MOT fail - brake imbalance - Ideas?

[Ian1976]

car failed its MOT today for 'front brake imbalance'

Any idea's?

I have stripped the pads out of both front calipers - all seem fine, 20% worn (evenly) at the most, discs are in good condition. No brake judder evident whilst driving. Both caliper pistons are free, as are all the sliding pins on the caliper/carrier. No evidence of any binding or pads being seized/stuck in the carriers.

starting to run out of ideas now....

had a brainstorm with a few work mates - all we could think was a possible master cylinder issue - maybe something seized/sticking and not porting enough fluid/pressure to one side. Possible or not?

What next?...

[Zoobeef]

Possible air in the line to one caliper. Give the system a bleed with fresh fluid

[02coled]

I had similar problems just last month. It took one clever mechanic a few seconds to tell me what it was (as he had the same problem and it was nothing to do with the front brakes).

Check the rear brakes it can be them causing the issue, but it will show up on the front because brake systems are cross linked. Front left and rear right work together as a pair as well as the front right and rear left. Its so that if one fails you can get to a safe stop.

So if all else fails and nothing seems to be wrong on the front brakes. Check the rear brakes!

Its worth a try.

Ask for the print out as well, so that you can find which one is causing the imbalance.

[wild rover]

Same problem found rear shoes out of adjustment.Adjusted problem solved.

[davepoth]

wild rover said:

Same problem found rear shoes out of adjustment.Adjusted problem solved.

Seems counter intuitive, but the car is likely to have "x-split" brake circuits, so the front left is tied to the rear right and vice versa.

[browny,s blower]

hi front flex pipe could be buggered inside
undo bleed nipple and press pedal hard (check resistance)