Descending speed and cornering traction for heavier riders vs. lighter riders.

Insightful additions to my answers from two weeks ago

Dear Readers,

In this recent post I discussed relative descending speeds and bike handling considerations for bigger riders vs. smaller riders. There is more to be said about it, and two readers have kindly sent me more interesting information on the subject. One submission is from Doug, a scientific researcher and the other is from a national road champion: Wayne Stetina.

While I don’t usually include last names here, it seemed appropriate given Wayne’s answer mentioning his lighter weight brother and to clarify the depth of experience from which he speaks about cornering. Wayne and his brother Dale (father of current gravel pro and former Tour de France rider Peter Stetina) won many national road championships between them as well as umpteen other races; Dale also won the Coors Classic twice and Wayne won it once.

Doug addresses the first part of my answer about how the difference in aerodynamic drag between the bigger and smaller riders is not big enough to offset the higher gravitational force on the bigger rider, resulting in higher descending speed for that rider.

Wayne addresses my statements about relative cornering grip and centers of gravity between the two riders and is a more useful answer than mine.

Enjoy!

― Lennard

First, relative descending speed:

Hi Lennard,

Nice to get your tech notes; appreciated! You wrote (correctly):

“Rather, it demonstrates that the wind resistance of a heavier rider relative to a lighter rider will not be higher by the same proportion as their relative masses.”

I think the formula you are trying to put into words is "ballistic coefficient" = W/CdA , units of force/drag-area

https://en.wikipedia.org/wiki/Ballistic_coefficient

Not strictly true for bicycles due to other forces like tire rolling resistance, but very close at high speeds where air drag dominates.

-- Doug

Second, relative cornering traction (which I said was a wash) and center of gravity (which I said depended on weight distribution and was generally higher for a taller rider):

Lennard,

Comparing cornering traction of heavier v lighter riders is far more complicated than I believe you realized.

1. Assuming equal tire size & pressure could not be more wrong. What you meant to assume is the same tire patch contact shape based on correct tire pressure relative to rider weights.