Some more on Tire sizes | FerrariChat
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Some more on Tire sizes

Discussion in 'Vintage (thru 365 GTC4)' started by whturner, Sep 25, 2004.

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  1. whturner

    whturner Formula Junior

    Nov 25, 2003
    315
    Western Pennsylvania
    Full Name:
    Warren Turner
    #1 whturner, Sep 25, 2004
    I followed an earlier discussion on converting to modern (and available) tires. I think it was on Tom Yang's site. I need to get tires for a Series II 300GT.
    According to the conversions listed on the following site, my original tires would be replaced by 225R70-15.

    http://www.longstonetyres.co.uk/help.php

    Does this make sense, and if so, are there any recommendations regarding make/model of tire?

    Thanks
    Warren
     
  2. dm_n_stuff

    dm_n_stuff Four Time F1 World Champ
    Lifetime Rossa Owner

    Dec 10, 2003
    43,516
    26.806311,-81.755805
    #2 dm_n_stuff, Sep 25, 2004
    Warren, what is the original size?

    These tires have a 6.8 - 7" tread width depending on manufacturer, your originals were, I believe 6.5". So, you're picking up a little tread width, but not much. a 215 would be the 6.5" width.

    Coker suggests a 205-70-15 for this car.

    Rolling diameter is important too, as this will effect speedo, etc.

    I don't know that spec for your original tire,

    but the 225-70-15 is approx 27.5 " 215 is 27" and 205 is 26.5", you should probably look at that pretty carefully.
     
  3. whturner

    whturner Formula Junior

    Nov 25, 2003
    315
    Western Pennsylvania
    Full Name:
    Warren Turner
    #3 whturner, Sep 26, 2004
    The tires on the car when purchased ~ 25 years ago, are not the original, which were probably Michelin XWX 205/70R-15 on 6-1/2" wide Borrani wires, or 7.0" Cromodora mags. The tires Coker sells for the late 330GTs are the XWX.
    But it appears that there is not a direct 1 to 1 relationship between the indicated tire size used at that time, and the equivalent sizes used on modern tires, which I would like to use due to better street performance.
    I am not as worried about the exact speedometer calibration (which is often not all that precise anyway) but the tire width, so as to avoid interference with the inner fender panel.
    A little OT maybe, but it was interesting to me that Ferrari lists Dunlop 205 SP X 15 or Pirelli 205 VR X 15 F Cinturato tires for the early cars.

    Cheers
    Warren
     
  4. dm_n_stuff

    dm_n_stuff Four Time F1 World Champ
    Lifetime Rossa Owner

    Dec 10, 2003
    43,516
    26.806311,-81.755805
    #4 dm_n_stuff, Sep 26, 2004
    215-70-15 looks like the best overall fit for original tire width and your 6.5" rims.

    There are quite a few HR rated tires in this size.

    As to clearance, in the good old days a tire shop could fit it, check it, and then you'd be good to go. I haven't been to a retail tire place in some time but maybe NTB or someone like that would be willing to take a few extra minutes on fitment, as long as you don't go on a Saturday morning.

    Pirelli p4000ST is a tire I've seen on a couple of 60's vintage F cars at shows. I really like the Sumitomo's I put on my Dino, but they don't appear to be available in this size.

    Hankook is an option, and so are the Yokos.

    good luck on this.
     
  5. DBR328&330

    DBR328&330 Formula Junior

    May 31, 2001
    605
    Winchester, VA
    Full Name:
    Daniel Reese
    #5 DBR328&330, Sep 26, 2004
    Warren,

    I just went thru this exercise this week on my 330 GT! Check Tom Yangs site for my recent thread on "tire choices"

    Original size tires= 205/80- no longer available

    According to Yang (and Kerry Chesbro), the best conversion is 215/75 15 and they both apparently chose Michelin Symmetry tires (minivan tires). I respect their decision very much especially the part on not getting super sticky tires which would over stress the old suspension.

    My current tires are ancient Pirelli P5s 215/70 15. Wanting to stick with Pirelli and after discussing with FOW and Tirerack, I chose Pirelli P4000 Super Touring 215/70WR15.

    Hope this helps,

    Dan
     
  6. whturner

    whturner Formula Junior

    Nov 25, 2003
    315
    Western Pennsylvania
    Full Name:
    Warren Turner
    #6 whturner, Sep 27, 2004
    Hi Dave and Dan:

    I think I am coming to the same conclusion you did on tires, which is reassuring. The confusion due to changing tire size nomenclature is a problem - the experts - like Coker - give such a range of equivalent tire sizes it would seem there should be no problem. Until you look at it in detail.
    The 215/70 - 15 has a 225/65 - 15 equivalent listing, and there are a lot of 65 aspect ratio tires to choose from. This would be about right for the ride height and rolling radius, but omits the issue of tire width.
    To add to the confusion, I ran across a road test which listed the tire fitment for the test 330GT as 205 x 15 XWX on the front, and 215 x 15 XWX on the rear. Makes me wonder!
    I will probably end up as you did, but will review what Michelin has to offer also.
    I have yet to get - the car is out of town - an accurate measurement of the tires presently on my car, which have a very slight contact with the inner fender panels. This ought to allow a fairly accurate upper limit on tire width. They are G (?)R-15 Firestones for Police use. Tells you how old they are!

    Cheers and Thanks
    Warren
     

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