Tailwind makes races harder

Jenko <[email hidden]> writes:

The main difficulty in MSR is not the wind or the climbs which,
excluding the Cipressa, are no real challenge

The main difficulty is boredom

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Jenko said:

Discuss.

http://www.ucolick.org/~bjw/misc/rbr/powergap_withvel.png

Jenko said:

Yesterday's MSR was, I believe, the fastest in history at an average speed over
45 km/h (well, I've just found that it was faster in 1990, so make this one is
the second). That was not because the riders decided to just go faster. As
usual, there was a break getting minutes and being caught at the foot of the
Cipressa, which is not particularly early. There wasn't either big horsepower in
the break so, if unlike in 1990 you are willing to rule out some new doping
technique, the extra speed can essentially be attributed to tailwind.

Now, tailwind is hardly noticed when sheltered inside the peloton, it's mainly
the riders pulling in front that benefit from it. This MSR edition was around 7%
faster than average. Translated into power, that's around +15% for the riders
drafting. If you accept blood lactate as a proxy for physiological stress, and
that blood lactate is proportional to W^4, we have a 60% increase in stress due
to tailwind alone. That's big. Being more conservative and assuming a
quadratical relationship between power and "hardness", as TSS does, it's still
+30%. The 7% time reduction doesn't compensate enough for that.

I haven't taken into account so far the impact of climbs, of which there are a
few in MSR, so I'll do:
1. In MSR climbs typically take a different direction than the main road, which
leads to cross and head-winds (not to mention the turns). This is indeed the
case at Cipressa and Poggio. The dominant tailwind effect is less present there.

2. Gravity. It reduces both the speed increase caused by tailwind, and the power
increase caused by the speed increment. The +15% above would become roughly +5%
power (+10% stress) in the MSR slopes

3. Riders go harder at climbs, with power there being around twice the power in
flats, so climbs take a relatively higher toll. However, less than 10% of MSR is
spent climbing. All in all, climbing and flats contribution to normalized power
during MSR is 60% and 40% respectively, with more weight for flats with tailwind.

With these numbers, we can estimate that tailwind yesterday made MSR more than
15% harder, which was noticeable on many riders in the finale, even if there was
not a big selection in the peloton.

But that's not all. The impact of tailwind is not the same for all riders. Since
it leads to a higher contribution of flats to TSS and to a higher increase of
required power also in flats, tailwind gives rouleurs an advantage climbers; big
motors over lightweights; Petacchi, Boonen, Pozzatto and Ballan over Freire,
Cunego, Bettini and Valverde. Props then to Sanchez, Nocentini and Paolini for
their good performances.

Discuss.

Jenko

Seems you're making a couple of false assumptions.

You state that we should equate blood lactate w/ physiological stress,
and go on to make reference to blood lactate being preportional to W^4
(which I'm assuming you are using as a term for wattage requirements.
Can't say definitively, as you haven't defined your terms).

Anyway, what you haven't taken into account is that the very thing
you're blaming for the increase in stress is the one thing that
actually made it less stressful. The tailwind made it easier to go
fast w/ less power, and therefore it is not safe to assume that the
extra speed came at the expense of extra wattage or stress.

You're assumption that the higher speed made the race more stressful is
only accurate IF the speed came at the expense of greater power
requirements. Hell, for all we know, the riders may have thought it to
be less stressful as the higher speeds came w/out any particular
increase in power requirements.

Higher speeds = higher stress only if the speed requires more power to
attain it.

You're making the same argument that a rider who goes 24mph on the
flats, solo... suffers more stress when riding at 26mph when in the
draft, when we all know it's easier to ride in the draft.

Fred

Quoted message said:

Seems you're making a couple of false assumptions.

You state that we should equate blood lactate w/ physiological stress,
and go on to make reference to blood lactate being proportional to W^4
(which I'm assuming you are using as a term for wattage requirements.
Can't say definitively, as you haven't defined your terms).

They are taken from
http://www.cyclingpeakssoftware.com/PowerTrainingChapter.pdf
Anyway, I'm more comfortable with a quadratic relationship between power and
physiological strain, and that's what I use for my conclusions. Sorry I wasn't
clear. What power to strain relationship would you suggest instead?

Quoted message said:

Anyway, what you haven't taken into account is that the very thing
you're blaming for the increase in stress is the one thing that
actually made it less stressful. The tailwind made it easier to go
fast w/ less power, and therefore it is not safe to assume that the
extra speed came at the expense of extra wattage or stress.

But only partially. See
http://www.tourdefrancenews.com/tourdefrance/experts/columns/0,5976,s1-12415-527,00.html?category_id=527
Basically, there are two factors: more rolling resistance and reduced wind
velocity. If we assume that drag reduction when drafting is proportional to
speed, a 7% increase in speed from tailwind results in 5% extra power. Not yet
the 15% I claimed, but I believe the drag reduction to speed relationship to be
superlinear. I can provide some anecdotal evidence to support it, but not
convincing hard data or references.

Jenko

Robert Chung said:

Jenko said:

Discuss.

http://www.ucolick.org/~bjw/misc/rbr/powergap_withvel.png

I remember that thread. But Ben was interested in the speed/grade threshold that
causes a rider to get dropped. In MSR, favorites don't get dropped, they just
pay a different toll because of distance and pace which affects their abilities
up the Poggio and in the sprint. I'm interested in knowing how wind affects
that, or why, despite a light overall tailwind in the Poggio, they went slower
through it, yet the attacker's managed to open a considerable gap.

The data in the link above suggests that tailwind eases the race for breakaway
groups (30% speed increase for a mere 5% power increase). However, when hidden
in the peloton a rider can have a drag reduction over 50%, and the numbers would
work against him.

Jenko

Dumbass -

Ya, tailwinds make a race harder. That's why the easiest races are the
ones that go right into the wind. Good argument.

-RJ

Forgot to mention: Do you know what makes a race really hard?
Downhills. The Red Bull Road Rage is the hardest race in the world.

-RJ

Jenko said:

Robert Chung said:

Jenko said:

Discuss.

http://www.ucolick.org/~bjw/misc/rbr/powergap_withvel.png

I remember that thread. But Ben was interested in the speed/grade threshold that
causes a rider to get dropped. In MSR, favorites don't get dropped, they just
pay a different toll because of distance and pace which affects their abilities
up the Poggio and in the sprint. I'm interested in knowing how wind affects
that, or why, despite a light overall tailwind in the Poggio, they went slower
through it, yet the attacker's managed to open a considerable gap.

The data in the link above suggests that tailwind eases the race for breakaway
groups (30% speed increase for a mere 5% power increase). However, when hidden
in the peloton a rider can have a drag reduction over 50%, and the numbers would
work against him.

Jenko

Jeezus - You're like a dripping tap

Take this from a guy who rode MSR in it's various incarnations
19 [NINETEEN] times

Boredom is the major difficulty in MSR, or in fact any Derby

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