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Power Data Estimates for the climbing stages

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Netserk

Netserk

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I don't think so. It's more difficult to compare, and the different stage designs matter here.

Enrico Zaina set the record on both Fedaia and Pordoi in the same stage. Stage 20, 17 days after the only rest day. This profile:

yKJjEDt.png


I've mentioned the 1995 Alpe d'Huez stage before. Hard stage and decent pace on CdF, still gung ho on Alpe.
 
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Red Rick

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Netserk said:
I don't think so. It's more difficult to compare, and the different stage designs matter here.

Enrico Zaina set the record on both Fedaia and Pordoi in the same stage. Stage 20, 17 days after the only rest day. This profile:

yKJjEDt.png


I've mentioned the 1995 Alpe d'Huez stage before. Hard stage and decent pace on CdF, still gung ho on Alpe.
Click to expand...
Lead group was 2 minutes off the 2015 CdF record? And I don't know how far the Pantani group was behind cause of the 1995 CdF lead group all finished over 2 minutes down on the Alpe.
 
Red Rick

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Nick2413 said:
What were the actual numbers for Vingegaard’s TT? Were they godly by overall standards or just week 3?
Click to expand...
Someone on /r/peloton actually ran the math in depth and found it was more likely to be ~6.9 for the climb

Over the last few days, we've all seen crazy estimated power numbers being thrown around for Vingegaard's ascent of Domancy during the Stage 16 TT. 7.6 W/kg is a popular number, but I've seen comments here and elsewhere claiming 8 W/kg as well.

The use of a TT bike, disc wheel, skin suit, aerobars, etc. make power estimation here much more difficult than on a long, sustained alpine climb where speeds are lower and aero matters commensurately less.

The trifurcation of the climb also makes power estimation tricky:

Segment 1, 1.45 km at 7.8%, was ridden by Jonas at 25kph. Here, aero drag makes up about 13% of total power demands.

Segment 2, 1.1km at 10.6%, was ridden by Jonas at ~20kph. Here, aero drag makes up about 6% of total power demands.

Segment 3, 3.5km at 5.2%, was ridden by Jonas at 32kph. Here, aero drag makes up about 25% of total power demands.

We can see, then, how small changes in assumptions on CdA, for example, might have large repercussions on our final numbers, especially over the shallower, high-speed Segment 3.

I thought it might be helpful to put pen to paper to show some of the raw calculations and how varying inputs affect W/kg estimates. To that end, I've put together the following presentation walking through my own process for modeling Jonas' estimated power for the Domancy climb.

___________________________________________________________________________

https://preview.redd.it/12oylsgohcd...bp&s=fdca87ee0c5fe5c02aa7f8775abcfb9d6885efc3

The course as-ridden is largely the same as shown on La Flamme Rouge and other sites; there was a small change in the location of T2 that reduced total elevation gain by ~11 meters, but this effect is small over the 6.05km course.

https://preview.redd.it/24eylm4whcd...bp&s=a2804f2cfd0f9eb6e982ace863c5888a9560b168

Power demands are made up of three factors: air resistance, rolling resistance, and gravity. The rider must meet these demands to climb at a given speed, and there is some power lost through the drivetrain.

https://preview.redd.it/7b1zwia3icd...bp&s=65c815e321e3b71b6bbe3ba3721c4ed8f05d1b9c

Air resistance, as we will see later, is more important on this climb than usual given the shallow back-half of the climb and the TT equipment used by most competitors. To estimate air density, I used local weather data from the time of the Stage 16 TT. FWIW, Neilson Powless' Strava has the temperature for the climb at 91F as well.

https://preview.redd.it/zn4pznjjicd...bp&s=5e41e65217f31a22a0e770c5e04a3811668da4f9

Rolling resistance is relatively straightforward. Bicyclerollingresistance.com publishes Crr test data for most top tires; I've seen bike reviews for Jonas' S5 that mention his use of Vittoria Corsa Speeds, so I assumed he put the same tires on his P5. PCS provided Jonas' weight and Escape Collective, helpfully, provided an estimate for the weight of his P5 in an article written before the Stage 16 TT.

