[T3] Brake Calipers

[Jim Adney]

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

> Adney, how much would it cost for a rebuild with caliper cores without 
> the plates?  How much would the plates cost by themselves?  Starting to 
> regret going the big business route and thinking I should not send my 
> cores out.

I am out of the larger late plates and they appear to be NLA. I will 
no longer be able to supply them. I can align the pistons properly 
and I'll look for a more permanent solution, but right now I have 
none. In practice the pistons seem to stay in position even without 
the plates, but I don't have much experience with this.

> Mind showing how you got the loss of 10 percent calculation for 40mm
> pistons?  I am curious of what affect 38mm, 39mm, 50mm have.

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%.

Note that there's no change in braking between early and late Type 3 
calipers since both use the same 42 mm pistons.

> The two calipers look to have the same size pistons.  Why could one not
> measure with a caliper the diameter?  Not accurate?

Any caliper is fine, you just can't get in there to measure the 
piston until the piston is removed. The face of the piston is smaller 
than the working diameter, so it's pointless to try to measure the 
face, which is all you can see with the caliper assembled.

> Here is what I got back from Rock Auto:
> > Thanks for your email. I do show that the FRC3079 has one bleeder and  
> > the FRC3080 has two. Here are the images we have from Raybestos: 
> >  
> > FRC3079: http://www.rockauto.com/catalog/moreinfo.php?pk=522216 
> > FRC3080: http://www.rockauto.com/catalog/moreinfo.php?pk=522919 
> >  
> > Did your mechanic assume that both have single bleeders, or did he  
> > actually check the calipers? We also show that Cardone lists the right  
> > side caliper with a single bleeder and the left-hand caliper with  
> > double bleeders. 

I have no way of knowing what those photos are of. There may indeed 
be late style calipers with single bleed valves but made for someone 
other than VW. They might have 42 mm pistons or they might be 
something else. They might even be photos of early calipers, since 
it's really hard to tell the difference in a photo of just one. The 
photo may not be of the actual part. I can't be responsible for what 
you buy from other places.

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