Trek Debuts New RE:aktiv Thru Shaft Shock Technology

Jul 12, 2017
by Paul Aston  
Trek released their original RE:aktiv suspension units early summer 2014. Working in conjunction with Penske Racing shocks, a high-end suspension manufacturer focused on the racing worlds of Indy and NASCAR, they initially brought the technology to the market using Fox as their supplier of this exclusive technology. For 2018/19 Trek has exclusive use of a new technology compressed down from motor racing and into mountain bike suspension. RE:aktiv adds the 'Thru Shaft' label, which is a replacement for longstanding internal floating pistons found on nearly all shocks.

Trek admits that this technology isn't brand new; AMP, White Brothers, Manitou, and RockShox all experimented with this technology back in the 1990's, but manufacturing techniques at the time meant that a reliable product was tough to create. Fast forwards twenty years and things have moved on, and Trek now believes they have a durable product with improved performance. Why does the performance improve? An IFP creates some friction and lag in all shocks; even as seals and coating have improved, there is always a static force to overcome. The Thru Shaft works around this issue by allowing oil to be displaced freely and eliminates the IFP and nitrogen/air charges.

More proprietary technology? Fox and RockShox will be supplying Trek exclusively with shocks for the next two years, but the technology is open source, so we may see this appear on other brands in the future. Penske still retains the patent on the regressive RE:aktiv valve, so this will continue to be unique to Trek for the foreseeable future.


Trek RE aktiv Thru Shaft



Trek Explains Thru Shaft:

How does RE:aktiv with Thru Shaft compare to other all-mountain or enduro shocks like the Fox X2 or RockShox Super Deluxe?

RE:aktiv with Thru Shaft is the only damper that eliminates oil displacement, the dynamic internal floating piston (IFP), and gas charge; as a result of this elimination, RE:aktiv with Thru Shaft has reduced hysteresis (lag) and more balanced damper pressures, which allows it to more quickly and effectively react to changing terrain. Overall, it’s a much more responsive damper with the same air spring performance.


What does all of that mean? How does eliminating oil displacement benefit the rider?

In a traditional air shock, the damper shaft displaces oil as the shock moves through its stroke. The IFP, a gas-charged piston in the damper, compensates for this constant change in damper volume. As the damper rod displaces oil, the increased damper volume creates enough pressure to compress the gas charge and move the IFP. As the shock rebounds and pressure is reduced, the IFP will start floating back to its original position, and the cycle continues. The rod pressure from the gas charge and the stick and slip effect of the IFP’s movement create hysteresis, or lag, which keeps the shock from working as quickly as possible. By eliminating oil displacement, we also eliminate the need for a dynamic IFP. With no dynamic IFP, hysteresis is dramatically reduced, which creates a damper that reacts to changing terrain significantly faster than anything else available.


How does RE:aktiv with Thru Shaft eliminate oil displacement?

Rather than a single damper shaft that displaces oil as it moves deeper into the stroke, Thru Shaft uses a shaft on either side of the damper valve that moves through a single, solid column of oil. As the main shaft enters the damper, the secondary shaft exits the damper on the other side. Conversely, as the main shaft exits the damper, the secondary shaft enters the damper on the other side. This results in a constant damper volume with no displacement and more balanced internal pressure.

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How does all this affect the rider?

It’s a more responsive shock. With no IFP force acting against the damper shaft, small-bump sensitivity is greatly improved. Eliminating the dynamic IFP also eliminates its friction and stick and slip effect, so not only is the shock movement easier to initiate, it also changes direction much faster. The solid column of oil and immediate pressure balance result in more support and efficiency with faster response to terrain throughout the stroke. In total, this shock amplifies the responsiveness of a standard RE:aktiv shock, and keeps your rear tire glued to the trail so you can ride with even more confidence.



With no dynamic IFP, how does the shock manage heat-induced fluid expansion?

The longer-stroke RockShox version uses an external reservoir for thermal compensation. Since the shorter-stroke Fox version has less total oil volume, Fox was able to include a thermal compensator within the main damper shaft. Due to the use of a flow control check valve, thermal compensation on RE:aktiv with Thru Shaft takes place during moments when the shock is static. This eliminates the need for a dynamic IFP function and an associated IFP gas charge, which is necessary for traditional dynamic IFP shock function.

Trek RE aktiv Thru Shaft
The RockShox Thru Shaft models use an external reservoir for heat induced fluid expansion, the Fox shocks package this inside the shock.

Do the added seals cause extra stiction?

Eliminating the dynamic IFP’s stick and slip effect and the IFP’s gas charge nose force on the main damper shaft greatly outweighs any potential added stiction from the additional Thru Shaft secondary shaft seals.




Trek RE aktiv Thru Shaft
At full extension, the Thru Shaft is out of sight inside the shock.
Trek RE aktiv Thru Shaft
At the shock cycles through its travel, the Thru Shaft can be seen between the lower mounts.



