Bicycle Suspension Design - The Main Challenge
One of the main challenges in bicycle suspension design is the difference in rider weights. A bike needs to work well for all riders ranging from 50 to 115 kg. The shock is capable of a setup for each rider in this window but, both the spring (air or coil) and damping are pushed to their limits for riders at the extremes of the scale.
The suspension design of the RAAW Madonna generates 160 mm of travel from a 60 mm stroke shock, producing 20% progression. That makes for an average leverage ratio of 2.67:1. This is a great average ratio, especially for lighter riders not approaching the higher end of the weight window. However, riders over 100 kg might begin to struggle with high pressures and white-flag-waving damping.
Not to worry. We now introduce a second rocker-link with a different geometry (Rocker 65) optimized for riders over 90 kg. The different geometry of the Rocker 65 is used to generate the same 160 mm of travel but now from 5 mm more shock stroke; 65 mm. This results in a lower average leverage ratio of 2.46:1, also with 20% progression. The anti-squat and anti-rise values stay exactly the same for both rocker links. This change in leverage ratio enables a lower air pressure or spring rate and happy damping for riders up to 115 kg.
To summarize, the Rocker 60 is best for riders up to 90 kg and the Rocker 65 is best for riders over 90 kg.
The different stroke lengths on the shock are fixed internally, but based around the same shock. A 205*60 shock can be modified to 205*65 and vice versa. But this needs to be done directly by FOX.
The Rocker 60 (transparent) and Rocker 65 (filled) are visually just a little different and weigh pretty much the same:
These are the two leverage ratio curves, both providing 20% progression:
For now all frame-kits and bikes are equipped with the Rocker 60. The Rocker 65 is available separately in the shop. In a few months it will also become an option in the configuration of a frame-kit or bike.