Hysteresis in Marginal Gains

Hysteresis in Marginal Gains

Hysteresis is the term for processes that behave differently in one direction than in another. Understanding it is critical for flying, for dampened suspension systems, and for being aero on your bike. Yep, in this episode we’ll be making liberal use of analogies that include a Tempurpedic mattress, a rolling tire,  mountain bike suspension and a fair number of Hitchhiker’s Guide and Top Gun references. Enjoy this episode of Marginal Gains! 

Interesting Links, Sources, and Additional Reading From this Episode

Hysteresis loops for inviscid flow in wings:

Transpulmonary compliance hysteresis

Got a question you’d like to ask Josh? Text or leave a voicemail at the Marginal Gains Hotline: +1-317-343-4506. You can also email us at questions@marginalgainspodcast.cc, or just leave a comment in this post!

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9 thoughts on “Hysteresis in Marginal Gains

  1. Nice explanation for why Crr scales exactly like hill slope, so a Crr of .005 creates exactly as much drag as climbing up a hill with slope of 0.005 (i.e., half of one percent). If you’re comparing a tire with a Crr of .004 against a tire with Crr of .005 (for a particular surface) the second tire would be like climbing a hill that’s .001 (= 0.1%) steeper. That may not seem like a lot, but over a 200 km race that’s the equivalent of climbing an extra 200 meters compared to the lower Crr tire.

    1. Very interesting! This addressed a question on light vs low crr (tubular like corsa speed that creates a light wheel, vs modern tubeless like say corsa speed that have superior Crr.

      1. Gatorsking vs gp5000tlr would be like a 0.35% extra grade at all times. Now should that be doubled to .7% with two tires?

        1. no. 1 tire with all your weight is equivalent to two tires, each with half your weight – meaning two tires do not have twice as much drag as one tire, but (because each tire is only bearing half the weight) the same amount of drag as riding a wheelie.

  2. As an aside, I’ve done a (very) little bit of work with neonates and NICUs, and had to learn a tiny bit about hi-fi pulmonary flow through immature lungs. I’ve occasionally wondered about respiratory rate and inhalatory volume while I’m on a bike gasping for breath.

  3. Hi Josh, question I’m hoping you could address for next episode. I’m wondering if you can unpack some of the science about helmets, and maybe the marginal gains of safety performance (opposed to aero performance) and how we could be marginally safer. Mips? Wavecell? Really been enjoying the podcast so far, would be great to hear your thoughts on this!

    1. To add, i wonder about aero performance between helmet sizes. I am small and aero, but my big helmet can’t help me. How much is the question? I presume the change is linear with surface volume as the coefficient of friction from the shape will be largely unchanged.

      Also, i see lots of different wind tunnel test. One giro helmet did not do so well, and giro stated that it was sensitive to angle of attack. On test was with dummies facing forward. Fine, but who is truly head up and forwArd in the true aero position. Is is more tucked in and head facing forward and down. Head straight down would slow an aero helmet. Or do i presume.

  4. Josh, your whole explanation about aerodynamic testing for airplane wings and F1 cars and your note of the different results between yaw-out and yaw-back bike wheel testing in this episode began to peel back some of the differences in wheelset wind tunnel testing. Can you rip wide open the technical, commercial and perhaps religious debate about the usefulness, beyond marketing purposes, of wheelset wind tunnel testing in designing wheels and predicting their actual on-the-road performance difference, the various approaches to it (wheel alone, wheel on bike, wheel with rider/mannequin, different speeds, yaw angle weighting, etc.) and the recent debate brought on by an independent outsider (Hambini Performance Engineering) using a transient approach taken from the aerospace industry to test bike wheels that are typically (only?) tested using static, wind tunnel protocols. Thanks, Steve

  5. This is an aero question related to the “aero trip” devises we see on cars, wheels, planes. Vortex generators? Tabulators. I forget the term.

    I wonder what if some 3m sticky raised but smooth silicon (or similar) strips would be beneficial to add on the trailing surfaces of the fork, headtube, downtube, heck… seat tube and upper stays. You could make an non aero bike a bit more aero.

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