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Old 12-07-2012, 07:47 PM   #49832
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Joined: Apr 2007
Location: Mendocino, NorCal
Oddometer: 1,622
Originally Posted by Schultz! View Post
Might be a bit off base here but is something to think about.

One of the many jobs I have had was a "Vehicle Testing Tech" for ford motor company. While that title encompasses many things there I spent most of my time working with the "Vehicle Dynamics" groups. (they specialize in the tuning of the suspension systems) I learned a TON about damper control, spring check loads and rates, steering inputs, sway bar efforts, ect ect. The one thing I took from all of it it all truly depends on the calibration of the ass behind the wheel. Engineer X would claim the the "vehicle feels soft and unresponsive" Engineer Y would claim (same vehicle mind you with all the exact same components) the vehicle has robust handling characteristics with a sport ride quality...needless to say the asses were not calibrated to the same standard. With that being said person X setup may not please person Y even if there the same weight bike ect ect.

The springs basic job is to keep the vehicle "suspended" at the correct height vs static weight, its the dampers job to tell the spring how fast it can move. The best way to set up a bikes suspension (as i understand it) is to get the spring rates that are designated for your loaded weight I.E. rider gear big gas tank ect. Once that's done get the rear sag adjusted properly and make sure the forks are not too far compresses or expanded, set all damper clickers to "0" and take a test ride.

Depending on your observations during your ride you will get a idea how the suspension is responding, diving while braking, harsh on initial compression too easy to bottom ect ect. do this for several iterations of your damper adjustments available and make mental and recorded notes during the rides, this right here may be good enough for the old butt dyno, but if it isn't then proceed to plan for a damper re valve.

Re valving dampers realy isnt all that difficult just very time consuming to get it "just right". Ive seen way too many people jump all over the "gold valves" spending wads o cash and being disappointed with the out come because race techs calibrated ass is different from theirs. I would say for (speculating so please don't shoot me) most aplications the stock valves them self's are fine, its the shim stackup that truly effects how fast and how much oil flows past the piston ports causing the damping effect A cheep trick to try before a re valve is if the daper is "harsh feeling" (as in too much damping) to try and change the fluid to a lighter weight, same goes for the inverse if the damper feels"squishy or soft" changing to a higher weight oil can change the dampers performance. If changing the fluid type doesn't "fix" the conditions your seeing I highly recommend reading some tech articles on fork/shock valving/shimming before shelling out huge $$$, like i said it really isn't all that hard just a bit of a learning curve to it.
Good info here Schultz. I especially like your recommendation to change oil weights first. It's easy and relatively cheap. Going to a heavier oil raises and steepens the damping curve. Lighter drops and flattens it. As for after market valving bodies,, the theory behind them is (Race Tech's anyway) that the shim stack should do almost all of the damping. If the bodies end up providing any damping, you end up getting essentially an orifice type damping (ancient tech). Works okay with slow speed damping, horrible with high speed damping. Think about whacking the end of a syringe with your hand versus pushing it slowly.
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