I’m just having a debate with someone…if a small person were to race someone larger, of the same power to weight ratio, would there be a difference in speed?

Assuming equal w/kg they should climb the same pace, but the bigger rider will be throwing off more heat and burning more kj’s so on sustained climbs should bonk faster. Bigger rider should descend and hit the flats faster (assuming everything else is equal). Really depends on the course, rolling stuff would favor the big guy. On a really hilly course the big guy is gonna run into trouble sustaining their effort earlier. If you’re looking to understand why the tiny dudes win gc’s factor in that it seems like the only way to get to the pointy end of w/kg is to get super lean. You probably aren’t gonna see someone bigger than 75kg hitting 6/wg. Even that seems pushing it.

I think if it’s a shallow slope and/or both riders are capable of keeping up a good speed while climbing, then the aerodynamics will still play a part in the equation.

Here you go… cipher to your hearts content: https://analyticcycling.com/QCHome_Page.html

I’m not sure how to search past podcasts but they talk about it one. If w/kg are the same the lighter person will move up the hill a little faster. Maybe due to gravitational pull? Not really sure how it happens and the science behind. Just remembered hearing so maybe you can go searching for more information :woman_shrugging:t3:

[image] JoeX: two riders outputting the same w/kg for the same time up the same slope will climb the slope (or traverse the curvature of spacetime) at the same speed. I think that will be highly dependent on where they are on their respective power curves during this hypothetical effort. Two riders with the same w/kg at FTP will almost never be exactly equal in terms of what they can put out in terms of power over time above FTP or how fast they recover from such efforts. And if you match w/kg, the physics of climbing may mean they are going the same speed but how long each can keep it up is not necessarily revealed by w/kg. w/kg is a significant measurement but, just that number alone will almost never tell you exactly how two riders will fair against each other in a specific test because w/kg is really always meant as “w/kg at X or for X duration” and in any kind of real world race, the riders will have different physical abilities plus racers will try to change the “X” in the equation to favor themselves and disadvantage the other guy.

[image] Nope0337: I’m not sure how to search past podcasts but they talk about it one. FAQ: How to Search for Ask A Cycling Coach Podcasts

I’m not really that interested in this, was just offering for someone else to do it if they wanted more information. But @batwood14 here you go! :blush:

[image] Nope0337: Maybe due to gravitational pull? Not really sure how it happens and the science behind. Just remembered hearing so maybe you can go searching for more information :woman_shrugging:t3: This. When on a flat surface, the gravitational force is perpendicular to the ground–so there is no force component opposing the direction of motion. However, when climbing, there is a component opposing the direction of motion. That force is proportional to the mass of the rider (plus bike, etc.). And increases with gradient. So the smaller rider has an advantage when climbing even if the power profile of the two riders are equal on a W/kg basis. And that advantage increases the steeper the grade. Reverse is true on descents, advantage to the larger rider there. Sorry, I"m an engineer :woman_shrugging:

Sorry, but you’re wrong. For equal W/kg you’ll have equal velocity wrt the road (and vertical velocity as well). Edit: To add some math. Power to ascend is equivalent to mgs*v (where m is mass, g is gravitational constant, s is slope, v is velocity relative to road). s is actually sin(arctan(s)) but for small angles (all climbs you’ll encounter on a bike) the approximation of just s is still valid. So solve for v and guess what? It is proportional to P/m (W/kg)

Ever get stuck behind a semi truck on a hill, chugging up at 35mph? And the same truck does 70mph on flat roads? Gravity. Even better analogy, say you have a pickup truck hauling a horse trailer. That truck can easily do 70mph on a flat road, with or without the horse trailer. But take that truck up a steep hill and the truck will climb up the hill faster without the trailer. Same with two cyclists with the “same engine” (ftp) but different weight. All because of gravity.

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Power to weight ratio debate

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mcneese.chad March 4, 2019, 9:33pm 30

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