Techs-Mechs: Unchained

Nothing is more fun than a 700-reply post about a mechanical failure. Ok, it was really about the controversy that ensued around the unwritten rule of attacking the Maillot Jaune when he has a mechanical, but I am interested in the mechanical failure aspects in such a high visibility situation.
From what I understand, Andy Schleck is running a chain watcher (or at least he was prior to Stage 2). A chain watcher is a metal or plastic fixed device that attaches to the seat tube or the front derailleur mounting bolt that acts as a barrier to prevent the chain from falling off to the inside of the small chain ring. So what happened?
A chain falls off for basically two reasons. Read on...
The first is a poorly adjusted front derailleur. Set the outer limit to far and the chain can come off the large chainring in the direction of the crank arms while upshifting. I have had this happen once, and I was able to pedal out of it, by shifting the front d inward which enabled it to catch the teeth and return to normal. It slowed me down but I didn't need to dismount and fix it by hand. But I was able to catch the chain with my pedal spindle. Had the pedal been behind the bb, it could have fallen off beyond the pedal and it would have required stopping and repairing by hand. If a front d inner limit is set too far to the inside a downshift will result in the chain popping off and winding up around the bb spindle area. I've never successfully shifted out of this situation on the fly. You can shift the front d all the way to the outside but usually the chain is far too loose to grab anything. A quick dismount is needed followed by needing to lift the chain by hand over the inner ring followed by a quick spin of the pedals to make sure it's fully on, and then you're back in business about 10-15 seconds later.
The second and more common reason for a chain to fall off is being cross-chained (big-big) and when you shift abruptly to the small ring, the 14 (or 16) tooth drop under load and at an extreme angle will cause a drop no matter how well you adjusted the front d. I'm not 100% sure what Andy was doing, but on an attack would he be downshifting? And what of the chain watcher? I suppose on a high mountain stage, he may have been saving a few extra grams by removing it (Contador's bike doesn't have one) but even the heaviest ones would scarcely weigh enough to matter, and the pro bikes are already flirting with the UCI weight limit (14.99 lbs) on climbing rigs so if a rider uses one, I'm not sure it's worth removing. Why doesn't everyone use one? I have heard from some cross racers that they don't use chain watchers because if the chain pops off and gets stuck behind the watcher it becomes a much harder repair on the fly while your opponents are passing you.
I haven't heard a definitive answer yet as to what happened exactly, but from the video it almost looked like chain suck followed by a dropped chain. Chain suck is when you have too much slack in the chain as it is coming off of the lower pulley and it makes contact with the upper pulley which causes it to lock up in the cog. As a visual for any of my fellow fisherman, it's essentially like a backlash when you don't set the free spool tension properly on a fishing reel. Usually this will bring you to a dead stop if the chain stays on the chainrings. I mention this because it looked like he had to pull it free but he also looked like he was waiving to the team car indicating more than just a dropped chain.
Any ideas as to what happened exactly?
Photo: Spencer Platt, Getty.
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I have no idea, but I do second your question of why he'd be downshifting...
…to attack.
It’s the thing that’s been bugging me the whole time about this.
I suppose he may have used a big gear to get away
and then down shifted to get into his normal high cadence. Also, the pitch may have kicked up a bit which isn’t always visible on video.
I realized I was stealing the title from Jens (sorry my friend) so I just changed the title.
Or if my chain suck theory holds any water
he may have been upshifting in the rear cogs. A 34t/11t combo is a prime condition for chain suck.
And for the record: I’m not blaming the Berner-design pulley system…if anything that would probably reduce the risk of suck since it keeps the chain angles more gradual.
It looked like suckage to me
The way the rear wheel bounced it looked like suckage. If the chain just drops, you come to a grinding halt. I wondered actually if he just hit some shit road, and it bounced the chain enough to suck it. But I haven’t watched a replay of the thing, so I’m not sure.
I can’t really imagine he’d be in the 34/11, gah, that would be a bit amateur hour. Of course, he could have been nervy and made a mistake.
He attacked out of the saddle, and may have been getting ready to sit down and pedal a smaller gear after the initial acceleration. So, the idea that he was going to a bigger cog is entirely possible.
I’ve never ridden SRAM road bits, so I don’t really know how the shifting handles at all.
