# going faster with same power



## notwist (Feb 26, 2009)

Consider two people with similar FTPs (w/kg) do roughly the same effort up a hill (same steady power) however one person is clearly faster reaching the top first. What things affect their speed aside from CDA and equipment? Does cadence (for example) affect speed or is it all about power output?


----------



## CBS78 (May 29, 2012)

If weight(rider + gear) and power numbers are truly identical the only other factors would be aero drag and rolling resistance. 

Cadence would not matter in speed if the watts were truly the same. 200 watts is the same at 10 rpm and 100 rpm. Now the higher cadence would be more efficient and keep your legs fresher but if power is the same a change in cadence does nothing for performance other than fatigues your body differently.


----------



## Cableguy (Jun 6, 2010)

Hills do not have perfectly constant gradients, and it's more speed effective to apply additional power when the gradient increases and less when the gradient decreases. So if two near identical people ride the same hill at a steady average 250w, the person who maintains a constant 250w will go slower than the person who varies power strategically but slightly from 260-240w depending on the relative gradient. Yet you would say both maintined a fairly steady average of 250w.


----------



## Poncharelli (May 7, 2006)

CBS78 said:


> If weight(rider + gear) and power numbers are truly identical the only other factors would be aero drag and rolling resistance.
> 
> Cadence would not matter in speed if the watts were truly the same. 200 watts is the same at 10 rpm and 100 rpm. Now the higher cadence would be more efficient and keep your legs fresher but if power is the same a change in cadence does nothing for performance other than fatigues your body differently.


This^^.

As a side note, I've always heard that if you have two riders with FTPs of 4 W/kg, and one rider weighs 170 and the other weighs 140, overall, the larger rider will demolish the smaller one. 

That's probably because the road doesn't always point uphill. When the road is flat, the larger rider has a NP capability of 310W while the smaller rider has 250W per their FTP. That's a HUGE difference in power.


----------



## asgelle (Apr 21, 2003)

Poncharelli said:


> When the road is flat, the larger rider has a NP capability of 310W while the smaller rider has 250W per their FTP. That's a HUGE difference in power.


First what is NP capability? Second, how are these numbers derived? I can't understand why someone's long term NP would be greatly different from their FTP. After all the number of legitimate "NP busters" is still very small.


----------



## Jay Strongbow (May 8, 2010)

CBS78 said:


> If weight(rider + gear) and power numbers are truly identical the only other factors would be aero drag and rolling resistance.


Close enough but if you want to get pedantic about it drive train and bearing friction too. Barely measurable and insignificant (except in extreme cases) but they are factors.


----------



## serious (May 2, 2006)

notwist said:


> Consider two people with similar FTPs (w/kg) do roughly the same effort up a hill (same steady power) however one person is clearly faster reaching the top first.


Strictly speaking, 2 people climbing with the same power and having the same W/KG numbers and the same equipment will basically reach the top at the same time. But if you introduce small differences, they could amount to seconds in a longer climb, hence you always have a winner!


----------



## Doc_D (Mar 16, 2006)

serious said:


> Strictly speaking, 2 people climbing with the same power and having the same W/KG numbers and the same equipment will basically reach the top at the same time. But if you introduce small differences, they could amount to seconds in a longer climb, hence you always have a winner!


This is not true....Assume you have a 100 pound rider with a 4 w/kg output and a 200 pound rider with a 4w/kg output. At lower grades the 200 pound rider would be much faster. If you play around with one of the calculators you'll see it's only when the grade hits a certain percentage that the lighter ride is equal or faster.

This drives me nuts when people use w/kg as a measure of performance. It's fine for comparing you to you. It's useless for comparing two different riders. Over a flat ground a 200 pound rider with a 3 w/kg FT will DESTROY a 120 pound rider with a 4 w/kg FT.

4 w/kg does not always equal 4 w/kg. Total power is a huge part of the equation. It's a real sore spot for me that total power is almost always discounted. Personally I believe in the real world, many times, total power is a better predictor of performance than w/kg. Neither is a good predictor without also taking the course profile into consideration.


----------



## asgelle (Apr 21, 2003)

Doc_D said:


> This is not true....Assume you have a 100 pound rider with a 4 w/kg output and a 200 pound rider with a 4w/kg output. At lower grades the 200 pound rider would be much faster. If you play around with one of the calculators you'll see it's only when the grade hits a certain percentage that the lighter ride is equal or faster.


I can do that, analyticcycling.com defaults except as noted
100 lb rider + 20 lb equipment, CdA=0.25, level ground 4 W/kg -> 10.15 m/s

200 lb rider + 20 lb equipment, CdA=0.25, level ground, 4 W/kg -> 12.7 m/s

200 lb rider + 20 lb equipment, CdA=0.5, level ground, 4 W/kg -> 10.18 m/s

200 lb rider + 20 lb equipment, CdA=0.75, level ground, 4 W/kg -> 8.94 m/s

So unless you say something about CdA, you can't tell who will be faster. Further, while you can believe anything you want, the published data shows that W/kg is a much better predictor of performance than W even for level ground (due to the alometric scaling of CdA).


----------



## Doc_D (Mar 16, 2006)

asgelle said:


> I can do that, analyticcycling.com defaults except as noted
> 100 lb rider + 20 lb equipment, CdA=0.25, level ground 4 W/kg -> 10.15 m/s
> 
> 200 lb rider + 20 lb equipment, CdA=0.25, level ground, 4 W/kg -> 12.7 m/s
> ...


