Shouldn't FTP calculations in Watts/KG take into account bike weight?

[tom1298372]

Say 2 people both have an FTP at 3 Watts/KG but person 1 weighs 80kg (240 watt FTP) and person 2 weighs 50kg (150 watt FTP).

When taking into account that a road bike weighs about 8kg and the rider needs to pull it along with them during a race, shouldn't the actual FTP calculations in Watts/KG be:

- Person 1:150 watt FTP / (50kg body weight + 8kg bike weight) = 2.58 Watts/KG

- Person 2: 240 watt FTP / (80kg body weight + 8kg bike weight) = 2.72 Watts/KG

 

[bridgy]

Say 2 people both have an FTP at 3 Watts/KG but person 1 weighs 80kg (240 watt FTP) and person 2 weighs 50kg (150 watt FTP).

When taking into account that a road bike weighs about 8kg and the rider needs to pull it along with them during a race, shouldn't the actual FTP calculations in Watts/KG be:

- Person 1:150 watt FTP / (50kg body weight + 8kg bike weight) = 2.58 Watts/KG

- Person 2: 240 watt FTP / (80kg body weight + 8kg bike weight) = 2.72 Watts/KG

No, because if the watts figure is taken from a power meter those watts are simply the amount of power that person is putting out through the pedals, and the watts/kg is their watts/their body weight. Bike weight is irrelevant to this. Obviously the bike weight, rolling resistance, aerodynamics etc will then affect what SPEED the rider does with those watts, but the persons w/kg FTP will be the same for them whichever bike they ride.

 

[tom1298372]

No, because if the watts figure is taken from a power meter those watts are simply the amount of power that person is putting out through the pedals, and the watts/kg is their watts/their body weight. Bike weight is irrelevant to this. Obviously the bike weight, rolling resistance, aerodynamics etc will then affect what SPEED the rider does with those watts, but the persons w/kg FTP will be the same for them whichever bike they ride.

That definitely makes sense. I guess I am eluding to the fact that there is more to the story than just Watts/KG when the rubber quite literally hits the road, but I guess the measurement itself still serves a purpose.

 

[T.M.H.N.E.T]

No, it's a measure of your performance vs your weight, not total weight. The bike is insignificant to the calculation

 

[ColinJ]

The fact is that W/kg is used for working out how fast the rider should be able to climb, in which case the weight of the bike IS relevant in the calculation but would be added in then.

If you were thinking of flat time trials then the rider's weight wouldn't really be much of a factor so you would be just looking at W.

 

[Ming the Merciless]

Isn’t W/KG a way of humble bragging or lording it over your mates if you aren’t a professional cyclist? The real test is who (on the day) gets up the hill the quickest when you are all going for it.

 

[cougie uk]

The bike isn't putting out any power so it doesn't count.

 

[Dogtrousers]

The only time I come across W/kg is in analysis of the climbs in pro races. And their bikes all weigh 6.8kg on the nose.

 

[Dogtrousers]

The bike isn't putting out any power so it doesn't count.

Are you quite sure of that?
Suspicious face emoji

 

[cougie uk]

Are you quite sure of that?
Suspicious face emoji

If it's meant to be mine is definitely slacking.

 

[bridgy]

Isn’t W/KG a way of humble bragging or lording it over your mates if you aren’t a professional cyclist? The real test is who (on the day) gets up the hill the quickest when you are all going for it.

Which will probably be the guy with the highest w/kg

 

[Ming the Merciless]

Which will probably be the guy with the highest w/kg

Highest w/kg over what duration? Someone who excels at 5 minute climbs may not be the fastest on 4 hour alpine climbs.

 

[bridgy]

Highest w/kg over what duration? Someone who excels at 5 minute climbs may not be the fastest on 4 hour alpine climbs.

Over the duration of "the hill" you mentioned in your previous post

 

[Ming the Merciless]

Over the duration of "the hill" you mentioned in your previous post

Which means we won’t know anyones W/Kg for that hill, plus if we did and two riders had the same all out W/Kg for that hill, the heavier of the two will be faster up the hill. You may even have a case where the lighter person edges it on W/Kg but they are not fastest up the hill.

 

[Dogtrousers]

The answer is, of course: Maybe.

If you want to calculate FTP in W/kg including bike, go right ahead. It's only numbers. You can calculate anything you like. Indeed the OP has already done this. But the numbers will be of reduced usefulness because the convention is to calculate it as FTP/rider's body weight.

So what you would have done would be to invent your own metric "FTP W/Kg (inclusive of bike)". But you'd be on your own using it.

I'm not really sure how useful FTP in W/kg is anyway, but there you go. I suppose it would be a handy thing to plot if you were simultaneously training to raise your FTP and dieting to lose weight.