Hey all... I fancy myself a suspension technology nerd but I believe that I (like most) understand just enough of it to be dangerous. I've envisioned a general suspension technology thread on this forum for quite some time. The point of this thread (as I have it envisioned at least) would be to discuss theories, past products/engineering and of course, new stuff.
Think of it as a place to discuss things such as:
-Discussing the impact/theory of mid valves and base-valves in forks
-Poppet valves vs shimmed compression valves
-Oil paths in certain shock architectures and what it means for the performance, tunability and end user (think DPX2 vs the new float X)
-Aftermarket suspension components such as; vorsprung luftkappe/secus, push hc97, dsd runt, mrp ramp control etc.
I sorta see this as a place to go off the deep end beyond what we would capture in the tech rumors and innovation thread. I have plenty of ideas for topics to kick this off, but I figured I'd throw this idea into the void and see if there is interest before running off into the sunset with my "great idea" that only I care about.
🤤 let it please begin
love it! homepaging now. hopefully it gets some traction and doesn't get bounced down (pun)
I'm interested. I know more about suspension than I used to, but I wouldn't let me rebuild a shock or damper. This forum could be a great place to learn new things and bounce ideas around.
Well, maybe this turns into me yelling into a wall about stuff no one cares about. Let's start with a layup discussion regarding rear shock architecture.
To my knowledge, there are three main damper architecture types that are commonly used in rear shocks at the moment.
-Twin Tube, Monotube and Bypass.
This link is for automotive applications, but it provides some good (over) simplification of the architecture types we're discussing for mtb applications. https://www.caranddriver.com/features/a15094969/automotive-dampers-expl…
I am not aware of a significant amount of true monotube dampers in mountain bike shocks. Forks are a different story… What has me interested in this is the correlation between the different product architectures and then the method in which they achieve tunability and user adjustability. I think we’ve all experienced vast successes and failures in this regard from both a product engineering perspective… but more importantly from a consumer education and product usage perspective.
We’ve come a long way from boost valve inline air shocks, pre-pedal platform and rapid recovery marketing mumbo jumbo. So let’s start with which products utilized which architecture and from there start to identify the method by which they are providing tunability or user adjustability.
Most inline shocks are monotubes- might be confusing the naming?
For MTBs- they are cheap, durable and package super well with an airspring.
regarding the DSD runt, I have one sitting in my parts drawer for my 36 (will be installing it soon). functionally it operates in the same manner as the Manitou IRT in that it turns a single positive air spring into a dual positive air spring (dual rate spring). I've got the IRT in my Mattoc, and it was a notable improvement over the token system. It definitely took more time to get properly dialed in, but IMO the performance improvement is worth it. Based on the similarities of how they work I'd expect similar performance from the DSD.
Twin Tube Dampers... When I think twintube dampers I firstly think Ohlins. Many years ago, when they released the TTX40 for motorsports applications, they released the following technical document that I found helpful to understanding twin tube dampers in general. https://www.ohlinsusa.com/files/files/Inside_TTX_A4-Europe1.pdf
While I'm referencing motorsports documents with these posts... it's important to remember that the packaging and as a result, oil volumes and oil displacement volumes we are dealing with in the mtb world are far less and it can make an apples to apples comparison to motorsports products impossible.
Steve from Vorsprung does much of the heavy lifting in this topic in this video https://www.youtube.com/watch?v=HQziEbxmLKw
Twin tube dampers that I know of:
-Ohlins ttx series
-cane creek double barrel series
-2020 (& later) fox float x2, DHX2 & dpx2
-What others out there?
Why are we discussing architectures on these shocks? Ultimately so we can get to discussing the different valving methods and theories between main compression piston valving, base valving and the different types of adjusters used to provide tunability. First I think we need to walk the dog on whom is using which architecture and start to dive into oil flow paths and then adjusters etc. What really got me thinking about this topic was my experience with the dpx2 and how it's architecture has a huge impact on how the adjusters function.
Dpx2 is mono tube😉
DHX2 and Float X2 were twin tube from launch so 2015/6.
DPX2 is some weird attempt at something it was never going to be. Its nasty and has bad crossover with compression and rebound adjustment.