Nice video. The rear wheel lift is a dead giveaway. And
you can see the rear mech binding up and the lower chain is completely void of slack,
I think it IS the Berner assembly
combined with the mechanics not really having a good handle on what the chain length should be for those things.
in theory though, it seems like an anti-suck
design since it is made to keep the angles more gradual, however when I think about it, a larger upper pulley could potentially cause the problem if the chain is a link too long.
I agree about the 34t. I would think he'd have at least a 36, but likely it was a standard
53/39t crank. Most pro’s of his level will really only use the compact for an Angrilu/Zoncolon type pitch. There was a long downhill, and I’m sure he wouldn’t want to be spinning a front 50t ring.
Maybe he tapped the lever too hard…
It has been common for many years to see riders using 52/34 110BCD in the mountians.
While this is Technically not recomended, it works fine providing your are not riding like a jackass.
I would imagine a med cage rear d would be recommended here.
I noticed Contador rides a standard chainring combo (53/39) and an 11-26 cassette. This combo would give him a minimum gear inch of 39 inches. Not super tiny, but certainly spinnie enough for top climbers with crazy power to weight ratios. This would give him a smooth front d shift and plenty of gear for the long downhills.
Also CollediateRacingRocks posted this article in Techs-Mechs: Tour Tech
http://www.bhpc.org.uk/HParchive/PDF/hp50-2000.pdf
That discussed the effects of friction on drive trains with respect to chainring/cog sizes. The results of the test showed that less power is lost with larger rings/cogs. in other words, a 53/19 would produce less friction than a 39/14 although the gear inches are practically identical (73.3 vs 73.2).
By that logic, a standard crank with larger cogs would be a better option. Of course pro’s don’t want huge jumps between cogs so they wouldn’t want an 11/29 cassette (not sure it exists in a standard casette) where a 50/34 with an 11/25 will give you the same minimum gear ration with a tighter cluster.
First, Pro’s are not logical; and I am speaking from experience on this.
Second here is the cassette options of the SRAM Red Group for your reference –
11, 12, 13, 14, 15, 16, 17, 19, 21, 23
11, 12, 13, 14, 15, 17, 19, 21, 23, 25
11, 12, 13, 14, 15, 17, 19, 21, 23, 26
11, 12, 13, 14, 15, 17, 19, 22, 25, 28
I'm speaking campy talk from my own experience.
they’re options (for 10 speed) include an 11/25 and a 13/26. I have swapped out the 23/25 cog on the 11/25 for the 23/26 cog when I need the range. The spacer between the two are identical and it works. FWIW, when I use the 13/26 (which is often), I find that I love the 18t and it’s nice to have a smooth transition from 17-18-19 where I spend most of my time.
I wish there was a video from the driveside of the bike. From the NDS, it’s hard to see the crankset, and you can’t really see the small chainring at all just long spider arms suggesting it may have been a compact.
If Celerity and Omne had been on that climb
we would have had video from that exact spot, I’m sure they would have picked that spot to stand.
And
Elizabeth would have had a crystal clear photo of the wheel bumping in the air. Cuz her camera rocks.
"Good thing I never said out loud that I was pulling for France, before this all started." -Mark Blacknell
by Chris Fontecchio on Jul 20, 2010 6:22 PM EDT up reply actions
The drivetrain in question is SRAM Red.
It is not good to infer compatibility options from other drivetrains.
Speaking of the Red Group – There is only ONE Cassette with a 16T cog!
WTF is that about?
I swear I use that cog more then all the rest combined.
Strange. . . .
Oh I jumped a long time ago.
I ran the 1st gen force and was impressed with the reliability of the kit.
When Red came out, I just so happened to be needing a new group for a new frame I was building up.
Honestly, the Red Group is the best shifting and most reliable drivetrain I have ever used.
The chainrings suck, and the brakes are OK; but the shifting system has really impressed me.
Oh, and I roll on a Force 12/26 ‘cause it’s gotta’ 16T and there are some damn big mountains here in TW.
