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I don't have a source for that, but I've always thought that low tire pressure doesn't really contribute that much compared to aerodynamic drag, even on the joy

I don't have a source for that, but I've always thought that low tire pressure doesn't really contribute that much compared to aerodynamic drag, even on the joyride home at 20 km/h on a heavier freeride rig.

wtallis 6y ago
I take a scout group on a week-long bike trek on the C&O Canal towpath most summers. That's a flat but unpaved trail, and most of the kids have hardtail mountain bikes because we also do trips for singletrack mountain biking. Over the course of the week, all the kids doing the trip for the first time get faster from day to day. When they start out and don't take my advice about tire pressure seriously, their sustainable cruising speed tends to be in the 8-9mph range. High tire pressure (and careful attention to ensure the brakes aren't rubbing) gets everyone up to at least 11-12mph depending on how hot the weather is. Drafting gets the group up to 14-15mph. So basically, in my experience on longer rides a low tire pressure will prevent you from getting up to the speed where aerodynamic drag is a big concern. And on hilly terrain you spend a lot more time either climbing at speeds far too slow for aerodynamics to matter, or on descents where you have no trouble at all overcoming drag to reach unsafe speeds.
ehnto 6y ago
If you're never going over 20kmph and you have big heavy DH tires on, you will still be experiencing a lot of rolling resistance for the majority of your ride. Considering my ride home is done at like 10-20kmph on a set of Maxxis Minions, rolling resistance should be making up ~50% of my total resistance. At 50psi I find I'm mostly on the centre of the tire, so not even rolling on the full 2.8" width like I would be at 20psi, which I can feel a difference in. CyclingAbout has a great video about aero and bikepacking which is a good intersection of what we're talking about here, though he's using fast rolling tires: > By the time you’re cycling at 30KPH, as much as 90% of the resistive force experienced comes from aerodynamic drag. And it’s not until you get down to 12KPH when rolling and air resistance are equal. https://www.cyclingabout.com/fascinating-aerodynamics-bikepacking-bicycle-touring/ https://www.cyclingabout.com/fascinating-aerodynamics-bikepa...

wtallis 6y ago

I take a scout group on a week-long bike trek on the C&O Canal towpath most summers. That's a flat but unpaved trail, and most of the kids have hardtail mountain bikes because we also do trips for singletrack mountain biking. Over the course of the week, all the kids doing the trip for the first time get faster from day to day. When they start out and don't take my advice about tire pressure seriously, their sustainable cruising speed tends to be in the 8-9mph range. High tire pressure (and careful attention to ensure the brakes aren't rubbing) gets everyone up to at least 11-12mph depending on how hot the weather is. Drafting gets the group up to 14-15mph. So basically, in my experience on longer rides a low tire pressure will prevent you from getting up to the speed where aerodynamic drag is a big concern. And on hilly terrain you spend a lot more time either climbing at speeds far too slow for aerodynamics to matter, or on descents where you have no trouble at all overcoming drag to reach unsafe speeds.

ehnto 6y ago

If you're never going over 20kmph and you have big heavy DH tires on, you will still be experiencing a lot of rolling resistance for the majority of your ride. Considering my ride home is done at like 10-20kmph on a set of Maxxis Minions, rolling resistance should be making up ~50% of my total resistance. At 50psi I find I'm mostly on the centre of the tire, so not even rolling on the full 2.8" width like I would be at 20psi, which I can feel a difference in. CyclingAbout has a great video about aero and bikepacking which is a good intersection of what we're talking about here, though he's using fast rolling tires: > By the time you’re cycling at 30KPH, as much as 90% of the resistive force experienced comes from aerodynamic drag. And it’s not until you get down to 12KPH when rolling and air resistance are equal. https://www.cyclingabout.com/fascinating-aerodynamics-bikepacking-bicycle-touring/ https://www.cyclingabout.com/fascinating-aerodynamics-bikepa...