Has anyone else noticed that tire pressure has almost no effect on speed?

Yesterday was the third time I went out and tested a tire's road performance at different pressures. (Mostly because I ran over a tack and had to ride home at about 5psi when it finally sealed.) The tire in question was a G-One Speed and I rolled it at 50psi, 40 psi, 25 psi and finally 15 psi.  Of the ten runs I did, every one came in within 5 seconds of each other (between 2:30 and 2:35 time) with none of the pressures consistently faster.  This is consistent with my other tests that showed me that running a nice off-road pressure does not hurt your speed on the road.  The 15 psi was too bouncy, but sure was super smooth over rough pavement.  Not too practical, but it was not slower.

Check out Schwalbe, rolling resistance and air resistance:

https://www.schwalbetires.com/tech_info/rolling_resistance

Jan Heine noticed this over 10 years ago, and has been beating the drum loudly to the point that now the whole industry has shifted (and helping pave the way for gravel bikes).  

You can read this if interested in more:  https://janheine.wordpress.com/2015/02/17/tire-pressure-data-and-details/

Ironically he was slow to embrace tubeless, which allows us to safely run low pressures over rough surfaces.  To some degree, if your tire can't deform enough to absorb the terrain you are riding in, you are probably loosing efficiency.

ccand51997 wrote:  Of the ten runs I did, every one came in within 5 seconds of each other (between 2:30 and 2:35 time) with none of the pressures consistently faster.

Can you tell us more about your tests? This is just pedaling on the flats over a fixed distance? Did you have a power meter?

I just used a loop around my house and rode at the same average power for multiple runs at each pressure.  It is not as rigorous as the testing above, but it is over roads of varying smoothness and cornering on asphalt/cement/asphalt transitions.  The total time for the loop was between 150 to 155 seconds, so the five second variation IMO was the breeze that was blowing, because there was no pressure that was consistently faster or slower.  In past tests, when I get a completely calm day I can do five minute runs that consistently run 0-2 seconds of variation.  

ccand51997 wrote:I just used a loop around my house and rode at the same average power for multiple runs at each pressure.  It is not as rigorous as the testing above, but it is over roads of varying smoothness and cornering on asphalt/cement/asphalt transitions.  The total time for the loop was between 150 to 155 seconds, so the five second variation IMO was the breeze that was blowing, because there was no pressure that was consistently faster or slower.  In past tests, when I get a completely calm day I can do five minute runs that consistently run 0-2 seconds of variation.  

Actually, this does seem about as rigorous as most of Jan Heine’s testing. 

Here's a RidingGravel thread which included a test run by Leonard Zinn (Velo News Tech Writer).  Very limited data but Leonard discussed how riders felt slower on softer tires yet their speed was higher.  His testing was on a downhill run with no pedaling.

http://ridinggravel.com/forum/?p=post%2Foptimal-gravel-tire-pressure-velonews-leonard-zinn-tests-9831154