does it do the same on sudden acceleration?if so you will have to jack the car up and give it a thorough check over,check for kinked and twisted tyres,loose wheel nuts,broken springs,struts inop,a/roll bar links and bushes,lower arm bushes/balljoints/loose bolts,steering system for play etc,the list goes on but good luck
howtomendit.com for free repair help, information and advice.
Try fixfault.com to fix cars.