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I guess it's possible because on the climbs you need to beat gravity more than the wind resistance but is there a formula to calculate how much the weight of the rider affect the climbing performance?

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    Absent significant wind resistance, the rider that produces the highest number of watts of power per kilogram of total system mass will climb faster.
    – Paul H
    Jul 29 at 14:48
  • So the heavy riders can't produce as much power on the climbs as they do on the flat road?
    – Ender
    Jul 29 at 14:51
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    Not what I said at all
    – Paul H
    Jul 29 at 14:51
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    If Rider1 weighs 60kg and can produce 300watts, that means 5 watts / kg. If Rider2 is 80kg and can produce 360 watts, that means 4.5 watts / kg. On a steep gradient Rider1 will climb faster even though he's producing 60 watts less.
    – Robert
    Jul 29 at 16:06
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    A lightweight cyclist can climb better not by producing less power but despite producing less power.
    – mkrieger1
    Jul 30 at 18:40

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Yes. This article goes into detail and shows the formula along with a few scenarios.

In short, power-to-weight ratio becomes more important than raw power as the grade increases. Aerodynamic drag is still a factor, so the advantage to the rider with better power-to-weight is mitigated.

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  • So, heavy riders can have big w/kg ratios only on flats?
    – Ender
    Jul 29 at 19:38
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    No. Power-to-weight is the same regardless of grade. If Alice weighs 50 kg and puts out 200 W, she has a better power-to-weight ratio (4 W/kg) under all conditions than Bob at 100 kg and 350 W (3.5 W/kg). That will be true under all conditions. On the flats, raw power is more important than power-to-weight ratio, so Bob has the advantage there. If you're willing to do the math, you can calculate the exact gradient at which Alice starts breaking even with Bob.
    – Adam Rice
    Jul 29 at 20:35
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    If for "Bob" you'd written "Chris" that would almost perfectly describe a ride I had a few years ago. Alice is a strong rider and light, leaving me for dust on the climbs. I caught up again on the flats, and quite quickly when we were riding into a headwind
    – Chris H
    Jul 30 at 11:29
  • @Ender Heavy riders have awesome power to drag ratios in descents, it's almost proportional to their weight!
    – cmaster - reinstate monica
    Jul 30 at 21:19
  • @cmaster-reinstatemonica The problem is descents last for much less time than climbs, so the heavier rider's advantage on descents doesn't come close to making up the disadvantage on climbs.
    – Andrew Henle
    Jul 30 at 21:47
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Yeah, those lightweight powerhouses do great on the climbs but then they get hit on the descents, where higher weight gives an advantage. Look up Jean Robic, famous post-WW2 Tour de France winner, little guy, very light and very strong, amazing on the ascents, and then as he hit the top his team would pass him water bottles, as they do, but filled with lead shot. After the organizers got wise and banned solid metal "water" he switched to mercury.

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    Wikipedia’s article on Robic gives more detailed versions of this story, with sources. The sources themselves are journalistic articles/books dating from 50 years after Robic’s peak years, so unless they source this story further back, they don’t conclusively settle whether it’s true or apocryphal — but the fact the story has been taken as plausible by cyclists and sportswriters for generations shows consensus that the strategy would be genuinely advantageous.
    – PLL
    Jul 30 at 16:37

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