97 Camry.....brake "rumble" finally solved.

[bcp477]

Aha ! After replacing lots of brake components, including the calipers (I'm refurbishing the car anyway)....and trying several different sets of pads (several brands and grades)....I have finally solved the brake rumble issue, so common on the 97 and 98 cars. It is obvious, as I suspected, that the issue is really due to overheating of the pads. This I confirmed by microscopic examination of slightly worn pads, in comparison with brand new, un-installed ones (same brand and type). The friction material on the slightly used pads (which had begun to display brake rumble), upon close examination, indicated that particles of the material had actually melted and been pulled out of the surface of the pad (perhaps these particles were then adhering to the brake rotor surface) , then re-deposited toward the edges. The end result is that, almost every time the brakes are used with this type of pad, the surface becomes pitted....and ultimately becomes uneven, due to the re-disposition of the friction material. It is hard to explain, but clear when examined closely (I am familiar with material forensics). I also enlisted the help of a friend who is a materials scientist, at a local university....and used their equipment for the examinations. The end result, simply put, is an uneven friction surface, which easily goes to explain the vibration and noise.....i.e., "brake rumble".

The "fix" involves nothing more than the "right" brake pad compound. I finally tried the new ceramic pads, ones by Akebono, to be exact - and this has ended the problem, at least for the last 600 or so miles (all the miles I have on the new pads). The standard copper laden, non- asbestos "premium" type pad material, offered by lots of manufacturers (and the standard factory pads as well), apparently simply does not have enough heat capacity for the Camry brakes. Perhaps the brakes are too small for the weight of the car....or, I suspect that the front brakes, in combination with the rear drum-type brakes (which have much less "stopping power" than discs) - are simply too small to do the job, with the standard friction material.

In any case, the high-end ceramic pads seem to have a great deal more heat capacity than the standard so-called "premium-grade" semi-metallic pad material. It is likely that, though I can't prove it, the ceramic pads wear differently as well, in that the grain structure of the material is finer than that of the "conventional" pads...and the surface doesn't pit and shear as readily.


As an aside, I have also completed the removal of the always malfunctioning ABS system from my car....and the process was easier than expected. Re-routing of brake lines was not that big a deal after all....and I was able to utilize standard lengths of pre-flared brake lines, in one case by simply adding a couple of extra bends (sort of an "S" curve), to take up the extra length. The brakes feel much firmer and more sure now....and braking distances have improved, I believe (though I haven't measured them). Of course, some of the improvement must be credited to the ceramic pads, but not all. Anyway, the brakes are now finished - I can move on to other matters.