I'd guess that 90% of shocks are monotube. My Integer strut is a monotube, I believe all EXT, Push, and most Fox, Rockshox are monotube (I think the exceptions are X2, DHX2 and Vivid. Do they still make Vivids?).
Twin-tubes aren't intrinsically superior to monotubes, just a different way to solve the problem. Most of the named technologies are ways to facilitate tuning, not necesarrily advantageous just by being included. The tune has to be appripriate to the bike, rider and usage.
Incorrect. DPX2 is definitely a twin-tube design: the damper shaft (that holds the base valve and connects damper body to the reservoir) is twinned, and oil recirculates through the reservoir/mid valves to/from the damper body and back. This means the (adjustable) resi/mid valves can have a more powerful effect because a large amount of oil is [re]circulating through them, and the (fixed) base valve doesn't have to handle all the non-shaft-displacment oil flow. On a mono-tube with a reservoir, only shaft-displaced oil goes through those resi/mid valves, and that smaller flow through the mids with the accompaning massive flow through the base valves ends up shrinks the usable window of adjustment.
I think this is what ebruner meant with "What really got me thinking about this topic was my experience with the dpx2 and how it's architecture has a huge impact on how the adjusters function."
And it might not have the one-way oil flow through the twin-tubes that I think Ohlins has, so there still is the hysteresis of forcing the oil to change direction when the shock movement changes direction. But considering the hysteresis of the entire system (seals, inertia, flex in the damper body and reservoir, etc), I think the large oil flow through the adjustable valves has a bigger real-world noticeable effect than a one-way oil flow.
X2 and dhx2 should probably be considered hybrid dampers as they have elements of both monotube and twin tube design due to having a base valve in the compression piston as well as circulating oil via the twin tubes too.
one and a half tube
The TTX also has elements of a mono tube damper as well..
Even the Ohlins, and I think everyone else in the bike world, has a base valve on the piston as well. It doesn't have to recirulate every single drop of oil to be called "twin-tube". In fact, having a base valve is great way to do what it says: set up a base-level amount of damping, that can then be adjusted with the mid-valves. And real adjustments of mid- and high-speed oil flows because of the amount of oil recirculating, not just closing off the bleed orifices like on a mono-tube inline shock.
So either everything is a hybrid, or everything that recirculates some oil around the base valves via a-tube-within-a-tube can be called twin-tube.
DPX2 is a Mono-Tube design. The displaced oil just happens to transfer through the shaft into the reservoir like the older Rock Shox Monarch shocks. This design is to allow ease of air can service. Nothing mysterious is going on.
Yes, I mentioned that monotube reservoir shocks all "just happen" to send oil through the damper shaft, but only displaced oil.
But does the oil flow in both directions at once in the Monarch and others? Can more oil flow through the base-valves than just that displaced by the shaft? Yes to both in the DPX2. It "just happens" to go both ways in the twin walls of the damper shaft, instead of one way directly in/out the upper eyelet and the other way though the twin walls of the damper body as TTX and X2 do.
So it might not have a double walled damper body, but it does have a double walled damper shaft, and most importantly flows oil in both directions at once, and thus partially bypasses the mid/main/piston valves, like any other twin-tube design.
(Edit: just realized I may be using mid-valve and base-valve backwards. I had meant base as the ones on the piston, and mid as the ones at the resi, but Fox uses the opposite. I might edit this to swap them.)
(Edit 2: yup swapped them here, but not in my older posts.)
Just for some clarity:
Base Valve(s): These are the fixed valves that displaced fluid moves through.
Mid Valve: This is when you are creating compression damping on the backside of the rebound damper piston. This is often just a check valve as creating force on the back side of a rebound piston can get tricky due to how easy it can cavitate. Mid valves are not found in rear shocks.
Damper Piston: Is what is attached to the shaft in a rear shock and is in motion.
Rear shocks are circulatory therefore you don't have fluid flowing in multiple directions at once.
-Darren
quoting myself to add that the EXT ERA fork has a similarly configured air spring (dual positive chambers)
i remember reading that cane creek was experimenting this when they were developing the helm, but opted not to pursue it for production.
