Brake parasitic drag

[aceofbase]

Does anybody know a method of measuring parasitic drag in the disc brake (pneumatically operated)? It's a kind of parasitic torque that presents in all modern brakes. After applying the brake and when it's released there is still some local contact between the lining and the disc. But after a few rotations of the wheel this torque disappears. I need to find how big is this parasitic torque (it's considered to be pretty small) and is the possibility that this torque can appear not only applying the brake but when driving off-road. Currently I'm thinking of some kind of a sensor that could measure the force between the pad and disc - but I didn't find any appropriate type of sensor... I could try to use the brake dynamometer – but it will be the last thing I would try, cause I want to measure this torque right driving the truck depending on the road conditions.

 

[aceofbase]

Actually there is one new type of non-dragging brakes: and I'm to find out if it worth that additional money that it's asked for. It uses electrical mechanism for forced retracting of the pads. But still it's interesting: all the brakes in the world have this problem (air brakes certainly) and nobody cared of it for a long time...

 

[patprimmer]

Twin spot callipers, that is one piston either side of the disk type, have a positive retraction device. It is the square section "O" rings that double as seals and retractors. If the pads are attached to the piston, the piston will also pull the pads back so long as the friction between the pads and the pad thrust surface is not to high.

Regards

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