https://preview.redd.it/92bq5yjvicd...bp&s=345cc07cc2f520e89d04c4e2d262b4772ca0596f

There is a significant aero difference (especially as speed increases) between climbing on aerobars and climbing on the bullhorns. I reviewed the GCN broadcast to estimate Jonas' position throughout the TT. The biggest question mark is between 5.2km and 4.6km. At some point off-camera, he transitions to bullhorns, but it is not clear when. I modeled Segment 1 with a CdA of 0.20, reflecting his use of aerobars, and Segment 2 with a CdA of 0.30, reflecting his use of bullhorns during the steep sections.

https://preview.redd.it/zz1020h6jcd...bp&s=42d1fff9c91ba1507de058a31686e5ad4621d92d

Crucially, after the T3 hairpin, Jonas is never again seen on the bullhorns. As his speed increases to ~32kph, he gets back into the aerobars and stays there. I modeled this whole Segment with a CdA of 0.20.



https://preview.redd.it/bwitzgwbjcd...bp&s=d44769e268287119a577d7bf5d125264f1ea376e

Doing the math for the above gets us 7.0 eW/kg over the 13:21 effort.

Now let's stress-test our numbers.

https://preview.redd.it/hxcu6ydpjcd...bp&s=fc1516479527fdd9e80d32019cf7dda31c17210c

If we make Jonas' CdA ~15% worse for each case, we see an immediate impact on the results - particularly in Segment 3. Our power estimate moves up by 0.2 eW/kg for that shallower section. His total power over 13:21 is now estimated at 7.13 eW/kg.

https://preview.redd.it/yj5euk81kcd...bp&s=cb97d8e613c3a5a2cacd8967420606deb3fb4c66

Here we model a much earlier transition to the bullhorns for Jonas on the Domancy climb. This does not have a large effect on total power estimate.

https://preview.redd.it/tx7iwr47kcd...bp&s=aa0f72680692b29d142cb26be673063d61e1c5ad

Here is the "new" Segment 1 and Segment 2, reflecting the modeled earlier switch to bullhorns.

https://preview.redd.it/648pcfhbkcd...bp&s=5a5e5bfafd931847376078550acd36d456b34117

Is a CdA of 0.20 reasonable? I think so, but this is the number to be taken with the biggest grain of salt. Noted aero specialist Remco Evenepoel, with a similarly small frame to Jonas, has an estimated CdA of ~0.17. In an interview with a Belgian newspaper, Wout van Aert said his CdA is around 0.22. It seems reasonable to estimate Jonas as somewhere in between Remco (and his 'aero skin') and the much larger WvA.

https://preview.redd.it/sqtlzzsskcd...bp&s=7323cb4f93f9bd7812dd95ed1553590b2664eb90

Is a road bike CdA of 0.30 reasonable? Again, I think so for a small-framed person like Jonas. I also went back and used Neilson Powless' published power data for the Domancy climb to back into his CdA on his Cannondale road bike, and got roughly 0.30 as well.

https://preview.redd.it/yeyat5g0lcd...bp&s=91b08c98bced227092175092110111d88c108bb4

My modeling puts the Stage 16 TT for Jonas as follows: Start to T2 (~19 minutes) ridden at roughly 6.0 W/kg, with a final 13:21 at 7.0 W/kg. Is there any precedent for these kinds of numbers? In fact, there is - the Puy de Dome climb on Stage 9 was modeled by others as a 6.2 eW/kg effort for 20 minutes followed by a 7.0 eW/kg attack by Pogacar for 14:50. This closely matches what I model Jonas' Stage 16 TT effort at.

https://preview.redd.it/tjgsjpdjxcd...bp&s=c9db91c8c1e206f5a0a38f3f3f08724d46e36deb

EDIT: Putting in Pogacar's time from T2 to T3 (minus 15 seconds for a bike change), my model predicts a 6.70 eW/kg effort. This puts Pogacar on a bad day, but still a pretty good one for us mere mortals!.

