Affect of caliper piston diameter on fluid temperature

[Robmarriott]

Odd one this but I recently found out something which made me question it.

On a Clio 172/182 road car the standard sliding front calipers use a single 54mm piston (on a 280mm disc)

On the Clio Cup race car, they still use a 280mm disc but with a caliper which seems to be from a Laguna, with a 60mm piston

The road cars suffer with terrible brake fade when used on track, the cup cars lost the fog lights and used a duct and deflector to direct air at the back of the disc to combat this but also the bigger piston.

Why would this be?

Would it help with the cooling of the fluid or is it more likely that they used a larger master cylinder and the pedal was better with the 60mm piston over the 54mm?

[Dave Brand]

Brake fade is caused by overheating of the pads, not the fluid. Fluid boiling is a separate issue.

The race cars will probably use larger pistons on the front to increase braking effort on the front relative to the rear. As a race car braking system doesn't have to cater for heavily-loaded conditions & the much heavier braking in a race compared on the road will result in increased weight transfer, less rear braking effort is required.

[Robmarriott]

I hadn't thought of it that way, I suspect the used a bias adjustable pedal box with larger master cylinders too so the pedal felt right.