For 2018, Thru Shaft is limited to higher end Trek models including the Slash 9.8 / 9.7, Remedy 9.8 and Fuel EX 9.9. It will also be supplied on Slash, Remedy, and Fuel EX carbon framesets. Expect to see the tech trickle down to cheaper models in the future, but buying aftermarket shocks to upgrade your old bike will not be an option yet.

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250 Comments

  • + 232
 I will hold out for Boost Shaft that will come out next year.
  • + 357
 your mom will hold out for the boost shaft Wink
  • + 20
 you mean next month?
  • + 12
 Plenty in the tank, as i can see - Loveleh
  • - 35
flag Duderz7 (Jul 12, 2017 at 10:28) (Below Threshold)
 I'm holding out for 28.125 wheels with 13x149.8967 rear and 19x110 front axles, cuz 12x150 and 20x110 is crazy talk.
  • + 5
 @jefftrancex1xtr: simply lovelehhhh, plenty in the tank. Good shot sir, bloody good shot. A bit of blinding!!!
  • + 2
 bad shock
  • + 5
 But is it metric? (Even though I still don't understand what exactly that means...)
  • + 72
 Poor shock is prairie doggin'
  • + 61
 Proprietary rear shocks: not even once.
  • + 2
 You said it.
  • + 53
 Fool me once Cannondale. Fool me twice Scott. Fool my thrice.....you can't fool me thrice Trek.
  • + 9
 @Triber66: Specialiezed was the one that fooled me when I blew out a triad on a stumpy and couldn't get anything better than the pos I already blew out.
  • + 0
 Proprietary="we've screwed up manufacturing some of our shocks, and, "screwed up" in this instance means, "massively improved by accident"". "We're planning to screw up more in the future, thanks team."
  • + 7
 @NickB01: My favorite quote lol.
  • + 2
 Haha @NickB01: pretty much exactly the same.
  • + 11
 I'm digging this competition between Trek and Specialized on who can fool the consumer with this suspension gimmickry..............I see a huge product recall in the next two years.......Thru Shaft Shock fails to deliver a stimulating ride.
  • + 3
 @rivercitycycles: well my 2016 re:activ shock started making a knocking sound 3 months in. Fox couldnt fix it because they dont have parts.... So it sits on my tool box and I now have a deluxe in there..

They should be recalled just so shops dont have to tell people theres no parts to fix them.
  • + 57
 Won't that shaft eat dirty doing the old in-out in-out?
  • + 16
 That's a very good question. I think I'd prefer my shock bits as little exposed as possible
  • + 36
 ur mum got my shaft dirty with the clap from the ole' out-in-out
  • + 25
 Same level of exposure as a coil shock.
  • + 36
 @remedy8point5: Ah yes, but coil shocks are God's gift to mtb suspension so they're exempt.
  • + 23
 @hamncheez: you are making enough posts about someone's mom in sexual terms that I am claiming Edypus complex on you!
  • + 2
 @WAKIdesigns: I just looked that up
  • + 56
 @WAKIdesigns: it's Oedipus bro.
  • - 2
 @Theeeeo: Depends on the language, but I'm not an expert on that matter...
  • + 10
 "Thru Shaft" condoms?
  • + 1
 @remedy8point5:not really the same tho is it? coil springs still only have one shaft exposed where as this has two. this has the thru shaft that can gather dirt along with the normal outer shaft that can also gather dirt. sorry if i'm not using the right technical terms lol
  • - 2
 @in2falling: that sounds like something that a raging feminist would like to see.
www.evilmilk.com/pictures/Social_Justice_Warriors_5.jpg
  • + 17
 @WAKIdesigns: what? @WAKIdesigns is not an expert on something? Get outa here!
  • + 3
 @DaySleep3r: Literally lol'd
  • + 0
 @WAKIdesigns: Read about the old DCRV for fun and found some of your pre-troll days comments LOLOLOL some many smile faces.....
  • + 1
 @WAKIdesigns: definitely doesn't depend on the language...
  • + 3
 @jts429: Yes it does. It's Oidipus in finnish.
  • - 3
 My bad, the mother fkrs name starts with O in most languages. Tower of Bible my friends...
  • + 1
 @toaster29: well it's a name, so I'm not so sure language makes a difference haga
  • + 1
 @jts429: Much knowledge in linguistics murican?
  • + 1
 @toaster29: ask my bald eagle
  • + 40
 have any of Trek's proprietary shocks over the last few years stuck around. Seems like everyone got rid of those DCRV shocks as soon as they could. I also see a lot of bikes with the Re:aktiv (or whatever it is) shock replaced with something else.

