Thanks Kev and John
Every day’s a school day! So the reason cars have bigger discs and pads is because they come with bigger callipers that have bigger pistons which provide a greater force on the bigger pads, the edges of which are further away from the axle centreline providing greater efficiency. Bigger pads. also provide better heat dissipation in the conversion of kinetic energy to heat during braking. If I’ve got all that right it doesn’t explain the advantage of chamfering such a large area of the pad furthest away from the axle centre line. I still can’t see the point of having a significant greater pad area when the pads are about half worn. Just to be clear I’m just replacing the pads on standard callipers and discs.