You seem well versed. Is there any data out there showing what the average CdA is of different weight riders? My gut feeling is that since people are 3 dimensional objects their frontal area's (and likely the CdA) increase in proportion to weight in a non-linear fashion. I'm guessing it's cube root type of function which means that a 200 pound rider really doesn't have all that much more frontal area than a 120 pound rider. But i have absolutely no data to confirm that, so I'll admit I'm just talking out my butt. I'll have to do some research and see if I can figure it out.


----------



## asgelle (Apr 21, 2003)

Doc_D said:


> You seem well versed. Is there any data out there showing what the average CdA is of different weight riders? My gut feeling is that since people are 3 dimensional objects their frontal area's (and likely the CdA) increase in proportion to weight in a non-linear fashion. I'm guessing it's cube root type of function which means that a 200 pound rider really doesn't have all that much more frontal area than a 120 pound rider. But i have absolutely no data to confirm that, so I'll admit I'm just talking out my butt. I'll have to do some research and see if I can figure it out.


Topica Email List Directory


----------



## spade2you (May 12, 2009)

Ride MORE. Study LESS.

As Cableguy mentioned, hill gradients aren't uniform and pace can indeed vary. On top of that, two riders will have 2 different power meters, so who knows how precise and accurate they are.


----------



## Srode (Aug 19, 2012)

FTP is about long runs 20 minutes or more. On a hill that requires less time to climb it's more about VO2Max probably which doesn't necessarily follow FTP - and it can be trained. All else being equal the Winner is the rider with the higher VO2Max on a 3 to 5 minute hill, maybe longer. If they are really putting out the same power all the way up, then it's rolling resistance, aerodynamics or weight of the bike probably.


----------



## tom_h (May 6, 2008)

FYI,
Why is Weight So Important in Cycling? Part*1 - Posts - TrainingPeaks Blog
and
Why is Weight So Important in Cycling? Part*2 - Posts - TrainingPeaks Blog

Among world-class, elite cyclists, the majority are over 6 W/kg FTP.

In 2012, Brad Wiggins won both TDF ITTs and the Olympics ITT. When he is in peak form, he weighs around 155 lbs, IIRC. Wiggins also reported that he averaged about 450 watts during a 55-ish minute long ITT (don't recall whcih one).

Road racing is not a heavy man's sport! 


View attachment 276708


----------



## serious (May 2, 2006)

Doc_D said:


> This is not true....Assume you have a 100 pound rider with a 4 w/kg output and a 200 pound rider with a 4w/kg output. At lower grades the 200 pound rider would be much faster. If you play around with one of the calculators you'll see it's only when the grade hits a certain percentage that the lighter ride is equal or faster.
> 
> This drives me nuts when people use w/kg as a measure of performance. It's fine for comparing you to you. It's useless for comparing two different riders. Over a flat ground a 200 pound rider with a 3 w/kg FT will DESTROY a 120 pound rider with a 4 w/kg FT.
> 
> 4 w/kg does not always equal 4 w/kg. Total power is a huge part of the equation. It's a real sore spot for me that total power is almost always discounted. Personally I believe in the real world, many times, total power is a better predictor of performance than w/kg. Neither is a good predictor without also taking the course profile into consideration.


We are talking about climbing here (see OP's post). Poncharelli already made your point for the flats, so no need to get sore. We agree there.


----------



## asgelle (Apr 21, 2003)

tom_h said:


> FYI,
> Why is Weight So Important in Cycling? Part*1 - Posts - TrainingPeaks Blog
> and
> Why is Weight So Important in Cycling? Part*2 - Posts - TrainingPeaks Blog


I just skimmed the first article, but I know I wouldn't attach any credibility to a coach who writes,
"Your starting strength to weight ratio at FTP is ..."


----------



## Alex_Simmons/RST (Jan 12, 2008)

notwist said:


> Consider two people with similar FTPs (w/kg) do roughly the same effort up a hill (*same steady power*) however one person is clearly faster reaching the top first. *What things affect their speed aside from CDA and equipment? *Does cadence (for example) affect speed or is it all about power output?


Different wind conditions have a large impact to climbing speed.

You did say _besides equipment_, but just to be clear:
- different tyres can have an impact (e.g. one on fat knobby mtb tyres at low pressure, the other on fast road tyres)

- a rider's power to body mass ratio might be equivalent but their power to (bike + body) mass ratio may not be the same

Difference pacing strategies, although you did say _same steady power_, so it might depend on whether the climb is steady gradient or a variable gradient.

You did say _aside from CdA_, but different aerodynamic profiles, in particular on shallower gradients, will result in different speed for same power.


So if we really take out the factors such as differences in:
CdA, 
gradient, 
equipment (relative mass and Crr), 
pacing, 
then you are left with wind. 
If that's the same for both, then if speed really is different, their power must also be different.


----------



## The Human G-Nome (Aug 26, 2002)

Although the OP did mentions hills, it should be noted that most of these numbers really reflect the rider as a TTist, and not as one in a group. In a group, the rider with the smaller surface area is not only talking on less wind/drag when pulling if he presents a relatively aero profile, but he's also taking on less wind/drag while drafting. A little guy can really hide behind a big guy in a race and barely have to work. It's like being behind a truck. A much larger rider does not share the same advantage. A really big guy attempting to draft a really little guy is going to suffer more. 

This is even true on hills, but of course to a lesser extent.


----------

