A 28c tyre pressure should be a fair bit less than a 25c to be equivalent. That's why at the same pressure they roll faster. A 28c at 90psi is absurdly hard, a 25c at 90psi is fine. Equivalent will be pumping the 25s to 110ish.
Armchair rant over, sorry
So, less than 1W improvement in Crr, which could easily have vanished with the aero losses and both of which are almost certainly blasted into nothingness with atmospheric pressure and wind conditions.
A 28c tyre pressure should be a fair bit less than a 25c to be equivalent. That's why at the same pressure they roll faster. A 28c at 90psi is absurdly hard, a 25c at 90psi is fine. Equivalent will be pumping the 25s to 110ish.
Armchair rant over, sorry