chas58

I know, right? They are 60mm Schwalbe S-One tires aka the big one. (yes they were horrible in the soft muddy patches - too much flotation, and no traction - but they are great on sand).

For reference:
they have 11-16 watts drag (depending on PSI)*
Continental gatorskins have 19-26watts drag (depending on PSI)
My Michelin race tires are 14-19 watts

My goal in this test wat to set the bikes up with similar rolling resistance and aero drag and see how compatible they were, given the mountain bike was heavier, had larger tires and somewhat different geometry.

They were amazingly similar in the first half of a 3 hour ride, but the weight (on rolling hills) just wore me out eventually.

In a short fast race ride, or riding into the wind, the gravel bike would have had the clear advantage with the drop bars. But again - the crossover between rolling resistance and aero is about 12-13mph, so aero isn't much of a hindrance at a casual endurance pace on a gravel ride.

Comparing 40 - 60mm tires - the big tires were super cush and had better traction in the soft (non muddy) stuff.

I wasn't really expecting the weight to make that much of a difference in endurance.

*ps: realistically they are going to have more resistance than 11 watts on a gravel ride, but it is an odd feeling to be riding on pavement at 15mph on a mountain bike and expending about as much energy as I would at 15mph on a high end skinny tire road bike.