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Tire pressure...

Discussion in '308/328' started by P Betz, Mar 11, 2006.

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  1. P Betz

    P Betz Rookie

    Sep 22, 2005
    14
    Lynchburg, Virginia
    Full Name:
    Peter Betz
    #1 P Betz, Mar 11, 2006
    I've searched and I can't find the answer to this rather newbe question. I recently bought a 1987 328 and had BF Goodrich g-Force T/A KD's put on at the recommended sizes: Front-205/55 Rear-225/50. In the manual it lists two different recommended tire pressures for stock tires. Goodyear NCT tires were recommmended at 33 psi all around. However, Goodyear Eagle tires were recommended at 33 psi in front and 36 psi in rear. All I could find in the threads was a small notation that the NCT had a treadwear of 140 and the Eagle tires had a treadwear of 220. The BF Goodrich have a treadwear of 200. However, I don't think this is likely the "real" difference. So, my question is: for what kind of tires do you inflate to 33psi all around and what kind of tires do you inflate the rear to a hgher 36 psi. Specifically, what about the BF Goodrich tires I just bought.

    Thanks for helping me on this one,
    Peter
     
  2. DGS

    DGS Seven Time F1 World Champ
    Rossa Subscribed

    May 27, 2003
    72,097
    MidTN
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    DGS
    #2 DGS, Mar 11, 2006
    I had the same dilemma when I installed the S03s on my 328.

    The ideal way to get the pressures right is to check contact patch, usually with a tread temperature gauge. If you over-inflate, the center will take most of the load and get warmer; if you under-inflate, the sides will take more load and get hotter.

    Then there's handling balance: you can tweak the tire pressures, front to back, to adjust oversteer/understeer balance a bit.

    I started out about 5psi under the tire's max cold pressure rating and adjusted from there, based on tread "footprint" in the driveway dust and seat of the pants handling "feel". I wound up with about 31 psi f/r. (You really can feel 1psi of difference on these cars, in "spirited" driving.)

    There are a number of places to get IR temperature readers or tread temperature contact "strips", if you want to be scientific.

    But the manual values are pretty useless on older cars: tires today have completely different compounds and characteristics than the older machines, so have different pressure requirements.
     

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