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Sure looks like an orifice damper to me.
https://nsmb.com/articles/formula-selva-c-fork-teardown/
On this topic, @iceman2058 's review of the Starling just dropped.
https://www.vitalmtb.com/product/guide/frames/starling/murmur-v3-29446
It seems the very linear, flat leverage curve of that frame plays nice with both coil and air, although I'm ver skeptical of the "11% progression over the total travel" claim.
I do prefer linear, modestly-progressive suspension myself. As its been said before, for a given sag (not spring rate), a progressive suspension design tends to wallow and doesn't hold you up as well. Of course its foolish to set up different suspension designs assuming the same sag....
Three example bikes with different progression and same amounts of travel. All straight lines for the sake of simplicity.
Force at the wheel due to spring rate alone with each bike having identical sag at the wheel (stiffer spring for more progressive bike). Lets say you are railing a long long berm and your rear wheel needs to support 400 lbs of force… if the berm is long enough shaft speed goes to zero (save for bumps in the berm of course) so spring is what holds you up. 27% bike will sit at 180mm of travel used and 37% bike will sit at 165mm of travel used. Also, area under each of these curves is the amount of energy the springs stores between top of travel and full compression. But to put into perspective how important damping is, if you ride off a ledge seated with zero damping you would bottom off an 11.8” ledge. Not much for a DH bike.
A multiplier for damping that conveys how much force will be felt at the wheel for a given wheel speed input and shock tune. This number multiplied by wheel speed multiplied by damping ratio is force at the wheel due to damping. This is where adjustments to the shock come in because about 60% travel is where these curves intersect.
If you factor damping ratio into this plot with a similar mentality as is followed for setting all bikes to have the same ride height you get this. This is more or less what a lot of WC riders because they prioritize pumping and why they can get to a point of using less than full travel as progression gets into the upper 30% range.
TLDR, you can make a more progressive bike be significantly more supportive than a less progressive bike at the cost of making it harder to use full travel. More progressive bikes do not inherently give up early travel easier than a less progressive bike. It drives me crazy a little bit when that assumption gets repeated as fact to be honest. All a more progressive leverage curve assures you is a larger differential between wheel force at top and bottom of travel. That differential can be used however you see fit.
Dang, Paul and Rulezman REALLY did it wrong. It's pretty simple, they didn't correctly correlate spring rate to the new leverage ratio. They used more travel because the spring rate was too soft, then they got into the progressive end stroke.
Forks are not linear. Even a coil fork has an air space that gets compressed and ramps up in a linear manner, but most forks are air, and a few are a hybrid of coil & air.
Air sprung. forks aren't linear. They are progressive. Even when all the volume spacers are removed, air is inherently progressive. Maybe the rate of progression is less than rear suspension, but it absolutely increases over the length of the stroke. That's why people sometimes get coil forks - they want something truly linear.
The differences you are talking about here are influenced by damping, not by spring rate or progressivity. More damping means the suspension moves slower, so it takes more time to absorb the same impact.
I feel like people are not grasping the physics involved. It's not about dynamic vs static forces. Here's an experiment for you to ponder:
Suppose you had 2 bikes, 1 more linear and 1 more progressive. You chose spring rates so that, for a large drop, both bikes use the same amount of travel - let's call it 90%. And let's say the damping is tuned to compensate for the differences in spring rate.
How would you expect these 2 bikes to react to small or medium sized impacts, with regards to how much travel they utilize in absorbing them?
Obviously the linear bike would use less travel, and the progressive bike would use more.
Right, but if you control for one variable (force required to bottom out fully), then a progressive linkage will use more travel on smaller-than-full-bottom-out impacts vs a more linear design.
I think progressive linkage designs are great for janky terrain (higher typical shaft speed), whereas more linear designs are better suited to riding in areas like bike parks or smoother terrain where the forces are more spread out over time/space (lower typical shaft speed).
Running the same dynamic ride height between setups makes the most sense because you get the geo between the two to be consistent. Conversely you could tune them to have similar sensitivity off the top and the progressive bike would be massively hard to bottom.
I definitely agree that more linear bikes are better suited to smooth terrain.
