Sliding block, Panhard rod, and PITAness

[Mike Valant <mev4474@domain.elided>]

I have a fair amount of experience with fitting both Panhard rods and
sliding blocks to 115-chassis  Alfas. For starters, I must admit that,
even when hopping back and forth between a sliding block-equipped car
and a Panhard rod car at the same track, I cannot tell a difference,
unless the car hops over a very sharp, fast peak in the road. In that
case, the rear end travel in droop can be enough so that the arc through
which the panhard rod travels just barely begins to go beyond the point
at which some lateral movement of the axle is evident. Even then, the
effect is barely noticeable and far from upsetting. It helps to have the
Panhard rod perfectly horizontal when the car is static.

As for the PITA factor, the Panhard rod has it all over the sliding
block. Here's a list of PITA-related factors:

1. The trunk floor has to be reinforced even more for a Sliding block
than for a Panhard rod, because there are more attachment points (three
or four verses one) for this system.

2. The sliding block "yoke" sticks down pretty far, and it is just
begging to become a plow during an off-road excursion.

3. The sliding block makes noise if the clearance between block and yoke
exceeds .001", and I usually have to have at least that much to avoid
dynamic binding.

4. The sliding block continuously tries to metamorph into a friction
device, complete with friction damping and excessive wear. On a race car
this is a non-issue (grease all zerk fittings once per weekend) but on
the street this would be a chore.

5. You have to provide a seriously strong mounting place for the sliding
block pivot on the differential, which involves a fair amount of
machining and welding (a bunch more than the Panhard rod setup
requires).


OK, so why do some of us still mess with sliding blocks? Mainly because
they are legal as period-correct equipment, and because they do work as
well as a Watts link when they are in good working order. Oh yes, and
they look good, too.

MeV

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