SRAM FORCE Cassettes –
11, 12, 13, 14, 15, 16, 17, 19, 21, 23
11, 12, 13, 14, 15, 17, 19, 21, 23, 25
11, 12, 13, 14, 15, 17, 19, 21, 23, 26
11, 12, 13, 14, 15, 17, 19, 22, 25, 28
11, 12, 13, 15, 17, 19, 22, 25, 28, 32
12, 13, 14, 15, 16, 17, 19, 21, 23, 25
12, 13, 14, 15, 16, 17, 19, 21, 23, 26
12, 13, 14, 15, 16, 17, 19, 21, 24, 27
12, 13, 14, 15, 16, 17, 19, 21, 24, 28
12, 13, 14, 15, 16, 17, 19, 21, 24, 32
I have heard mixed reviews on the Red cassettes
but it looks like a lot of pros choose Force cassettes.
And any reference to my fishing skills
is purely coincidental. I spent 13 hours on the water this weekend off of cape cod, The tuna were practically jumping into the boat and I didn’t have a single hook up. Just sad…
13 hours?
So dad had cable installed on the boat?
"Good thing I never said out loud that I was pulling for France, before this all started." -Mark Blacknell
by Chris Fontecchio on Jul 20, 2010 2:26 AM EDT up reply actions
By the way
this is one of my favorite threads of the Tour. A community discussion of chain suckage vs misshifting. A critical moment in the Tour, and most of the other forums (not that I have time to read them) are just saying he had a problem of some sort. Here, we drill down to the bare facts. Chapeau.
"Good thing I never said out loud that I was pulling for France, before this all started." -Mark Blacknell
by Chris Fontecchio on Jul 20, 2010 2:27 AM EDT reply actions 1 recs
I think my lack of comprehension of this thread
explains why I rarely seem to be in the right gear & my chain comes off more often than it should. However at least I can put it back on a bit quicker than Andy did though.
"I was just trying to keep warm" - Ian Stannard on finishing third in KBK
that is why we keep coming back here
dear leader
"Contador just gained a great chance to win, but he lost the chance to win greatly." - Gerard Vroomen
Excellent
Now I want a statue in my honor. And not one of those puny under-30-foot ones either.
"Good thing I never said out loud that I was pulling for France, before this all started." -Mark Blacknell
by Chris Fontecchio on Jul 21, 2010 2:01 AM EDT up reply actions
Here's an idea
Turkmenistan’s current dictator decided that the statue of the former dictator Saparmurat Niyazov should be demolished. The statue is 12 meters high, gilded and it rotates to always face the sun. Perhaps if you write to Gurbanguly Berdimuhamedov and put in a request he will be willing to sell it to you.
Badger, badger, badger, badger, badger, badger...
by TheFigurehead on Jul 21, 2010 4:26 AM EDT up reply actions
You are however...
allowed to cut and paste a picture of your own face onto the statue.
Bunch of slack-jawed faggots around here. This stuff will make you a god damned sexual Tyrannosaurus, just like me - Jens Voigt, Predator (1987)
Great idea!
I wonder if he’ll take some XL PdC bibs in trade instead?
"Good thing I never said out loud that I was pulling for France, before this all started." -Mark Blacknell
by Chris Fontecchio on Jul 21, 2010 5:38 PM EDT up reply actions
Perhaps you should throw in a pair of armwarmers too, just in case
Badger, badger, badger, badger, badger, badger...
by TheFigurehead on Jul 22, 2010 3:40 AM EDT up reply actions
All these unanswered questions
Next year: onboard webcams aimed at front/rear derailleur so that tech geeks are fully updated at all times.
Root Cause Analysis time.
If we want to dig down, we can.
Problem: Chain Shifted off the Small Cog onto the frame (?).
’Note: This is what it seems but I have not seen good video to clearly show.
Likely Causes:
Component:
R. Der. – SRAM – Unlikely
Berner Rear Derailleur Cage – Possible unknown compatibility issue
*Cassette – SRAM – Unlikely
*Chain – SRAM – Unlikely
*Hub: Zipp – Unlikely
*Dropout Alignment – Possible Contributor, but could not be the ‘root cause’
*R. Der. Hanger Alignment – Possible, but unlikely
*Rear End Alignment – Possible Contributor, but could not be the ‘root cause’
Maintenance:
*R. Der. Adjustment – Possibly
*Cable Adjustment – New Bike = Housing Compression
User Error:
*Gear Selection – Possibly chose marginally compatible gearing.
