Braking performance is limited by: - angle of CG to front wheel, tan(vert angle) == max stopping acceleration in g (assuming front/all wheel braking, rear whee

Braking performance is limited by: - angle of CG to front wheel, tan(vert angle) == max stopping acceleration in g (assuming front/all wheel braking, rear wheel only is different) - the coefficient of friction (generally in the rangeish of 1) - shear strength of the rubber in the tires (wider/more is better if you're at other limits) - other braking system issues -- heat dissipation, crap brake pads The thing about single wheels is that the CG -> contact patch vector basically defines all of the instantaneous dynamics of the system. If you want to go from turning to braking, you have to change position, and there are limits about how fast that can happen that don't apply in a multiwheel system.