Shifting while accelerating
 

Regarding today's TdF stage, I heard a commentator speculate that AS's chain came off when he shifted under acceleration. I know that with the old derailleurs you were supposed to back off while shifting, but I thought the modern designs claim they can shift under acceleration. Can someone clarify this? What else would have caused the chain to come off?

He might have not shifted the lever all the way, may have inadvertently hit the shift lever like when gripping the hoods tightly.

My assumption is that he tried to shift the FD to the big ring, which of course would have put ridiculous strain on the chain.

It looked like he tried to shift to the big ring. But why would he do that at that point on the climb? It makes no sense.

There was no mechanical failure. The chain didn't break. He missed the shift. But again . . . why? Was it pure brainlock? (If Andy had been riding Di2, it couldn't have happened.)

Shifting under load sometimes happens. How else are you expected to get up the mountain faster if you have strength to do it. You may lighten up a half stroke or so but some big sit down moment is not needed. He had more power to give, and went for a shift.

Looks like his heel may have caught the chain.

I could not tell if he was shifting but he hit a bump in the road that knocked his chain off. My feeling is that he shifted and accelerated at the same time that he hit the bump. The combination knocked his chain off. From the TV camera it was easy to see. But from the other racers point of view it may have not been so easy to see what happened while riding with such intensity and being so focused on riding hard.

The ONLY rider who could use that excuse was Vino, who was the first to respond to Schleck's attack, and was maybe 10 feet behind when the chain dropped.

Contador was still thirty feet behind when Andy sat up and started looking down at his chain dragging on the asphalt. Menchov and Sanchez were another 30 feet back from that, not making any kind of response at all.

There is zero possibility that Contador, Sanchez, and Menchov were unaware of Schleck's issue.

Let's see... Armstrong didn't stop, and Kloden didn't stop, Levi didn't stop, Gesink didn't stop, Hesjedal didn't stop, Rodriguez didn't stop... Seeing a pattern here?

Nobody is saying anyone should have "stopped".

All those riders you mentioned continued at a normal pace up the mountain.

Contador attacked with all his might in order to take as much advantage of the mechanical as possible.

There is a big, big difference. Hopefully you can see that.

As for Menchov and Sanchez, they would not have attacked if Contador hadn't, but once he went they had no choice but to follow.

The difference I see is that Andy CAUSED his mechanical issue while HE was attacking them. They were covering his move. Then Andy screws up. Now everyone is supposed to stop and wait for Andy to catch up, AGAIN! Thank god Cancellara wasn't up ahead or he would have shut down the stage AGAIN. Or course, the Saxo boys didn't have a problem when everyone was stuck behind Frank Schleck's crash. They put the hammer down. That's the only reason Andy is in the position he's in.

:eek:
Logic!

Sorry, carry on with the prosecution.

Either way AS has to take responsibility for what happened which I think he has. He's got SRAM Red and from the video he shifts with his right hand 2 pedal revs before it seizes. It appears as if he was shifting to an easier gear but I'm not sure. If that's true then that would have moved the chain inward which could explain the chain hopping off the small ring. I don't see where his foot hits the chain but it's a little fuzzy. I do see the bottom of his chain bouncing like crazy and his rear derailleur move forward moments before the lock up.

I've got Red, about to put it on a new frameset, so I'd kinda like to know if that's a problem (not like I'm generating the kind of power they are but one can hope). Cheers

Hmm, not a bad theory.

I watched the video several times and I didn't see his hands move at all. I don't know why people are saying he was shifting.

It could have been accidental from gripping the hoods. All it takes is a finger to shift. Not the whole hand to move. Especially if the lever is only moved partially. But it could have been the heel as well. What ever it was, something happened and it was most likely caused by something Andy inadvertently did.

Check out the front shot of Andy two pedal revs before he locks up. His right index finger moves the shifter inward about 1-1.5". It's fast. Might have to have HD and go frame by frame to catch it. GL

Hmm. But the chain came off the front. How would shifting the rear cause the chain to pop off the front?

I grabbed an unmounted SRAM Red shifter and verified that a single click, move to smaller cog, is barely visible from the front. A double-tap to shift to a larger cog is about 1-1.5" so I'm now sure he was shifting to an easier gear or two. I could guess what happened afterwards but I'd be wrong.

I maybe be incorrect, but it appeared to me that he was already accelerating in the big ring for quite some distance. Other than that, I have no explanation other than just simple misfortune.

The side shot they highlighted on tv showed he was in the small ring. You can see the chain lines go below the large ring outline.

After he popped the chain he tried to move the front derailleur outward (driving the left shifter all the way) to get the chain back up to any ring but Bob guessed it went all the way over the big ring. Then when he fixed it the first time you can see before he got his feet in the pedals they spun backwards and popped the chain back off. Just a series of bad situations.

At this time I don't blame Red but as soon as I can get on my bike I'd like to see how many pedal revolutions it takes for the chain to switch cogs. If it's less than two then either Andy was putting on so much torque that it prevented the shifter from moving right away or something mechanical didn't work right at the worst possible time. Cheers

Lennard Zinn Analysis
 

Here's Lennard Zinn's analysis: http://velonews.competitor.com/2010/...ome-off_130090

^Sounds like if you have Red, you might want to look into the upgraded RD. Is that something available to the public yet?

Contador's mechanic modified Contador's SRAM Red rear derraileur with oversized pulleys, different cage (no loop as mentioned in the velonew article linked above); maybe Saxo'x mech should modify Andy's too:
http://imgur.com/0IHBk.jpg

http://imgur.com/mehyA.jpg

wow that's a clean ****ing chain.

looking at that chain, seems to be some scuffing on it, the type caused by sandpaper. Any reason they may do this? Smooth the link edges or something? Does not look to be manufactured or wear marks.