My car has failed MOT on brakes imbalanced across axle rear - my question is a few months back I had wheel cylinder and brake pad done - should I take it back to the garage could they have done something wrong?
Thanks in advance.

  • 1
    Take it back to the shop, maybe they didn't get a;ll the air bled out on one side.
    – Moab
    Sep 17, 2019 at 16:44
  • Mystery abbreviation “MOT”??
    – zipzit
    Sep 18, 2019 at 3:30
  • 1
    @zipzit from 'Ministry of Transport' - the compulsory roadworthyness inspection that cars in the UK have to have every year.
    – Nick C
    Sep 18, 2019 at 9:01

2 Answers 2


The likely causes of differential braking are:

  • hydraulic imbalance (air in system, failed proportioning valve, etc)
  • ABS unit not properly bled
  • different co-efficient of friction on brakes (one pad glazed, the other not, as an example. Could also be a difference in finish on the rotor/drum/metal brake surface.)
  • dirt/debris/stones interfering with braking action

For resolution, I would probably first visually inspect, then bleed the hydraulics. If it was still not balanced, then I would pull the pads and sandpaper them to a fresh surface. For starters.

For testing, I would jack up the rear of the car, and with a breaker bar or similar leverage try turning the wheel and see if the drag with uniform brake pressure (could be engine off) is about the same.


You say "wheel cylinder" - was that just one, or both sides? If it was just one, chances are the other, old one isn't working as well as the new one, which is causing the imbalance.

Hopefully they did the pads on both sides, as they must always be replaced as a full axle set.

  • Yes they said they did both rear cylinders and brakes. Thank you.
    – D Scofield
    Sep 17, 2019 at 15:23

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