Brake imbalance on rear???

[gary d]

Failed the m.o.t. on rear brake imbalance. figures were as follows nearside 2.24kn offside 1.06kn resulting in a brake imbalance of 53% maximum permitted is 30%. I ordered a second hand caliper from Ricerocket and fitted on the retest the figures read nearside 1.87kn and offside 0.91kn 51% imbalance these figures are for the rear brakes when service brake applied, no issue when the park brake is applied figures for parkbrake were N.S. 1.65kn O.S. 1.72kn
My neighbour (a mechanic of sorts) has suggested the limiter/bias valve which limits the amount of force applied to the rear brakes may be at fault? Has anyone experienced this problem, do you know if the fto uses one of these valves if so where is it situated? and where do i get a new one???
Your help would be very much appreciated.

[steelroe]

Common fault on the FTO, the proportioning (bias) valve is located above the steering rack behing the engine, Just follow the brake lines from the Servo to the valve, It has 2 lines going in and 4 out.

[steelroe]

Also I hae plenty for sale.

[steelroe]

Just to clarify if you have ABS the bias valve will have only 4 pipes connected to it, if you do not have ABS it will have 2 in and 4 out.

[gary d]

I have ABS Rory, are your valves new and how much are you looking?