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Tire size question (x-post)

Discussion in 'Technical Q&A' started by Gary(SF), Sep 6, 2004.

  1. Gary(SF)

    Gary(SF) F1 Rookie

    Oct 13, 2003
    3,637
    Los Altos Hills, CA
    Full Name:
    Gary B.
    Sorry for the cross-post, I initially posted in Modern, but the question really applies to all models...

    I'm considering trying some of the new Dunlop R-compound tires (SP Super Sport) on my 360. They are very competitively priced ($129 ea!) they're getting good reviews on the Porsche boards, and are suitable for street use to some degree so you can drive them to the track, much like Toyo RA-1s. My question is, with the closest rear being 285/30-18 vs the stock size of 275/40-18, there is a difference of 1.7" in diameter. Will that cause problems with the ABS, or any other implications, like maybe too low in the rear compared to the front? The front tires are much closer but not exact: 225/40-18 vs 215/45-18. Any thoughts appreciated. Here's the TireRack link for those of you interested:

    http://www.tirerack.com/tires/tires...uper+Sport+Race

    Gary
     
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  3. jrotsaert

    jrotsaert Karting

    Aug 15, 2004
    80
    Reading, UK
    Full Name:
    Jean-Marc
    I'mk asking myself the exact same question and have not found anyone with an answer yet- though my dealer is on it...

    Have you call Bob Woodman Tyres? they typically know all this stuff. I'm in Europe so it would be unfair to ask them and not buy from them.

    JM
     
  4. ferrarifixer

    ferrarifixer F1 Veteran
    BANNED

    Jul 22, 2003
    8,520
    Melbourne
    Full Name:
    Phil Hughes
    Turn the battery off at the isolator for 10 minutes or more. Fit the tyres. Restart the car and drive without wheelspin or abs application up through all the gears for 5 minutes or so, at least 3 times up and down the box anyway.

    Remember to do the same again if you change back again.

    You shouldn't need to turn the ASR off for this, but this depends on the software version and whether your car is F1 or stick shift.

    The speedo gets its info from an average of the two front wheel speeds, so there will be no effect if front sizes remain the same.

    The rake of the car is very important in chassis balance at medium and high speeds, but a slightly lower rear end helps braking stability anyway, so you won't be too badly off.

    When you drive the car on track, feel the balance and come back here for more advice!
     
  5. phong69

    phong69 Karting

    Aug 17, 2004
    226
    Raleigh, NC
    Full Name:
    Phong Nguyen
    I posted a similar question on the ferrariforum board and got mixed responses. Allegedly, one guy got his factory warranty discontinued due to the change in tires and how it may screw up the computer. I am going to switch out my Michelin Pilots when they wear out for some Kuhmos. If you look in you owner's manual, Ferrari actually recomends 225/40/18 and I think 265/40/18 for snow tires. Therefore I don't see any problems with switching them out.
     
  6. jrotsaert

    jrotsaert Karting

    Aug 15, 2004
    80
    Reading, UK
    Full Name:
    Jean-Marc

    Thanks for the advice. Doesn't seem like we addressed the rear ASR/ABS topic though. Can you tell me more? Incidentally, I've been told that Pirelli just came out with a Corsa tyre for the Modena... Should be available in a few days. The front will be 235/40 and the rear 295/35.

    Due to get more info tomorrow
    JM
     
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  8. jrotsaert

    jrotsaert Karting

    Aug 15, 2004
    80
    Reading, UK
    Full Name:
    Jean-Marc
    Ferrari fixer, do you have more info re track tyre size for a 360 modena?
    I have a 2001 F1
    THX
    JM
     

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