Nys pedal incident

[avanti]

"Shimano requested an investigation, as it would with any equipment failure. They seemed convinced the pedal came unscrewed from the crank arm and, after looking into the issue with the team, both parties agreed today that this was the case."http://www.cyclingnews.com/news/mystery-of-nyss-missing-pedal-solved

The pedal/crank threads tighten during pedaling (that's why opposite have different threads - LH or RH). I'm not a believer in this explaination - maybe stripped threads or sheared pedal spindle was the cause.

 

[TERMINATOR]

The pedal/crank threads tighten during pedaling (that's why opposite have different threads - LH or RH). I'm not a believer in this explaination - maybe stripped threads or sheared pedal spindle was the cause.

Pedals do NOT tighten when you pedal. There is almost no torque translated through the pedal spindle since the pedal is connected to the pedal spindle through greased ball bearings. A 4 year old with buttered hands can apply with more torque with his fingers than the pedaling action of a pro cyclist.

Therefore, if the pedal is not tightened it can definitely work its way loose from vibrations during a race.

 

[gbshaun]

Look up "precession". The rotating nature of the direction of the radial force (not through the bearings) causes a turning force in the opposite direction. This is why LH pedals must have a LH thread.

Shaun

 

[ergmonkey]

Look up "precession". The rotating nature of the direction of the radial force (not through the bearings) causes a turning force in the opposite direction. This is why LH pedals must have a LH thread.

Shaun

Shaun, excellent first post. Welcome to the forums!

Nonetheless, your post does still reflect your considerable inexperience with these forums. May I be so bold as to help you make sense of this place? Here are a few guidelines for posting in these forums:

-users uniformly replace the scientific method with pseudo-science, science by inapposite analogy, or explanation by metaphor; thus, any theory which has arisen from a thoroughly tested and proven hypothesis under controlled conditions is to be discarded; anything which the scientific community might label a "law" is to be expressly refuted or ignored; the cyclingnews forums are not a scientific jurisdiction

-numbers are not to be used unless they have been pulled out of thin air; obviously, this means no known equations and absolutely no established coefficient values for things like gravity, drag, and friction; but, it also means that actual performance numbers such as times and known power outputs are disfavored, as well (unless, of course, those numbers have been fabricated); rather, users are encouraged to broadly reference percentages of largely unquantifiable phenomena (e.g. in his day Merckx was at least 15 % better than the competition and today's peloton is 10% better still, therefore Merckx on EPO would be 50% better than today's top riders)

-finally, please remember that a proper explanation by analogy or metaphor is only truly compelling when it demonstrates contempt for another party--said party may be an active rider, team manager, cyclingnews forum user, or any combination of these three

 

[Broken Spoke]

Shaun, excellent first post. Welcome to the forums!

Nonetheless, your post does still reflect your considerable inexperience with these forums. May I be so bold as to help you make sense of this place? Here are a few guidelines for posting in these forums:

-users uniformly replace the scientific method with pseudo-science, science by inapposite analogy, or explanation by metaphor; thus, any theory which has arisen from a thoroughly tested and proven hypothesis under controlled conditions is to be discarded; anything which the scientific community might label a "law" is to be expressly refuted or ignored; the cyclingnews forums are not a scientific jurisdiction

-numbers are not to be used unless they have been pulled out of thin air; obviously, this means no known equations and absolutely no established coefficient values for things like gravity, drag, and friction; but, it also means that actual performance numbers such as times and known power outputs are disfavored, as well (unless, of course, those numbers have been fabricated); rather, users are encouraged to broadly reference percentages of largely unquantifiable phenomena (e.g. in his day Merckx was at least 15 % better than the competition and today's peloton is 10% better still, therefore Merckx on EPO would be 50% better than today's top riders)

-finally, please remember that a proper explanation by analogy or metaphor is only truly compelling when it demonstrates contempt for another party--said party may be an active rider, team manager, cyclingnews forum user, or any combination of these three

It's funny cos it's true!

Better yet, actual experience trumps any scientific theory and I've had this happen, coincidentally(?) with a Shimano SPD pedal though certainly not XTR-level. The thing is, getting a detached pedal off the bottom of your shoe is not a simple flick of the wrist even with the tension dialed right out and I didn't see Nys clomping up the finish chute with a pedal stuck on the bottom of his shoe. It's possible the thing disengaged as it let go, but...

I guess the defence of "the stoopid fat Belgian spanner monkey didn't do it up right" is a bit more palatable to the Shimano PR team than "our all-new XTR pedal snapped and we're looking into it". Look for the brand spanking Di2 groupset on said spanner monkey's bike next week.

Oh yeah, did Ergo mention conspiracy theories?

 

[hmsgenoa]

For me the answer is simple, after many years of assembling bikes and winding the cranks backwards to get the pedals in quickly. If the pedal has come undone the bearings in it have failed - or at least are too tight.

 

[Greyhound Velo]

Since this comes up regularly at my shop and anywhere else cyclist congregate, I created a graphic (using my leet Paint skills ) to help explain how precession works in bearing systems, specifically for a left pedal in this case.

To keep the explanation as to why a loose pedal spindle unthreads itself as simple as possible, I'm going to break it down into sections.

-As you can see, the direction of travel of the surface of the bearing, where it contacts the spindle, is the same as the direction one would turn the spindle to tighten it into the crank arm, which is why precession is not the reason a loose spindle unthreads itself while pedaling. If it has any effect at all it will be to tighten the spindle.

-It is true that if the pedal spindle were to "lock up" and stop rotating, it would unthread itself. This is essentially what happens when you remove a pedal: You temporarily "lock" the spindle to the pedal body with the pedal wrench and turn the cranks forward, in the same direction as when riding the bike, and the spindle unthreads from the crank arm.

-As long as there is no significant friction in the bearing system, the spindle will stay where it is, even if it isn't tight. The problem is that rarely are bearing systems perfect, they all have some friction to varying degrees due to wear, contamination, and lack of lubricant. If enough friction is present it has the effect of "locking" the spindle to the pedal body for minute amounts of time and will eventually cause the spindle to unthread.

In the case of Sven Nys' pedal, it's the middle of the season and he has likely used those pedals a few times in mud, sand, and who knows what else that could cause some contamination of the bearings, not to mention the pedals have been power washed multiple times which could blast some of the grease out of them. Also, the race where he lost the pedal was in below freezing temperatures, so it's likely that the grease in the bearings was stiffer than normal from the cold, exacerbating the problem of contamination. Finally, it's possible that his mechanic installed the pedals finger-tight while preparing the bikes for that day and never went back to snug them down, or maybe he just missed the one (I'm speculating here, but even at the pro level these things happen occasionally). All of which adds up to the pedal working its way loose and falling off.

Fortunately Sven was able to keep himself upright and it was at the end of the race, so it wasn't too big of a deal. Imagine what could have happened had he been bunny-hopping barriers or climbing the Kwaremont when it came loose . Assuming the pedal wasn't tight, I guarantee you that his mechanic will never make the same mistake again!