Brake issue

[Timbopbmw]

My PBMW 318 has developed a brake issue this year and i cant seem to get to the bottom of it.If i run over any rumble strip's the brake pedal travel extends.This caught me out first at silverstone when trying to make a pass into the complex,had loads of pedal travel then the back snapped round on me (see motors tv july 3rd).so straight away i was looking at the front pads backing off when rumbled.The front wheel bearings did start to rumble and were loose when warm.so they were changed, and also master cylinder.the calipers are only 1500miles old.I still have this problem and have to pump up the brake with my left foot on the straights,which is a pain.
Has anyone else had similar experience's??
TIA

Tim

[stratos]

I have had this happen with old and new calipers. Sometimes the caliper seals have a slight springyness to them which encourages the piston to retract. You could try fitting new seals and / or fit some light springs behind the pistons to keep them out (this is standard practice on most racing calipers) (springs available from AP Racing etc ).

[Jhonno]

Heard of this before

The rumble strips vibrate the disc moving the pads away from it!

[ShakeyC]

I agree too encoutered it many times before usually on older cars through wear and tear, new piston seals and new brake fluid should inspire bit more confidence on the pedal.