just another gosling
Join Date: Feb 2007
Location: Everett, WA
Bikes: CoMo Speedster 2003, Trek 5200, CAAD 9, Fred 2004
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There seems to be a difference of opinion on this. If you use the online power calculators, on a 6% grade, one pound loss = 1 watt saved . . . about, depending on rider weight, etc. On an 18% grade, it's about 2 watts saved/pound lost. If you believe that, you're much better off focusing on maximizing your power at LT than on weight loss, if you're anywhere in the weight ballpark. However, if you've maxed your power, then weight loss is the only thing that helps.
OTOH, Carmichael estimated that Lance saved about 1 minute/kg lost on the Arcalis climb, stage 7. The bike calculators give a result of about half of that. My experience is that it's closer to Carmichael's estimate, though I don't have power figures to base that on. It just feels like body weight loss makes more than a 1w/lb. difference. But maybe there's more to it than just weight, like it was lead or something. Maybe the leaner body is more efficient, especially out of the saddle, and maybe a leaner body is also more aerobically efficient.
Pretty hard to study this, because losing body weight will probably affect power output and endurance, so lots of loose variables.
I believe the online calculators are correct as regards the watts saved by losing bike weight. I'm just not so sure about body weight.