Putting in WvA's time from T2 to T3, my model predicts a ~6.3 eW/kg. This seems reasonable to me for a 78kg rider up a 9% climb. Note that in raw watts, that's 489!

Also, my model predicts Powless would have to do 6.36 W/kg to climb from T2 to T3 as fast as he did. This is slightly higher than the W/kg he actually rode based on the power data posted on his Strava. This supports the general accuracy of the model; if anything, it may read too high.

https://preview.redd.it/qco1n7kdlcd...bp&s=949b3d051ee57ae98397e3427f84cd4a0e615d74

Here, I try to stress-test my model by using a completely different methodology. Relative power measured through VAMw/kg has long been used by those without a power meter to turn straightforward VAM numbers into a W/kg estimate (it was made particularly famous by Michele Ferrari, but we won't go there). If we use VAMw/kg to estimate relative power for Jonas' effort, we get ~6.9 eW/kg. But wait - we can double-check this estimation methodology against Neilson Powless' published power data. Comparing his predicted VAMw/kg with his power as ridden shows an error of 1.3% (low). Applying this error to Jonas' 6.9 eW/kg gets us a final estimate of 6.97 eW/kg.

https://preview.redd.it/3vcg8f3dmcd...bp&s=4b20339dacb14d20c3df24b460efeec6448b3960

So how can we get to 7/6 eW/kg, for example, with this model? If we assume a CdA of 0.37 for the entire climb ridden as one segment, Jonas' eW/kg is now 7.6. Note that this CdA more than doubles the power we estimate going to aero drag, largely due to the last 3.5km ridden at 32kph.

https://preview.redd.it/2bylzhglmcd...bp&s=ddf4e69db353633039e71d1c49e55eb94b6df36d

Finally, as an aside, we can also use this model to project the effect of a bike change in Pogacar's case. Here, I estimate his climbing Colnago at 7kg and his TT bike at 9kg (rumored to be the case). I kept largely the same CdAs and followed largely the same methodology, although to find the time gain/loss I held power constant at ~6.8 W/kg across the effort to back into velocity.

By this estimate, Pogacar's bike change cost him almost 30 seconds, with about 60% of that delta coming over the last 3.5km, which was ridden at 29-31kph, where aero starts to make a large difference.

Let me know what you guys think - I set up my model in Excel to be able to quickly see the results from changing parameters, so I'm happy to stress-test other assumptions.

Thanks!
Click to expand...
 
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Netserk

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roundabout said:
I don't think it makes sense to compare Vingegaard climbing mostly (for approximately 10 minutes out of 13.3) in the TT position to what happened on the Puy de Dome unless one makes an explicit assumption that power loss in the TT position is zero.
Click to expand...
He assumes no power loss when evaluating Pogi's bike change:

"Finally, as an aside, we can also use this model to project the effect of a bike change in Pogacar's case. Here, I estimate his climbing Colnago at 7kg and his TT bike at 9kg (rumored to be the case). I kept largely the same CdAs and followed largely the same methodology, although to find the time gain/loss I held power constant at ~6.8 W/kg across the effort to back into velocity.

By this estimate, Pogacar's bike change cost him almost 30 seconds, with about 60% of that delta coming over the last 3.5km, which was ridden at 29-31kph, where aero starts to make a large difference."
 
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Riek s

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Netserk said:
He assumes no power loss when evaluating Pogi's bike change:

"Finally, as an aside, we can also use this model to project the effect of a bike change in Pogacar's case. Here, I estimate his climbing Colnago at 7kg and his TT bike at 9kg (rumored to be the case). I kept largely the same CdAs and followed largely the same methodology, although to find the time gain/loss I held power constant at ~6.8 W/kg across the effort to back into velocity.

By this estimate, Pogacar's bike change cost him almost 30 seconds, with about 60% of that delta coming over the last 3.5km, which was ridden at 29-31kph, where aero starts to make a large difference."
Click to expand...
I assume that in itself is also an error, since you loose power in that more compromised position. 5% isn't a wild performance loss on the TT bike (guess for most pro's they way it out between aero and power). Ofcourse we have no idea on how much power someone looses since it is very specific to body type and position choice. but i assume Pog has an idea how much it differs for him.
 
