Good info - but it left me with more questions...
Adding the preload shim made the shock firmer, right? How is it done?
as for the stock oil at 7 weight - moving to a 15 weight should also make it firmer, right? are there weights between 7 and 15?
Great questions Trampld.
Remember we are only taking forks here, with the rear shick it is what it is. But you can adjust pre-load on your shock.
The shims add to firmness by taking up part of the softer travel that the fork will move through. In other words it is putting you into the firmer part of the spring sooner. Also it is introducing more compression into the spring sooner. You add compression when you sit on the bike and/or travel over a bump. Maybe an engineer can add to this? Our stock fork spring is a dual weight spring, with a good percentage of it being light, I
THINK it is .80, and the firmer part is 1.00. But most of our travel occurs in the .80 range. My race tech springs are one weight for the whole spring, .90. DI uses .95.
The thicker oil will do two things for you, increase both compression and rebound damping. Because the oil is thicker it take more energy to force it through the ports (holes) in the damping rod. This will add to firmness too. The rod is in the bottom of the slider of your fork.There are a variety of fork oil weights, 10, 15 and 20 are most common.
It is a bit of work to get the oil out of the fork leg however. For some reason, I'm sure to keep costs lower, there is not an oil drain port.
So that gives you two options, 1) Remove the fork legs completely from the bike and pour it out or 2) Use a vacuum pump to pump it out. DefyInertia covers #1 in very good detail on his spring install thread (and other spring thing too). I've got a thread on the pump process too. Look in the Mods section. The cool thing about oil is you can mix two oil weights together and make your own weight. ie: half 10, and half 15, gives you 12.5. Its a bit of a pain but we don't have many options here.
As HavBlue stated you can introduce air pressure. We do not have a fitting to do this but you can kind of fake it. 1) jack the front of the bike up (a one gallon paint can under the header will do this very well). Your fork legs are now fully extended. Now remove your fork caps and then reinstall them. Now the caveat...I have no idea how the fork is built by the factory. I assume they are assembled fully extended so this may not do anything. However if you do open the caps up and do not fully extend the fork leg, and then replace the cap, you will no longer have the correct volume of air in the leg. When it does extend it is in effect creating a vacuum inside the leg. (yeah i know this is small but for most guys our fork is way under sprung). I'm sure a motivated person could have the fork caps drilled and tapped and add a Schrader valve.
Another way to increase the "effective" volume of air is to increase the amount of oil in the leg. Because you are replacing air, which compress, with oil that does not, the "effective" air pressure is increased. The stock amount of oil is about 400ml, you can add 50ml to it. Make sense???
I hope this helps, this area is my number one gripe about our bike.
