Testing a Proportioning Valve?

autopar3000 said

Like trapster, if I drag the brake for a little while and then try to stop the car, it feels like the front brakes do more work and it stops better. Maybe because the rear brakes heat up a little and don't work as efficiently, thereby leaving the fronts to do more work? Or maybe by dragging the brake the proportioning valve is cutting down a bit of pressure to the rear?

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it could just be the disks and the pad material. I had (have) some Cyclpro - Chrysler pads that didn't have a lot grab or pedal feel - especially with a disk that's worn smooth. Or the calipers aren't working. If it feels like the front, I'd focus on the front.

Rear brakes help the most on the initial and light braking inputs. While under hard braking weight shifts forward reducing the traction of the rears. That's when the proportioning valve is needed.

As far as heat goes, with street use, you will have to try really hard to heat the linings to a temperature where the friction declines. A really long steep downhill in the mountains might get there if riding the brakes. That's true both for the fronts and the rears. In fact their performance may increase slightly after a couple applications in a row.