RE: Suspension question Oversteer/Understeer?

["Neal Tovsen" <ntovsen@piper.hamline.edu>]

Gottcha. Makes a lot more sense that way!

Neal

> -----Original Message-----
> From: Owen [mailto:mr.peepers@home.com]
> Sent: Wednesday, March 31, 1999 1:44 AM
> To: Neal Tovsen; Scirocco-L (E-mail)
> Subject: Re: Suspension question Oversteer/Understeer?
> 
> 
> I know more based on experience (just from playing with 
> different pressures
> at the track) than from the physics side of things.  
> Basically i think there
> are two elements to it.
>    1.  Side wall stiffness.  if you have not enough pressure 
> in the tire, it
> will allow the sidewalls to flex, and the tires to roll over 
> on themselves,
> and you loose grip.  with more pressure you'll get a stiffer 
> sidewall and
> less flex, keeping more of the contact patch on the ground
> 
>    2.  the contact patch itself is controlled by a 
> combination of pressure
> and suspension geometry.  What helps you set this up is a 
> pyrometer (tire
> temp gauge) and a pressure gauge.  after each run you take 
> tire temps (asap,
> so the tires have no little time to cool down).  You take and 
> outer, middle
> and inside reading as well as pressure.  here is an example 
> of what you
> might get
> 
>                         O        M         I
> 
>                        95       103     117           Ok, you could
> interpret this as having too much negative camber,
> 
>                        95        105    94             this 
> would be an
> instance where you are going to lower pressure.
> 
>                        95         80     95               
> here you would
> want to raise the pressure.
> 
>                        110        90    89              If 
> you get something
> like this, you'll want to dial in a little more negative camber.
> 
> I hope that kind of explains it.  Basically your tire temps 
> give you an idea
> of how your tires are contactin the ground, and i guess you 
> could say the
> the hotter the temp, the more that part of the tire is 
> contacting the ground
> that others.
>     you ultimatly want to have even temps all accross the 
> tire.  then you
> are getting full contact out of the tire.  raising and 
> lowering the pressure
> generally controls the middle of the tire.  if you 
> overinflate, the tire
> kinda baloons, and the middle bulges out, if you 
> underinflate, the middle
> sags, and the outer areas of the tire will tend to contact more.
> 
> Hope that makes sense, and will score you some new cars in 
> Grand turismo :)
> 
> 
> Owen
> 87 Scirocco 16v #38 C-SS.
> http://www.geocities.com/MotorCity/Garage/1571
> 
> 
> >How does the tire pressure thing work? I haven't done any 
> auto racing, but
> >if you're experiencing oversteer, you want more traction on 
> the rear to
> >balance the front, right? Wouldn't /lowering/ the rear air 
> pressure (or
> >raising the front) make the tires more supple/flexible, thus 
> giving more
> >traction?
> >
> >I noticed that both Andre' and Owen speak of raising the 
> rear pressure.
> >Considering that, IIRC, both you guys have racing 
> experience, I'd believe
> >what you say before my above logic. Could you explain how this works?
> >
> >I think I'm gonna have to go play with this in Gran Turismo 
> and see what
> >happens... Gawd that game rocks!
> >
> >Neal (playing the ignorant fool...again...)
> 
> 
> 

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