Hello Vital MTB Visitor,
We’re conducting a survey and would appreciate your input. Your answers will help Vital and the MTB industry better understand what riders like you want. Survey results will be used to recognize top brands. Make your voice heard!
Five lucky people will be selected at random to win a Vital MTB t-shirt.
Thanks in advance,
The Vital MTB Crew
It's not a pneumatic bottom out per-se, there's a shorter piston inside the coil spring that is tunable and is there to add ramp up over the last... 30 % of travel? Or even more?
https://www.pushindustries.com/products/acs3-fork-coil-conversion-kit?v…
he all but confirmed it will be coil on MTBR suspension forums, when someone asked what spring type it will be using, Darren said
"Not really known for our air springs 😜"
Yeah thats kinda my point. You can idenpendatly change progression via flip chip, which they state is their patent.
But obviously with a differerent leverage curve you would setup your shock slightly differently, but their patent doesnt claim that, just independent adjustment.
IDK, it just sounds like marketing bullshit to me
We know from that article that the new bike uses both the flip-chip at the shock mount and a different dogbone link to change the leverage curve, so I think it's very plausible they can keep it similar before the sag point while changing the behavior after it. That would be unique compared to every other progression-adjustment system I can think of right now, and could be patented.
The fun thing with patent law, at least in the US, is you can patent anything if you are specific enough. For example DW link and Horst link are conceptually identical. DW link is pretty much a Horst link set up where the lower link is super short instead of being the entire chainstay. If the Horst link patent had been written in a more broad manner it’s likely DW would never have been patentable. So it will be interesting to see how this Norco one plays out. It would be easy to do a Santa Cruz link set where a flip chip on the lower link combined with different upper links gives control over progression without altering leverage ratio at the sag point. I’m guessing the Norco patent won’t be broad enough to prohibit that even though both are flip chip plus a linkage member.
Latest bikerumour podcast with Chris Canfield is pretty interesting. Particularly the discussion towards the end which centres on his new layouts: https://bikerumor.com/podcast-086-chris-canfield-explains-multi-link-suspension-designs/
I *think* this is the related CF3 pending patent with the x3 selectable axle paths: https://patents.google.com/patent/US20210380195A1/en?inventor=Christopher+Canfield&page=1
I was reading the PB Norco article and came to the quote we were discussing before:
"The second patent applies to the method of leverage curve progression adjustment we’ve designed into the bike which allows us to alter the level of support from the rear suspension in isolation without needing to alter shock tune, damper settings, spring rate or shock pressure."
This time I read it as the patent covering altering the level of rear suspension support through altering the leverage curve progression, not through tuning the shock (through pressure/spring rate, damper setting or damper tune). So not that it's there to alter it without changing the shock tune, but that it's there to alter the behaviour of the suspension BESIDES tuning the shock as well. On most bikes you're left to tuning the shock and that's it.
Can someone please explain to me where the hole in my logic is: if you have a Lyrik or Pike and you add volume spacers, you reduce the positive air volume and increase the ramp up.
Now with the new Boxxer they are saying that with the change from 35mm to 38mm and the extra travel, that the fork was ramping up too quick (which we saw with the Zebb as well), but surely the larger legs and increased travel equals larger positive chamber which equals less ramp up?
So now they have gone to a smaller self contained positive chamber (requiring higher pressure) in the Boxxer (and probably soon to be seen in the Zebb as well) which supposedly has less ramp up? Doesn’t that seem contradictory, or am I confusing more/less ramp up with more/less controlled ramp up?
ps. This also correlates to their recommendations that longer travel versions of the same fork require fewer volume spacers.
It could have just been poorly worded, but lots of bikes have flip chips to alter progression. I doubt that could be patented.
new trek supercaliber gen 2
https://www.vitalmtb.com/features/lighter-weight-more-travel-trek-super…
It doesn't quite work like that. The compression ratio of the positive chamber is based on a few things that are fixed (once teh fork is out of either and exists in the physical). In order to think it through, you need to start by considering the volume. The formula for the volume of the air chamber is V=pi*(radius ^2)*height
For our usage, that is volume = pi * piston area squared * air spring travel distance. This formula is quadratic, meaning that small increases in the radius of the piston surface area, have significant impact to the overall volume.
In our case:
For a 38mm piston surface area the volume is 3.14 * (19 ^ 2) * 200mm = 226 cc's
For a 34mm piston surface area the volume is 3.14 * (17 ^ 2) * 200mm = 181 cc's
So, for an 11% chance in piston surface area, the volume is impacted by 20%.
Now that we've grasped how impactful slight changes in piston area have to the overall volume, you can move into compression ratio. Simplified, compression ratio is the following: CR = (Displaced volume + Compressed volume) / Compressed Volume. Said another way: CR = (volume compressed or displaced by the air spring + volume compressed above the air spring) / Volume compressed above the spring. As you can see, we now have 3 variables, all leveraging the above and first mentioned volume formula, which is again, quadratic with regards to piston radius.
