As usual, there is no one magic bullet that will transform a poor brake to an effective one. Within the limitations of the design, everything has to be correct. Roundness after spokeing, Correct brake shoe type, Brake shoes turned to correct diameter and concentric with bearings. Many brakes were bought by manufacturers on cost and pressed steel drums polish and have a lower frictional value than iron. On many makes, the pre war malleable single sided brake drums were superior in efficiency to post war pressed steel drums, even if they looked full width. The Dominator used an iron lining cast into an aluminium drum, but the process was faulty, as in use the aluminium grows away from the iron lining. There is no heat path, the lining bakes the brake linings and if used hard, the unsupported lining breaks.
It is a big subject and my home made race brakes are amongst the best on the track, but are a Dural body for high heat dissipation and strength and a thin iron lining shrunk in w3ith about a 0.030″ interference. Iron has a very good frictional value, but a poor heat transmission ability, so the answer is to have the iron liner thin so heat will pass though to the alum body as quickly as possible. With 0.030″ interference, the whole job will not get hot enough for the alloy to grow away from the iron liner and so loose the heat path. Folks are also fond of putting a nice thick powder paint coating on brakes which certainly does not aid the heat to escape. As regards the suggestion to reduce the trailing shoe lining. Titch Allen advocated this years ago, but recently I saw several folks who’se opinion and judgement I respect, confirm the effectiveness of the ploy. I thought it worth mentioning, as anything that improves the efficiency of brakes on todays crowded roads without major surgery is to be welcomed. I have not tried the method, but it just made sense to me.
What I have done in the past that makes a good brake, is to use different grades of linings on leading and trailing shoes on my MM and these brakes are beyond reproach Roger
