Tire pressure suggestion for modified FF

Discussion in 'Technical Q&A' started by gabriello, Oct 4, 2017.

  1. gabriello

    gabriello Rookie

    Aug 30, 2017
    Hi guys, i have a 2013 FF and it’s been modified to

    Front 255/30/21
    Back 335/25/22

    I’ve been looking all over google and still not able to find the proper tire pressure for it, I’ve asked one of the wheel shop and they suggested to use 32 & 34psi respectively which I’m doubt about it. Do you all experts know what should be the right PSI for it? Thank you so much !!! Appreciate!!!
  2. Redneck Slim

    Redneck Slim Formula Junior

    Mar 10, 2011
    Palo Alto,CA,USA
    Full Name:
    Walt Kimball
    The "right" tire pressures for stock tires are determined by the factory through extensive testing,and even then they can need some adjustment for how you use the car. With custom wheels and tires,you have to experiment. Normally "custom" means wider,so you start with stock psi or a little less. See how the tires are wearing-inner versus outer tread-and adjust accordingly. No one can answer your question unless he has been through the same experiment.
  3. Mitch Alsup

    Mitch Alsup F1 Veteran

    Nov 4, 2003
    When the tire pressure is correct (and the suspension correctly aligned) there will be a linear temperature gradient across the tread on the tire. You can measure the temperature with a probe tipped pyrometer (about $100, lasts forever, can save big$$$ on tire expenses....).

    The outside edge of the tire is cooler since it sees cooler road air passing by than the inner edge.
    When the middle of the tread is the average of the outer edge and inner edge, the air pressure is correct without regard to what the sticker on the door jamb says.

    The pyrometer can also be used to set Camber, Toe, and Caster is you are good at it. So you can set up your car to your driving style.
  4. gabriello

    gabriello Rookie

    Aug 30, 2017
    Ok, thank you guys for the reply, will look at that
  5. tazandjan

    tazandjan Two Time F1 World Champ
    Lifetime Rossa Owner

    Jul 19, 2008
    Albuquerque, NM
    Full Name:
    Terry H Phillips
    Start with 32 psi front and rear and work from there. That is halfway between the recommended pressures for Michelins and Pirellis.

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