Climbing and W/Kg

I have a question about climbing and W/kg. At what gradient does W/kg dominate over absolute watts? There must be some physics answer of course tho it’s out of my depth.
I used to just assume it always matters, but I know big power riders can climb w the best of them (like WVA) on single digit gradients but featherweights take the cake when it’s double digit. Does anyone have a link to some article that sheds light on this question: when does it really matter?

It depends on gradient & speed. Aerodynamic drag increases with velocity squared.
Try a calculator such as this one: http://bikecalculator.com/
And you can play around with speed, gradient, weight etc and get a graphical representation of how the forces compare.

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I don’t think that’s really a matter of gradient that much…

Ofcourse the steeper the hill, the more W/kg is needed to maintain a certain speed. A study done by Cervelo suggests that at everything over a 6% incline, weight trumps aero. For pro’s it might be a slightly steeper incline even just because they climb at higher speeds so aero is more important for longer. So perhaps that’s already the article that you’re looking for but I can’t find it right away.

But the reason there are only a few “costauds” that climb with the climbers is different I think. Let’s assume the avg. incline is 7.5%, then the aero disadvantage for the bigger rider won’t be that much either so we can discard that part of the equation.

If say a 60kg climber puts out an all-out attack of 20’ and they do 380W, that’s 6.33W/kg. As long as the 75kg rider can then produce 475W for 20’, they should then be able to go with the attack.
I have a screenshot of Wout’s Garmin from I think a 2020 training camp where he did a 20’ test within a 4h+ ride and averaged 471W (I believe in shape he’s like 75-76kg so about 6.28W/kg).

And I had one somewhere of Ganna’s Garmin or whatever indicating he did some sort of 12’ test at 517W (PCS states 83kg I believe so 6.23W/kg). These two are about the most powerful guys with regards to absolute power there are, maybe followed by an even bigger boy like Max Walscheid.
To me it seems like there a lot more guys in the lower 60kg range that can do 380-400W than there are guys in the 75-80kg range that will do >=475W for 20’. Possibly due to their lower weight, the lighter guys can snap more uphill as well while the big guys have to mostly TT their way up.

And then there’s methanol fueled Lance Armstrong who did 500W for 30’ on the Col de la Madeleine at about 73kg.

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Where are these numbers from? It sounds impossible this ever happened.

Regarding the overall question.
There are a few factors. Gradient definitely is one. The cervelo study that was quoted earlier suggests 6%. I recall they meant at pro speeds (so likely less for amateurs).
However, aero always matters and hardly any climb is equal gradient throughout.
So on flatter sections or headwind sections, you’d benefit from going more aero, while on steep and/or tailwind sections, aero will matter less.

What I do is keep my pedaling out of the saddle for the steep and calm parts, and try to maintain low and aero for the rest.

Also, power should be adjusted to the speed you go. The slower you go, the more will additional power do for you.

Ultimately however, on a 6% climb (and anything above that), your weight will be a big an relevant factor. Most major climbs in the Alps are between 5 and 8%, and you see how well the light guys fare there.
Hardly any big climb is double digits for extended periods.

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I know Lance mentioned it on the podcast he did with Peter Attia. 7 w/kg, where 10% come from EPO according to Lance.

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Great Podcast! But wasn’t it 20% that come from EPO?

Lance said 10 at least for him. I listened to it too. Cool podcast and mind boggling to think he smashed away 500w for 30 like it’s easy!

So back to the question tho, holding all factors constant besides absolute wattage and body weight of two riders, I would want to know at what gradient does the feather weight have higher speed than the big guy.

Y axis: speed
X axis: gradient
Two curves:

  1. curve of say 5.25w/kg for 75kg rider (394w)
  2. curve of 5.25w/kg for 60kg rider (315w)

Question: at what gradient do these curves intersect? What do these curves look like across relevant gradients (0-15%).
This would be super interesting if someone has some spreadsheet with that suggested bike calculator from @adrian_r and we could plot these things.

On every podcast with LA I’ve heard lately including Peter Attias recent one he drops that in, the figures I remember are 495w for near 30mins.
178 - Lance Armstrong: The rise, fall, and growth of a cycling legend - YouTube

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Yeah 500 on EPO, 450 clean. I guess that’s around where WVA is based in the pic @JoeriN shared

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Thanks for clearing that one up

I have yet to listen to a podcast with LA (likely not happening anytime soon).
500 for 30 is still hard to believe, but why not.