Agreed.
The thing I am confused about is, it seems like there is an ideal overall progression rate sweet spot (taking into account the progression of the linkage plus the progression of the shock).
Some designs use a more linear linkage with an air shock (which adds progression above the linkage's rate).
Others use a more progressive linkage paired with a coil shock (which adds ~0 progression above the linkage's rate).
So why all this debate over progressivity of linkage? Seems like whichever you pick, you can then get a shock that compliments it. Most of the issues are when bikes are specced with a shock that doesn't mesh well with the linkage's progression rate, either due to the shock's progressivity (or lack thereof) or its damping is not appropriate.
I think it's awesome that bikes are coming out with a wide range of progressivity, given the constraints of shock choice. You can pick the bike + shock combo that best suits your terrain.
Yeah personal preference is such a huge portion of it that there will never be a one size fits all. I know for a fact that I will not get along with an 11% bike that only has 135mm of travel regardless of whether or not it has an air or coil shock, but I'm not everyone. The only downside to relying on air for pressure for ramp is you get more variable rebound between top and bottom of travel.
The availability of choice would work if shocks were easy to get and people were willing to swap out shocks. It's mostly a nope on both fronts - other than a custom valved boutique shock or a medium/medium tune from the big ones it's really hard to get a shock to fit your frame. Regardless of the air vs. coil conversation complicating things even more.
Not to mention the lack of information on shocks, shock tunes, suspension kinematics, etc. Hard to make a change if you don't know where you are, where you're going, or how to get there.
This. A middle range stock tune from a manufacturer for those that don't care as much as the vital crowd does. Then provide all kinematics info so those that do care can get an appropriate aftermarket tune.
Has anyone heard when the Fox wireless dropper is getting released? This has been rumored for months now.
If you met someone at the trailhead, asked them what % progressive kinematic their frame had and what is the leverage ratio they would look at you like you were an alien holding a rectal probe.
"I bought it because it was blue" would be their response. Normal people don't care about this stuff lol.
I've tried them all over the years, from literally Regressive designs, through to 45% DH monsters. I keep coming back to 25% been my sweet spot on a coil for an enduro/long travel bike. It's my goldilocks number.
What is more important, is the Ratio from beginning to end is a linear line, this makes tuning the shock so much easier and effective IMO.
I wish I was that dude who bought his bike because it looked sick (in blue) but we are nerds, we obsess over the details that no one cares about. I love it lol
I'm just another idiot, but the very next image in the Formula teardown story you linked looks like a shim arrangement on the backside of the CTS valve. I think of an "orifice damper" as something that uses a cone or needle to marginally adjust how open or closed an orifice is at all shaft speeds, not a shim that opens or closes the valve at different shaft speeds.
"Ben shows the shim against the bottom of the blue valve. The rounded edge of the nut beneath allows the shim to flex when oil is forced through the circuit."
I'm not sure anyone has ever described me as normal
Most dampers (very broad generalization here) use an orifice and needle for low speed damping and then a shim stack of some sort for high speed. This is usually similar on both compression and rebound.
This is why I don't talk to people at trailheads... they would think I'm part of some strange cult.
Interestingly, as far as the response with the most consistent change in damping as felt at the wheel over travel, a slightly concave leverage curve is closer to a line. This is because damping as felt at the wheel is inversely proportional to leverage ratio squared. Example below
I had you at "rectal probe" didn't I?
I did see that, I guess they could be using a single shim for high speed compression. I know a single shim is often used as a check valve for oil flow though.
I’d love to get my hands on a couple of the valves to see how they work.
I was trying to find pictures of the other valves to see of maybe they had different arrangements, but there doesn’t seem to be much info out there. All I’ve definitively seen is that they all have different port machining. Some cutaways would be very useful. The Formula tech doc is pretty useless and full of marketing fluff.
https://www.rideformula.com/wp-content/uploads/2023/03/CTS-Compression-Tuning-System.pdf
A shock tune guide would definitely be nice from the mfgs. I mean how they compare to each other in a graph or something. I bought a Vivid C1 back in January because it was a real good price, relatively speaking. It was marked down, I guess because it was "for" a SB160 which meant it had mounting hardware for that bike and the tune. Hardware didn't matter as I had that for my bike, and the tune wasn't that different. Only thing was the Compression was C37, and after contacting Fezzari (Ari) they informed me the tune they ship the La Sal Vivid with is C34. From the shim stack it looks like the C37 tune is "heavier" than the C34 but not really clear beyond that how the difference in performance compares.
