OK, what tyres are you using?
Some tyres are more sensitive than others when it comes to the relationship
b/n footprint and tyre pressure. Also, tyres vary enormously in the
sidewall/corner stiffness.
It is a little tricky because in cars that aren't perfect in controlling
camber
changes with (roll) suspension travel (e.g. our cars) generally see
increased
grip with increased tyre pressure well beyond the normal operating pressure
that modern designs use. The reason is that the tyres become
more resistant to roll under (which dramatically reduces the contact patch)
with higher pressure. If you are lucky enough to have tyres with stiff
sidewalls,
you can run lower pressures because these don't need high pressure to
resist roll-over.
The trouble is that grip (for a given contact patch) decreases with
increasing
pressure (due to compliance), and the theoretical size of the contact patch
decreases with increasing pressure (slowly for radials, quickly for crossply
tyres).
Reduced compliance will see skittery behaviour, reduced theoretical
patch size lowers overall grip level. The two effects are both related to
pressure but are different.
(More: the theoretical contact patch area is directly
related to weight and pressure whereas the actual instantaneous
patch area is related to weight, pressure, compliance, and the shape
of the road surface)
So you have a juggling act to minimise roll-over while minimising grip
losses
due to static/dynamic patch size.
Mike
-----Original Message-----
From: Michael Graziano <mgrazian@ltcm.com>
To: Mike Gigante <mikeg@vicnet.net.au>
Date: Monday, December 28, 1998 1:30 PM
Subject: Re: Overinflated Tires -> Skiddish
>Thanx,
>
>Already done.
>
>Mike
>
>Mike Gigante wrote:
>>
>> Another possible reason is loss of oil in the shocks. Use an oil can with
>> 20wt, or 30wt motorcycle fork oil (or ATF) to top up the shocks and see
>> if it helps.
>>
>> Mike
>>
>> -----Original Message-----
>> From: Michael Graziano <mgrazian@ltcm.com>
>> To: MGList <mgs@autox.team.net>; Spridgets <spridgets@autox.team.net>
>> Date: Monday, December 28, 1998 6:15 AM
>> Subject: Overinflated Tires -> Skiddish
>>
>> >Hey all,
>> >
>> >I've got a question about tire pressure. The Midget had developed a
>> >skiddishness (sp?) on the highway about a month and half before I put it
>> away.
>> >It tended to be real sensitive to road ruts, and the steering was more
>> mushy
>> >than usual.
>> >
>> >A few weeks ago someone mentioned to me that overinflated tires could
cause
>> >that. I remembered that I had 35psi in each from the day I autocrossed
it
>> on a
>> >Police test track. When I decreased the pressure to 26psi, the
>> skiddishness
>> >went away.
>> >
>> >Any ideas as to why this happens?
>> >
>> >Mike
>> >
>
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