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MRP Noken will help use more travel on Zebs.
PM sent..The Bartlett will blow away the Zeb. And i have one cheap.
I would go the Zeb - the not reaching full travel thing is largely friction if they aren't sliding 100%, which also affects the 38 too and not a deal breaker IMO, it just gets blown out of proportion. Getting full travel isn't a metric for good forks, but if they are too progressive the MRP Noken is a good solution anyway. The current 38 with Grip X2 is good but I would probably rather wait for whatever the new version brings
Is it though? I have a zeb that has zero friction in the bushings with my hub installed, it slides to bottom very freely, bushing feel really good. When running a smashpot in it I could bottom that fork all day long but still have good support, but after swapping back to air and running it I can either get mid support or use most of the travel, not both. When I set the spring to use most of the travel it feels like crap, zero support, and when I set the spring to give mid range support it won’t use but 165mm of the 180mm of travel. I ran the charger 3.1 and the MRP lift with a modified tune that I spent a few months iterating on that used a de-dished piston, all modeled through re-stakor. Dropping in a bone stock ohlins 38m.2 made me give up on the zeb. I still want to try the noken on it but I have a hard time wanting to screw with something that just works… I prefer the zeb chassis to the ohlins for the 180mm travel but overall I feel like I’m just trying to polish a turd. And as they say the only way to polish a turd is to freeze it first, lol
I'm not going to tell you how to live your life, but the Noken is way cheaper and easier than all the modifications you've already made. I thought it made a huge difference on my 180 Zeb, and when I took it off I had all the same symptoms you described (support or full travel, but never both). I think the Noken is a lifesaver for the long travel Zeb.
I put a 190mm Zeb ultimate 3.1 on my (170mm stock) ebike, I mostly did it to raise the front/BB and came into it knowing that 190mm was hard to reach. In my experience, my go to "pretty stiff" settings result in mostly 170-180mm of travel being used (~70psi for 80kg rider on a 24kg bike). Over last summer going to bike parks I let a bit of air out (5 psi) for comfort and was getting full travel on the bigger hits.
Make sure to pump it up in stages, compressing it every 20psi, and use the little bleed screws to release trapped air every so often.
Agreed here. The Noken saved my buddy from tossing his Zeb into the trash pile. He loves it now after doing this quick/cheap 'upgrade'.
This is why the new Zeb has the LinearXL on it (their version of integrated Noken).
Based off the images, Linear XL modified lowers volume while the Noken modified the spring volume.
Can someone explain to me base valving vs mid valving and when you might change one over the other?
I have been currently messing with a DHX shock and bought some tunes off of fox initially to get a firmer compression tune and a faster rebound tune. Once you have 2 of their tunes you can basically build all of their stock tunes. I think* I get that your mid valve is doing most of the damping and your base valve is more for fine tuning what your mid valve. On the dhx it seems like the LSC knob is just adjusting how close it moves the washer/shim to the piston so its just choking off the piston ports before it get to your shim stack. Is this correct? Is there a way with this shock to build a base valve that is similar in stiffness to where I am at or is it just part of the design? Its not a dyno per-say but I have been using a BYB kit to validate some of my adjustments I've made but almost always end up close to closed.
I haven't done any real custom shim stack builds before other than buying race tech valves for my dirt bike and doing some minor swaps. I am a bit of a novice in this department but its been fun trying a few different setups.
Ill add some more tomorrow, but in basic terms -
Main piston - normally most of the damping, especially at low speeds when the volume of oil through the base valve is low. Increasing the stiffness of that stack causes a larger drop in pressure behind the piston.
Base valve - mid to high speed, as well as adding range to the adjuster. Its main job though is adding back pressure to the system to prevent cavitation. So the stiffness of the BV limits how firm the main piston can be, although that can be overcome with higher reservoir pressure (but that adds apring force and friction). Too much BV stiffness creates hysteresis and extreme pressures inside the shock.
Most of the time, you want the base valve to be stiff enough that you can safely make adjustments to the main piston without cavitating, and then the bulk of your tuning on the main piston.
With the DHX I recommend using a BV tune with no extra bleed, then you should be able to make more noticeable changes at the main piston, without needing to alter the base valve
Or to put another way, just use the main piston, and only increase the base valve if the main piston is too stiff and risking cavitation. Or vice versa
So if I still ending up pretty closed off then I should still continue to tune my mid valve until I can start opening my compression adjust open not try tuning my BV to open my compression. I did pull the bleed shim out of my BV already. Thanks for then info so far. I will be patiently waiting for your next post.