I run HSC full open, LSC one click less than full open. I always wonder if the C34 tune would work better but its not the easiest to change the shim stacks, and they aren't cheap either.. if they are even in stock.
Apologies for the long post on that, just saw the tune remark and totally agree I wish it was clearer.
I'm with you. I bought an over stroked Vivid that was tuned specific for my new bike and it was a totally different tune than what came stock. I know not apples to apples, it's a Decoy 29 vs Decoy, but I can't imagine the kinematics are all that different, although the tunes (stock) R55/C26 vs R25/C34 seem as though they should be different? I really have NOOOO idea but I would like to. At the very least if I'm spending all this money I want to get the best out of it but also I care enough to know... so I sent it to Fluid Focus. All will be good now.
I think an orifice damper is just that, an orifice damper. The needle adds another layer of complexity. The catch is that different orifice arrangements will cause different damping characteristics - having the same overall void cross section, but in many small holes as opposed to few large holes will change the way the oil flows through them because of the viscosity of oil (compared to something like water, but water will be affected too obviously) and the resulting difference in flow regime (laminar, turbulent, etc.).
This is before the shims come into play. Putting the exact same shimstack on a piston with a different orifice arrangement will also cause differences in how the shim stack behaves as the bending mode, and thus the stiffness of the shims, will change. QED, fold a piece of paper in half (two orifices on opposite sides of the piston, an extreme case) vs. fold/bend it into a cup shape (the Formula CTS with many small holes). Things like to bend over a line, 3D bending is a PITA to achieve and will make the exact same piece of metal to behave quite differently.
Also, a single shim as a check valve is also a different thing as it's also usually spring preloaded so it can move away easily and does not impede oil flow in one direction (when it opens) but does when the orifices are closed. It should hardly add any restriction if it is used as a check valve proper.
If someone wants to go through some light evening reading and cover all the basics, here's a good book: https://www.goodreads.com/book/show/2847388-the-shock-absorber-handbook
As for dampers & co, still waiting for someone to license Multimatic's spool valve patent...
i dont care about those details, i just put in a different cst and immediately feel the difference. you put it in and then decide how much of the effect you want by adjusting the compression adjuster, way easier to setup then a fox grip2 imho.
also, coil spring. so so supple <3
can we please get back to rumors and stop the compression, damping and leverage ratio talk in here. pretty sure there must be a nerding out on suspension thread in here somewhere 😊
THX!!!
The constant whinging that tech rumours is getting derailed is kind of annoying and derailing in itself. In my opinion its OK to discuss the tech rumour or current happenings for at least a page or two, and then they generally dissipate or move to other threads. If a legitimate large rumour or release happens it naturally takes over the thread anyway, they're discussing damping and leverage because there isn't a lot happening right now. Plus, Primoz, Teamrobot and Cascade make up some of the best and most knowledge members and are creating a valid discussion.
For better or worse tech rumours is kinda the default thread to discuss anything new, I don't think it should become only a news feed thread that some people seem to advocate for.
Any more rumors on the new Santa Cruz bikes? Megatower/Nomad and Hightower/Bronson being turned into two platforms instead of four with flipchips for the rear wheel size?
please enlighten me what‘s so hard in discussing those topics in a dedicated thread which i‘m sure will be greatly frequented? damping vs. springrate vs. leverage ratio isn‘t news at all.
i (and i guess most) come here for news and rumors about new tech and don‘t want to scroll through pages full of tech talk that isn‘t rumors!
Specific topics fly under the radar (you have to go look through the forum to find them unless someone links to them) and subsequently there isn't as many eyeballs in them, "outside" opinions, etc. That's why this topic gets derailed so often, so many people engage in it and it gets pulled into multiple directions.