PART TWO - EVALUATING & SETTING COMP & REBOUND DAMPING
Regarding evaluating your own bike's suspension potential there is no other "true" way to do it then taking notes on where your suspension settings are at to start with & then do a bouncing evaluation. What you are trying to do with this evaluation test is to change settings & then bounce the bike around to get a feel for what damping occurs as the bike's suspension is compressing (comp damping) & when it bounces back up (rebound damping). Dialing out comp damping several more turns or about a dozen clicks out from maximum (counter clockwise) will give you a setting that offers no comp damping from that damping circuit. The same holds true for the rebound damping circuit. The spring itself will offer some though & getting a feel for what that feels like on your particular bike is important. Then you want to see how much of a change there is between that/those settings & 1 click or 1/2 turn out from maximum.
Basically you want to be able to see/feel big differences in feel when changing settings when you are bouncing up & down on a bike's suspension while it is at rest. If not, then we know your suspension is already compromised which means it may be a combination of things at play that are making your bike handle badly. Once you determine that things internally are working at least at a decent level then you can get into how a bike should feel when you bounce it at rest. Unless you explore how it feels with no damping & with "supposedly" tons of damping dialed in at rest you will get into problems when you try figuring out what it’s doing on a road. You cloud up the analysis with lots of other physics issues that can make things complex to separate if you have more than one suspension issue going on. Having worked around suspension tuners that do this stuff on race bikes I have learned this is the way they help people out. Otherwise you are just guessing using those tried & true suspension issues lists you see floating around. Those that say when your bike pushes wide at the exit of a turn your compression damping is set too high, etc. Those lists are great, unless you have more than one issue going on & most of the time most street bikes have 2 or 3, sometimes more issues happening. If your rider’s sag is not set, and your bike has old worn fork slider bushings combined with old fork oil those lists will be pretty much useless because what is making you drift wide is not the comp damping although it can play a role. Best to set things to a good baseline first & then use lists like that to help you fine tune your settings.
If you do the bouncing test & can feel quite a bit of difference between no damping dialed in & lots dialed in you have a baseline to work with. If you have your rider's sag set you can figure out how much comp damping is happening up front. From your "zero" comp damping setting go ahead & dial in (clockwise) either a few clicks or turns of comp damping & bounce up & down on the bike. Is there any added resistance to your bouncing? To double check dial out the same amount of damping you just added in & then bounce it again. If you felt nothing extra resisting then go ahead & try adding one more turn or 2 clicks from that point & try bouncing it again. Take notes on where your "zero" point was, that is how many clicks or turns it was out from maximum damping. If you found new resistance from that point back the adjuster back out 1/2 turn or one click to see if you "overshot" the point where resistance was kicking in. Going back to your zero point is a good way to do it as well as you are double checking your work. Go back & forth until you find that point where comp damping is finally kicking in. Why do this? Because as your fork oil gets old & when the internal slider bushings wear this point will move, in some cases radically. Find that point & document how many clicks or turns it is out from maximum. From that point you want to use 2 clicks or so closer to maximum as a good street baseline for comp damping. I use "or so" as some suspensions will just start kicking in a little comp damping at 1 or 2 clicks out from maximum! Yup, I've seen it from a few bikes. In that case if you need to ride the bike without changing the fork oil set comp damping at 1 click or 1/2 turn from maximum & realize your suspension pretty much sucks as a baseline & don't expect too much.
For rebound damping (once again set rider's sag first) do the same analysis you did with comp damping but try it with the rebound adjuster at least one click out from maximum or 1/2 turn out from maximum. If you set rebound to maximum & leave it there the bike will not handle right even if it is set at a desired popping back rate. Finding out where the rebound starts to kick in will help you gauge how old the fluid is & what state of decay things are at. Record that reading & keep it & the comp notes handy for when you do this stuff again. I think a good setting for a "smooth" track is when the bike's suspension rises up slowly after being compressed. That is a little less than a second for the front end to come all the way up after you push it down. That setting will not work on a bumpy track or on your typical streets that aren't that manicured. For street use I dial the adjuster 2 clicks further out (from maximum) or 1/2 turn & then use that as a baseline. Ride the bike again over some bumpy roads & if the bike still reacts harshly over a set of bumps keep backing out that rebound adjuster in small increments until the ride over surfaces like that is bareable. If you never ride over very bumpy road surfaces & like to go faster over smooth road surfaces keep that rebound adjuster cranked up.
Now do all that you just did up front to the rear of the bike. When you are done park your bike next to a wall & stand up a little on the footpegs & while balancing the bike bounce the bike's suspension up & down. It helps if a friend watches this. You want the bike's front suspension to bounce down & come up at the same rate & in unison with the rear. Dial in more compression damping to the side that is bouncing down faster than the other & the same with rebound damping. Ask your friend for input as I have found this is helpful. Then take the bike for a ride down a street with little traffic that you know has some bigger bumps/dips in it. Ride over these bumps & pay attention to what the front & rear suspension are doing. You want them to be in sync so that if you are riding hard over a series of bumps the front & rear will go up & down together & setting the suspension up that way will keep the bike under control. Also bouncing up & down on the pegs as you ride down a quiet street with a smooth surface to double check your work is a good idea.
Checking & setting rider's sag will take you about an hour and a half, doing the comp & rebound stuff about the same or possibly a little longer. I have ridden a poorly set-up TLS on a race track several times before I started learning these things rather slowly. The difference between a nicely set up bike & one that is just the way it was sold stock several years after it was released is truly amazing. It’s like they are 2 different bikes. I have ridden a few friends/members bike's at street speeds that scared me. I cannot imagine what it would be like trying to ride them fast & around corners at speeds way slower than that found on most tracks. Makes you wonder?