GCN tests advantage of lighter bike

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djconnel
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by djconnel

http://velonews.competitor.com/2015/05/ ... oad_372211
or
https://www.youtube.com/watch?v=le_LSWfGJUo

Nice video by GCN: testing a bike with or without 1.92 kg of ballast. One rider went constant power and the improvement was basically exactly what you'd expect from power-speed equations: 35 seconds saved over 22 minutes from 1.92 kg mass difference (2.65% time difference: 1.92 kg is 2.65% of 72 kg, which is ballpark). The other rider rode on feel and he was around 94 seconds faster on the lighter bike, claiming he could push himself harder with the lighter bike.

Principal weakness of the study is they seem to have failed to test for rider weight difference, primarily due to water loss. A scale to weigh riders + bikes before and after each rep, then avg the results, would have been better. But I won't be picky: very rarely do "media" make such an effort to be quantitative.

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emcardle
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by emcardle

What I found weird about the second test was he rode to perceived effort and not watts. Its well documented that the placebo effect has a huge influence on tests like this.

justkeepedaling
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by justkeepedaling

One guy rode with power, the other by feel. The one with feel had a greater delta. That's placebo. But repack to the end conclusion

Tenlegs
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by Tenlegs

GCN do make some good vids, here's a couple from 2013 along similar lines - body v bike weight.
Probably posted before but worth watching if you've not seen them.

https://www.youtube.com/watch?v=5DRQwKREgvI
https://www.youtube.com/watch?v=lBA99QVqnwI

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djconnel
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by djconnel

Well, if a rider is able to produce more power on one bike vs another, then that's worth something. If I use a bike with one pedal instead of two, at the same speed the power will be almost exactly the same, but you can't produce as much power, so it's valid to conclude that 2 pedals are a good feature, not just "placebo".

Even if the pedaling is the same, if you can motivate more power production, that's real and valuable. Amphetamines have been abused by pro cyclists for close to a century, and all they do is motivate more effort. Same with pain killers.

But if the "placebo" is "I think a light bike should be faster so I'm going to ride faster", then I agree this isn't worth much, because it's not reliable. At some point if you realize it's not as faster as you thought, it will cure you of that placebo. So I certainly wouldn't buy a light bike based on the video results unless the 2% number was good enough for me.

On the body weight vs bike weight question: more body weight means more internal dissipation shearing body tissue. That won't show up on a power meter. So I vote for "the body" unless it's muscle mass which provides more anaerobic capacity.

Tenlegs
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by Tenlegs

"more body weight means more internal dissipation shearing body tissue"
had to Google it but yeah I'll go along with that, and there was me just thinking I'd be better off cutting back on chips & pies than spending $**** on lighter parts.

aaric
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by aaric

bike weight and body weight reduction aren't mutually exclusive. :beerchug:

And if you make a lighter bike a reward for hitting a goal weight, they can reinforce each other

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