At least it doesn't have an inane autosag valve on it.
  • + 6
 Whilst this would be an interesting development coming from someone else, T have a history of acronim labelled suspension tech that seems impressive to A. Joe in the show room, but in reality does not work that well - DRCV... Is this any difference?
  • + 6
 Drcv with vorsprung corset , totally different and served me well
  • + 5
 i have 2 years riding my DRCV bike.. i'm starting get tired of it, it used to leak air, had to refill it like every 2 to 3 weeks, i sent it for a full rebuild, and now i have to refill it before every ride.. :'( and have tu run like 50psi more than what is recommended for my weight because if i don't, it will bottom out really easy :'(
  • + 13
 Proprietary shocks just aren't worth the hassle, especially when they have weird eye-to-eye x stroke measurements like the DRCV did.
  • + 13
 At least you can just ignore the Autosag. DRCV was awful! I had a Fuel with DRCV shock and fork. The shock failed twice, and was recalled once and leaked air always while the fork was only recalled once. I was honestly relieved when someone broke into my garage and stole it because my insurance deductible was a smaller loss that I would have taken selling the dumb thing!
  • + 7
 DRCV wasn't bad if you never tried to leave the ground. If you tried to bunny hop or jump or whatever, as soon as you would get the right amount of bounce the secondary valve would open and you would lose every bit of that bounce momentum.
  • + 3
 @WaterBear: It's wild can we all just use a non-proprietary stroke and eye to eye. It's brutal for the consumer and forces them to look elsewhere no matter how good the geo may be
  • + 5
 I have seen this also, but to be honest I had a trek slash for a few years with the drcv kashima ctd shock or whatever that was, and I thought it was a great shock. Never leaked air, felt awesome and responsive. Rode a lot of dh with it. I replaced the seals because they were cheap and sold the bike to the next guy still going strong.
  • + 1
 @jorge269: Sounds awesome! Sign us up all for more of that Trek.
  • + 1
 @eswebster: i'm 70kg.. i have to use that awful thing with 250 psi :c and that air leak is really annoying, i'd like to get a new frame.. perhaps a yt capra, but i need to work harder :c
  • + 24
 Question: How do the improvements compare to designs using a bladder, such as the DVO Topaz? These have no friction due to seals. They still must expand and compress, so there may be hysteresis, but there should be no benefits with regards to stiction.
  • + 9
 I think there is very little hysteresis in the DVO shocks from what I have seen. Also, super low hysteresis is not something that is overly important in mountain biking asour bumps are not as small nor as minor as those in cars. If you watch the video by Steve from Vorsprung he explains this in finer detail.
  • + 8
 I remember Steve from vorsprung suspensions mentioning that hysteresis is not a very big deal within mtb in one of his videos.
  • + 2
 @tcmitchell: Can't agree more
  • + 5
 @Happymtbfr: True, but if you watch the video where he explains the Penske regressive valve in the DRCV shocks, he mentions that part of what makes them regressive also increases, in his words "things that would look like hysteresis in any other shock." So maybe this is a solution because the valving is more sensitive to hysteresis than a normal shock.
  • + 3
 The bladder still needs pressure on the back side just like the IFP. This eliminates that extra pressure on the shock shaft, and elimating that additional "spring rate" that comes with it.
  • + 1
 @groghunter: do you remember which video covers that?
  • + 8
 @krisrayner: the pressured up bladder in a MX shock does a couple of things, One the shock shaft area fluid displacement but the big one is it reduces cavitation behind the piston as pressure drops. This does not address that. And a bladder has very little hysteresis and friction!
  • + 3
 @krisrayner True it doesn’t remove that small spring rate that comes with the bladder, but when setting sag and air pressure that spring rate is always there and is taken into account during setup. On coil shock the ifp or badder adds a nice little bit of progression to the shock, especially toward the end of the stroke which I think is good
  • + 2
 @MX298: I agree. I would be worried about cavitation I this shock, especially if you start working it hard
  • + 8
 @tcmitchell: You are spot on!
  • + 3
 @Happymtbfr: Go look on their youtube channel: it's not a tuesday tune video, it's a separate video where he takes apart a DRCV shock & explains what's different about it.

Coincidentally, I watched it just last night.
  • + 58
 Hysteresis by definition is when any characteristic of a system has some dependence on its time history. In the case of dampers, that means its force vs velocity characteristic varies somewhat depending on what has been happening with the movement of the damper up until the instant in time that we are looking at. For example, dampers will typically generate less force at speed X if they have been accelerating rapidly up to that speed than if they have reached a steady-state velocity at that speed. Effectively this is lag, and if it is excessive and uncontrolled then it can inhibit performance. However, when damper curves are viewed graphically, there can be many different causes of what looks like a lag in damping force response, but not all of these are actually a true lag. For example, position sensitive dampers will always look like they have a ton of hysteresis when tested on a dyno because we are effectively plotting a 3D curve in 2D. However, they can have extremely little lag in terms of force buildup - it just depends where in the travel it currently is, not necessarily where it was before. Likewise, dynamically unstable valves (eg regressive valves) can create seemingly unstable damper curve responses on the dyno which is partly because the inputs typically generated by dynos are controlled by velocity and very good at maintaining a smooth velocity profile that, whilst great for characterising most dampers, is a little bit unrealistic compared to actual inputs on the bike.

