Date: Wed, 16 May 2012 18:00:12 -0700
Reply-To: Scott Daniel - Turbovans <scottdaniel@TURBOVANS.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Scott Daniel - Turbovans <scottdaniel@TURBOVANS.COM>
Subject: Re: Recoined Brake Shoes. Means: Arced ?
In-Reply-To: <CAB2Rwfh5ZkEOZBpZV_e6msy3v=Y=hvkMtKqMCgUs=jU+npcrZg@mail.gmail.com>
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Brake shoes are not usually radiused these days..
25 years ago it was part of any brake drum job ..
radius, or 'arc'
the shoes to match the curvature of the drum .
That's illegal now even, I believe..due to hazardous particles getting
into the air ..
it used to be done right in the shop where the car was being worked on ,
or by the Brake Truck Guy who came around selling brake parts and
arcing shoes for shops.
what i read here today was that recoining is tweaking the shoe itself ..
a different deal slightly.
and ...
I have not had to do this ever as vanagon brakes just don't seem to wear
for me much at all..
but the conventional wisdom is to space out the bottoms of the shoes for
more full contact across the whole face of the brake shoe and lining.
next time I'm doing drum brake work on a vanagon ...I'll try that
method out.
I can advise not to use very cheap brake drums..
I had one out of round, and newish , and with the biggest balance weight
I have ever seen on any drum..
which easily fell off. From a vanagon specialist shop too. pretty sure
............which is just too typical.
On 5/16/2012 5:33 PM, neil n wrote:
> 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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