thank you gentlemen.

yes. I'd read a bit about how brake shoes can be radiused. If my use
of that word is correct.  ;)

If i get my hands on another set of raybestos "pro" shoes I'll see if
they're the same thickness along entire lining.

On 5/16/12, David Beierl <dbeierl@attglobal.net> wrote:
> At 01:09 PM 5/16/2012, neil n wrote:
>>think the wear patterns indicated that the top 1/3 of shoes were
>> contacting
>>drums but I haven't looked in some time.
>
> Look in the archives for Dennis Haynes' discussions on spacers for
> the bottom pivot.
>
> If the lining material is of constant thickness, there's no possible
> way for it to have full effective contact throughout its life in a
> setup with a fixed pivot point.  Whatever point touches first will
> start to wear in a small patch which will gradually spread as the
> brakes wear in.  The better the initial fit, the larger that initial
> patch (or perhaps two patches) will be.  Perfect fit requires that
> the lining radius of curvature precisely match the drum in its
> present condition of wear, and that the pivot be shimmed until as
> nearly as possible the entire lining contacts the drum simultaneously
> when the brakes are applied.  This will quickly wear into full
> contact.  At the end of service life the cylinder end of the lining
> will be worn to minimum thickness, while the pivot end will be
> considerably less worn.  The cylinder end of the lining will always
> do more work, and because our brakes are set up in a leading and
> trailing shoe arrangement the shoe where the cylinder end faces the
> oncoming brake drum will do more work.
>
> Back when drum brakes were used for front wheels where most of the
> work gets done and cars didn't have vacuum-assisted brakes I believe
> they had more elaborate arrangements for some, with double leading
> shoe setups with (I presume) two cylinders and such; and there were
> brake shops that would individually fit shoes to drums and so
> forth.  And my grandmother's (late '50s/early '60s) Studebaker had band
> brakes.
>
> The (front) disk brakes on my Saab 96 took this wear thing to an
> extreme.  They were Lockheed brakes, single-cylinder with a pivoting
> instead of sliding arrangement, and new pads looked like a ski
> slope.  When they wore down to level, they were used up.
>
> Yrs,
> d
>
>

--
Neil n

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