Date:         Mon, 26 Dec 2005 17:12:08 +1300
Reply-To:     Andrew Grebneff <andrew.grebneff@STONEBOW.OTAGO.AC.NZ>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Andrew Grebneff <andrew.grebneff@STONEBOW.OTAGO.AC.NZ>
Subject:      Re: Speaking of rear disc brakes...
In-Reply-To:  <20051223013212.GLYZ25916.priv-edtnes56.telusplanet.net@YOURC05FDFAF94>
Content-type: text/plain; format=flowed; charset=iso-8859-1

>I've locked up the front brakes on several Vanagons (both early & late).
>Trust me, it can be done.

I've locked the front brakes of my stock 57 
split! It wasn't so difficult. In fact those 
brakes were FAR better than my T3's... despite 
being decades older and lacking discs.

>All this talk of rear disc brakes is crazy!  Fact, the front brakes of a
>vehicle do about 60 to 70% of the stopping.  So if you want to stop faster
>you really need to clamp on to the front disc better.  Right now I bet you
>CAN'T lock up the front wheels as you don't have a big enough clamping area
>and a big enough master cylinder to apply the necessary pressure.  Also, you
>NEVER want the rear brakes to lock before the front brakes.  The issue with
>the Small Car setup is that there is no brake proportioning valve included.
>They say the rears never lock before the front... I would like to know how
>they tested that?  Was it on loose gravel or an ice covered road or was it
>just slamming the brakes on a tarmac road?  If your rear brakes lock before
>the front brakes, the rear of the van will begin to slide and you will have
>a messy situation on your hands.  You NEED a brake biasing valve in the
>system if you go to rear discs!
>
>I think everyone wants the rear brakes as they are sexy and give the van a
>sense of "bling bling"   I think getting the rear drums media blasted and
>then powder coated makes them look pretty sharp.  Installing some 280mm or
>288mm Audi brakes on the front with a larger master cylinder will make the
>van stop on a dime.

According to Hansen (maker of Porsche brake kits 
for T3s), whose kit is TÜV-approved, the stock 
mastercylinder is up to the job. He doesn't even 
mention adjusting the stock proportioning valve 
(maybe they weren't fitted to US-market vans), so 
this must be OK as well.

Braking depends on: pad area, swept area, radius 
of the swept area and of course pad material, 
brake temperature and condition of brakefluid 
(and, usually overlooked, tire compound is 
vital... long-life hard-rubber tires dramatically 
increase braking distances). Poor caliper 
rigidity and hose expansion should not be an 
issue in a "normal" street vehicle, but may 
affect initial braking rates and pedal feel.

Rrear brakes are more for braking stability than 
anything else, though they will be more important 
for retardation in a heavily-loaded vehicle than 
a light one. If you have even been pushed under 
brakes by a trailer, you'll know how nasty it 
feels to have the rear brakes lock!

The real benefits of discs over drums are:
-appearance
-ease of checking remaining lining thickness
-ease of lining replacement
Drums are PIGS to work on! And ugly to boot.
--
Andrew Grebneff
Dunedin
New Zealand
Fossil preparator
<andrew.grebneff@stonebow.otago.ac.nz>
Seashell, Macintosh, VW/Toyota van nut

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