To significantly increase your average speed over a short distance requires a big effort, it would be simple if they knew at the start, but if your speed needs to increase between short amount of time of the stage winner crossing the line and your current point on the road, then it's too much effort to make it worthwhile.
This is all supposition and guesswork on my part, I admit I don't know how it actually works in practice, but it seems obvious to me that they must have a reasonable idea in advance of when the winner is going to finish to be able to come in so close to the cutoff time.
Also, doesn't the coefficient alter not only on the stage but the actual average speed of the stage winner? So that leaves even more room for cocking it up.
Yeah, it goes up by 1% for every kilometre per hour faster the winner rides. For Friday's stage, that means they would have had around 4 minutes less time to reach the finish if the winner had got there 1km/h faster than expected. On Thursday, if the winner had been 1km/h faster than expected, it would have reduced the cutoff time by around 9 minutes.
Given that they were only 17 seconds outside the cutoff on Friday, and a bit over two minutes outside the cutoff on Thursday, I'd say it looks like they had a pretty good idea what time the winner was expected in. Those are tiny margins in the context of the length of the race each day.
Like I say, it's only supposition and guesswork, but this is what the figures suggest to me. And I don't know how feasible it would be for a lone rider or a small breakaway group to ride 1km/h faster than expected over a mountain stage, but surely it would take a significant amount of extra effort on their part? I know the peloton sometimes ride that much faster than expected on flat stages, but that's a whole different ball game.
Edit: Just spotted your last reply- I didn't think anyone in the bus sprinted for the line on Friday, didn't Magnus Backstedt even comment on it? something like "I'm surprised they didn't make an effort to sprint for the line considering they were only 20 odd seconds short of the cut off"
Well, maybe "sprinting" is too strong a word for it but it looked to me watching it on telly like Cav was at the front of the pack and among those pushing hard to get to the line as quick as possible. But I bow to Maggie's superior knowledge and understanding of these things.
d.