Ex.: 52/34 110BCD w/SRAM RED Cassette. – This may create an issue at the gearing combo – 34~11.
*Shift Timing – Possible Contributor
On cable adjustment, wouldn't this need to be combined
with a maladjusted rear d? The limit screw should prevent the chain coming off if adjusted properly even if the housing has compressed or the cable was left a little too slack.
I agree on user error.
Technically no.
As both issues needed to occur to achieve this.
The example you give is correct, but the opposite can be done also.
If the Limit Screw was not in the correct location, but the cable tension was correct to keep the R.D. from advancing beyond the cog. this issue would not occur either.
So, both issues would need to be looked into before the actual ‘root cause’ could be identified.
Of course in the real world of bouncing riders,
hard pedal turns and aggressive shifting even the most perfectly adjusted system can still fail.
Yes, curious
how many watts he might have been putting out. This must have been at least a part of the problem.
(interesting thread BTW)
moo
If he'd attacked in the big ring and then changed down
He could have dropped the chain. Sometimes you know it’s happening and change back to the big ring to stop it, apply a softer change and Bob’s your father’s brother: chain all good.
It’s the bunny hop that gets me. That suggests chain suck to me. Simply dropping a chain will lead you to spin uselessly, but the wheels won’t jam. That is, of course, unless the ‘spare’ chain gets sucked up: a combination of dropping the chain and chain suck as it went. That hasn’t happened to me (it’s normally one or the other) but why could it not?
If it was chain suck on it’s own, that suggests that he was spinning too low a gear: again, probably after having changed down from the big ring, since there’s no way you’d attack in a low gear.
Did the Chain Suck happen in the Front or the Rear?
This is key in locating the Root Cause.
I cannot identify this.
Side note: Has anyone ever attacked and then during the attack shifted from the Large ring Into the Small?
Anyone?
. . . . . . . . . . . . . . . . yeah ‘cause you would never do that unless you completely blew your wad; which the kid didn’t as he seemed as if he was getting ready to kick in the turbos.
I just don’t understand why people keep saying he went from the Big to Small ring as if that action would occur under the specific circumstance in question.
But he had the gap already
masybe he was going back to hard, seated riding in the small ring. I don’t see why that isn’t a possibility.
I'm all but convinced that if he shifted at all it was rear
the video quality ain’t great, but I can’t see any left-hand motion before the chain drops (and Zinn argues that there was a k-edge chainwatcher in place, but I can’t see it in the video or photos I’ve looked at).
It’s easy to see the left-hand motion AFTER the chain drops as Schleck tries to sweep the chain back on, though. It’s hard to conclude, therefore that we would have seen a left-hand downshift because the sram motion is so slight.
But anyway, my theory remains focused on the Berner pulleys combined with a lack of clear guidelines about the chain-length necessary with them: since I can’t see Schleck shifting, for the moment I’ll suppose that something occurred to foul one link in between the pulleys, which caused the chain-suck.
Riis
Riis claimed he didn’t shift, it was a bump in the road.
If he were well down his cassette, I suppose it’s possible that there could be enough slack in the chain for it simply to bounce and suck. I was chatting about this one with SurferBoy last night and he suggested that the mechs may have run the chain a link or two long for the mountain stage. A slightly looser drivetrain will lessen the friction a bit – barely noticeable, but there – especially in the big ring-bigger cog combos you might run in hilly terrain. A slightly slack chain in a small-small combo? Yeah, that could suck on rough road, I suppose. Or, the slack chain, bouncy road, tangles somehow in the pulleys.
Gah. Wierd incident all around, though, really.
Ugh... 'its own'
I don’t like to cringe when reading my own writing, so I apologise to those who likewise suffered.
that guy knows way too much.
"Ants don’t worry, they operate like a fantastic team, they accept obstacles and deal with them in a positive manner, they don’t complain and remain positive. An ant doesn’t work on emotion, is proactive and always chooses the ant role."
he mentions them
but says it’s hard to see whether or not it was on the bike andy was riding at the time. he also says that he’s seen bikes for andy and cance both with and without them.
and i was mostly referencing his general knowledge of cycling equipment. maybe he doesn’t know as much as sheldon brown did, but i doubt many people know more than he does.