I like that hydraulic bottom out is becoming more popular on "mainstream" suspension. The industry seems to be slowly stealing ideas from trophy trucks and other offroad motorsports. Will we see position sensitive damping and mid speed damping control in the next few years?
I believe that mid valves are common in rear shock? Especially RockShocks with piggiback all use mid valve, they have 2 compression stack, one on the piston and a base valve near piggyback. I think that Bomber CR does that as well. Or maybe this is just a naming thing?
Pretty sure most of the shocks out there have a compression shim-stack on the main piston, maybe we are talking about two different things?
HBO and Position Sensitive damping have been around since the early 2000's. The original FOX 36 released in 2005 had HBO... we've had SPV, Boost Valve, Curnutt, etc which have all been position-sensitive systems. HBO is still useful, but position sensitive less so now that most bikes have a pretty good rising rate linkage rate.
-Darren
All I'm asking for is a mtb adaptation of KYB SSS
Rear shocks do not have Mid-Valves.
Let's take a 170mm travel trail bike:
Front wheel travel is 170mm, fork travel is 170mm.
Front Fork Wheel Velocity Range is 0-9m/sec, fork velocity is 0-9m/sec
Rear wheel travel is 170mm, shock travel is 65mm.
Rear wheel velocity is 0-7m/sec, shock velocity is 0-2.7m/sec
This is due to the fact that rear shocks are driven by a linkage or pivot system so the motion is not directly 1:1 like a front fork.
Because forks are dealing with a larger travel and velocity range, mid-valves were introduced as another tuning element to reduce compromise over these larger ranges. They provide support in the middle of the travel, or in the mid-velocity range.
Mid valves are found on the backside of the rebound piston and have two elements. The first is free bleed, or float as it's sometimes referred to, which prevents the mid valve from producing compression damping at low-velocity ranges where it's easy for cavitation to form. The second element is the compression stack, or compression spring, etc which actually creates a small amount of compression damping in a specific velocity range before opening fully.
-Darren
MTB's have had it for years! The KYB SSS is just a marketing term for Speed Sensitive System. It's not really an actual thing, but rather Yamaha adopting an aggressive damper tune from their racing program and offering it to the masses as the standard production spec. Generally speaking, the media guys who test bikes are amateur racers so production MX suspension was always a bit on the soft side. Yamaha goes aggressive with the production-spec and voila! Test riders around the globe rejoice and report that it's the best suspension system out there!
Everyone here should read this if you have not yet, pretty sure it's available in e-form. It will answer many of the questions posed here, and cut through the confusion.
You can then ask the important questions like why is RockShox so enamored with digressive compression and rebound stacks?
In regards to mid valves on fork dampers, many of them can have a rather large compression effect that can produce spiking at higher velocities and add to a harsh feeling. To test this on yours; close the (low speed) rebound adjuster all the way, which closes the bleed around the mid valve forcing more fluid through it instead. Now push on the fork, for some dampers it will feel as if you added tons of compression damping. Although you would never ride this way (rebound fully closed), it illustrates the effect the mid valve can have on compression damping when the bleed is overwhelmed. This is also why it is especially helpful for heavier riders who have the LSR adjuster near closed to have the damper re-valved. The more the LSR bleed is closed, the more the mid valve will produce a spike in compression. If you can add rebound damping via the shim stack instead of closing the LSR needle, you are able to keep the LSR bleed more open and allow more fluid to bypass the mid valve on compression.
Ok, so how do you call elements in such architecture like RS Super Deluxe (prior 2023):
thanks for sharing your experience, I plan on going for a runt myself. I worked at Fox suspension for a few years and helped DSD a few times, acquire some Fox parts. I should have pulled the trigger back then, but it looks like BTI sells them so I plan on snagging one when back in stock. What made me decide to get a runt, was actually trying a Helm. You can bleed the air off and effectively make it a dual rate spring, which greatly improved the feel. So adding that functionality to a 36 should be sweet
best feeling shock I've ever had was my Fox RC4(had that boost valve) on my Turner DHR(DW link generation). Been chasing that dragon on my trail bikes for 10 years now with no success
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