More importantly though, hysteresis is a buzzword (like cavitation) that is thrown around a lot because it sounds uber techy, but is also very commonly misunderstood. A lot of shocks market themselves as "low hysteresis" which is absolutely relevant if it's for an F1 car that needs huge forces very suddenly at low velocities, but not so important on long travel suspension on mountain bikes.
  • + 3
 @Happymtbfr: @VorsprungSuspension I do note that Penske is using this style of compensation on their F1 shocks: www.f1technical.net/features/10660

That article speculates it is due to hysteresis.

Also of note is that they do seem to still use a pressurized chamber of some sort to prevent cavitation & provide space for thermal expansion... I'm guessing the thermal compensator they talk about is doing both duties here as well. It seems that through shafts generate a much smaller pressure delta across the piston, so the amount of pressure needed to prevent cavitation is probably much less than a typical shock.
  • + 8
 @VorsprungSuspension: If only I could upvote you twice.

If you're really worried about hysteresis, better dump your clutch derailleur. That makes x10 the difference as losing a seal in an IFP
  • + 4
 @hamncheez: Agreed, a average user has absolutely no need to care about this stuff. No modern, serviceable shock is going to have appreciable problems due to hysteresis or cavitation.

I talk about it purely because I'm interested in suspension design, & what goes into making a shock that doesn't have these problems.
  • + 1
 @groghunter: I also am here for the comments.
End of the day, I'm a weekend warrior, but I still want my Cane Creek Helm and CCBD Coil CS to synergise together for 'the perfect ride'

The problem is, I'll never know exactly where 'the perfect ride' is. Bike feels damn good though
  • + 3
 @VorsprungSuspension: Can people physically hire you for bike park days to help them set up their suspension?

I mean, I'm in Australia, you're no use too me..... but I would totally pay a 'guru' to come and ride with me to help me get the best out of my suspension.
  • + 2
 The Topaz I have responds so well to small bumps, it took me a while to realize that I no longer had to tune around maximizing grip in those situations. I think the bladder is awesome in that regard, and might honestly be the technological advancement endpoint I settle on, because once the air spring curve and compression is dialed, it's hard to make a bike feel bad.
  • + 3
 @Waldon83: Vorsprung does setup clinics in the Whistler Bike Park. I'm thinking of hitting one up in the future once I learn a bit more myself.
  • + 3
 @tehllama: same here with the Topaz. That shock tuning capabilities are outstanding (specially the neg chamber)... Mi topaz microsags under the bike's own weight.. #whataboutthatstictionpolice
  • + 10
 @groghunter: through-shaft shocks do offer some pretty cool opportunities for minimising hysteresis on short stroke track cars for sure, because you can use a big piston, small shaft and have a very large piston annulus without having a big heavy shock. Cavitation really should not ever be an issue on those since they can build up positive pressure in front of the piston in either direction. Nothing wrong with discussing any of that stuff, my comment before wasn't a dig at anyone!

@Waldon83 only in the Whistler Bike Park right now sorry!

@tehllama bladders definitely cut out one of the sources of friction, and in an air shock where the negative spring can be designed to negate the gas charge preload very closely, they do pretty much cover all bases. They aren't perfect though - assembly of shocks using bladders is less precise than IFPs and there is more room for error. For coil shocks, the through-shaft system makes sense from a theoretical standpoint (packaging is a bit of a pain though), unless you want to use something like Countermeasure to negate the gas charge, but then that system has its own associated issues (noise/knocking among other things).
  • + 2
 They claim that:"hysteresis is dramatically reduced", yet present no numbers whatsoever nor a single plot.
  • + 2
 @tcmitchell: www.penskeshocks.co.uk/car/dampers/throughshaft even penske are using Gas pressurised chamber to eliminate cavitation ... i can only see in the near future those shock are being less constant and losing traction after few months of use...
  • + 1
 @sparkylab: Interesting. I wonder if these shocks don’t have a gas pressure in the oil expansion chamber. Something gotta keep it from simply flowing into the chamber during compression and rebound
  • + 1
 @tcmitchell: I suspect the "thermal compensator" that they don't talk much about is essentially an IFP or bladder, but that contradicts their marketing speak, so they leave it out. It probably does have a much smaller pressure than a typical IFP.
  • + 1
 So if I sum up things a little:
1. Trek ask Penske to design a shock valving based on their track experience.
2. Trek does a lot of marketing communication on their new shock tech
3. But some yeas later they realized that implemented regressive valving in MTb shock made become hysteresis an issue
5. So Trek ask Penske to design a new solution to deal with increased hysteresis
6. Trek made a lot of communication into solving an issue (hysteresis) that is not relevant with standard shock and present that as a huge improvement...
  • + 1
 @gnralized: Well, it's all a bit speculative, but I'm of the opinion that the benefits of through shaft may have an outsized impact on DRCV dampers, yes. It certainly seems to be the reason for Penske using this compensation method in their F1 dampers, & it seems silly to not think the impetus to go this route came from the Penske folks.
  • + 1
 @groghunter: Thank you for all your explanations.
Looking in details at the rockshox implementation, it seems that the upper shaft (above pistion and contermeasure) is thinner in diameter than the lower shaft. I wonder if the small piggyback is not for compensate a small volume change due to shaft diameter differences.
  • + 1
 @gnralized: Looking closer at it, that piggyback also seems to have something that is obviously a floating piston... so there goes all their marketing speak about reducing sticktion due to less seals.
  • + 1
 @groghunter: I would think a much simpler solution is to replace the IFP in the shock shaft with a bladder, but that's none of my business *sips tea*
  • + 1
 @WaterBear: every solution has tradeoffs. an awful lot of people burst the bladders on their 1st gen charger dampers. misaligned bladders were supposedly a big part of the issues with the DB Inline as well.
  • + 2
 @VorsprungSuspension:

