replacing brake discs

[Simon J]

In line with Don's comments above it's interesting that the Volvo Performance Brakes are promoted by Volvo not in terms of their absolute stopping power, but rather in terms of their ability to withstand repeated heavy use as a consequence of their larger (both in terms of diameter and thickness) discs. The same is obviously true of the AP set.

However it isn't correct to assume that the larger pads of the AP or Volvo kits improve the stopping power as pad area is irrelevant in relation to braking torque. (The larger pads will of course improve heat dissipation) But obviously the larger diameter discs will increase braking torque for a given pedal pressure, and this, combined with the more aggressive pads of the AP kit would undoubtedly account for their apparently prodigous stopping power. As far as I can determine, the Volvo pads are nowhere near as aggressive as the Ferodo DS2500 but Volvo decline to give any specific data on them.

And while the four piston AP calipers would logically seem to be better than the single piston Volvo ones, it's worth noting that the same type of single piston caliper as the Volvo was used by BMW on the M5 up until the latest model!