FORMULAS:

Tire Height = Wheel Diameter + (2 x (Section Width / 25.4) X (Aspect Ratio / 100))

Rollout = Tire Height X PI

Wheel Rpm = (Vehicle Speed / 60) X (5280 / (Rollout / 12))

Engine Rpm = Wheel Rpm x Rear Gear Ratio x Transmission Gear Ratio

EXAMPLE TIRE SIZE: 100/90-18

OLD TIRE SIZING: 3.25-19 or 4.00-18

Motor Spec:
RPM

Gear Sizes:
Front Teeth
Back Teeth

Coefficient of drag Cd

Frontal area in sq/ft A

Rolling resistance factor Cr

Wind Factor Crw

Vehicle weight in lb W

Angle of incline in deg.

Wind Speed

Sidewall Width Angle of incline force (lbs)
Tire Height Rolling resistance (lbs)
Rollout
Gear Ratio
Max mph

100	Section Width	Total width of the tire at the sidewalls in millimeters. This is measured from the outside of the sides of the tires when mounted and not the tread or rim width.
90	Aspect Ratio	Percentage of the section width that is the sidewall height. For example the 215mm section width multiplied by an aspect ratio of 40 gives a sidewall height of 86mm
18	Wheel Diameter	Wheel diameter at the tire mounting surface in inches.

3.25	Section Width	Total width of the tire at the sidewalls in millimetersinches. Not sure yet how this is mearured.
19	Wheel Diameter	Wheel diameter at the tire mounting surface in inches.

Sidewall Width				Angle of incline force (lbs)
Tire Height				Rolling resistance (lbs)
Rollout
Gear Ratio
Max mph