In terms of brake pad material, the term 'soft' is rather a misnomer. It really refers to the pads tempurature range and friction level. Hard pads = higher temperature range; soft equals lower.
I would doubt seriously that changing the pads will have any impact whatsoever on the effectiveness of the handbrake.
I am not familiar with the rear brake setup on the ARP4 but when I converted to rear disc brakes on my Plus Eight in 1990, I modified the handbrake 'tree' to increase the leverage and effectiveness. It rise to a state of 'just about legal'.
I agree with you, David.
It's the clamping ratio that is important and only mechanical leverage will supply this.
The issue with using the same pads as parking brakes is that the pads cool and thus shrink, lessening any original leverage applied. I assume the ARP4 calliper uses the same pads..?
