gear change = tire change
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gear change = tire change
i added 31 inch tires on my 84 150 (stock was 29). now i am up grading gears from 2.73 to 3.08. Will the gear change equal out to the tire change, so i dont have to calibrat my speedo or odometer? my dad figured out the tires are 7% increase from stock, so what is the % increase or decrease on the new gears?
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From: Kalispell, MT
here's the formula to figure rpms at a given speed with a given gear ratio and tire size....
formula: rpm=mph x gear ratio x 336/tire size.......thus...
rpm= 65 x 2.73 x 336/29
rpm=2056
rpm=65 x 3.08 x 336/31
rpm=2170
therefore, your rpms will only jump about 115 rpms when you change to the 3.08 gears and 31 inch tires....as far as your speedo and odometer go...i can't answer that...but your rpms will be close to the same....
MontanaFord
formula: rpm=mph x gear ratio x 336/tire size.......thus...
rpm= 65 x 2.73 x 336/29
rpm=2056
rpm=65 x 3.08 x 336/31
rpm=2170
therefore, your rpms will only jump about 115 rpms when you change to the 3.08 gears and 31 inch tires....as far as your speedo and odometer go...i can't answer that...but your rpms will be close to the same....
MontanaFord
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