I just came across this which I think is quite clear :
The British army teaches drivers of tracked vehicles with mechanical steering brakes, which is everything up to and including Chieftain, but not vehicles with hydrostatic steering like Warrior or Leopard, to make SHORT full brake applications, not long gentle ones which WILL overheat brake disks or drums, whether submerged in oil or not. The brake surface cannot be cooled by the oil if held on for a long period as it has been squeezed out, and the result will be premature wear on the linings and overheated disks or drums which will then either grab or break up with serious results. There are many instances of M113s and FV432s that have suddenly turned 45 degrees and shot off the road into the bushes (or buildings) because the driver has been trying to correct for drift by holding a brake on for long periods.
David