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Thread: How much will this change RPM?

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    Senior Member RACING JUNKIE BEAST477's Avatar
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    How much will this change RPM?

    If I change my slicks from 33x16.5-15 to 32x16-15 how much will this change my RPM at the stripe? Right now it's 7100. Both of these tires are M/T with stiff sidewalls.
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  2. #2
    Senior Member RACING JUNKIE fla1976's Avatar
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    I figure you'll slow about 4 mph if you stay at 7100 rpm or you'll have to raise your rpms another 222 rpm. That is using my spreadsheet. Here is a site you can try also.

    http://www.golenengineservice.com/ht...rs.html#DRcalc

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    Senior Member RACING JUNKIE TheYellaBrick's Avatar
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    Need to factor in tire growth at the top end. Does the Mfg have that kind of info available ?
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    Senior Member DYNO OPERATOR
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    75 RPM per inch of roll out change, brother

    Mike, if the two tires at pressure are 3" different in circumference as the diameter implies, then there will be an additional 230 RPM at the stripe with the shorter tires. Measure the actual circumference of your old tire and the new one to verify the roll out is 3" shorter as guessed.
    Bruce

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    Senior Member RACING JUNKIE BEAST477's Avatar
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    Re: 75 RPM per inch of roll out change, brother

    Quote Originally Posted by TopspeedLowet
    Mike, if the two tires at pressure are 3" different in circumference as the diameter implies, then there will be an additional 230 RPM at the stripe with the shorter tires. Measure the actual circumference of your old tire and the new one to verify the roll out is 3" shorter as guessed.
    Bruce
    Thanks Bruce, that's what I was looking for.

    I should've put in my thread that at the same mph how many more RPM's will it turn. Thanks guys.
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