Re: diffs and opinion II

[quk@isham-research.demon.co.uk (Phil Payne)]

In message <0.1201fdcf.2530bfe5@aol.com> OorQue@aol.com writes:

> And while I'm at it, the idea that a misaligned car would cause it to
> "understeer-oversteer-understeer" in the way that's been attributed to the
> Torsen diff is laughable.  Misalignment can certainly cause a car to handle
> poorly but not in the way that Dave and Phil are suggesting, as a careful
> study of the Type 44's rear suspension design would show.  Now, if they
> wanted to suggest that the misalignment caused it to
> "oversteer-understeer-oversteer," I wouldn't argue -- that's definitely
> possible -- but that clearly wasn't their claim here.

Undrsteer-oversteer-understeer is exactly the scenario.  The Type 44
(like the Type 85) is _disposed_ to understeer.  This is entirely a
deliberate choice by Audi's designers, who have reasoned that a
non-involved driver reacts more safely to this situation than to
initial oversteer - as found in the majority of RWD 'sports' vehicles.

'Opposite lock' is not immediately intuitive for the untrained.

Hitting a corner under power in a Torsen Type 85 or Type 44 causes the
first slip to be understeer.  Always happens.  If the Torsen shifts
torque rearwards, it causes that axle to start to slip as well.  You
can work the torque distribution into a slip distribution as long as
the slip produced by each axle is proportional to the input torque.

And this is the point - if the axles are set up such that the same input
torque produces different slip, you _WILL_ get what we call spider bite.

Doing an alignment at a track?  This suggestion convinces me more than
anything else so far.  I've never seen a portable BEM Muller or
Pro-Align rig.  I know that Audi (in the BTCC) always took cars
off-circuit for two things - bodywork repairs and alignment.  Now if
Audi Sport, with their multi-million dollar service investment, can't do
alignments in the pits, then no amateur stands a chance.

--
 Phil Payne
 UK Audi quattro Owners Club
 Phone: 07785 302803   Fax: 0870 0883933