"Ants don’t worry, they operate like a fantastic team, they accept obstacles and deal with them in a positive manner, they don’t complain and remain positive. An ant doesn’t work on emotion, is proactive and always chooses the ant role."
no . . . he does not mention the berner pulleys
specifically, he mentions the changed jockey pulley assembly, but does not consider how those two ginormous pulleys might change shifting behavior.
Further, a little examination of photos should make it clear that Schleck’s bike was fitted with a rear der with the berner pulleys.
(photo linked, snarkily enough, from a Graham Watson photo available on VN’s site).
so . . . as Zinn concedes, his theory about SRAM’s design flaw, while in the realm of possibility in other circumstances, does not comport with the reality of this event.
His gearing looks
pretty standard. That looks to be a 53/39t crankset and the rear cluster does not appear to have a “granny” gear. I think he shifted off the small cog when he upshifted.
I just watched the video I posted on the 58" big screen
Riis and Schleck claim that he did not shift.
I can’t see a shift—and even the finger-tap to down-shift results in some fore-arm rotation apart from normal (and the slightly more exaggerated throw to upshift produces more wrist and forearm motion. You can definitely see, for example, when he tries to sweep the chain back onto front derailleur).
Further, had he tried to shift the chain up the cassette, the derailleur pulleys would have been pulled forward—which does not appear to happen.
If Schleck did shift, it was a downshift.
Again, what appears to me to have happened was that something-whether a road bump, a down-shift, or a combination of the two— caused a chain-link or two to get jammed between the pulleys, which caused the rear-wheel hop and yanked the chain off from the underside.
so he mentions the changed jockey pulley assembly
but not the berner pulleys. are there two sets of pulleys on his rear derailleur?
maybe that picture wasn’t available when he wrote his piece, or didn’t have time to sort through all the pics available. i don’t know, and neither do i care.
either way, i will restate my original point, which i feel is completely unaffected by your retort, that that guys knows way too much. he might not know every single thing, but he is one of the most knowledgeable and well respected technical authorities around, whether you like his analysis or not.
"Ants don’t worry, they operate like a fantastic team, they accept obstacles and deal with them in a positive manner, they don’t complain and remain positive. An ant doesn’t work on emotion, is proactive and always chooses the ant role."
two significant problems remain with Zinn's 'analysis'
1. It’s wrong. And it was easy to determine from available video which pulley assembly was on Schleck’s bike.
2. It’s misleading. Zinn claims that the “loop” on the pulley assembly can catch in the cassette teeth in a severe chain-suck event. I’ve been riding SRAM since 07, and have an early generation rival rear derailleur. I’ve launched the chain off the 39 twice by trying to shift from 53×21 down to the 39 (in races, on a hill—I forgot I was in the big ring and panic-shifted, the other was just stupidity). Major chain-suck occurred in both cases (in one the chain wound up between the 39 and the chain-stay). If what Zinn claims could happen would happen, it would have then. It didn’t. There are no marks of any sort on that metat chain-guide.
What Zinn describes did not happen. And there are many reasons why, the most significant one of which is this: even if somehow the jockey pulley assembly did rotate back into the cassette teeth, the chain will almost always prevent the metal chain-guide from engaging with the cassette teeth.
But even if you could somehow twist the rear derailleur enough that the pulley assembly would not rotate in line with the chain, that chain guide will not engage with the cassette teeth. I just spent a few minutes trying to make it happen by taking the chain off the front chainring and rotating the pulley assembly backwards into the cassette teeth. At the most you might get a momentary buzz/rattle—but not a jam of the sort that happened to Schleck.
In short . . . in this case (and there have been others), Zinn ventures an opinion based upon something he perceives to be a design anomaly and makes claims about the consequences of that anomaly without bothering to test out whether his scenario could happen. There are guys in shops all over this country and the world who know as much as Zinn . . .
great, then there are guys in shops all over this country
that also know way too much.
so you don’t link the guy or his analysis, that’s fine. how about next time you express that opinion without trying to shoot down my opinion of the guy? the guy’s knowledgeable, that’s a fact. more so than me, that’s another. i’m impressed by his level of knowledge, you don’t have to be.
