[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

RE: Diffs, sometimes opinion



In message <000601bf11f6$6e55b180$0100a8c0@Home> Dave.Eaton@clear.net.nz writes:

> redux:
> 1) phil (mb torsen ur-quattro) fails to find evidence of the bite in 18
> months of driving. hard.
> 2)phil obtains a type 44 and gets a spider bite.  immediately.  chorus of
> approval from various interested parties noting application of scientific
> method, honesty, integrity etc, right phil :-)
> 3) phil looks at rear chassis setup and finds it well out of wack
> 4) chassis setup fixed, and car behaviour exhibits no further evidence of
> bite.

I've since had a long chat with Martin Parker about the whole idea.

His take is that - once you get into a 'slip' situation - the Torsen not
only shifts torque, it also effectively shifts 'slip'.

The force at the contact patch is made up of a number of components -
the obvious ones are the forces produced by the engine and brakes, which
act along the tyre, and the sideways centripetal force, normally
considered to be at right angles.  The tyres are rotating - and a badly
set up axle adds an extra force.  The movement involved may be of the
order of fractions of a millimetre, but as Martin pointed out the force
is for practical purposes irresistible.  It's actually the strongest of
all the forces present.  In normal driving, absorbed without comment
by the sidewall -  but at the limit enough to tip the balance.

Martin is convinced (and so am I, having discussed it with him) that
spider bite is a _real_ phenomenon on a poorly set up car.  Moreover,
he's also convinced that it can happen on a car that is within tolerance -
hence the comment in the manual that: "Die angegebene Werte sind so
genau wie moeglich anzustreben".

His final comment?  "Why do you think I insisted on ramping and checking
your [Type 44] before I drove it?"

I have to give him his due.  That's exactly what he did, despite my
repeated suggestion that he test-drive it.

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