as an Suspension Designer i would add following to your information: on IFPs the pressure differential between the oil and gas side ( besides the initial pressure created by the stction force of the nominal sealing force) is nearly zero - therefore the friction force of the sealing is quite low. Especially compared to a shaft sealing on a thru shaft damper, that always has to seal the oil pressure against atmospheric pressure. Sealings create a friction force highly dependend on the pressure they have to oppose.
  • + 23
 This has gotta stop! How many seals have to die just to make suspension products? Do the celebrities know about this?
  • + 21
 AMP Research did this back in the 90's and the problem was the seals would blow (almost on command) on the compression side. I am looking forward to seeing if trek figured out this problem.
  • + 9
 The AMP was little more than some simple shafts, piston and o-ring seals. Modern quad-lip seals and coated shafts will perform far better than that ancient relic. For those worried, it is the same basic level of sealing needed on the existing shaft for a regular IFP shock. This design just adds another of the same design, so I don't think there is a major concern unless you question the main seal already.
  • + 2
 How did the AMP compensate for thermal expansion? If it didn't use anything like the new Trek shocks use as described in the article, that might be a likely answer.
  • + 3
 @Rooster09:

They didn't, but there wasn't a lot on the shocks as they were long-stroke / low leverage designs. The Amp Mac-strut bikes (B2 thru B4) had nearly 2 inches of shock shaft travel for only a 3" wheel travel. In comparison, a GT RTS of the same era had the same wheel travel but got it from moving a shock shaft only one inch. They also spec'ed automotive grade oils as their background was in motorsports. One of the acceptable fluids was ATF fluid, which in terms of shock oil works out as about an 8 weight fluid. Its also designed for high heat applications.
  • + 18
 So the real question(to me atleast), does this mean this rear shock is user serviceable? Without having to nitrogen charge a IFP, this looks like something any home mechanic can service? Kinda shocking to me that it hasn't been brought up, but I guess Fox doesn't want anyone rebuilding their stuff without paying someone to do it...
  • + 2
 I'm with you, that's an attractive aspect of the thru-shaft designs to me. If I could bleed/pressurize fresh oil in my shocks at home I would be a happy man.
  • + 15
 Sounds like more monthly bullshit to me
  • + 14
 The old RE-aktiv wasn't reactive enough so now Trek is going to give us the shaft.
  • + 10
 So you take two additional seals to get rid of one seal? I assume that those new shaft seals have to deal with high pressures and therefore will face not insignificant friction. Friction plus dirt equals wear and air bubbles in the oil. Perfect fit for Trek.
  • + 2
 You only replace one seal with a smaller one that moves more. I think the result is the same amount of friction.
  • + 8
 The advantages are: with this, you break both seals free at the same time, rather than there being a lag for the IFP to break loose due to it floating independently of the air shaft. With a thru shaft, they're fixed to each other, so any motion that breaks the main seal free also starts moving the oil shaft. Second, you don't have a secondary air spring to push against when compressing the shock, though the impact of that spring is debatable (except in the fox shocks that intentionally use that air spring as a bottom out adjuster.)

as for dirt ingress, from a sealing perspective, this is essentially just the shaft from a coil shock. If we can keep the oil clean on those, this shouldn't pose any extra challenges.
  • + 2
 @groghunter:
From my understanding, the ifp move to compensate fluid volume reduction due to main piston shaft displacement. So I was thinking that even if they are not mecanicaly linked, since fluids are incompressible, as soon as the main piston move, the ifp should move too, even if their respective displacement length is not the same due to different diameters (but same volume displacement). So can you please explain how the ifp is floating independently of the air shaft ? This is a genuine question, I'm not ironical.
  • + 2
 @gnralized: As I understand it, it has to do with a few things: first, it's a static force that has to be overcome, which takes a small amount of time, even with a incompresible medium. Second is any slop or play in sealing surfaces, in that the ifp has to switch directions & move the seal each direction, in which case it takes a little movement to switch directions. Third is that oil is incompressible in an ideal circuit, but in the real world will always have some dissolved gasses in it that can compress.
  • + 4
 @emptybox: actually you'd have to replace it with two (or a twin-lip seal, which is effectively the same from the friction POV)... any shaft exposed to the outside environment will need both a pressure seal lip/surface and a dust scraper lip.
  • + 1
 @VorsprungSuspension:
But how much friction does the dust lip have compared to the pressure seal
  • + 1
 @VorsprungSuspension: I'm thinking that you are probably the person to answer this question.... So as I understand it this shock needs the additional seals so the shaft can protrude through the damper circuit and out the back of the shock. I watched the video but just can't understand how they can't make the same shock without the IFP gas section but also without the strut sticking through the oil and out of the arse of the shock. How does the the through shaft eliminate the IFP space? Just don't build either in.
  • + 6
 @emptybox: depends how they design it, but usually more stiction than pressure seals - especially ones like this that start off under very low pressure (if any - wasn't clear whether these things are substantially pressurised or not), since pressure seals rely on that very pressure to hold them tight against the surface they're sealing. Dust scrapers aren't holding any substantial pressure so they have to be tighter to begin with.