Yeah the standard base valve tune with no bleed is suitable for all of their standard main piston configurations. - just checking it is also pre-2025 DHX? They added different BV tunes after 2025
Its a 22 that I got as an old stock for the cheap but thought it would be a good base mono tube to mess around with. It came with a LMB2 tune but the tune is now closer to a LF
BV
Mid
Update, I got a Telum and my Vivid feels like a potato in comparison.
The Telum actually has damping at mid speeds, no weird ride height issues, and it’s noticeably more sensitive. I was expecting this shock to be better but I was not expecting it to be this much better. Rock gardens that would unsettle the Vivid don’t even phase the Telum.
Oh yeah with that 2-stage compression stack it will be super light.....I'm not sure how much the second stage will be doing with the 0.2mm total crossover gap and 12mm OD shim in there.
If you're lucky, it might be equivalent to their CL tune, but I would also look very closely at the compression shims once you have torqued the piston bolt - a small clamp shim and big face shims are super prone to flexing away from the piston once tightened down. There should be ZERO daylight between the face shim and piston. It's easiest to tune a single stage stack, or the the bare minimum use a 0.1mm crossover, preferably a little larger than the clamp like 14-15mm, but you add a lot more complexity when playing with that.
I grabbed some screenshots of tests showing the internal pressures in a shock when changing the base valve vs main piston, just need to add a little more explanation
Nice stuff! Love reading stuff like this. Those screenshots would be interesting to see!
Thanks for the response. I was roughly basing my tune off of this fox tune but still trying to make it a bit stiffer. Maybe I should try to pull one of the crossovers out or just go to a single stack.
Question, I have a brand new RockShox Super Deluxe Coil Select Plus, Rx Trail Tune shock off a 2024 Spec enduro. I was gonna sell it..BUT my 2023 yeti 160E has a cavitating Fox X2 ( I know, Surprising..😆). I have never been happy with that X2 even as a Fox fanboy. To get the soft top then midstroke support I want I was still blowing thru the travel like crazy..Even with 3 volume spacers and set in the 30% progression setting. I ride hard but it was just Long Island NY( not the crazist trails). It may have been a dud from the start..But, I feel like I should try this RS coil, With the HBO. At least till I get the X2 rebuilt. My fox is 205/65 trunion, And the RS is 205/60 trunion, But it has a 5mm plastic spacer below the rubber bump stop. Should I clip that out, Or does it not matter just to try it out? Also Fox and RS hardware for the spacers and shaft thru the lower eyelet is still the same, Right?
I made a standalone thread before I noticed this one exists, figure here is the best place to ask this:
Do shock manufacturers intentionally design the IFP charging mechanism in a way that requires a special tool or adapter? Is it to ensure riders need to go to a bike shop for a nitrogen recharge? Most people I have asked say charging it with normal air is fine, since air is 78% nitrogen anyways.
I asked grok and most of the reasons it gave for this design choice seem a bit weak. I don't imagine it's significantly more cost effective than a shrader valve. Maybe its slightly smaller but that also seems like an issue that could be solved easily w/ engineering choices. Perhaps a shrader valve leaks more than the pellet system, but if it could be filled easily then it wouldn't be much of a problem.
Rock shox enters the chat.
All you need is an adaptor (it's cheap) and a shock pump. They say it's perfectly fine to pump it up with ambient air.
Fox is complicating things needlessly. But their products are rife with complications and proprietary tooling that changes every generation.
About 50 to 100 euros worth of tooling will cover at least 2 generations of RS products service procedures. The Vivid is a bit special, but the super deluxe series and the forks are a joy to work on. You don't need special clamps as parts have flats machined into them so you can grab them with a vice. Shafts have leading chamfers to mount sealheads so you don't need seal bullets. Etc.
Still doesn't fully make sense to me though. Why even need an adapter, why not just have a second shraeder valve for the IFP?
The more I think about it the more it seems like companies intentionally do it to prevent users from doing IFP pressure themselves. The most generous reasoning might be, that they assume most riders could get confused and fill the IFP thinking they are filling the air can? Clearly labelling the valves could fix that though.
If you clip the spacer out your HBO needle wont engage correctly. I wouldn't do it but you can run it on the bike and just have a little less travel than you had before without doing any harm. I think you can use the fox top hats on the the RS shock but you have to push the DU bushing out.
Is it a pressure thing? Schrader valves have a limit to their max pressure, depending on the configuration
There's probably a few reasons -
A full size schraeder valve will reduce frame clearance or IFP volume, and both are usually at a premium already. Picture below is a DVO with full size schrader, vs a Fox X2 cap
The sunken schraeder design like rockshox and new fox shocks is actually a standard part - its the same thread as inside a regular schraeder and is also ubiquitous in the HVAC industry. So the adapter is easy to find is fine to use with a standard shock pump
I like the pellet sealing systems, it does seem to give a more reliable seal and isn't that hard to use
And theres a good chance it is to add friction for someone to play with it themselves. It's not very useful as a tuning tool, but dropping it too low will cause your shock to pump full of air in no time. It's also very confusing when you pump it up to 200 psi then screw the pump back on to check and its more like 120psi....due to the small volume.
