225/45 R18 tire questions

Discussion in 'Mazdaspeed 3 General Discussion' started by Rgurleyjr, Jul 20, 2019.

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  1. Rgurleyjr

    Rgurleyjr Greenie Member

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    So two of my tires are shot, other two are like new. Bought the car 5 months ago and haven't had tire issues till now.

    Just realized my tires are not factory size but a common size speed owners buy. I'm not a tire guy, never have been.

    Since I have 225 45 18s on the back, going to stat with that size. Read something about the speedo being off.

    Question is will I be going faster or slower than what speedo says and how many mph? Should these tires use same psi as stock?
     
    Rgurleyjr, via a mobile device, Jul 20, 2019
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  2. mangosmoothie

    mangosmoothie Silver Member

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    My quick google comparing tire sizes shows a 3.6% difference. It's a larger tire, so the speedo will read about 3.6% low. When 60 is indicated youre going about 62-62.5.

    I would run the stock pressure, but I'll let someone who knows more answer that one.
     
    mangosmoothie, via a mobile device, Jul 20, 2019
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  3. Rgurleyjr

    Rgurleyjr Greenie Member

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    Thanks! Dang, I already drive fast, surprised I haven't gotten a ticket yet.
     
    Rgurleyjr, via a mobile device, Jul 20, 2019
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