Power Data Estimates for the climbing stages

[E_F_]

You're welcome. I am a mechanical engineer with 25 years of experience. At a ~10% gradients rolling resistance and gears add up to 5-7% of the energy budget. Even if the new tech during the last 20 years really moved the needle by reducing it with say 20-40% (would be huge), we are talking about ~1-2% of the energy budget. That's ~5-10 W. This is not the improvement we are seeing. We are talking about an increase vs post-EPO era and pre-2020 numbers of 10-15% or +50 W. That is definitely not due to the mechanical improvements of the bike.

Next you're gonna tell me tiny improvements to the aerodynamics of the bikes themselves don't actually make a huge difference...

 

[topt]

You're welcome. I am a mechanical engineer with 25 years of experience. At a ~10% gradients rolling resistance and gears add up to 5-7% of the energy budget. Even if the new tech during the last 20 years really moved the needle by reducing it with say 20-40% (would be huge), we are talking about ~1-2% of the energy budget. That's ~5-10 W. This is not the improvement we are seeing. We are talking about an increase vs post-EPO era and pre-2020 numbers of 10-15% or +50 W. That is definitely not due to the mechanical improvements of the bike.

mechanical engineer ? Ok; please explain to me how rolling resistance differ based on gradients ? thank you
5-10 watts ? you really need to read up on tyre rolling resistance; there is 4-5 watts difference PER TYRE betwen most modern Conti GP 5000 tubless and the best tubular tyre which is Victoria Corsa that uses latex tube not butyl.
Gearing is totaly impossible to predict but please try a run with 11-23 cassete on 10% gradient;dont you think there is a reason pros dont climb standing up anymore that consumes more oxygen....

 

[topt]

Sponsored I'd think. Nevertheless your trouble remains: W/kg are W/kg - they account for the weight of the bike, the rolling resistance, from the tyres, from the road, the drag on the bike, on the jersey, from the wind. Of course they will never be perfect, as we don't have data from bike computers from back then - but arguing that they can't be perfectly reasonable estimates, that tell us enough to make comparisons to the present isn't fair.

no they dont, they dont compare equipment changes to historical results

what you they they are lying modern bikes climb faster, come on

 

[E_F_]

no they dont, they dont compare equipment changes to historical results

You're just wrong about that. I don't know what more to tell you.

what you they they are lying modern bikes climb faster, come on

Of course the new equipment is (slightly) faster. At least ignoring the fact that in a few cases older bikes may have been slightly lighter than the current regulations allow, which could well be too much of a disadvantage for other improvements to overcome. The thing is though... It doesn't matter. The real comparisons we make are in W/kg.

 

[E_F_]

mechanical engineer ? Ok; please explain to me how rolling resistance differ based on gradients ? thank you

I'm not an expert here, but my guess would be, that when you ride your bike faster your wheels cover more tarmac. They roll more - and so the rolling resistance hinders you more. It's like aerodynamic drag, really.

 

[topt]

I'm not an expert here, but my guess would be, that when you ride your bike faster your wheels cover more tarmac. They roll more - and so the rolling resistance hinders you more. It's like aerodynamic drag, really.

rolling resistance is a constant, gradient doesnt matter; its in my experience also the biggest gain next to gearing (that we cant really measure) compared to Pantani times

 

[Netserk]

I'm not an expert here, but my guess would be, that when you ride your bike faster your wheels cover more tarmac. They roll more - and so the rolling resistance hinders you more. It's like aerodynamic drag, really.

It's because the perpendicular force to the road from gravity is no longer the only component of the vector. Then comes that any given resistance takes less power to overcome the slower you are.

The first one was two sentences, and the third one technically wasn't even a sentence. You have to get your facts straight when you come after me!

You don't have 4 posts in a row in this thread.

 

[topt]

You're just wrong about that. I don't know what more to tell you.

Of course the new equipment is (slightly) faster. At least ignoring the fact that in a few cases older bikes may have been slightly lighter than the current regulations allow, which could well be too much of a disadvantage for other improvements to overcome. The thing is though... It doesn't matter. The real comparisons we make are in W/kg.

how am I wrong, how do they measure W/kg for Pantani and compare it to Pog that inclues changes in equipment ?

 

[topt]

You're just wrong about that. I don't know what more to tell you.

