I have just put new shoes on the rear of my pick up, the old ones were past their best. The problem now is that the rears lock up under hard brakeing long before the fronts. I relise they are more likely to as there is little weight over the rear axle. Should this happen though ? Shouldn't there be a valve or something which compensates for when there is a load or not? Is there a way i can manually adjust the rear brakes so they are more balenced with the fronts? i.e. locking at the same time.

Thanks

Should be a compensator--maybe stuck.

Can I unstick a compensator or is it a replacement only job?

First you need to do an operational test (see photo).

If the lever is not moving, clean it thoroughly with hot water under pressure, blow it with compressed air to dry, then soak it with WD40 (arrows) and check again in half hour..

If all that doesn't unstick it, replace.

when I lowered mine I ended up completely removing the brake compensator, I went for the setup that uses the pressure regulators screwed directly into the brake master cylinder.