Instrument to measure braking performance?

Here is the photo. The rotor and caliper were painted “ purple “

The paint began to strip after the 5 year mark. Lots of people complimented the look.

This is how people do it on the island. In the USA, only the caliper is painted.

Differential GPS is a poor acceleration measurement tool, especially when there are 3-axis accelerometers built into nearly every smart phone than apps can use to get actual acceleration data. (every one I’ve ever had, anyway).