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Fulcrum Pin Controversy id f9IIlVQ17153

To: Triumphs Mailing List <>
Subject: Fulcrum Pin Controversy id f9IIlVQ17153
From: Pete & Aprille Chadwell <>
Date: Thu, 18 Oct 2001 11:47:22 -0700
The fulcrum pin orientation question I posted has exposed some 
controversy, I'm afraid.  Funny how some of these issues seem to 
present such an obstable to finding the 'right' answer.  I received 
an email from one list member who points out that there was a 
correction issued in a 1992 Practical Classics magazine where 
apparently the magazine admitted that the caption and photo on page 
78 of the Practical Classics & Car Restorer Triumph TR6 Restoration 
book shows INCORRECT installation of the upper fulcrum pin.  A few 
other responses had generally supported the instructions from the 
book, which recommends that the curved part of the fulcrum pin should 
'bulge' toward the engine and prior to the above information, I had 
come to the conclusion that my fulcrum pins had been intentionally 
reversed at some point in order to gain some negative camber in the 
front wheels.

This new information casts doubt now on the whole question
 I think 
everyone agrees that the part in question is asymmetrical, and as 
such the orientation of the fulcrum pin HAS TO affect the camber of 
the front wheels.  On my TR6 the curve of the fulcrum pin bulges AWAY 
from the engine and yet the camber of the front wheels was set (at 
last alignment) at around .75 deg negative.  In other words, the 
orientation of the fulcrum pins on my car has not resulted in a 
greater-than-normal amount of negative camber.

Of course, the other variable in this equation is the number of 
alignment shims installed under the lower wishbone pivot brackets. 
The basic idea is that the greater the number of shims used, the more 
NEGATIVE camber will be introduced, since adding shims pushes the 
LOWER end of the vertical link AWAY from the longitudinal centerline 
of the car.  Also, adding more shims behind the FRONT lower wishbone 
arm than is used in the rear tends to decrease caster and adding more 
shims in the rear than in the front tends to increase caster.  All of 
this is somewhat theoretical, as I expect that on each individual 
chassis the lower wishbone support brackets are welded in SLIGHTLY 
different locations. As a result, each car will require different 
numbers of shims in different combinations to achieve the same toe, 
camber and caster specs.

With all of that out of the way, I've just taken 'inventory' on the 
number of shims installed on my car for purposes of comparison.  This 
is only for the front suspension, mind you.  And these numbers may 
change in a couple of weeks when my suspension is back together and I 
take it in for another alignment.

Right Front: 1 shim
Right Rear: 6 shims
Left Front: 4 shims
Left Rear: 3 shims

This combination was arrived at 12 years ago after I took it to a 
front end shop for an alignment after rebuilding the front 
suspension.  (new bushings, ball joints, etc.)  As I recall, this 
combination yielded about .75 deg negative camber and I think the guy 
was only able to get about 2.5 deg positive caster on both sides. 
All of this, of course, with the upper fulcrum pin installed with the 
curve pointing AWAY from the engine.

Pete Chadwell
1973 TR6

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