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Question on tire sizes.

Discussion in 'Vintage (thru 365 GTC4)' started by Ak Jim, Jul 11, 2025 at 2:52 PM.

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  1. Ak Jim

    Ak Jim F1 Veteran
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    #1 Ak Jim, Jul 11, 2025 at 2:52 PM
    Correct me if I’m wrong but Ferrari used Michelin XWX tires in the Daytona and 365GT4C. The rim size on these cars are 15” x 7.5”. If you look at the Michelin site or any published tire size vs rim size chart they say that a 215 70 15 tire should be on a rim with a width of 5.5”-7”. In other words the tire size 215 70 15 is too narrow to fit a 7.5” wide rim. Why did Ferrari chose to do this? Michelin makes the XWX in 225 70 15 which is designed for a rim width of 6”-7.5”. Is there a reason to not put 225 70 15 size tire on a 365 GTC4 or 365 GT4 2+2 other than that’s not what the factory used?
     
  2. miurasv

    miurasv F1 World Champ

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    #2 miurasv, Jul 11, 2025 at 2:58 PM
    Ferrari used 9" wide rims using the XWX 225/70 VR15 tyres for the rear on the 512 BB. The 225 width XWX do look too wide for the 15" x 7.5" width rims imo.
     
  3. Edward 96GTS

    Edward 96GTS F1 World Champ
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    #3 Edward 96GTS, Jul 11, 2025 at 2:58 PM
    check tire fender clearance. it might be an issue.
     
  4. TTR

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    #4 TTR, Jul 11, 2025 at 5:27 PM
    AFAIK, there are likely several specific reasons "Why did Ferrari chose to do this ?", but aside from aesthetics and potential clearance concerns, technically speaking, I can't think of any for not to install 225/70 VR15 XWXs on 7.5" wheels, if you want to.

    People change to & use non-OEM recommended tire sizes on OEM size wheels (& vice versa) every day and have been doing it for far over 100 years already.
     
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  5. miurasv

    miurasv F1 World Champ

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    #5 miurasv, Jul 11, 2025 at 5:39 PM
    Last edited: Jul 11, 2025 at 5:57 PM
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  6. swift53

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    #6 swift53, Jul 12, 2025 at 2:27 PM
    I have seen 9" BB wheels in the rear with 265 Avon ZZ's, fit perfectly. and 225 up front on std. wheels.

    Alas, not being manuf. at the moment.....
     
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  7. swift53

    swift53 F1 Veteran
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    #7 swift53, Jul 14, 2025 at 5:34 PM
    Possibly Michelin TB's? Why not, and keep the others on another 'proper set of wheels.
     

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