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Power differences

by WeLoveHills
Wed, Feb 05, 2020 00:21
5

Hi everybody, I wonder if anyone can answer this (daft?) question.

Does it seem possible that there is a 60w difference (160w and 100w) between the power produced by two cyclists on the same 10-minute segment, considering that both cyclists were on the same group ride and did the segment at the same speed? The only explanation I can think of is that one of the two cyclists was drafting much more efficiently than the other. Any other possible causes? Thank you

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WeLoveHills | 5 years ago
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Thank you both. That makes sense. So a lighter rider on a carbon bike will need considerably less power than a heavier rider on a steel bike, say, to do the same stretch of (flat) road at the same speed. But their w/kg will be much more similar, I suppose.

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fenix replied to WeLoveHills | 5 years ago
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Don't get hung up on bike weights. Its a marginal difference. 

The build of the rider is far more varied and would make more of an impact. 

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mtbtomo replied to WeLoveHills | 5 years ago
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The flatter the road, the less difference weight makes. Drafting will be much more likely to be the difference in this case. You can easily save a third of your energy drafting someone else. It can be proven by calculation and in the real world. I've been on rides with similarly fit people (i.e. similar power ranges), and they're doing tempo power on the front and I'm barely doing low aerobic. So could be say 270w on the front and 200w in the draft. As per other posts, rider size/shape alone will make an aero difference too.

Also, are the figures Strava estimates or genuine power data? Different power meters, even from the same brand can be a few percent different.

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peted76 | 5 years ago
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Yes, I'd say the variations in power within a group ride are very normal. 

As Liam says, weight, aerodynamics of the rider/bike, drafting, plus if you really wanted to get into it, drivechain efficiency. 

I'm hobbit shaped, I put out a lot less power than my more human shaped ride mates on the same sections on the same rides. 

A far better measuring stick of 'fairness/fitness/speed' would be watts per kilogram, which is just more honest.  (avg power divided by weight)

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Liam Cahill | 5 years ago
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The big difference will probably be the weight of rider and bike. Then smaller factors would be differences in the aerodynamics of each rider and bike, rolling resistance and drivetrain efficiency. Drafting will make a difference, but it depends on the gradient of the climb and the speed at which it was ridden.

The difference between me and one of my training buddies is 20kg (in my favour). It makes a massive difference, not just on the climbs.

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