Handbrake Problem

hi guys
my car is alfa romeo 155 Q4.
i have a problem about handbrake system.
handbrake cables and rear disks and pads.
but the car slides on the slope i mean the handbrake dont works on the slope roads.
without slope roads handbrake works.
help me?
thank you

hi guys
my car is alfa romeo 155 Q4.
i have a problem about handbrake system.
handbrake cables and rear disks and pads are new.
but the car slides on the slope i mean the handbrake dont works on the slope roads.
without slope roads handbrake works.
help me?
thank you