Summary
Highlights
The process of measuring sag involves three distinct measurements: 1) With the motorcycle hanging (wheels off the ground) to find maximum suspension extension. 2) With the motorcycle on the ground, without a rider, to see how much the suspension compresses under its own weight. 3) With the rider mounted on the motorcycle, to measure compression with the rider's weight. The differences in these measurements indicate if the motorcycle's suspension is adequately preloaded for the rider and intended use.
A detailed example is provided using a whiteboard. Measurements (R1, R2, R3 for rear and F1, F2, F3 for front) are taken from the axle to a fixed point on the sub-chassis or fork. Important notes include measuring consistently, avoiding braking when the rider is on the motorcycle (as this distorts readings), and understanding that subsequent measurements (R2/F2 and R3/F3) will always be shorter than the preceding ones as the suspension compresses.
Carlos Morante introduces Alejandro Montoya, co-founder of Morante Racing Motos, and begins discussing the ninth chapter of their motorcycle setup series. The focus is on suspension adjustments for both road and circuit use to correct undesirable effects and adapt the motorcycle to the rider's style and weight.
Building on the previous chapter, Carlos reviews the locations of suspension adjustments: fork preload (top), extension/rebound hydraulics (typically top), compression hydraulics (typically bottom, with exceptions), and monoshock adjustments for preload, compression, and extension.
This chapter focuses on 'how much' to adjust rather than 'where.' A crucial first step is understanding the starting point of spring preloads to then adjust compression and extension based on rider weight, riding style, and spring resistance. Preload refers to the compression of the springs in the fork and shock before they begin to function, measured in millimeters. An example with an Öhlins shock demonstrates how to calculate preload.
SAG is introduced as the next important measurement. It indicates the movement of the suspensions based on the preloads, essentially reflecting how soft or hard the motorcycle's suspension is. While it doesn't give a complete picture, it's a vital starting point, especially for competition. On the road, sag combined with rider weight and use dictates the necessary adjustments.