Yep, you set preload by tightening the collars. It's hard to determine revolutions because you add them so slowly. So I usually measure the threads showing (in mm) past the lock collar.
The frame blocks direct access to the collars so I use a spanner mounted to a 3/8" socket with a 1" extension. BTW, in this picture, the spanner is set up to loosen a collar, not tighten. DDD
I found that it's easiest to add preload from the left side of the bike as seen in this next shot. It's a tricky affair, but as long as the spanner is securely in a notch and it is resting straight on the collar, then it doesn't really move. Just make sure you apply your torque in a perfect rotation motion. In this photo, I'm pushing slightly down on the driver. You may have to choke up on the handle and get your fingers under the head of the driver to make sure that you're apply that perfect torque.
Before making any adjustments, you need to loosen the lock collar. I use screw driver and a rubber mallet. It kind of boogers the notches so I don't recommend using it often. Loosening and tightening the lock collar isn't too bad, but I definitely recommend a spanner for the main collar.
Once the lock collar is loosened, I put a scissor jack under the right side of the frame so as to lift the rear wheel a little. At this point the bike is supported by the jack, the kickstand, and the front wheel. Make sure you have the wheel turned left all of the way into the lock or it might startled you when it flops over while lifting the rear. Lifting the rear takes the load off of the spring so you're only fighting preload at that point when you add more preload. Fighting both can be difficult.
Once you put a few turns on the collar, you're going to want to take it off of the jack and measure the static sag. I use the Racetech method where you measure it fully extended, then you take two measurements without the rider (free sag) and two measurements with the rider (static sag). Really you're shooting for static sag, so checking the free sag supposedly gives you an idea of whether or not you've got the right spring. Maybe an expert in this area can explain that one too me. Anyhow, when you take the two measurements each, you take this first one as the bike settles on the way down. The second measurement is taken when the bike settles on the way back up. So get on it carefully using a natural riding position while you balance against a wall with your elbow for the first measurement. Then while balancing a second time bounce down and let the bike settle on the way up. You take the average of these two readings as a way of compensating for stiction. You subtract that average from the fully extended measurement to get the static sag.
So how do you do this by yourself. Well I use the following setup.
That's a wooden dowel bungied under the seat and a telescoping magnetic retriever bungied next to the axle. When I'm balancing on the bike, I reach back carefully and extend the retriever until it hits the dowel and then I get off. Then I measure from the tip of the retriever to the middle of the rear axle.
It actually really easy to measure the full extension with the retriever too. You stand on the left side with the bike on the sidestand and pull up on the passenger handle until the rear wheel is off of the ground. Then extend the retriever until it hits the dowel and then push it to the side a tad so that when you put the wheel down it doesn't compress the retriever. Piece of cake.
BTW, checking the front sag is even easier if you use a loose ziptie on the right fork leg. To get the extension, push up on the right bar until the front end lifts, then slide the zip tie up and measure from the bottom of the slider (silver leg) to the top of the zip tie. Now you can do the same for measurements for free sag and static sag using the ziptie in the same way that you used the telescoping retriever.
To adjust the front preload, just throw a wrench on the red hex head cap on the top of each fork leg. I'm not sure what the starting position is, so I just called it 0 degrees and made sure that I carefully measure and record how many degrees of rotation that I add. I ended up putting three full rotations (tightening) to get 33mm of static sag and I'm about 180 lbs with full gear and a burrito in me.
