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Old 08-19-2008, 08:23 PM   #13 (permalink)
chrisp993
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Join Date: Jul 2006
Location: Bloomfield Hills, MI
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Disagree with Lotusmark - Hoosier have specific recommendations on their website for 1800-2200lb cars, see: https://www.hoosiertire.com/Tctips.htm

The default recommendation for 1800-2200lb car is 34-37lbs HOT. However, they also say:

Quote:
Independent rear suspension
With IRS and proper geometry up front, tire pressures can be reduced from the recommendations listed above. When there is adequate camber gain and good roll control, the Hoosier radial tire will perform very well at the reduced air pressure. This results in a bigger "sweet spot" and easier control at the limit.
and

Quote:
When tuning at reduced pressures use the following formula to determine the minimum safe pressure: Divide the total vehicle weight, including fuel and driver, by 100 to arrive at the minimum safe pressure. Example: Your car weighs 2750 lbs. as raced. The minimum safe (cold) pressure is 27.5 psi.
So, from this, minimum safe COLD pressure would be about 22psi and the Hooiser recommended pressure would be somehwere in the lower 30s

This matches well with what I've found to be the best HOT pressure to be in the 31/32psi range F/R. This needs a COLD pressure of about 23/24psi depending on the day etc. Experiment to find where in low 30s works for you. This HOT pressure gives me nice even temp gradient, 20F spread and perfectly even wear across the tire - note this is with fairly aggressive alignment of 1.75deg/2.8deg neg.camber F/R

Also, note the Hoosier website comment:

Quote:
Higher pressures will improve the performance capability but will require a more sensitive feel to take advantage of the increase. One characteristic of the tires is the tendency to "skate" initially (when inflation pressures are correct). It is important to resist lowering the pressure to attempt to eliminate this feeling. Dropping the pressure too far may improve the "feel" of the tire however it will also lower the performance and increase the wear rate.
This matches my experience - I've run the Hoosiers at lower pressures e.g. mid to high 20s HOT and they feel a bit better initially, but don't grip as well. With the higher pressures they will "skate" for a couple of laps but work better IMHO.

YMMV
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Last edited by chrisp993 : 08-19-2008 at 08:53 PM.
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