PVC spacers and fork oil level and progressive springs
Hello! I've never seen this mentioned before. Has it occurred to anyone that a PVC preload spacer takes up way more air volume in the top of the fork than the stock thin steel spacer? I ran the numbers and I need to lower my oil level by 22mm to keep the same air space up top! That's kind of a big deal! I know my Hyperpro springs are thicker and beefier and thus more voluminous, which may be why Hyperpro recommends a 170mm oil level, down 25mm from stock.
It also occurred to me that with a progressive wound spring, depending on the rates, a lower oil level / higher air volume might be desirable to reduce the progressive effect of the air, since the spring is already progressive.
On my 2005 650 I installed the HP springs and lowered the oil to 170mm. It was kinda stiff and not using the last couple inches of travel, so I reduced the level down to about 185mm. That seemed a little more compliant, maybe. Now I'm installing Gold Valve Emulators, so I had to cut new preload spacers about 1/2" shorter out of PVC. I suppose I could have cut the stockers down, but for some strange reason I like to hang on to the stock stuff. The forks are modified and reassembled, just need to add and adjust the oil. I'm going to try 205 - 210mm and make sure that covers the damper rods and emulators.