.html
fascinating conceptDog
Dec 17, 2001 11:44 AM
http://www.perceptions.couk.com/precess.html

Totally escaped intuition; I guess Sheldon does know his stuff.
So, in Conclusion. . .MisJG
Dec 18, 2001 1:23 PM
It sounds as though you people whose pedals are un-threading while riding need to check that your bearings are clean and lubed and that nothing is in the way of the pedal spinning freely. A properly operating pedal will tighten itself, so your pedals are in need of some attention!