Help me understand these charts, oh man of science. Excuse my lack of understanding of physics.
On the top chart, the '16 Bronson and Intense Tracer 275c start at 2.6 mm of something. What is that something? I don't understand the "y" axis.
Then, it takes a lot of something to get the Tracer to its inflection point of 50mm of wheel travel. I assume that something is "force" translating into a feeling on the bike of a firm platform for the first 60 mm of wheel travel. Or, maybe it's the opposite. It takes very little to get to the inflection point, and then it firms up, translating to plushness on small trail chatter, but a "dead" feeling while pedaling as the suspension soaks up energy.
Help me Obe Wan - you're my only hope. Please use plain language.
The Y axis is leverage. For each 1mm that the shock compresses, the rear wheel moves through its travel by 2.6mm.
The lower the leverage, the greater the force is needed at the rear wheel to move the wheel, compared to parts in the travel that are higher in leverage. Having the highest leverage part at sag, where you spend most of your time pedaling, makes the suspension seem most sensitive at that point. This chart is mostly useful for determining which shock to get, and/or how to tune the shock. The actual feel of the bike's suspension feel is greatly dictated by the spring rate; the leverage curve just slightly modifies the spring rate. They ideally should be designed with each other in mind.
The lower the leverage is before sag, the lower the spring rate (ex. a 350 lbs coil vs a 400+ coil, or lower air pressure) you would need to reach the general recommended sag range (25-35%). This is because it takes relatively more force to get to sag, than if the curve were flat, like that Yeti SB6c, and especially so versus a curve that were straight up progressive.
Forces = estimation of the spring rate, after being affected by the leverage rate
Observe the "gradient" line on this forces chart (green-blue curve, on the top image). You will see that the Intense requires over 2200N of force to initiate shock movement when fully topped out. This translates to harshness when you touch down from a jump or roll over a large enough hole that allows the rear wheel to extend fully into it, including rolling off of rocks and other rollers/senders/hucks. For each mm of travel, it takes up to 62 N at that point towards sag, but it decreases due to the leverage increasing. Since you have the spring set up so soft to counter this, you wind up with an *extremely* soft spring at sag, requiring only 3 N of force to move the suspension through a mere 1mm of travel, while the Bronson requires 8 N of force to move the suspension 1mm.
** note the difference between "eVOL and DebonAir" springs on the newer '16 models, and the older school springs, regarding the stiff initial stroke. In the first chart, only the Intense has an old school spring, while in the second chart, only the Hightower has the new school spring.
A linear setup will look more like the Hightower's, in the bottom chart. A progressive setup will look most like the Nomad's. Linear is depicted by a straighter line from start to end, while a progressive setup is depicted by a concave upward curve. A linear setup will feel predictable and firm throughout, not notably softer or harsher through any of its travel--to someone seeking a comfortable ride, they would notice that the suspension is notably firm at normal sag rate, and then run much a softer spring rate and experience more bottom out, then add tokens and wind up with a more progressive setup, which manages to get them what they're looking for (a softer early and midstroke), but with a compromised damping tune (originally tuned for a linear setup). A progressive setup will feel extremely soft through the beginning of its stroke and not offer any real support until a little past midstroke--to someone seeking an efficient feeling firm tune, this will feel like wallow and dive, but it will feel comfortable, plush, and great for single impacts like landing jumps and occasional rocks, but would feel like more travel is needed for stretches of big chunk.
Getting too far from the stock tunes will put you in an unknown area that would likely require a suspension expert to correct. I recommend finding a bike that matches what you want in your ride, with little change from stock as possible. I personally find the firm linear suspension matches what I want in a fast sporty feeling efficient bike. I'm not after plush comfort, but I also don't want any particular harshness nor spikes. If I were to use a Shockwiz to help tune, I'd choose efficient spring rate-balanced damping. Someone who wants plush comfort and to utilize all their travel, should choose aggressive spring rate-playful damping. Aggressive means something different in Shockwiz terminology; it means to aggressively push Shockwiz's base tune to the softer side, to use more travel, which would be too soft for "aggressively" charging chunk with reckless high speed. Playful means springy, with soft but still taut spring and very low damping. Efficient is the firmest setting, ideal for setting PRs, offering the most support of all the tunes; though, this might not be firm enough for the fastest riders, as shockwiz was made to fit the broadest customer base, with average mainstream riders in mind.
I'll stop here, to let you digest this much. There's a lot more too it that I can go on almost forever about, regarding how this affects stock tunes of damping circuits, ride height, dynamic geometry, how anti-squat is factored into the ride quality, chain growth and kickback, brake squat and how a rear linkage counters forward rotation from braking by compressing, instant center and how it dictates all these values, etc. I could offer feedback regarding how doing this or that to the suspension should feel, verifying what I expect should happen by comparing it to what the owner actually experiences. If that meshes, can move onto more in-depth suspension tuning help.