@bigtim imagine you have a bottle of water that's full right to the top with water. You stick your finger in the bottle of water, the volume of your finger occupies space that water used to occupy, pushing water out the top of the bottle. That water has to go somewhere obviously, so in this case it just overflows and leaves the bottle. We don't want that to happen with our shocks, so we seal them up to stop the oil getting out, but that means we still need some method of compensating for the volume of the shaft as it enters the sealed chamber. You can either introduce an IFP with an elastic medium behind it (pressurised gas or a spring or whatever) that can move out of the way, or you can cut a hole in the other end, and have as much volume leaving the shock as you have entering it.
  • + 2
 @VorsprungSuspension:
Oh well I thought it was the other way round. Thank you
  • + 12
 Your 2018 non-thru shaft shock is already two years obsolete. That's some shocking news.
  • + 8
 Yeah, let's make a super sensitive shock which will be likely to fail and then put in onto a single pivot bike, add 400g cassette, a clutch derailleur (which paired with single-pivot chain growth will act like sensitivity reducer), add 1000g tires, and maybe some bushings. Sounds like a recipe for marketing BS.
  • + 1
 haha great
  • + 10
 Where's the shock made by the company that made shocks for tanks? That's the one I want to see come out.
  • + 4
 I heard that tanks use friction damping, not oil damping,,,,,,,it works like,,,,,,,,a disk brake
= ̄ω ̄=
  • + 14
 Nitro shox and the oleo damper with a metering pin. Still waiting. ..
  • + 0
 Not sure what company you're referring to, but an 'E' named company is doing stuff for horstmann which is doing the suspension for BAE. curious which one you're talking about.
  • + 3
 @emptybox: Yeah that's the one. Thanks.
  • + 2
 @squirrelbomb:
Many tanks use the oleo damper and it's oil dampend. It's also used in planes
  • + 1
 yeah! brewng it already!
  • + 4
 that was the Millyard bike, thing is a beast
  • + 6
 Correct me if I'm wrong but I believe a Pinkbike reviewer has one of the Nitro shock for a test as we speak...?
  • + 1
 @greglikesspecialized:
Thank you for that !
  • + 1
 @doe222: unicorn of bikes
  • + 7
 You had me at open source. So year one is for team bikes. Year two we get a demo ride. By 2020 we will know whether they are any good. Trek open sourced boost spacing and now a 2.6 tire is the new normal.
  • + 4
 Twin-tube dampers basically eliminate the need for this since they dramatically lower the backpressure needed, and the Ohlins uses a bladder instead of IFP. Also, now that you can't use an X2 or CCDB, you are stuck with the crappier dampening valves of the regular float or even worse the monarch.
  • + 3
 I don't know about the Ohlins but the CCDB still has a regular ol' IFP in it to compensate for the oil displacement caused by the damper shaft, just like the shock in the video.
  • + 0
 @WaterBear: the ifp/bladder is not the problem with Re:aktiv vs real suspension shocks like CCDB, Ohlins, EXT or Float X2. The problem is that Float/Monarch like air shocks should not be placed on bikes with 140+ travel, more expensive than 3-4k since their performance compared to the forementioned ones is nowhere near as good. They get the job done, they are cheaper to make and they fit all frames since they are small. They are also light. But putting such shock on a Slash is a fkng joke.
  • + 2
 @WAKIdesigns: You may have a point, but I was merely stating that there doesn't appear to be a difference between a single tube and a twin tube damper with respect to IFP stiction, which was what @hamncheez seemed to be saying.
  • + 2
 @WaterBear: There is a large difference. The compression of a twin tube isn't controlled by the oil entering the piggyback, since the oil is cycled back behind the piston head. Thats why the shafts are much smaller; the external reservoir on twin tubes is half the size, if not less, so much less oil is being displaced. Also since the oil cycles in a twin tube, the back pressure on the IFP on a cane creek is dramatically lower than a traditional design, since the dampening is always from a high pressure to low pressure; it never has to 'suck' the oil through a dampening channel.
  • - 1
 The problem with IFP in reservoirs is that ot can get tipped and in somecases can fk up the reservoirs inner surface. Bladders explode though. There is no escape from suffering
  • + 1
 @hamncheez: Maybe I'm being thick here, but the same amount of shaft has to enter the shock body of a TT damper as for a ST. Shock stroke is what it is.

