I was working for Midas in the UK in the eighties, responsible for training all branch staff in brake servicing, and consequently I had excellent technical support and ongoing training myself from the major suppliers in Britain at the time; Girling, Mintex, Lockheed, AP etc.
Much of what is written in that post is true to high temperature racing applications and should not really be a worry to normal road use, but, given the higher ambient temperatures in Australia (less cooling effect) and, as mentioned above, the heavy modern automatics favoured here; Commodores, Falcons etc, the symptoms can be relevant.
The later paragraphs, regarding brake fluid, are straightforward and have been discussed previously on this (or another?) forum, particularly I remember making the point that you NEVER should top-up brake fluid and the reasons why.
The deposits shown in Figure 4 ae quite common, and as the author states not always easy to see, but usually if you have the rotor off the car, by tilting it against the light you will see this effect.
Unfortunatley the policy at Midas back then, and probably similar today in our local K-Mart type service shops, was to resurface, or 'skim' the discs (rotors) at every pad change. This makes for a better pedal feel, and is obviously more efficient from the first application of the pedal, rather than waiting for new pads to wear in to the worn surface, but the real motive was it is all profit.
The lathe is already there, and a good operator will have one rotor being machined in the five minutes it takes to remove the other, so a set of pads at say $100 retail ($40 trade) can be sold as a $200 job.
The problem is that eventually the rotor gets too thin, and can no longer dissipate heat as well, and it will definitely then either warp or crack, and I have seen both even if the author above has not.
That is why a rotor often has a number stamped on the edge meaning the minimum thickness below which, scrap it.
Another common cause of 'warped disc syndrome' is a less than 100% clean mating face between the rotor and the hub, a ten micron piece of grit here could mean a hundred or more micron run-out at the edge of the disc.
Although the symptoms listed above do seem common here on the Falcon/Commodore type large sedans, (and a complete disaster on late model Falcon One-Ton Utes) I have never had any problems with pads and rotors on any of my Mercedes, all automatics, all (except the 190E) quite heavy, all driven quite hard, and never had any fluid problems apart from once boiling away my pedal completely in the 280E coming down MacQuarie Pass, my excuse then was I had only just bought the car, no excuse really, ALWAYS flush brake fluid through if you have no proof it has been done recently.
A final note, although we like to keep our alloys clean, I advise against using those dust protector discs that fit between the wheel and the brake as they severely cut down airflow to the rotor.
This kind of info is not only useful, but essential to us all, and joking apart, is what makes forums like this worthwhile.
Chris M.