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Nick2413

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Riek s said:
I assume that in itself is also an error, since you loose power in that more compromised position. 5% isn't a wild performance loss on the TT bike. Ofcourse we have no idea on how much power someone looses since it is very specific to body type and position choice. but i assume Pog has an idea how much it differs for him.
Click to expand...
Agreed he must be pushing more W on the road bike but re bike changes I’ve always wondered if power losses on a TT bike aren’t as low as road bike at the end of a TT given it’s more position related than fatigue.

Maybe overthinking it, but say he can push 7W/kg on the road bike fresh and 6.5W/kg on TT fresh, then late into a TT that 7 would go down but would the 6.5 remain the same if staying on TT bike since he’s still physically capable of 6.5? (I know they say 6.8 above but for purposes of theory)? I know he rode the final climb harder than rest of stage but there would still be some fatigue limiting the super high output on road bike, rendering the main benefit of the road bike to be weight loss.
 
Red Rick

Red Rick

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roundabout said:
I don't think it makes sense to compare Vingegaard climbing mostly (for approximately 10 minutes out of 13.3) in the TT position to what happened on the Puy de Dome unless one makes an explicit assumption that power loss in the TT position is zero.
Click to expand...
Nick2413 said:
Agreed he must be pushing more W on the road bike but re bike changes I’ve always wondered if power losses on a TT bike aren’t as low as road bike at the end of a TT given it’s more position related than fatigue.

Maybe overthinking it, but say he can push 7W/kg on the road bike fresh and 6.5W/kg on TT fresh, then late into a TT that 7 would go down but would the 6.5 remain the same if staying on TT bike since he’s still physically capable of 6.5? (I know they say 6.8 above but for purposes of theory)? I know he rode the final climb harder than rest of stage but there would still be some fatigue limiting the super high output on road bike, rendering the main benefit of the road bike to be weight loss.
Click to expand...
On the TT bike you can just switch to climbing on the handlebars if it gets too steep. On the handlebars the power difference shouldn't be big at all, the difference should mainly be bike weight, and Vingegaards TT bike was probably not much heavier than a road bike.

However, power loss in TT position is definitely a thing, but it's also an added edge a rider can have, especially if it it affects fatigue later in the ITT. Most riders way underperformed the numbers they would do had it been a 6km Combloux MTT on a road bike. Vingegaard is basically the only one that got close to his other numbers.

In contrast to Vingegaard is Pogacar, who probably had a heavier TT bike, causing him time loss on the first climb, who probably had more loss of power in TT position and thus had to push harder on the flat, in addition to losing time in every corner, and then on top of that had to do a bike change as well as just not having his best day.

Netserk said:
He assumes no power loss when evaluating Pogi's bike change:

"Finally, as an aside, we can also use this model to project the effect of a bike change in Pogacar's case. Here, I estimate his climbing Colnago at 7kg and his TT bike at 9kg (rumored to be the case). I kept largely the same CdAs and followed largely the same methodology, although to find the time gain/loss I held power constant at ~6.8 W/kg across the effort to back into velocity.

By this estimate, Pogacar's bike change cost him almost 30 seconds, with about 60% of that delta coming over the last 3.5km, which was ridden at 29-31kph, where aero starts to make a large difference."
Click to expand...
It may not have cost Pogacar 30s because of Pogacars power loss in TT position, but if we contrast it to Vingegaard's power loss in TT position it definitely explains a large part of the delta. In the final section the s/min he loses is even bigger than in the KOM section where Pog just ships 15s changing bikes.
 
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Netserk

Netserk

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roundabout said:
I understood the part you quoted to mean the effort from the bike change to the end.

It would not make sense otherwise considering that Vingegaard's power output for the first part was estimated at 6 W/kg,
Click to expand...
Yes, but he explicitly assumes no power loss when in a TT position from the top of Domancy to Combloux. Which is obviously wrong, as Adam Yates wouldn't have been standing on the pedals if so.

WUx3rMg.png
 
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