Ya never know what sort of question or topic is going to bring some listee's
inner egghead roaring to the surface. I find these kinds of posts both
interesting and tedious, oddly enough (and that's not a knock on Kim or
anyone else, btw). I still read 'em all the way through 'cause I feel like
I'll miss something if I don't. Just one of the odd/amazing/unique things
about this list community- I sometimes feel that if I'm on this thing long
enough, I'll eventually know at least one thing about everything in
existence. Might even learn something about Vanagons. : )

Carry on,
Robert

----- Original Message -----
From: "Kim Brennan" <kimbrennan@MAC.COM>
To: <vanagon@GERRY.VANAGON.COM>
Sent: Monday, August 16, 2004 1:10 PM
Subject: Re: Rotor thoughts

> That's not true. You don't have to do a chemical analysis of the metal
> (which actually will likely give you very little information of value
> anyway). Of far more importance when dealing with metal is the
> crystalline structure.
>
> The crystal structure can reveal flaws that will lead to failure. It
> can reveal nonhomogenous composition. Depending on the nature of the
> material crystal structure can sometimes be revealed by patterns.
> Analysis of meteorites, for example is done by polishing the surface
> and then etching with acid. In industrial applications spectroscopic
> imaging tends to be used. Rotors being cast, should have a crystal
> lattice that is revealable. Forged metals tend to reduce the size of
> the crystals (removing the gaps in the crystalline structure, and
> improving the strength of the forged material.)
>
> You have continued to claim that your rotors are "bad", without
> describing that nature of the problem (other than "rust", which is
> perfectly normal on rotors.) Are the rotors warped? Are they cracked?
> Are they out of balance? If so how did you determine they were out of
> balance? Wear patterns can often times be extremely illuminating, hence
> why pictures are valuable.
>
> While state inspections vary, most places are concerned with.1)  Do the
> brakes work? 2) Are the materials within tolerances? 3) And are the
> materials up to the standards of the day (not necessarily TODAY's
> standards, but the standards of the original manufacture date of the
> vehicle.) Tolerances are measured (hence the micrometer measurements.)
> Standards for the rotor are usually resolved by visual inspection.
> Hence the need for a picture.
>
> If your rotors are rusty on either wear surface after having driven the
> vehicle to the end of the block and back. The Rotors are probably NOT
> the problem. The calipers and pads need to be checked out. The pads
> should be in contact with the rotor. The caliper should move back and
> forth. The piston should respond to the brake pedal.
>
> On the other paw, if you have rust cracks WITHIN the rotor (as opposed
> to just on the surface), that could be a sign of a faulty rotor. Again,
> a picture would resolve that issue very easily.
>
>
> On Aug 16, 2004, at 3:27 PM, Eric Zeno wrote:
>
> >      The only way to tell if the manufacture cut corners
> > in the alloy in the materials is to do a chemical analysis
> > of the material. Obviously I'm not going to do this.