# 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!

Hysteresis loops for inviscid flow in wings:

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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• John Drysdale

This is an aero question related to the â€œaero tripâ€ 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.

• John Drysdale

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.

• John Drysdale

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

• John Drysdale

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.

• Steve Goldstein

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