>>1211420It is not about tire width, it is about pressure, however you need wider tires to get away with lower pressures.
Also there are two major factors in rolling resistance:
>hysteric lossesSidewall and tread deformation, decreases with lower tire sieze and higher pressures.
>suspension lossesEnergy lost when riding over small obstackles (road buzz) since they push you up for a split second but there is no ramp down, so you don't get the potential energy back into kinetic energy.
A 25mm tire can absorb most road buzz with no issue, given that it is pumped up to a reasonably low pressure.
For me (59 kg) this is 2-3 bar depending on the roughness of the road.
A 23mm tire can also absorb most of the road buzz on normal roads, but you run into its limit faster and need a higher pressure.
You can also alter the characteristics of a tire by changing ita pressure:
A 25 mm tire running at 2 bar is verry plush and has high hysteric losses, but low suspension losses.
At 3 bar hysteric losses decrease and suspension losses increase.
At 4 bar hysteric losses are almost as low as they get, suspension losses are high now.
There is no point in going any higher on the road, only on a velodrome with perfect surfacw you will see even a neglectible decrease in rolling resistance.
(exact pressures increase with weight)
In gravel/sand/mud you sink in a little, how much you sink in dependa on contact patch sieze and weight.
Since contact patch sieze depends on tire pressure, I tested my roadbike (25mm) vs my MTB (2,25") on gravel:
When running 1bar in my roadbike I sunk in less than I did when running 6 bar in my MTB.
However in snow this may be desireable, since a high pressure tire can cut through the snow and grip to the surface below.
TL;DR
25mm is good for road and gravel, 23mm is good for mainly road and anything below that is only realy good for smooth road in therms of rolling resistance.
