[T3] Brake Calipers

[Jim Adney]

On 11 Aug 2011 at 20:56, Adriel Rowley wrote:

> > From: jadney at vwtype3.org

> > On 10 Aug 2011 at 11:31, Adriel Rowley wrote:

> What is the purpose of the step?  So the plates are to keep the pistons 
> aligned?

The plates are to keep the pistons aligned. The step is to assure 
even wear across the face of the pad in spite of the fact that the 
moving rotor is trying to "twist" it.

> > It's based on the area of the pistons, so take the ratio of the
> > squares of the diameters, which for 40/42 comes out to .9070 or
> > 90.7%, which is not quite 10% less than 100%.
> >
> So then 50mm give about 20 percent increase, which would upset the 
> balance right?  Couriousity killed the cat... ;)

No, you forgot to square the ratio. It's more than 41%.

> > Note that there's no change in braking between early and late Type 3
> > calipers since both use the same 42 mm pistons.
> >
> But the force is spread out more due to the larger pads, right?  I did 
> try the late calipers (going to do an update after this), and they feel a
> major improvement over the 40mm pistons.

Spreading out the force spreads out the wear, but, in general, 
friction depends only on the total force, not on the area.

40 mm pistons were used only in Type 1 Ghia calipers. All Type 3 
calipers have 42 mm pistons.

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