[T3] 412 Brake Caliper Question

[Jim Adney]

On 4 Mar 2016 at 11:25, Dave Hall wrote:

> I don't know the answer, but here's a theory for no mechanism:-
> The Type 3 Haynes manual says the compensating system was needed because the
> front axle design could produce disc flexing, pushing the piston back and
> increasing the gap between piston and disc, leading to a delay in braking
> while the extra gap was closed up.  The Type 4 had a quite different front
> axle and suspension arrangement, as well as thicker discs that may well not
> show the same problem, which meant no compensation system was needed.  I
> don't know what the 914 front axle was like though.

That's certainly the purpose of the mechanism, but the part that 
might flex is the axle stub on the steering knuckle. Once VW made 
that 2 mm larger in diameter in mid-68 I don't think there was much 
need for the compensation. Nevertheless, I like to see it there if 
the car came with it.

I've always wondered why our late calipers came with it, since that 
was after the axles were strengthened, but maybe the answer is in the 
fact that a few Type 4s were made in early '68 with the smaller dia 
axles, so VW kept the mechanism in place so all correct calipers 
would be suitable for all cars. Frankly, I'm surprised they didn't 
just assign a new part number for late Type 3s and install a cheaper 
caliper on those cars.

But by the time they got around to the late Type 4 caliper upgrade in 
late '72, there was no reason to keep that mechanism, because this 
caliper would not fit on any older cars with smaller axles.


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