The advent of antilock TV brakes (and increased computer vehicle control) circa 1998 kept us from any longer using the magnificent Kelsey-Hayes brake controller. Dead simple effective.
For a given combination rig one should know the setting to lock the brakes on a dry surface at a low speed. And record it. Then, another note to see what setting locks it on gravel.
This is done with an observer. One brake will probably lock sooner than the others (brand new trailer; an otherwise new TV). So it will take several tires to observe both port & starboard. Brake mechanical adjustments may ensue.
Would be good to also do same for a wet surface.
Locked brakes will cause the TT to travel even faster in some instances, so knowing the point of lockup is the reason for testing. Maximum application of force short of locking is the ideal.
Hitch lash up is critical. Assuming full propane, fresh water and normal load aboard, maximum transfer of TW to TT axles is beneficial. As is care to get bearing preset correct, etc. As 90% or more of rigs as do not exhibit best possible lash up, it behooves one to be painstaking.
A greater braking load is present in the leading TT axle of a tandem or tridem, so scale work should also try to uncover any gross discrepancies side to side, as well as front to rear. One weighs the TT individual wheel positions on a segmented scale.
For purposes of testing, those who do not run full pressure on trailer tires otherwise should start any tests with full pressure, IMO.
Even new TT may not be receiving full amperage at the electric drum brake. Re-wiring in a "star" pattern using ANCOR wiring, terminations, fuses, junction box, etc is an upgrade. Test equipment measurements are needed.
The older the TT, the more likely corrosion and undersized wiring, etc, may degrade performance. The system may work, but not work as well as it could. Overkill in componentry is just right.
Electric over hydraulic disc is a substantial upgrade (see comparison test on TUSON website between new electric drum and hydraulic disc as conducted by reviewer "Mr Truck"); and where antilock is also installed another step up. State of the art.
It wasn't always easy to accomplish, but a well sorted rig could stop faster than the TV solo, traditionally. This may not be so easy today due to overriding computerization, but tire technology is so far advanced over 1966
that -- given best brakes -- it should be close in 2016.
And the heavier the TV (past what is necessary) the worse the braking, overall. Longer stopping distance. Thus making TT brakes even more important.