Originally Posted by
grumpus
To oversimpify, rolling resistance is energy lost in the process of deforming the tyre as it contacts the ground. Make the tyre thicker by adding an extra layer and there's more rubber to flex and heat up.
This ^^.
To
undersimplify
, there is "Elastic Hysteresis" involved...
"Elastic hysteresis is the phenomenon where a material does not follow the same stress-strain path during loading as it does during unloading, with the area between the two paths on a graph representing energy lost as heat due to internal friction. This energy loss is inherent in viscoelastic materials like rubbers and polymers, where the uncoiling and re-coiling of molecular chains during stress cycles causes the energy dissipation. High degrees of hysteresis are useful in applications like shock absorbers, while low hysteresis is desirable in car tires to minimize heat buildup." (Google AI overview)