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Re: [T3] 73 Front Brakes on a '70


On 2 Dec 98, at 13:48, Sandin, Karl-Olov wrote:

> I have measured the pistons for you, and the diameter is 30 mm. The
> calipers have 6 (six!) bleeder valves...only God knows in which order I
> should bleed this system... Don't really need to - just want to change the
> fluid. Any hints?

Thanks for the measurements.  The quad 30mm pistons have only 2% more 
area than the single 42mm pistons, so I am surprised that the MC was 
changed.  I would think that the brake balance would be virtually 
unchanged if VW had stuck with a 19mm MC and 22mm rear wheel 
cylinders.  Perhaps the change actually was to the Volvo style step 
bore MC!  Does anyone know?

Bleed one circuit at a time.  The bottom pistons on a caliper will 
each have one bleed valve at their tops (one inside, one out) which 
will be just below the center of the caliper.  The top pistons will 
both bleed through the single bleed valve at the top of the caliper.

Just look at the caliper and think about how the fluid must pass to 
get to the pistons.  You need to open valves that are at high points 
to get rid of air, low points to flush fresh fluid.

I'd be willing to bet that the calipers for L and R are the same, 
with perhaps the only difference being some piston alignment plate or 
some such thing.  Perhaps not even that difference.

Jim 
-
*******************************
Jim Adney, jadney@vwtype3.org
Madison, Wisconsin, USA
*******************************

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