Anti-Squat Geometry

anti-squat-geometry-kawasaki

The typical sportbike has the countershaft in front of and slightly above the swingarm pivot, giving the motorcycle anti-squat geometry. (Courtesy of Kawasak)

As we have discussed, when a motorcycle accelerates, load is transferred to the rear and increases the weight or load on the rear suspension. This acts to compress the rear suspension just as forward weight transfer under braking acts to compress the front suspension, causing the motorcycle to squat under acceleration. By using characteristics of the rear suspension design and the layout of a typical chain drive, however, we can give the motorcycle anti-squat geometry tendencies that offset the compression from load transfer, in turn improving handling performance on corner exits as the motorcycle accelerates.

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Suspension Analysis – Squat

suspension squat data

Suspension data for a typical lap showing speed (black), front fork travel (blue), rear wheel travel (red) and squat (green).

One important aspect of motorcycle setup, especially as bikes become more powerful, is how the suspension reacts when the motorcycle accelerates. As we have discussed previously in the section covering front and rear weight, load transfers during acceleration and braking and acts to compress or extend the suspension. This load transfer causes the bike to “squat” to the rear under acceleration, and in an extreme example, all the weight can transfer to the rear wheel in a wheelie.

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