BruceHarrisJr said:
Why is it that Ohlins shock absorbers raise the height of an LT? I recently purchased an '05 LT that had Ohlins installed new at time of delivery. I am told that the stock shocks and Ohlins springs are the same length-true/correct? If so, why do the Ohlins raise the height of the LT?
The stock shock and the Ohlins are the same length, but they have different spring rates and pre-loads.
Over-simplified:
When the bike is taken off the stand (i.e., all the weight is carried by the wheel), X pounds is carried by the front suspension, regardless of which shock is there. Assuming no spring preload, if the stock shock has a spring rate of X lbs./inch, the suspension will "sag" 1 inch. If the Ohlins has a spring rate of 2X lbs./in., the suspension will sag 0.5 inch -- i.e., make the bike stand "taller" since it doesn't drop as much as the stock shock.
Spring rate also interacts with pre-load. If you have the stock shock pre-loaded ("pre-squeezed") by 100 lbs., it's pushing back against the ends of the shock wih 100 lbs of force, so you have to pull 100 lbs of motorcyle onto the shock before the suspension starts to move.
Example:
For the stock shock, assume the bike applies 300 lb. to the shock when it is taken off the stand, and it has a 100 lbs of preload and a 100 lbs./inch spring rate. The bike will sag 2 inches (300-100preload =200 lbs to be absorbed by the spring after the pre-load is overcome, 200 lbs./100 lbs.per inch=2 in).
For the Ohlins, assume 150 lbs. of preload (higher preload), and a 150 lls./in spring rate (stiffer spring). The bike will sag only 1 inch (300-150=150 lbs to be absorbed after pre-load, 150/150 lbs. per in=1 inch sag).
So, that's why you are being advised to dial out some of the Ohlins pre-load to lower the bike -- if the pre-load is reduced to 100 lbs, the bike will sag 300-100=200, 200/150= 1.33 inches, or 1/3 inch lower than before. Of course, trading off preload for height also increases the likelihood of bottoming out -- like all things, pluses and minuses to every choice!