In the simplest of terms, the quadratic nature of the volume calculation, shows up multiple times in the path of calculating the compression ratio. Said another way, since the swept area of the fork/cylinder is going to remain constant for this discussion, the fastest and most impactful way to impact the compression ratio is through the piston surface area. Adding a small amount more, gets magnified significantly as you walk the dog through the formula's.
This isn't even taking into account some of the other, not intuitive things that add up like this same quadratic equation showing up again when compressing the air in the lowers. If you want your eyes to really roll back in your head, you can throw adiabatic expansion into the mix.
So... to simplify. The piston surface area is the biggest and most impactful thing from a design perspective.
@ebruner thank you for the explanation/science lesson! 🙂
That both explains and significantly complicates the whole thing at the same time 🙈
Basically it’s not as straightforward as I initially thought…
But for sure very interesting news. Current version is a beast. Their suspension is so good, it makes you wonder why such a small company can create something that works so fine and the big names often don't nail their kinematics.
Uuuuum... Pretty sure the compression ratio (V_start:V_end) defines the ramp up. What the larger diameter of the piston does is provide the same force at a lower pressure or a higher force at the same pressure (through the surface area). Technically the ramp up should be the same. That's why the shocks started getting more cavernous eyelets and additional sleeves to increaser the ending volume and reduce the compression ratio. And that's why triple chamber solutions also work as they effectively lower the compression ratio, but linearly through the travel. And that's why Intend made the 1,5-crown fork, to increase the air spring volume.
Didn't look into the new Boxxer, but with a spring cartridge you could lower the piston diameter and increase the positive chamber size by wrapping it around the smaller piston - if you have a 32 mm piston and the accompanying sleeve for it to run in, you can use the 32 to 38 mm space of the stanchion as the positive spring, greatly increasing the positive volume and thus the ramp-up. For example.
I'm quite glad I just skipped to the last line on that one.
I think what RS is talking about is the ramp up in the lowers. The trapped ambient pressure in the lowers adds to the overall spring rate when the fork is compressed. I'm guessing they kept the ID of the lowers relatively similar to the old forks and just used thinner bushings for the 38, thus there's less volume in the lowers.
If you only use a spring cartridge with a smaller diameter, the spring-side ramp-up from the lowers will also be reduced as the volume is increased with the stanchion being opened up.
Apparently connecting the bleedports of the Zeb reduces the ramp-up. If true, I'd say it's because the damper side is experiencing exactly this - a much larger lowers volume overall with less ramp-up. Bleeding the spring-side air to the damper side will offset some of that issue and bring it to somewhere in the middle of it all ramp-up-wise.
How would you connect the bleed ports though?
With this: https://www.everflow.it/webshop/tuning-parts/airlink/ (credit to @TEAMROBOT for the source).
You guys are having trouble bottoming out a Zebb? Weird…
Oh wait! I just remembered: I’m a 100 kg American fat body.
Curious piece of tech, can't say I've ever seen that before!
I'm pretty sure my 170 Zeb has only hit 170 once and I had the sore elbows to prove it for a week after that one. Gotta get on those push ups....
What would happen if you just put pneumatic filters on the Release Valves of the ZEB so the presure in the lowers is the same as on the outside.
95kg an no issues using full travel on my 170 & 180mm zeb on Big hits if i ask it to.
a friend had issues getting full travel on his so he had it serviced/bushings done and its been excellent ever since.
Like I mentioned in the other thread, connecting the two lowers can cause the oil to flow from one side to the other, depending on the fork orientation. That would of course cause oil starvation in the lowers, which is not a good thing. The same miiiiight happen with filters and I'd still be vary of dirt being pulled into the lowers.
More importantly, a somewhat high enough level of air permeability to cover the pressure ramp up and actually offgas the excessive air in the lowers might not be reachable if you have the filtration capabilities to prevent dirt ingress.
I think it would make sense to solve this issue in a different manner to be honest.
Someone messed up I guess?
https://www.wideopenmountainbike.com/2023/08/rockshox-reprise-the-vivid-downhill-shock
I wonder how much lower the actual street price is going to be after 3months, if it stays close to the rrp it would be the most expensive RS shock ever made 🤔
Looks like it's not just an air version of the coil shock given the new damper. Does the mean a coil vivid is also coming?
I am a total layman when it comes to suspension, but it sounds to me like the damper in the new Vivid was designed to combat some of the negatives of an air shock i.e stiction, being supple in the first part of the stroke. So it doesn't seem like tech isn't necessarily needed in a coil shock.
Hoof it got pulled right after I read it: to sum up what I remember: big difference with the SD is an early stroke oil bypass, after the first 30% of travel the main piston engages, plus the HBO seen on the SD. Retail price between $550 and $580 depending on stroke. Did I miss anything?
BTW, I guess that press release article means it's already in the hands of journalists. Must be close to a release. I don't think they will introduce a new Vivid coil, or at least it's not being tested at WCs.