[T3] Brake Calipers

Jim Adney jadney at vwtype3.org
Sat Aug 13 05:28:13 PDT 2011


On 13 Aug 2011 at 10:20, Jens Vagelpohl wrote:

> On Aug 12, 2011, at 19:28 , Jim Adney wrote:
> 
> > On 12 Aug 2011 at 16:10, Dave Hall wrote:
> > 
> >> I think most VWs after the Type 3s got aome sort of brake proportioning
> >> valve.  Type 4s had a prssure limiting valve on the rear, and our 74 Camper
> >> did, plus all the watercooled VWs we've had since.
> > 
> > I'm betting that Type 4s got the same proportioning valve that 914/4s 
> > got. It just send a fixed fraction of the front circuit pressure to 
> > the rear brakes. I have one of those on my shelf if anyone wants one.
> 
> They look similar in the parts book drawings, but the 914 part has a
> unique 914 parts number. The Type 4 part has a 411 parts number. 

That's interesting, and I guess it makes a lot of sense. The 914 has 
rear disks, with little tiny pistons AND the proportioning valve, 
while the Type 4 uses the same rear drum cylinders as the Type 3. 
Both have front calipers with 42 mm pistons. I never got far enough 
into a Type 4 to notice that there was a proportioning valve in that 
rear line. I'm surprised. I would have guessed that the F/R brake 
balance would be pretty much the same as a Type 3.

The valve I have is from a 914. It has a spring inside and I remember 
that it has a stepped piston to give the proportioning ratio. It's 
possible that they were made with different diameter steps, but my 
bet is that the spring, which is somewhat external and adjustable is 
just adjusted differently.

It's been decades since I've had it apart, so I don't remember what 
effect different adjustments of the proportioning valve would have.

-- 
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Jim Adney, jadney at vwtype3.org
Madison, Wisconsin, USA
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