Of course the new equipment is (slightly) faster. At least ignoring the fact that in a few cases older bikes may have been slightly lighter than the current regulations allow, which could well be too much of a disadvantage for other improvements to overcome. The thing is though... It doesn't matter. The real comparisons we make are in W/kg.

no, they werent; Pantani Bianchi from 98 was 7 kg

 

[E_F_]

It's because the perpendicular force to the road from gravity is no longer the only component of the vector.

I think that makes sense to me, though I'm not quite sure it counts a full explanation.

You don't have 4 posts in a row in this thread.

Ah, thought you meant my little chat with @solo80k... Glad I didn't cause you any nuisance!

 

[peterfin]

rolling resistance is a constant, gradient doesnt matter; its in my experience also the biggest gain next to gearing (that we cant really measure) compared to Pantani times

Rolling resistance is approximately a constant per unit of distance covered so in the energy budget won't change with the gradient. That is correct. What does change is the potential energy you need to overcome in order to climb. This start to dominate the energy budget at 2-3% gradients and is +90% at gradients of +10%. Per unit of distance it only depends on the gradient, the gravity constant and the total mass (rider + bike).

 

[E_F_]

Look! Multi-quote!

rolling resistance is a constant, gradient doesnt matter; its in my experience also the biggest gain next to gearing (that we cant really measure) compared to Pantani times

I won't argue with that. It sounds plausible.

how am I wrong, how do they measure W/kg for Pantani and compare it to Pog that inclues changes in equipment ?

They look at the speeds, and calculate how many Watts they would have taken to reach, when taking the gradient, rolling resistance, drag, weight of equipment, and wind into account. Then they divide by the weight of the rider. That gives us our most important measurement of climbing performances. It seems strange for a bike industry insider not to know this.

no, they werent; Pantani Bianchi from 98 was 7 kg

A short while ago someone in this thread mentioned Armstrongs bike being lighter than the current rules allow.

 

[topt]

Rolling resistance is approximately a constant per unit of distance covered so in the energy budget won't change with the gradient. That is correct. What does change is the potential energy you need to overcome in order to climb. This start to dominate the energy budget at 2-3% gradients and is +90% at gradients of +10%. Per unit of distance it only depends on the gradient, the gravity constant and the total mass (rider + bike).

if one tyre is 10 watts faster than the other that means you need to push 10 watts less for same speed, it doesnt have to be complicated

 

[topt]

Look! Multi-quote!

I won't argue with that. It sounds plausible.

They look at the speeds, and calculate how many Watts they would have taken to reach, when taking the gradient, rolling resistance, drag, weight of equipment, and wind into account. Then they divide by the weight of the rider. That gives us our most important measurement of climbing performances. It seems strange for a bike industry insider not to know this.

A short while ago someone in this thread mentioned Armstrongs bike being lighter than the current rules allow.

so than we know how much rolling resistance Pantani tyres had ?

yeah he did, go look at the link

 

[E_F_]

so than we know how much rolling resistance Pantani tyres had ?

We know what tyres he used.

 

[topt]

We know what tyres he used.

thats good and rolling resistance they measured at ?

 

[E_F_]

thats good and rolling resistance they measured at ?

Why don't you go look it up, before you start questioning the calculations?

 

[Netserk]

Why don't you go look it up, before you start questioning the calculations?

Do you think the questions are meant for getting answers?

Look, I know I'm not one to talk because I barely post anymore except to make snide comments or cheap jokes, it's not like I put any effort into my posts these days, but I sincerely believe something needs to be done about the Pogačar thread in the Clinic. People are just posting their every thought there, making 50 posts per minute just to say "ugh this sucks" or "you're all losers for not loving pogacar", fanboys vs haters discourse up the wazoo. The noise-to-signal ratio is insane and it renders the whole thread basically unusable

 

[topt]

Why don't you go look it up, before you start questioning the calculations?

I know damn well there arent any, thats the whole point

 

[Raest]

