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aeration, not cavitation
I was told that the air bubbles in the oil would cavitate under the pressure, and leave carbon deposits in the damper?
regarding Jackson's STFU placement... I find that exact spot is where SC VPP bikes get noisy. With the way the rear triangles are shaped, the chainstay drops down in relation to the lower link pivot, that drop section of the chianstay gets closer and closer to the chain as the suspension cycles. In general, my MT1, MT2, Nomad 6, HT2 have all made noise when the chain slaps that drop section of the chainstay. They are otherwise silent bikes... unfortunately, only making ALOT of noise when hammering through chunder and twanging the un-tensioned side of the chain.
thanks all on the jackson STFU thing. why, though, would they not run a lower chainguide roller? i get chains now are good and may not derail (although i wouldn't take the chance with a rider as gnarly as jackson), but wouldn't the lower roller help mitigate chain forces impacting the chainring?
A chain guide is so close to the chain-ring, this does the same thing but better by constraining the chain closer to the cassette, less whip essentially.
Seems like they're going to the larger shaft diameter found on the DHX and Neo DHX.
I have to assume that an actual roller, will keep the un-tensioned chain tight enough that it will start to transmit feedback to the chainring as the suspension moves. I think the chain slapping around is the thing they are trying to fix, and a roller could fix that problem, but introduce a butterfly effect of other concerns. That bottom of the chainstay slap that SC-VPP bikes have, is way more significant then I've experienced it on any other bike.
For me, I've run an STFU (on top) and then an ochain+stfu. From that experience, I've also just added an STFU to my trail bike as I do not want the complication or elasticity to the engagement on that bike. I have to say, that while the ochain tames the actual feedback you feel through your feet... just the noise of the chain slap being tamed gives you a lot of perceived benefits of the ochain.
thanks @ebruner
clearly, can't argue w/ the bike performing exceptionally under jackson with how they have it set up.
It's pretty hard for aerated dampers to start cavitating - once the oil is foamed up it gets more elastic and cushions the oil so you get less pressure drop behind the piston cause cavitation. It might happen in certain shocks if the air collects at the top, between main piston and base valve (and would develop a distinct pop or knock sound) but its pretty rare and would usually foam up enough to be spread around. The Float X2 almost has the opposite problem- the original valving meant they had very little pressure difference across the main piston and needed massive internal pressure to generate any damping at all. Usually the foamy X2 shocks I see are super clean inside - a sign that they foamed up way faster than they should. If there's black deposits inside thats usually just regular breakdown/oxidation of the oil or wear of the internal components. If a shock is cavitating badly there will normally be other problems that appear earlier like causing the air to suck in, or violent knocking and top out issues.
The other black deposits I see on the surface of shims are normally shocks that haven't been serviced in a long time and could be related to localised cavitation but I think thats combined with certain oils that oxidise worse than others like highly modified high VI types
You could run both - the lower guide wouldn't necessarily damp out the bouncing (or potentially make it worse by shifting to a higher frequency) and maybe they found the STFU was enough stop the chain bouncing off too
Canfield doesn’t like it 😬
Interesting. What is their latest patent?
And does Canfield have deep enough pockets to litigate Trek?
Wouldn’t that only matter if Trek want to sell it?
I-Track demands their logo even on bikes that aren't for sale. Free to use, but marketed.
As for Canfield, it's the CF3 patent that's used on the Vampire Fastarossa.
The STFU, it's positioned bang smack in the middle if the chain where it will whip around the most. It's easiest to support and calm it down there. An idler might help, but it will add some more drag (very little, but still add) and probably won't do that much compared to that STFU placed there.
That's what i did last year on my bike. I switched to single speed after breaking numerous derailleur and since nowadays I only ride park for fun. My chain tensioner has no clutch so I was looking for a way to quiet down the bike and reduce chain slap. I kept the lower chain guide because I didn't have a N/W chainring. I can confirm a STFU on the bottom of the chainstays works very well since it limits how much the chain can slap downward. The only downside is that the chain would tag on the STFU while the suspension cycled so the rubber gave out after 1 day. I believe BC setup would be superior for this.
2025, the year the DCD comes back. That wasnt in Vitals predictions.
That's basically what Benoit runs. It's an old guide meant for 2x and 3x drivetrain system chain retention in place of the lower roller. Can't remember the bike brand that introduced them. Liteville or Bionicon?
EDIT: Bionicon C.Guide
Anyone knows if DT-Swiss is working on new 240 Hubs?
Spotted: https://www.instagram.com/transalpes.ch?igsh=MWh4bjh6ZDRvYXRueg==
Does that look any different from the current 240? Just had a look at one of mine, and couldnt really spot any difference other than the sticker/logo.
Obviously internals can be different, but outside does not seem to be different.
Re: Goldstone's upside down STFU. Just spit ballin here, but maybe that's in play due to the clutch being turned off or detuned to essentially be off. Given how SC's VPP designs have a wide range of chainstay length growth and shrink, the bike may work better without a clutched derailleur. Noticed something similar on my Trance X when I forgot to turn the clutch on. It was loud through chatter but felt like it tracked better. Obv an apple:orange comparison but a bigger bike and hella faster rider may notice it more.
Regarding the position of the STFU:
A length of material spanning a distance at tension will have a resonant frequency. Cutting it right in half with something that would contact the material can cause it to resonate faster at the same velocity on both sides of that contact because that contact essentially creates a point around which the whipping motion can pivot.
Guitar strings do it. Wires stretched across distance at tension do it. There are multiple potential resonant frequencies along the length of the material and creating a pivot by limiting motion at one point can cause that material to resonate at those different frequencies in front of and behind that pivot.
I wonder if that would also apply to a bike chain?
It would be super interesting to test a centered STFU vs a slightly off-centered (by like 6% of the entire length) STFU position.
I wondered the same, but there may be less of an effect, because the driving frequency is not constant and unlikely to match the resonant frequency, and the links only approximate a flexible object, meaning they can only oscillate at finite points (every 1/2 inch), rather than being able to form continuous waveforms. The finite length of the links effectively forms a high pass filter, where any oscillation with a wavelength shorter than 4 links becomes impossible. All this goes to say is that yes, offsetting the STFU from the center point of the chain will probably have a favorable effect, but when we shift, the length of the lower chain section changes, so you can't target the same percentage from the center in every gear.
I was having some of those same sorts of thoughts but I couldn't figure out how to say it...I ran out of brains!
Pivot officially introduces Lifetime Warranty and a Courtesy Bearing Replacement program:
https://www.vitalmtb.com/news/press-release/pivot-cycles-announces-premier-lifetime-warranty-courtesy-bearing-replacement-program
What about seat- or chainstays?
Pivot have solid rear triangles.
woosh
I dunno, its not infrequent that could be serious.
I won't profess to be a patent expert nor have i read what the Canfield patent covers but we built a few prototypes at Rocky years ago with adjustable main pivots. I believe prior art could be applicable here and nullify Canfield's application.