Car brakes

[dickturpin]

Struggling to get my car front brakes balanced for not. The piston is free and the sliders are lubed. Car drives fine and tester says they are OK under light braking but harder braking takes them out of tolerance. Reading around 380 on one side and 320 other.
These are disc brakes on my vw. Problem is I can't check if I've sorted it without going back on rolling road.

[dickturpin]

Forgot to add, it has new discs and pads in.

[red98]

Might need bedding in a bit......find an empty road/car park.build up speed, take hands off steering wheel or hold lightly and apply the brakes  (  no H+S sh*t here in the red household  :lol ) if it pulls to the side its not balanced, pull to the right you need to look at the nearside caliper, offside if it pulls to the left...if it was my car I would run it around for a few days to let the new pads bed in 

[Fazerider]

I've exactly the same problem with mine.
I thought the discs were in a poor state so changed them and the pads prior to the MOT. It passed the test with no issues (other than some welding on one of the sills). On the way back from the testing station the brakes felt uneven, I tried braking slightly harder and the left front wheel locked up... clearly the right caliper is doing nothing.
Next plan is to replace the caliper seals in the hope that'll cure it, but the piston felt reasonably free so I suspect the fault lies with the master cylinder or servo.
I'm not familiar with these modern devices, it's the first car I've had with power assisted brakes. :lol

[Frosties]

Might need bedding in a bit......find an empty road/car park.build up speed, take hands off steering wheel or hold lightly and apply the brakes  (  no H+S sh*t here in the red household  :lol ) if it pulls to the side its not balanced, pull to the right you need to look at the nearside caliper, offside if it pulls to the left...if it was my car I would run it around for a few days to let the new pads bed in 

Totally agree with Red on all counts. Check tyre pressures before you go out though as this can give a tug to one side if below pressure.

[Dead Eye]

Had this come up on my MOT as well...

Hadn't really noticed any imbalance whilst driving but I hope to get out and do some tests and re-bleed the system



Edit: Oh and yes, new discs and pads all round on mine

[dickturpin]

Re greased the offending sliders and lubed the piston again then tried Red's suggestion. It seems straight and balanced to me so will have to resubmit and see what happens.

[dickturpin]

All good today. ..thanks for the suggestion Red.

[unfazed]

Most likely a dodgy rubber brake line between the caliper and the car body, it would be fine in normal use, but expands under hard braking reducing the force to the caliper.