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Message: [QUOTE="John Curea, post: 87990, member: 17497"] Bud-Man, Piston rod size impacts the midvalve and base valve. A larger diameter piston rod will cause the midvalve to have less swept volume than a smaller one. The opposite will occur to the base valve, as a larger piston rod will displace MORE fluid through the base valve. JTT Yes, a larger cartridge (or for that matter a smaller piston rod) will have have more swept volume of fluid past the midvalve. Even with different size cartridges a 12mm piston rod will displace the same amount of fluid through the base valve. Its the ratio of swept volume to base valve volume that changes. Example- A late model YZ with a 32mm cartridge and a 12mm piston rod has a swept volume( amount of fluid through the midvalve) of about 6 times that of the amount of fluid that flows through the base valve. Where as a late model KX with a 28mm cartridge and a 12mm piston rod has about a 4.5 to 1 ratio. As you can see with the YZ, that has much more swept volume we have to have more float to get the similiar effect of the KX set up. I hope this helps, it took me a while to grasp the concept, but it really makes total sense. I will try and "rattle" Jer out of his roost to come in here and go into much more detail and give better examples. [/QUOTE]