when i have changed direction from forwards to backwarse or v.v. as i apply the braks they shudder something shocking. this does not happen if after reversing i do not brake, just role to a stop and then drive off but if i brake during revering it happens and then it happens againg if i brak while going slow forwards (10km/h or less). i think the pads are ok, although i have heard that the problem could be the pins in the callipers. is this so? and if so what should i do and what might it cost?