And yes people will/do confuse it with the air spring, or think its something they "need" to check
This is my probably controversial take, but charging the IFP is not hard at all....the tools are very commonly available with the bare minimum of searching for 99% of shocks out there. If you find that too much of a barrier then you possibly aren't ready to be rebuilding your own shock sorry. But they really aren't that hard to find so if you want to do it you can go ahead and get stuck in!
Fox does have a bunch of unnecessarily proprietary tools and procedures for their shocks, but the IFP tool isn't one of them. The coil shocks are mostly doable with simple tools (not the new DHX2 though)
Lastly - a gentle reminder for people that when your shock gets squishy/noisy, that is aeration or air mixed in to the damping oil. It is NOT cavitation - which is when the oil inside gets pulled under a vacuum and boils, creating a pocket of gas or gas bubbles inside the oil. They can make noise (sometimes a whistling or knocking) and return to normal at slow speeds. A cavitating shock will likely become aerated in short time though as the vacuum will pull air past the shaft seal.
Yeah thats correct - losing 5mm of stroke doesn't matter to try the shock out anyway
Ok here is the first example of pressures inside the shock and what changes when you tune the base valve VS changing the main piston. The first picture is the compression damping of the 2 different arrangements -
Both are quite firm tunes, that are similar-ish in overall damping rate. The blue line has a firm tune on the main piston with a softer base valve and lots of free bleed and the turquoise line has a firmer base valve and moderately stiff main piston. This is a pretty extreme case but it shows the best difference in what happens inside the shock. Neither are really ideal, the Turquoise curve is "safer", but there is a bit more hysteresis and would probably feel a little harsh with maybe not as much support at very high speed. The lines have a gap because the damper makes a little more force as its slowing down compared to speeding up.
Second picture is the measured pressures inside the damper as it goes through its compression cycle.
X-axis is time, as it moves from a (momentary) stop at the bottom to stopping at the top. The rebound stroke is clipped off at each end. Y-axis is pressure and force (Newtons and PSI - they are in a similar range for the different lines hence no separate Y-axis for force).
Purple is the damper force you feel at the shaft, orange is the pressure in front of the piston and red is the pressure behind the piston (rebound chamber). Turquoise is the reservoir/IFP pressure.
If you increase the pressure inside the whole shock, its only acting on the area of the shaft so you need a huge pressure to get any force. If you have a lower pressure behind the piston, that difference in pressure acts on the piston area, which gives more damper force for a smaller change in internal pressure.
The "safe" tune causes both chambers to rise - creating a peak around 450psi which is not too bad but if you wanted to go stiffer or as the shock reaches higher speeds, the massive pressures can cause damage to the seals, harshness or can produce a knocking sound/feeling
The stiff main piston has a much lower peak pressure (300psi), but the pressure behind the piston drops dangerously close to 0psi, which is where cavitation occurs
Generally, if you stick with the suggested tunes from a manufacturer they should be similar to the "safe" plot (probably a lot softer though) and you will be safe to add more damping at the main piston. There could be some outliers there, I'm still testing different brands but from what I can tell as long as you stick to the correct IFP pressure and use their supplied tunes it should be pretty safe. Since they are normally quite soft to begin with, if you try adding too much stiffness at the base valve it will create some pretty massive pressures to get the desired damping!
Dang thanks for the thorough reply! That all makes sense to me. I do agree it's not all that difficult to do if you have the motivation to get er done, but it's still not as easy as most other things on an air shock.
I have a separate question since you seem to be quite knowledgeable regarding suspension stuff. That issue where the shock pump hose fills with air when it connects to the IFP/air can and gives a lower psi reading. It's the act of re-connecting that gives a lower psi reading right? If I fill it to 200 psi and then disconnect my pump, I can trust it's still at 200 psi?
Just wanna make sure so I don't have any issues out on the trail.
I made a small air chamber with a schrader one side and a gauge the other to test my shock pumps for accuracy (I was bored).
What it also illustrated with my 3 different shock pumps was that there is no loss of air when disconnecting/unscrewing the shock pump chuck.
I could see a situation where if the rubber seal in the end of the chuck is perished or permanently compressed that you could in theory lose some air before the chuck has disengaged the schrader poppet.
Yes. The pressure "dropping" on reconnect is the air pressurising the hose. Same mass of air has to fill a larger volume which obviously means a drop in pressure.
Checking the pressure I mount the pump twice and add the delta between the two values to the first value to get the pressure that was in the shock initially. It's not exact but I think it's good enough.
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