1. The parametric models used to estimate power outputs are pretty accurate. The guys at lanterne rouge use a model that's based on the Martin et al. model (1998) and they get really accurate values out of it to the point where they have worked as analysts for Visma. As far as I know there are a few sites that used those parametric models to estimate power outputs and they generally do a good job as there is a lot of data available to validate and refine them. I haven't looked into the math too closely though or followed the literature on those but I've seen no evidence to suggest that they are not accurate, both published and anecdotal (e.g. Vingegaard is on record after PdB saying that the estimate power values was very close to his measured output).
2. The marginal gains values are suspect and in particular the drag savings of the aero bikes. They are typically tested in ideal conditions in wind tunnels, and only the frontal drag is measured AFAIK (though I could be mistaken). Another question also is whether they measure drag coefficients with the wheels and disk brakes on or not as disc brakes are more draggy than rim brakes. Even if that's the case though then once you place the rider on the bike then they are going to disturb the flow behind the fork anyway so I am not sure where the saving is made. One other aspect that is not publicised is what tyre is on the bike when it's tested for aero-efficiency. If it's tested with a 23 mm (for example tyre) then the team(s) stick a 28mm on it this will have a negative effect on drag. This is not taken into account when the GCN presenters rave about the aero savings of the bike that paid for their salary. So the supposed benefit of the decrease in rolling resistance from the wider tyre will be offset to some extent at least from it's increased drag.
3. This is entirely empirical but then again there no independent bike comparisons so it will have to do. Cam Nicholls recently did a back to back test comparing a 2013 BNC team machine vs the 2024 model. The 2013 model was marginally...faster.

In general IMO most the supposed marginal gains is marketing spiel which is conveniently used by the teams as a smokescreen for the ridiculous numbers they have been producing over the last few years.

 

[zlev11]

the percentage of rolling resistance as overall resistance when climbing is so small it almost doesn't even matter. it's mostly gravity. if you wanna talk about rolling resistance in TT's then sure, there is something there. but the difference between tires from 25 years ago does not overcome 4 minutes on one of the most doped riders to ever race. to suggest so is laughable and almost doesn't even warrant engagement.

 

[zlev11]

This is entirely empirical but then again there no independent bike comparisons so it will have to do. Cam Nicholls recently did a back to back test comparing a 2013 BNC team machine vs the 2024 model. The 2013 model was marginally...faster.
In general IMO most the supposed marginal gains is marketing spiel which is conveniently used by the teams as a smokescreen for the ridiculous numbers they have been producing over the last few years.

yup, the fastest ever road bikes were made between 2010 and 2017. everything since has just been an exercise to gain back aero and weight from the mess the stupid disc brakes made.

 

[peterfin]

if one tyre is 10 watts faster than the other that means you need to push 10 watts less for same speed, it doesnt have to be complicated

Power consumption due to rolling resistance is proportional to speed so you need to mention the speed as well. If the tires reduce rolling resistance with 10 watts at 60 km/h it will be 3-4 watts at a 20-25 km/h climb speed.

As said before, energy consumed is +90% defined by the potential energy needed to climb the mountain when the gradients are about 10% or more. Weight of the rider+bike is the only factor that matters. The weight of the bike has not changed significantly in 20 years. So watt/kg is the relevant metric to compare riders during that period and it is the rider and not the bike that influences it. All the other stuff might explain a difference of 1-2% but not a difference of 10-15% ... unless there is an electric motor involved of course.

 

[Krzysztof_O]

Power consumption due to rolling resistance is proportional to speed so you need to mention the speed as well. If the tires reduce rolling resistance with 10 watts at 60 km/h it will be 3-4 watts at a 20-25 km/h climb speed.

As said before, energy consumed is +90% defined by the potential energy needed to climb the mountain when the gradients are about 10% or more. Weight of the rider+bike is the only factor that matters. The weight of the bike has not changed significantly in 20 years. So watt/kg is the relevant metric to compare riders during that period and it is the rider and not the bike that influences it. All the other stuff might explain a difference of 1-2% but not a difference of 10-15% ... unless there is an electric motor involved of course.

It's less than 90% though. On a typical Tour climb 1800 m/h of VAM (exactly 0.5 m/s) is usually estimated to be about 6.5 w/kg. The w/kg needed to overcome the gravity alone is exactly half of gravity acceleration in this case: 4.9 w/kg. This means 75% of power is used against gravity and 25% against remaining resistive forces. That being said, I think we are talking about 1-3% improvements here (roughly 30-60 sec on PDB climb), not 10-15%.

 

[Netserk]

It's less than 90% though. On a typical Tour climb 1800 m/h of VAM (exactly 0.5 m/s) is usually estimated to be about 6.5 w/kg. The w/kg needed to overcome the gravity alone is exactly half of gravity acceleration in this case: 4.9 w/kg.

No, you are missing the weight of the equipment.

If bike, clothes, helmet, bidons etc. are 12.5 % of the total weight, it takes 5.6 W/kg to overcome gravity in your example.