Yes, oil circulates in a twin tube design. But the internal volume of oil is being displaced by the same amount.

Edit: The shafts are probably smaller because they don't have to house a channel for the rebound damper.
  • + 2
 @hamncheez: Oh, I derped. You're saying because the shaft is smaller it's displacing less oil volume.

Yep. That's true.
  • + 4
 @WaterBear: haha yes.

On traditional designs, they make the shaft thicker intentionally, so more oil is displaced, making it easier to control the compression. I'm not completely knocking the traditional design, the elvensix by push uses it, but its just executed to perfection, something you're not getting on a fox float or monarch.
  • - 1
 @hamncheez: Twin tubes work great, but what confused me is that guy from EXT claims that twin tube design sloshes oil through too many valves for a shock installed in a bicycle. According to him forces and shaft speeds are too little for Twin tube to make sense. Apparently their Storia and Aria are said to be the best.
  • + 1
 @WAKIdesigns: I think the twin tube is better for heavier riders. Most shim stacks are tuned for ~170 pound rider, and low speed rebound/compression adjustments only move a needle through an auxiliary port without affecting the shim stack. Since I'm over 200 pounds (90ish kilos) its a struggle to get high speed compression set well. On my float, then Monarch, I had to run the climb switch in the middle position to keep off the bottom on turns, minor g-outs, and small drops. Especially on the MOnarch Plus, the middle position kills a lot of traction on the loose and chattery. Now I have a DBair and its night and day better.
  • + 8
 Interesting to hear there will be a Slash 9.7.
  • + 0
 There is one, comes with sram nx (11s), rockshox yari and sram guide r
  • + 1
 @Fcanepa: ... And probably be priced MSRP about where the Orbea Rallon comes with GX Eagle, Lyrik, and GuideRS...
  • + 1
 @tehllama: the 9.8 comes with eagle gx, fox 36 and guide rs, not sure if its going to maintain the same price as last year
  • + 2
 For those who care, the 2018 9.8 and 9.7 Slashs are now on Trek's website.
  • + 4
 Okay so I see that the marketing wank is strong with this one.... look at that "traditional shock" video and tell me what you see wrong with it.... nothing... hmmm... what was that? something but you can't put your finger on it? I'll tell you what is a lie with that one: oil is a liquid is it not? which liquids do you know of that compress?? NONE! That video clearly shows a liquid compressing.... marketing bullshit to the highest degree right there.
  • + 5
 That might just be the crude animation. The IFP doesn't move 1:1 with the main piston, it only moves enough to compensate for the volume of the shaft. But your larger point is correct - the video clearly exists to sell the new technology. And most liquids are not very compressible.
  • + 7
 It's the nitrogen chamber wich gets compressed
  • + 9
 It's not the loquid compressing (although it is just a crude animation) it's that the IFP moves less than the actual piston. The IFP moves due only to the volume change by the shaft entering the fluid. So if the shaft had 1/10th the area of the IFP, the IFP would move 1/10th the amount that the shaft does.
  • - 1
 nitrogen charge... air is 80% nitrogen. What you need is the needle to fill the chamber. It won't be perfect but it will do more than well.
  • + 5
 @pinhead907: ...The oil displaced is equal to the added volume of the damper *rod* protruding into the oil, not the volume that appears to be displaced by the piston.

Why the hell are people downvoting @shredteds? He is exactly right.
  • + 1
 @WaterBear: that's what I said, bro? Except I used the word "shaft" instead of "rod". I think what others pointed out a little more clearly than me is that the white portion below the IFP is air or nitrogen or some gas, not liquid.
  • + 1
 @pinhead907: Maybe I replied to the wrong person? I dunno. @CrispiRider certainly seems to be seeing some problem there that I don't.
  • + 5
 Old design which has been used for long time on Cannondale Lefty,,,,,,,,,never heard of damping advantage about Lefty and now Terk tells me that this is better?
不要天天就想着搞个大新闻
  • + 4
 Seriously this is just like the old Rock Shox Judy cartridge dampers that blew out all-the-time back in the 90's. There was a small aftermarket industry offering replacement cartridges and upgrades (White Bros, Englund Total Air, Risse, etc) since they would fail with alarming regularity.
  • + 2
 I think I blew maybe 8-9 of those. I had a DHO when I was racing NORBA nats back then. Almost every stop I would go by the Rockshox truck to replace/warranty it. They stopped fixing them and/or started to charge for it, no more Rockshox for me after for almost 20 years. I have a Boxxer on my DH bike with a Damper Cartridge. Much better.
  • + 2
 They failed because Rock Shox used plastic shock bodies and simple O-ring seals. The aftermarket replacements, and what rockshox themselves eventually switched to, were alloy shock bodies which didn't suffer the same problems with blowing. The original racer-only Diablo forks (which was the original name for the Judy) being hand built pre-production models, also used alloy thru-shaft shock bodies.
  • + 3
 I too blew many Judy's but have yet to be blown by a Judy
  • + 1
 @FarmerJohn: Comment win!!!!
  • + 3
 I am guessing that user air can self service has gone out the window with this one then? might be an important thing to consider as it appears to have two points of entry for all that lovely winter crud to get in? (or year round crud here in the good old uk!!)
  • + 1
 Nope fully user serviceable
  • + 2
 I just spent the day riding my new fuel ex with the new shock. It's as smooth as any coil over I have had. I've been pretty fortunate and have new bikes every year since 2010. I've ridden all the versions from drcv to realtiv to this new thru shaft. There's been improvements on every change. You guys should read up on the Penske design, it's pretty sick. By the way, what's wrong with having the balls to make progress and move our sport forward? Link below

