Hmmm....that's an interesting angle to this. Would anybody suggest this
too?
Thanks
Larry
----- Original Message -----
From: "James Creasy" <black94pgt@pacbell.net>
To: "Lawrence Lane" <firstcard@hotmail.com>; "Michael R. Clements"
<mrclem@telocity.com>; "John J. Stimson-III" <john@idsfa.net>
Cc: <barx7club@rx7.org>; <BA-AUTOX@autox.team.net>
Sent: Friday, July 06, 2001 4:30 PM
Subject: Re: [3] Oversteer Understeer
> tuning steer characteristics with tire pressure is a last-resort measure
> because it reduces the total grip of the car.
>
> in a stock class you dont have many choices; in an SP class, it is better
to
> do bar tuning.
>
> HOWEVER, i recommend you totally forget about your tire pressures and
> anything about the car until you have driven 10-20 events. it just doesnt
> make much difference, and you might be adjusting the car to an incorrect
(or
> unoptimal) driving technique. its all about the driver.
>
> -james
>
>
> ----- Original Message -----
> From: Lawrence Lane <firstcard@hotmail.com>
> To: Michael R. Clements <mrclem@telocity.com>; John J. Stimson-III
> <john@idsfa.net>
> Cc: <barx7club@rx7.org>; <BA-AUTOX@autox.team.net>
> Sent: Friday, July 06, 2001 3:30 PM
> Subject: Re: [3] Oversteer Understeer
>
>
> > Thanks for all the help everyone. I've concluded that after every run,
I
> > should raise or lower my tire pressures to induce a certain handling
> > characteristic. However, I have a very limited amount of time (ASP)
since
> > there are so few cars running in my group. Is it legal to leave your
> > equipment on the grid?
> >
> > THanks
> >
> > Larry
> >
> > ----- Original Message -----
> > From: "Michael R. Clements" <mrclem@telocity.com>
> > To: "John J. Stimson-III" <john@idsfa.net>; "Lawrence Lane"
> > <firstcard@hotmail.com>
> > Cc: <barx7club@rx7.org>; <BA-AUTOX@autox.team.net>
> > Sent: Friday, July 06, 2001 2:53 PM
> > Subject: RE: [3] Oversteer Understeer
> >
> >
> > > I've found a simple technique that seems to work well over the years
> with
> > > different cars & tires. Chalk the corner of the tire and keep dropping
> the
> > > pressures until the tire rolls into the chalk, then bump up the
> pressures
> > a
> > > PSI or two. This worked on the BFG R1s, the Kumhos, and also on the
> > > G-Forces, with my '95 RX-7 and my Panoz. The point where I measure the
> > > maximum cornering Gs on my accelerometer, and the best autox times,
was
> > the
> > > point where the tire had just enough pressure to prevent rolling into
> the
> > > chalk.
> > >
> > > In other words, less pressure generally provided more grip, as long as
> the
> > > tire was not so low that it was rolling onto the sidewall. That is,
use
> > just
> > > enough pressure to maintain the tire's shape, and no more.
> > >
> > > After you have discovered this optimal point, you can adjust up or
down
> a
> > > PSI or two in front and back to make small tuning adjustments to
> > understeer
> > > vs. oversteer.
> > >
> > > As you can see there are varying opinions on this. I am merely citing
my
> > own
> > > experience, which is limited to two fairly light and well balanced
cars,
> > > both with stiff suspensions on R compound tires. It might work
> differently
> > > for different cars or different tires.
> > >
> > > -----Original Message-----
> > > From: owner-ba-autox@autox.team.net
> > > [mailto:owner-ba-autox@autox.team.net]On Behalf Of John J. Stimson-III
> > > Sent: Friday, July 06, 2001 14:10
> > > To: Lawrence Lane
> > > Cc: barx7club@rx7.org; BA-AUTOX@autox.team.net
> > > Subject: Re: [3] Oversteer Understeer
> > >
> > >
> > > It does depend on the tire, but in general there is a "sweet spot"
> > > which provides the maximum grip. Below that pressure, the tire is too
> > > soft and tends to roll over onto the side of the tread and/or lift the
> > > inner edge. Above that pressure, the tread bulges a bit and reduces
> > > the area of contact between the tire and the ground.
> > >
> > > There is also a secondary effect described by Andy Hollis, wherein
> > > higher pressures increase the effective spring rate of the tire. If
> > > the effective spring rate of the tire is comparable or softer than the
> > > spring rate of the suspension, then changing the spring rate of the
> > > tire can have a significant effect.
> > >
> > > At your next event, ask someone to show you how to use chalk or shoe
> > > polish to judge your inflation pressure.
> > >
> > > On Fri, Jul 06, 2001 at 12:18:44PM -0700, Lawrence Lane wrote:
> > > > I was told at the track by someone I met that the more air pressure
is
> > > given,
> > > > the tire will have more traction. I thought this sounded weird, but
I
> > > thought
> > > > I'd try it out. So, I inflated my 18"s to 35 in the front and 40 in
> the
> > > rear
> > > > to decrease oversteer. I'm not sure if it was the car or not, but I
> > > > experience a huge amount of oversteer. What is the general rule
about
> > > this?
> > > >
> > > > Thanks
> > > >
> > > > Larry
> > > > FD3S
> > >
> > > --
> > >
> > > john@idsfa.net John
Stimson
> > > http://www.idsfa.net/~john/ HMC Physics
'94
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