Brake MC pushrod length

["Jim Adney" <jadney@vwtype3.org>]

> I challange someone other than Jim A. to help answer my question. 
> Winner gets a cold beer next visit to Portland.
> 	Section 2-4.5 of the Bentley suggests that it is very important not to
> mess with the factory Master Cylinder brake pushrod length.  Just to
> impress this upon us, they show a diagram with the critical dimension
> "a".  Well, they never do say what dim. "a" is!!  Anyone?
> 
> P.S.  My pushrod has a rounded off looking nut, and measures exactly
> 150mm from tip to center.  Did the PO mess with it?  

I measured 3 that I had lying around: 154, 154, 149mm.  So 150 does 
not sound outlandish.  The point of the dimension is that each one 
was set at the factory to match, or make up for, differences in the 
dimensions of that particular body.  I suspect that VW had some kind 
of jig that made this easy, but I have never seen or read of such a 
thing.

What they were after is explained in a somewhat roundabout way in the 
Bentley manual.  They want a length that will give 1mm of free play 
when the pedal is some particular distance from the kick panel.  This 
gives sufficient pedal travel even if one of the tandem systems 
fails. So there is no universal correct length.

Muir is wrong.  Don't adjust the rod length unless you measure the 
pedal to kick panel distance and determine that it is wrong.

Here's what you should do:

Adjust the pedal stop plate until you get the right pedal to kick 
plate distance.

Adjust the pushrod until you have 1mm of free play at the MC.

Sorry, just couldn't resist.  ;-)

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