[Fot] Toyo hot/cold tire pressures

[Norlin Engineering]

I used to do a lot of engineering and chassis tuning for one of the top Club
FF teams here in the Northwest.  That was back when 25-30 car fields were
the norm.
 If you were working with a driver that could run at the front of this field
(staying in the lead draft), then fine tuning of the tire pressures was a
must.  We'd adjust to 1/2 PSI. If the driver was a couple of seconds off the
pace, they couldn't tell the difference of a couple of PSI as long as the
balance was close.

Of course this was on bias ply tires.  I've heard that radials are more
forgiving, but I think we need to hear from a tire engineer to be sure of
that.

The other thing that was needed was to purge the tires with dry nitrogen.
Otherwise there was no consistency, particularily here in the NW with our
moist air.

Like Bill says below, we'd check the pressure hot and then see what it
dropped to when cold to get a good starting spot.  The best way to check hot
is during a practice session coming in straight off a hot lap, same as tire
temps.  We used the wear pattern as much if not more than the pyrometer to
determine camber settings.

Finally, if a car looses it's balance and the normal adjustments don't seem
to work right, it's time for new tires.  It's impossible to set up a car on
bad rubber.

Jim Norlin


-----Original Message-----
From: fot-bounces+norlinengineering=comcast.net at autox.team.net
[mailto:fot-bounces+norlinengineering=comcast.net at autox.team.net] On Behalf
Of Bill Babcock
Sent: Monday, July 30, 2007 6:56 AM
To: WEmery7451 at aol.com; keithfiles at btinternet.com; tony at tonydrews.com;
toodamnfunky at comcast.net; fot at autox.team.net
Subject: Re: [Fot] Toyo hot/cold tire pressures


I check hot tire pressures, and correlate it to cold later, but that's just
so I can predict what cold pressure will result in what hot. I don't know of
any reason to equalize tire pressures that way. When you read tire
temperatures you always find one or two wheels that are a lot colder than
the others, usually because of the nature of the track. When I find a tire
that's running a lot hotter on a given track I pay closer attention to the
difference between center and inside edge temperatures. That hard working
tire will affect handling a lot, and getting the temperature spread across
the tire to be equal will often improve lap times.

-----Original Message-----
From: fot-bounces+billb=bnj.com at autox.team.net on behalf of
WEmery7451 at aol.com
Sent: Sun 7/29/2007 11:11 AM
To: keithfiles at btinternet.com; tony at tonydrews.com; toodamnfunky at comcast.net;
fot at autox.team.net
Subject: Re: [Fot] Toyo hot/cold tire pressures

In a message dated 7/29/07 4:43:21 AM Pacific Daylight Time,
keithfiles at btinternet.com writes:

<< At RA in May I ran somewhat less pressure in my Toyo tires on my TR4 than
T ony and after much experimentation elected on 28 front and 26 rear which
gave me the balance that I was comfortable with.  >>

Does anyone try to adjust their tire pressures based on measuring tire
pressures after you come off of the track?  For example, If I start with 24
pou nds in slicks before going onto the track, and then measure the tire
pressures after coming off of the track: LF= 30 psi, LR=29 psi, RF=28 psi,
and RR=28 psi. The LF and LR are then dropped down to 28 psi.  Measure the
pressures after the tires cool, write down these readings, and start with
these pressures for the next trip onto the track.  This one guy who drove
the NASCAR series one year told me that that is what they do.

My readings are not as accurate as they could be.  First there is a cool off
lap, and then nobody is allowed to stop right after coming off of the track.
Everyone has to mutter back to their location in the pits.

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