well, i don’t stipulate to the optimal pressure being above 5bar for a 28mm tire for most riders on most roads. there is 1 certain violation of my rule, which is a 5mm difference between tire and internal bead width; then (as you say) the pressure question, then the insert question. the only other gentle disagreement i have with you is on the “we will never know.” i’m pretty sure we will know.
Our testing so far has shown over 70kg on smooth road, 5bar and below is not optimal. Those roads at UAE are silky smooth and DeGendt is 69kg.
This is my ONLY beef with hookless. To get optimal I need to push the limits of safety.
FYI the CPA seems to be unhappy. https://velo.outsideonline.com/...ill-be-a-mass-crash/
Maybe someone needs to look into this insert thing.
yeah, i’m not saying your testing is wrong. i’m just saying i’m not yet ready to stipulate to that. maybe it’s just that my roads aren’t smooth enough. i just can’t find an occasion where in my own testing for my own 77kg body that for a 28mm tire anything above 65psi isn’t slower. and even 65psi is high. if i lived in the UAE or even germany it would probably be different. but in the US or at least in the state everybody loves to hate (california) even freshly laid pavement is rougher than what you reference in the UAE. for me, cycling efficiency (acknowledging that efficiency is probably not the right word) - the translation of energy intended to speed - includes both a mechanical and biomechanical component. i say intended because i don’t know whether muscle vibration keeps the energy from translating to speed, or keeps me from using the energy at all. i just know that muscle vibration is a documented problem. that biomechanical cost approaches zero on a UAE road so i take your point there. i just can’t replicate anything like that where i ride and my roads are, by US standards, pretty good.
I showed a picture of the road we tested on. It’s not silky smooth. Cracks every 10-20m. It’s much rougher than UAE. As rough as most triathlons I have done.
Here are the two closest riders to your weight. Although they are 9 and 3kg less than you.
At 5 bar one is giving up 2 watts, the other 1 watt. Not much, but this grows as weight goes up. One guy is 68kg the other 74kg
At 65PSI (4.5 bar), they would be giving up 4 and 2 watts.
X axis is pressure in bar. Y is watts lost compared to “optimal”
28mm 5000TT tires.
FYI, we measured the vibration felt by the rider. In theory we could correlate this to fatigue
