Originally Posted by cyccommute

You are just naturally going to be slower on gravel than on pavement. Even with lower pressure, there is a limit to how well a rigid bike will handle the gravel. The rigid fork doesn’t deal well with the variation of the surface. Any ruts or soft spots will resist changes direction because you need to countersteer into the rut or soft spot. But you can’t countersteer because the fork traps you against the rut or soft spot. You essentially have to plow through it but you don’t have the tools to do that. Lowering tire pressure doesn’t fix the problem.

You’d get more speed on the asphalt bits with 70 to 80 psi but than you have to drop pressure on the gravel bits. Constantly changing tire pressure is a pain. Pick your poison and put up with slow asphalt or bouncy off-road or constantly deflating and inflating tires.