It's a coefficient; just like drag coefficient, the load (area for aero) must be accounted for. It's pretty well shown on pg 38 with the 15" and 17" examples: while the 17" shows a LOWER COEFFICIENT in the best case scenario vs the 15", clearly the actual rolling FORCES for the 17" are worse than the 15"; in fact the
worst 15" value is better than the
best 17" value!
Pg 24 shows that the heavier the tire, the higher the r.r.
force; shown even more graphically on pgs 30 and 32.
Pg 31 shows coefficients with the big tires outperforming the small. Yup, big ones do better at high loads. The empty light end of my car isn't subject to high loads.
I did not expect to see r.r. increase with increased diameter!
Unfortunately I did not see much useful info relating to width except for what may or may not can be read into pg 30 results.