Really could use some tire help.... In English-not mathematical gobbledygook. Please? | FerrariChat
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Really could use some tire help.... In English-not mathematical gobbledygook. Please?

Discussion in '360/430' started by MB_Fahrer, Nov 3, 2014.

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  1. MB_Fahrer

    MB_Fahrer Formula Junior

    Dec 22, 2009
    685
    Colorado
    Full Name:
    Rick
    #1 MB_Fahrer, Nov 3, 2014
    Last edited by a moderator: Sep 7, 2017
    Took my 360 to the track today and really gave it a **** good thrashing. I have an entirely new respect for just how wonderful a car I wound up with.It's actually the first car I've ever owned that is perfect out of the box. Such a beautifully balanced machine. Not so much a car, but an extension of the human body. Was able to just dart right along with a flick of the fingertips. Far better than my 996 cup car, or the 991 GT3 I drove on the ring in August, or...well, basically everything else I've driven to date. More on that later though.

    I have spent the last four hours searching around the internet for two things, which I simply cannot find. First, I want a set of snow/ice tires. I am going to use an extra set of challenge wheels that I have laying around. Can somebody just give me the sizes to use? I cannot figure out what percentage front to rear and circumferences blah blah blah....can you please (really, I'm begging on hands and bloody knees at this point) just tell me in plain English what sizes I can use? For instance, Can I use a 225/40/18 and a 275/35/18? If not, then what size? Please don't come back with some front to rear ratio, as math is not my forte. Not in the least. Flunked every math class all the way through high school and college. Only graduated with a couple hefty donations and a few hosted parties.

    Next, I need some nice sticky rubber for the track. I'd rather not use the Pirelli slicks that are on the challenge wheels currently. I really have nothing good to say about those. I'd prefer to use BFG R1's or R1-S's as they just better. If not, then any other semi-slick will suffice.

    I am more than happy to roll the fenders to help stuff fit if need be. Rather just find some rubber that fits underneath stock, but whatever has to happen will happen.

    Thanks in advance!
    Ricky

    PS, I'll write up a thread with how the trackday went tomorrow.
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  2. SCKOMS

    SCKOMS F1 Rookie
    Silver Subscribed

    Oct 21, 2011
    3,903
    Lake County, IL
    Full Name:
    Spiro
    #2 SCKOMS, Nov 3, 2014
    There are plenty of calculators available on line that will tell you what sizes will fit. It's not that difficult to do teh math, either. My understanding is that you need to be within 5% on the diameter. The max tread width will be determined by the width of your rims.
     
  3. greyboxer

    greyboxer F1 World Champ

    Dec 8, 2004
    12,665
    South East
    Full Name:
    Jimmie
    #3 greyboxer, Nov 3, 2014
    Last edited: Nov 3, 2014
    Doesn't the owners handbook specify summer & winter tire sizes & the associated rim widths ?

    I think the 18 in Challenges are standard width but if your challenge wheels are 19" you'd be better off putting the winter tires on your standard rims and then look at the recommendations here for sticky 360CS tires
     
  4. tazandjan

    tazandjan Three Time F1 World Champ
    Lifetime Rossa Owner

    Jul 19, 2008
    39,170
    Clarksville, Tennessee
    Full Name:
    Terry H Phillips
    #4 tazandjan, Nov 3, 2014
    Jimmie- Ferrari recommends 225/40 18 F, 265/40 R winter tires. TireRack has none in those sizes. Without math, kind of hard to recommend substitutes.

    Not sure what the wider Challenge 8" front wheels do to the rubbing problem on front tires on the 360. The 10.5" rear wheels should cause no problems with most substitutes.
     
  5. Gated

    Gated Formula 3

    Dec 21, 2009
    1,117
    #5 Gated, Nov 3, 2014
    The closer they are in % then the more accurate your spedo. Over 3% variance is not recommended so here a list of comparable sizes.

    Front:

    205/40R18 = 24.5x8.1R18 -2.4%
    235/35R18 = 24.5x9.3R18 -2.4%
    285/30R18 = 24.7x11.2R18 -1.6%
    215/40R18 = 24.8x8.5R18 -1.2%
    245/35R18 = 24.8x9.7R18 -1.2%
    255/35R18 = 25x10R18 -0.4%
    295/30R18 = 25x11.6R18 -0.4%
    225/40R18 = 25.1x8.9R18 Equal
    305/30R18 = 25.2x12R18 +0.4%
    265/35R18 = 25.3x10.4R18 +0.8%
    235/40R18 = 25.4x9.3R18 +1.2%
    315/30R18 = 25.4x12.4R18 +1.2%
    215/45R18 = 25.6x8.5R18 +2.0%
    275/35R18 = 25.6x10.8R18 +2.0%
    245/40R18 = 25.7x9.7R18 +2.4%

    Rear:
    215/45R18 = 25.6x8.5R18 -2.7%
    275/35R18 = 25.6x10.8R18 -2.7%
    245/40R18 = 25.7x9.7R18 -2.3%
    285/35R18 = 25.9x11.2R18 -1.5%
    335/30R18 = 25.9x13.2R18 -1.5%
    225/45R18 = 26x8.9R18 -1.1%
    255/40R18 = 26x10R18 -1.1%
    295/35R18 = 26.1x11.6R18 -0.8%
    345/30R18 = 26.1x13.6R18 -0.8%
    235/45R18 = 26.3x9.3R18 Equal
    265/40R18 = 26.3x10.4R18 Equal
    305/35R18 = 26.4x12R18 +0.4%
    245/45R18 = 26.7x9.7R18 +1.5%
    275/40R18 = 26.7x10.8R18 +1.5%
    315/35R18 = 26.7x12.4R18 +1.5%
    225/50R18 = 26.9x8.9R18 +2.3%
    255/45R18 = 27x10R18 +2.7%
    285/40R18 = 27x11.2R18 +2.7%

    Handy: Tire Size Calculator
     

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