Wout is officially listed 78kg, would be interesting to see how much his FTP drops when he gets in GT-shape.

Back to climbing:
Another factor with raw watts vs W/kg is that the weight is always a naked rider without gear.

Example:
Rider A: 300W / 60kg (bodyweight) - 5W/kg
Rider B: 370W/ 80kg - 4.63W/kg (-7.4%)

Rider A has 1kg of clothing (incl helmet and shoes), 2kg of gear (spares, water, head unit), and a 7kg bike
Rider B has 1.2kg of clothing (helmet, shoes a little larger), 2kg of spares (should be identical), and a 7.5kg bike (quite a large penalty for the larger size).

So system weight for rider A would be:
60+1+2+7 =70kg
Rider B: 80+ 1.2+ 2+ 7.5 = 90.7kg

Relative system Power:
Rider A: 300/70 =4.29W/kg
Rider B: 370/90.7 =4.08Wkg (-4.9%)

What all this convoluted stuff was meant to show is that the real weight of System is much heavier than a naked rider, and will likely differ little between riders of different weight. Therefore, relativ system power is closer together than it might seem at first glance.

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True about system weight. Given they can make bikes safe and below UCI limit, at the pro level it should be approximately the same despite frame size (I suspect at least)

I plugged in valued at 5.25w/kg for a rider 60kg and 75 kg and kept changing gradient from 0-15%. The heavier rider had higher speed the whole time (tho they converged as gradient increased). Does this seem right or am I missing something?

If W/kg stays equal, the higher absolute wattage will always be faster. The difference will become ever smaller the steeper the gradient.
I think the question at hand is rather, where is the point where the heavier/ stronger rider gets dropped by the lighter rider, with a higher W/kg.

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The differences in bike weight in the pro peloton should be absolutely minimal. 200g or so. Also, a heavier rider is not necessarily taller.
Cavendish, Pogacar and Alaphilippe are all about the same height, but built very differently. Same for say Wout and Froomey.

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Try this one:
https://www.gribble.org/cycling/power_v_speed.html
You can see a graphical representation of how much power you need for a certain speed and gradient. The graph will show you how much is aero drag, rolling resistance & gravity. As with everything, how good the numbers you get are, relies on the input.

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That’s probably only true for shorter efforts.
If we are to believe that approx. 100grams of carbs is the maximum intake regardless of body weight.
That’s only about 450 calories IN per hour.

So two athletes with different body weight will take in the same amount of calories, but their output will be vastly different. So the longer the race goes on, the bigger the deficit for the heavier rider, and probably less able to perform at their peak on a “final climb”.

The piece that you are missing is the CdA of the riders. If w/kg are the same, then the rider with the higher w/CdA will have the higher speed until the gradient increases, and the speed becomes so low that CdA no longer matters. After that point, then the riders will have the same speed regardless of the gradient.

The power required to climb at a certain speed equals the power required to overcome the rolling resistance of the road, plus the power required to overcome the wind resistance, plus the power required to overcome the gradient of the hill.

This graph simplifies things at a 5% gradient and also assumes the CdA is the same for the smaller rider and the bigger rider, which we know likely isn’t true. I would assume the two riders with the same w/kg on a 5% gradient, factoring a lower CdA for the smaller rider, would break even around 4w/kg effort on a 5% gradient. The steeper the gradient, the higher the w/kg would need to be to break even.

So when you get world tour riders going up a 5% gradient full gas at 6w/kg, then the Wout’s, Rohan Dennis’ and Ganna’s of the world can actually be faster than pure climbers with higher w/kg.For the average cyclists, this happens at the lower gradients.

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I wouldn’t be surprised if at a certain gradient v the shape of the rider v where the muscle mass is located etc come into play but a larger rider does seem to be able to go faster in the right conditions going by a few TdF examples.

Or was the Hot Fanta actually something else :rofl:

Tour de France – Re-Cycle: When man mountain Eros Poli conquered Mont Ventoux - Eurosport

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MA Lopez 6w/k for 50 minutes at altitude in the Gamoneiteru…Non of the big/powerful guys can do anything similar.