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Thread: tire swap what rpm

  1. #1

    tire swap what rpm

    we are running a s-10 350 sbc , turbo 350, with ford 9 inch with 4.86 gear.and hoosier 32.0 x14.5 x15. want to go to smaller and shorter hoosier 29.5 x 11.5 x15 right now at finish line we are at 6000 rpm's .any ball park idea what rmp might be now. thanks.

  2. #2
    Senior Member DYNO OPERATOR
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    I'd say around 6400-6500rpm.....

  3. #3
    Senior Member MASTER BUILDER
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    4.86 32"tall tire @6000 RPM
    should be @ 118 mph

    if the only thing that chages is RPM then these would be your #'s

    4.86 29.5" tall tire at 118 mph
    should be just over 6550 RPM

  4. #4
    Senior Member EXPERT BUILDER
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    my math @ 118 mph would be a tick below 6500.so id split diffrence and say right on at 6500,good luck

  5. #5
    Senior Member RACING JUNKIE fla1976's Avatar
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    speed

    According to my spreadsheet, the RPM will be 6505 @ 117.83 mph.
    But, the only sure way to know is ,DO IT.

  6. #6
    Senior Member EXPERT BUILDER
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    MPH X 336(WHICH IS THE CONSTANT) X REAR GEAR RATIO / TIRE DIA.


    THIS FORMULA WILL WORK NO MATTER WHAT MPH YOU PUT IN.BUT THIS FORMULA IS WITH A TIGHT CONVERTER.A REAL LOOSE CONVERTER WILL OBVIOUSLY BE MORE RPM.

  7. #7
    Senior Member EXPERT BUILDER
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    Everytime I change tire size every inch is about 2-300rpm in the 1/8th.


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