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308 tire pressures

Discussion in 'Technical Q&A' started by jw6513, Dec 29, 2003.

  1. jw6513

    jw6513 Karting

    Nov 24, 2003
    50
    Arizona
    Full Name:
    Jim Whitney
    I just upgraded to the 16 inch wheels on my 78' 308, and am running 225/50 fronts and 245/45 rears. If someone has optimized the tire pressures for that set up (street use - stock suspension), I'd appreciate them sharing it with me. Thanks, Jim
     
  2. funshipone

    funshipone Formula Junior

    Jan 2, 2002
    618
    Harrison Twp. Mi. US
    Full Name:
    John Bicsak
    I have a 1984 QV 16 inch wheels Goodyear F1 tires same size as you 33psi front and rear and that is what label says on sun visor also in auto book.
     
  3. jmillard308

    jmillard308 F1 Veteran
    Silver Subscribed Owner

    May 29, 2003
    5,688
    Perth West Oz
    Full Name:
    John Millard
    I would run 4 or 5 lb over what the book says for a 308QV or 328. This will optimise braking and handling without being too severe on the bumpy bits.
    I would think somewhere mid to late 30's would be somewhere on the money
     
  4. dwhite

    dwhite F1 Rookie

    I am using 32 front 33 rear with S03s on an 83 QV . Higher pressure in the front was giving a push. Still fiddling.
     
  5. funshipone

    funshipone Formula Junior

    Jan 2, 2002
    618
    Harrison Twp. Mi. US
    Full Name:
    John Bicsak
    Our roads in Michigan are to rough for pressure higher than 33 PSI. In the spring I am going to switch from Goodyear to Michelin Pilot Sports have been told much better ride and handling.
     
  6. Birdman

    Birdman F1 Veteran

    Jun 20, 2003
    6,683
    North shore, MA
    Full Name:
    THE Birdman
    jw6513,
    Where did you get the wheels? Are they the aluminum Ferrari clones from Superformance in England? I am planning on getting a set and wondering how you like them?

    How did you decide on those tire sizes? Seems a tad wide for the 7" and 8" widths of the wheels. I was thinking about using 205/50 and 225/50 front and rear. Can you post some pictures what what those tires look like on there?

    Thanks!

    Birdman
     
  7. Dave

    Dave F1 Rookie

    Apr 15, 2001
    2,722
    Little Rock
    Full Name:
    David Jones
    34 front 36 rear
     
  8. enjoythemusic

    enjoythemusic F1 World Champ

    Apr 20, 2002
    10,672
    Worldwide
    Full Name:
    Steven
    Birdman,

    As you have seen the car here... With the Etoile 16" rims and Kuhmo Supra tires using 35-36 lbs of pressure all around. Have played around A LOT with pressure and felt that this gave the best for SUMMER driving and good tire temps. Do not have enough data for winter/cold tires and cold road, though it seems to like a touch less pressure (will try 33 when i get back home). Therefore when it comes to winter driving, the jury is not out.

    Enjoy the Drive,

    Steven R. Rochlin
     
  9. Mitch Alsup

    Mitch Alsup F1 Veteran

    Nov 4, 2003
    6,335
    Start out one day with 36 PSI cold in both the front and the rear, then drive out to you favorite deserted road. By the time you get there you should be in the 39-40 PSI range warm. This is way too much pressure, but it allow you to find the correct pressure by releasing air.

    Drive down the road at at least a brisk pace (8/10ths) and listen to the handling of the car. If the car oversteers, drop some pressure (1 PSI) in the fronts, if it pushes drop some pressure (1 PSI) in the back. keep working on one end of the pressure situation until you find the balance point where the car feels neutral. The difference in pressure front to rear is now correct; and what we need to find is the total amount of pressure for optimal grip.

    Drive down the road again, feeling the amount of grip in the tires. There is a small pressure range where grip is optimized. One end of this range is characterized by quick reactions to steering input (higher pressure), while the other is decidely slower to respond to steering input (lower pressure). Decrease both ends of the car by the same amount of pressure (0.5 PSI) until you find the lower pressure end of the good grip.

    Now drive to a gass station and add 1-2 PSI and see if the car is now centered in the sweet spot of grip. If so, drive home and let the car sit overnight. In the morning, go out and read the tire pressures and write them down. This is the cold pressures you want for that set of tires. Take the car out for a drive and afterwards, measure the tire pressures again and write these down as HOT pressures. Now you are equiped to A) find the pressures you car wants, B) set the pressures either warm or cold, C) understand how pressures are determined.
     
  10. branko

    branko F1 Rookie
    Silver Subscribed Owner

    Mar 17, 2003
    3,710
    Birmingham, Alabama
    Full Name:
    Branko Medenica
    Mitch, excellent formated solution to the question.
     
  11. jw6513

    jw6513 Karting

    Nov 24, 2003
    50
    Arizona
    Full Name:
    Jim Whitney
    I got the wheels on eBay....through QV London. You can get them through superformance as well (URL below - hard to beat 600 pounds for a set). I am very pleased with the wheels, as they are well made and look right for the car. I wanted to go with traditional Ferrari wheels. I don't have a picture. I went with the 225f / 245 r tires to get a little more grip....and I'm happy with the results....look good and work well...Good luck.

    http://www.superformance.co.uk/parts/dino3/wheels2k3.htm#wheels
     
  12. sindo308qv

    sindo308qv F1 Rookie

    Nov 1, 2003
    3,518
    miami.fl.
    Full Name:
    sindo
    I have the factory 16's with so3's on my '84308, I keep it at 33 to 35 all around at most.
     
  13. Mike C

    Mike C F1 Veteran
    Owner Lifetime Rossa

    Aug 3, 2002
    6,061
    Southeast USA
    Full Name:
    Mike Charness
    For the street on my QV with the "upsized" tires, I use 32-33 all the way around as the warm pressure.

    When I'm driving at the track, I'll usually run 36 in front and 34 in back (I want the fronts higher when I'm putting in hard braking and turning on a roadcourse).

    Mike
     
  14. pma1010

    pma1010 F1 Rookie
    Silver Subscribed

    Jul 21, 2002
    2,556
    Chicago
    Full Name:
    Philip
    Another data point: 34 all round on the street. 36F, 32R on street tires at the track on my GTB
    Philip
     

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