"Ants don’t worry, they operate like a fantastic team, they accept obstacles and deal with them in a positive manner, they don’t complain and remain positive. An ant doesn’t work on emotion, is proactive and always chooses the ant role."
If you'll re-read my posts
I haven’t typed a word about your opinion.
I dislike his analysis of what happened in this case because it’s wrong. Mine might not be correct, but it’s bound to be closer than ZInn’s.
But people who don’t know any better (not saying,that you fit in that category)—and who think that Mr. Zinn knows everything follow his statements—accept his version of events then post stuff on message boards about how SRAM derailleurs cost Andy Schleck the yellow jersey.
I suppose I’m easily ticked off by sloppy analysis these days because I’ve been dealing with so much crap literary analysis of Hawthorne these days . . .
i can see that
i don’t think the dude knows everything, just that he knows a lot about cycling equipment and that’s something i respect. i know a little bit, i put together and work on all my bikes, and am always learning new things. anyone who has more knowledge than me has my respect.
what i meant by you criticizing my opinion was that the only thing i originally expressed was my admiration for the man (the knowing way too much thing), and everything seemed to flow from there.
"Ants don’t worry, they operate like a fantastic team, they accept obstacles and deal with them in a positive manner, they don’t complain and remain positive. An ant doesn’t work on emotion, is proactive and always chooses the ant role."
Crap analysis of Hawthorne?
After he did such a great job on Moby Dick?
"Good thing I never said out loud that I was pulling for France, before this all started." -Mark Blacknell
by Chris Fontecchio on Jul 21, 2010 5:41 PM EDT up reply actions
well, that's a touchy subject actually
had Hawthorne made his positive opinion of Moby DIck public whilst it was being savaged in the reviews . . . Melville’s fiction career could well have been different.
Of course, it might well be that Melville turns out to have really been the epic poet of the Darwinian revolution (e.g. Clarel) instead of the novelist of the turn away from wind and muscle power (Moby Dick and Billy Budd).
I could really use one of those K-Edge chainwatchers
except for on my MTB. Which has the Worst Chain Suck In the World. So bad that it might even suck more than its rider.
"If you're looking up at us, you're scraping bottom." - Chris Fontecchio
i put one of those dog tooth on my mtb
and a chain guard on the outside. i run a 1×9 set up. works pretty well, except when i go upside down, and the one race i did this year, where i dropped the chain 3 times with the rubber side down, other than that, golden, and i ride rigid, so there’s plenty of bumps.
"Ants don’t worry, they operate like a fantastic team, they accept obstacles and deal with them in a positive manner, they don’t complain and remain positive. An ant doesn’t work on emotion, is proactive and always chooses the ant role."
Same set up here.
But of late, I’ve seen some chain drop on bumpy terrain. It’s a chain wear issue.
Still, when it happens it is a pain in the ass to dig it out from behind the keeper. So much so that fishboy and gr have been able to catch back up to me while I do so. :- )
my chain definitely needs replacing.
maybe that’s the problem as of late.
"Ants don’t worry, they operate like a fantastic team, they accept obstacles and deal with them in a positive manner, they don’t complain and remain positive. An ant doesn’t work on emotion, is proactive and always chooses the ant role."
Chainwatchers are super awesome.
But they won’t necessarily end chain suckage on a mountain bike. Usually gear choice and shifting timing are the key in the dirt. On technical descents – bumpy shit, basically – I typically go big ring-big cog. That keeps the suck to a minimum, and if it’s bumpy downhill terrain, you probably aren’t pedalling much anyway.
My measured response:
)(#)!(#!@)(!$) #)(!*#!#! @ $)#(!# !#)(!#! $&$^*&^%8/98879/81928321379!#(Q&#(#&!(*!$
"If you're looking up at us, you're scraping bottom." - Chris Fontecchio
Wow
Just wow.
Nice sig.
"Good thing I never said out loud that I was pulling for France, before this all started." -Mark Blacknell
by Chris Fontecchio on Jul 20, 2010 6:20 PM EDT up reply actions
Re: Chain Suck...
…every description of it I find talks about it happening on the chainrings, not pulley wheels. Same thing though, somehow it wraps all the way around a pulley wheel?

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