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Tire size question

Discussion in '348/355' started by jmiff348, Jun 9, 2010.

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  1. jmiff348

    jmiff348 Formula 3
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    #1 jmiff348, Jun 9, 2010
    Help... I've reviewed a few threads on this but can't quite figure it out. I purchased a set of 18" 3-piece speedlines for my '94 348 spider. The fronts are 8.5" wide, rears are 11".

    I assume the fronts will carry the same size tires as a typical F355 stock setup (225/40/18), which is the size that's currently mounted on the fronts (fronts look good - no problem here).

    The rears currently have 265/35/18's installed, which are WAY too narrow (and maybe even too short IMO) for these wheels. The 265's are "stretching" to fit across the width of the rims (265mm = 10.5" m/l). Since the rear wheels are 1" wider than stock 355 18's (I believe), what size tires do I need here?
     
  2. Organiser

    Organiser Formula Junior

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    #2 Organiser, Jun 9, 2010
    You will need 295`s for those.

    Regards,
    Phil.
     
  3. jmiff348

    jmiff348 Formula 3
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    #3 jmiff348, Jun 9, 2010
    Thanks Phil. I assumed 295's based on the 11" wheel width. What about the height? 35?
     
  4. f355spider

    f355spider F1 World Champ
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    #4 f355spider, Jun 9, 2010
    Possibly even a 30 series. What you will need to do, is look at the various individual tire specs online, of the brand/model tires you are interested, and find ones that most closely are in diameter to a 265/40/18. There is some variance amongst brands and tire models.
     
  5. Organiser

    Organiser Formula Junior

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    #5 Organiser, Jun 9, 2010
    Hi,

    Best to check as above, I found the nearest % wise to the original 17`s by using a tyre company calculator which gives the correct size to fit (not sure whose it was now)?

    I have Bridgestone Potenza re050 235 -40 -18`s on the front and 295 -35 -18`s on the rear.

    Regards,
    Phil.
     
  6. eyboro

    eyboro Formula Junior
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    #6 eyboro, Jun 9, 2010
    I have 295/18/35 355 rear a perfect fit and size for stock wheels so I don't see any problems for speedline 11" wheels. 235/18/40 should fit fronts
     
  7. jmiff348

    jmiff348 Formula 3
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    #7 jmiff348, Jun 9, 2010
    Phil, are you running 11" wheels on the rear? Also, do you happen to have any pics of your car with these tires?

    And BTW, thanks for the catch regarding the OEM 17's. I was comparing with 355 specs, since these are 18" wheels. Why did I think that was a good idea??? Anyway, based on the calculations I found in another thread, it seems that the closest match to OEM (348 spider) rolling diameter will be exactly what you fitted on your car...

    Rear-
    255/45/17: (17*25.4)+(255*.45*2)=(431.8)+(229.5)=661.3mm
    295/35/18: (18*25.4)+(295*.35*2)=(457.2)+(206.5)=663.7mm

    Front-
    215/50/17: (17*25.4)+(215*.50*2)=(431.8)+(215)=646.8mm
    235/40/18: (18*25.4)+(235*.40*2)=(457.2)+(188)=645.2mm

    Thanks for the help! How do you like the Bridgestones?
     
  8. jmiff348

    jmiff348 Formula 3
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    #8 jmiff348, Jun 9, 2010
    Thank you.
     
  9. tazandjan

    tazandjan Three Time F1 World Champ
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    #9 tazandjan, Jun 9, 2010
    You did it the right way by crunching the numbers. Next you can look up the recommended wheel width for the size tires you chose. This list also has diameter.

    http://www.tirerack.com/tires/tires.jsp?tireMake=Pirelli&tireModel=PZero+Rosso

    The PZero Rossos have the most extensive size list, other makes have similar specs.

    tirerack.com, tires by brand, pick type tire, hit specs.

    Taz
    Terry Phillips
     
  10. jmiff348

    jmiff348 Formula 3
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    #10 jmiff348, Jun 9, 2010
    Perfect, Terry. Thank you.
     
  11. Organiser

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    #11 Organiser, Jun 10, 2010
    Hi,

    No problem, glad to help.

    Sorry, no pics. Car is off the road at the moment with the engine out awaiting a cambelt and rear bushes when I get around to doing it!!

    I have 10.5" 360 challenge rims with 15mm taken off the rear mounting flange for the 295`s.

    I like the Bridgestones, good when warm, and don`t wear too quickly!! A friend also has them on his 348 ts in the same size.

    Regards,
    Phil.
     
  12. ferrari 512 tr

    ferrari 512 tr F1 Rookie

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    #12 ferrari 512 tr, Jun 10, 2010
    has anyone fitted 295's on the stock 360 modena wheels?
     
  13. Saint Bastage

    Saint Bastage F1 Rookie

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    #13 Saint Bastage, Jun 10, 2010
  14. f355spider

    f355spider F1 World Champ
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    #14 f355spider, Jun 10, 2010
    Last edited: Jun 10, 2010
    They should be fine, since they are the same width as the stock 355 wheels, and there are several forum users with 295's mounted up...I've seen several threads over the years discussing it

    I would think one should go wider in front, otherwise you are going to induce more understeer by going up three sizes in the rear. I would want to go up at least a size or two in front.
     
  15. potxoli

    potxoli Formula 3

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    #15 potxoli, Jun 11, 2010
    I'm running 285s in the back of my 18" 355 wheels. Bridgestone RE050A. Great tire at a great price.
     
  16. jmiff348

    jmiff348 Formula 3
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    #16 jmiff348, Jun 11, 2010
  17. Saint Bastage

    Saint Bastage F1 Rookie

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    #17 Saint Bastage, Jun 11, 2010
    Any time Bro
     

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