Sport Rider Photos
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This diagram depicts the internal differences between a standard cartridge fork (left) and the Showa BPF fork (right). Because the BPF basically converts the lower fork tube into the "cartridge", it doesn't need many of the parts necessary in a conventional cartridge fork, such as the internal cylinder and the sub piston, saving weight. Also, because spring preload is now located on the bottom, there no longer needs to be a sleeve running up to the top fork cap. The comparatively huge main piston in the BPF allows substantially more fluid flow through the damping orifices (which can now both be positioned in the main piston instead of separately), which drops fluid pressure and dramatically reduces the tendency for cavitation that causes irregular damping issues.
2009 Kawasaki Ninja ZX 6R Comparison Diagram