Calculators

RPM Calculator

RPM =	gear ratio x mph x 336.1355
	tire height (inches)

assumes tranny is 1:1
for an overdrive, multiply to RPM (3000 RPM * .75 = 2250 RPM)
for an accurate tire height, measure from the ground to the center of the wheel and mult by 2

Metric Tires Sizes

example: 265/85 R16

tire section (widest part) = 265 mm = (265/25.4) = 10.4"
sidewall height = 10.4" (265) x .85 (aspect ratio) = 8.84"
tire height = (8.84" x 2) + 16" = 33.68"

Ramp Travel Index - RTI

If you don't have a ramp, but know how high you can raise a tire keeping the others on the ground, you can estimate your RTI with this equation:

RTI (20 deg) =	tire height
	wheelbase x 2923

RTI (23 deg) =	tire height
	wheelbase x 2559

RTI conversions
RTI (20 deg) x .875 = RTI (23 deg)
RTI (23 deg) x 1.142 = RTI (20 deg)

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