Rear brakes locking up

[Bernieszy]

Hello I have a lada samara I have a problem with the rear brake (s, I am not sure if it is one or both) I have replaced the proportional valve and the master cyl, It only happens when you push really hard on the pedal not under normal braking. Can anyone offer me some ideas on what the problem could be?
Thanks Bernie

 

[yes2mud]

Not familiar with these motors,has it got rear drum brakes?Your problem sounds like a sticking wheel cylinder.If the rear linings are low the cylinder may be sticking due to the piston moving out further for drum contact.If the rear cylinders are just a bit corroded but not scored,they can be polished up and re-sealed.Hope this helps.Geoff.

 

[JohnD]

Or it might be that the front brakes are weak.

In NZ do you have a periodic vehicle safety check that includes brake function? Over here the MOT tests braking on each wheel on a rolling road.

Is it disks front, drums rear?

Are all the pistons moving freely, and the disks clean and bright where the pads have been rubbing on them? With plenty of pad thickness?