All due respect Chris but that method IMO is not even close. The pressures are set 'static', reversing and braking will tell you nothing. Brake bias is always set for forward motion as the weight of the vehicle is thrown forwards, the front dives and the rear lifts taking the load sensing lever with it, the greater the distances between the body and the axle the less pressure is applied to the rear brakes. I know you understand how it works but I am pointing out why the reversing and braking method is flawed. As you said Chris not very scientific at all, you also said how much difference it made when trying the adjustment from one setting to the other, your 'farmer's' method may or may not be close but you simply cannot substitute a 'loose surface' for a decent set of gauges.
Not wanting to go too deep into this but, even the choice of spring rates can affect how the brake bias works, softer front springs equals less bias to the rear and vice verse. A manufacture sets the 'base' setting for the bias based on an asphalt surface with a typical coefficient of friction, I cannot remember the figures but when loading asphalt to pour into pavers we could not use too much 'release oil' or it affected the final friction factor, i.e. the typical traction environment the vehicle will be used in. We used bias valves in rally cars that would be on grippy or loose stages adjusting for each, and given that the typical road car will spend most of it's life on tarmac that is what the factory setting will be based on.
The more I think about this the more it worries me about the amount of cars lifted that have not had the brake bias recalculated. Don't get me wrong, this is an age self preservation thing and not a 'high an mighty' way of thinking, I am after all one of the guys years ago that used to fit Ford Classic front struts with disc brakes on our V8 Anglia's (stop nodding Frank
), and it did improve our braking power at the front but, the rear drums were useless and how much they contributed to braking is unknown but, they never locked so you never spun. Then we fitted the stronger 'Atlas' axles and got rear discs and they would lock the rear if you breathed on the pedal, we had dual master cylinders with adjustable push rods, at the end of the day there was never a perfect setting for all conditions.
Getting the brake bias right on a standard car let alone something raised, or with a drawer system or other unknown weight and so on is near on impossible. Suffice to say, if you get it working how you like it then that is good enough (for you) but, when in an emergency situation where you stand on the pedal and REALLY need to stop and god forbid you hit let us say a wall and suffered damage, would a little extra rear braking bias stopped you say a foot shorter and saved the prang? Given the various modifications people make to their vehicles that I would bet in reality there are very few cars set up correctly.
This is such a subjective issue that it generates all sorts of opinions but, IMO Mr 'T' got perhaps 98% of the LC 80 design right 1st time, the early braking systems being (shall we say) adequate were reworked, given the re-development they had to put in, I doubt they come up with the pressure figures for the LSV by chance.
regards
Dave