# Motorcycle Rake and Trail Calculator

Trail is an important dimension in motorcycle chassis design as that value has a large effect on how the motorcycle will handle. Trail is defined as the distance the front tire’s contact patch “trails” the imaginary point where the steering axis intersects the ground, as shown in the diagram at right. In brief, with more trail the motorcycle is more stable but requires more effort to steer; with less trail, the motorcycle will steer quicker but be less stable. This value is also sometimes referred to as mechanical trail. This page includes HTML and Excel versions of the motorcycle rake and trail calculator.

Trail is defined as the distance from the point at which the steering axis intersects the ground to the front tire’s contact patch, while normal trail is defined as the perpendicular distance from the steering axis to the tire’s contact patch. Both are dependent on rake, offset and front tire radius.

Because we are dealing with the “feel” of the motorcycle, normal trail must also be considered. Normal trail is defined as the perpendicular distance from the steering axis to the front tire’s contact patch, and is also shown in the diagram. This dimension is more appropriate in many cases because it is more important in terms of the actual forces involved in steering and stability calculations.

The HTML version of the rake and trail calculator will calculate mechanical and normal trail based on values for rake, offset and front tire radius. Rake must be input in degrees, as measured from the vertical. Front tire radius and offset can be in any units, provided they are the same for both measurements; the output will be in the same dimension. For example, if you enter offset and radius in millimeters, the trail value will also be output in millimeters.

The Math

Mechanical trail is calculated as:

$\displaystyle Trail=\frac{Rsin(\theta)-d}{cos(\theta)}$

θ = rake

d = triple clamp offset

Excel rake and trail calculator.

Normal trail is calculated as:

$\displaystyle Trail=Rsin(\theta)-d$

You can also download an Excel version of the rake and trail calculator here: Motorcycle rake and trail calculator version 3.0. Using this Excel file you can find mechanical and normal trail values for given rake, offset and front tire radius inputs.

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Revision notes:

• Sept. 5, 2016: Version 3-0 with new interface and normal trail
• Aug. 27, 2014: Version 2-2 to fix error in circumference/radius conversion cell.