probably a daft question but although I'm good at setting brakes up and adjusting them so the pads contact at the same time I wondered why they don't do this themselves ?. the way i see it if one pad contacts before the other it meets resistance from the disc and so the brake fluid should push the other pad out to the same position until the pressures are equal and the real work starts.I'm sure however we've all seen the scenario when they are uneven and on applying the anchors the disc can be seen to bend over in one direction. What am I missing here?
They do.
If the piston seals are clean.
just had a thought ..is it because the disc bends a little before the other pad can move out past it's original seal position so that when the 2nd pad contacts, the disc has already been bent over a little and so the pads are never really properly centred ? (if you no what i mean ) sorry for the waffling!
oh yes ...piston seal friction !
Thats it kaiser - if the resistance to the disc flexing is less than the resistance to the piston moving in the seal the disc flexes first. the first bit of movement of the piston is distortion of the seal without any movement of the piston thru the seal