why does my break pedal vibrate when i break hard?

sounds like the brake discs are warped which would give a shudder through the pedal. Easiest way to sort it out is replace the discs.

Colin
May 2010

if discs were warped then you would have a vibration through steering under braking as you only mention brake pedal vibrating this points to abs. i take it you have looked at discs for cracks,rusted areas[due to lack of use ] which could also cause pedal to pulsate.

q
May 2010

Hi. Definitely warped front discs as ChicksFan says. Front discs and pads will need to be replaced. It'll cost a couple of hundred quid at a garage although for a basic DIY home mechanic it's an easy job. You can get the parts for less than a hundred pounds for most vehicles

Connoisseur
May 2010

Warped brake discs. Replace the discs and pads with new ones.

The problem can be caused by braking from high speed to a halt (say at traffic lights), then sitting there with the foot brake on. While the rest of the disc can cool, the part of the disc held by the brake pads stays hot, causing hot spots, and warps the metal.

ChicksFan
May 2010

without knowing what vehicle you are talking about,i would suspect it to be ABS coming into operation and if so is normal under very heavy braking!

k
May 2010