shop.penskeshocks.com/PENSKE-RACING-SHOCKS-7700-THRU-ROD-SHORT-TRACK-SHOCK

shop.penskeshocks.com/files/downloads/PS_7707_TR_088C%20(REV%201).pdfREV%201
  • + 1
 Why the double post? And since you asked, this thru-shaft design seems clearly worse than using a bladder, if your goal is to reduce internal seal stiction. (Reason being added design complexity, weight, and increased or more complicated service intervals).
  • + 2
 I feel like I got the thru-shaft from Trek's last proprietary shock. While the DRCV worked fantastic when it worked, and why wouldn't it work with so many patented acronyms buzzing about it, it was addled with the risks of any new and propriety technology; limited options for replacement and yoked to the supplying brands for service/replacement. I like (/ often love) Trek bikes and how they ride but have always been turned off by the race for patents, proprietary tech and over-branding. That Slash might be my next bike though as it checks all the boxes I'm looking for.
  • + 2
 Last year, Sram came out with the metric shock sizing to put an end to the countless shock and mount sizes, trying to standardize all those parts and make a rider's life easier.

Now here comes Sram and Fox again licking Trek's a$$ and making exclusive shock sizes to Trek.

Can anybody understand this?!
  • + 2
 If the main internal shaft is one long solid rigid piece, the biggest advantage I see to this shock is the lack of bind at full extension, having such a long crossover length between guides. Other than that, compared to a standard remote/piggyback reservoir shock, I see no advantage being that you loose shaft displacement metering.
  • + 6
 Still not going to buy a Trek.
  • + 2
 So this will only work on bike designs that utilize yolk mounting, correct? I guess that means they are modifying the design of their bikes as currently this is not how they do it. Maybe mounting the shock upside down so the shaft can come out on the rocker link side?

Great if it produces better shocks but many current bike designs could not use this I suspect.
  • + 0
 Ideal bike,at full compression with thru shaft upside down shock = knee kebab
  • + 4
 you do need a place for the shaft to live, but the shaft is essentially fixed in the frame: functionally, it's all one rigid piece that's attached to the fixed eyelet on the front triangle. It doesn't move, the yoke just slides along the shaft. Basically, if it fits somewhere at full extentsion, you'd have to be a very poor engineer for it to hit something at compression, because some part of the bike would have to move into the area the shock previously occupied.
  • + 1
 the 2018 frame/sus designs remain unchanged.
  • + 1
 It looks like a double trunnion mount
  • + 2
 It's a yoke. Yolks are for eggs.
  • + 1
 So will overall shock length need to grow to clear everything?

It appears that not all of the shock "stanchion" (is it called a stanchion on a shock?) will be used at full compression. Based on that last picture stroke length will be fairly different than overall stanchion length. Interesting.
  • + 1
 Google "cannonade headshok damping", very similar in many ways.

I am in no way biased but Cannondale were well ahead of the game in terms of suspension design over the major brands.

The simple fact is that we are being fed all of this nonsense when all we really need is a coil shock that weighs nothing with different models offering varied damping performance (basic(lsc+lsr) and pro(hsc/lsc + hsr/lsr) for instance).

No more multi shafts with moondust charred bladders and unicorn horn air cans that require more maintenance than Trumps wig.

........Closest there is at the minute is a Fox x2 coil w/lever.
  • + 1
 I don't know about Cannondale but I agree with the rest of what you said, excepting that I like air shocks for various reasons. Things like negative spring adjustment are nice ways to combat air shock stiction, but such adjustments won't blow your mind. Access to effective external R and C adjustments, like what you describe, has the biggest effect on your actual experience.
  • + 1
 You know, Microsoft is launching their new Xbox OneX this fall with backwards compatibility all the way back to original xbox games... so come on Trek and Fox, launch this new gimmick shock with 100% backwards compatibility right away or get lost with your bullshit.
  • + 1
 you would still need a frame that could accommodate the shaft moving in and out of the shock body
  • + 4
 Buy a coil shock and never look back.
  • + 1
 Amen Brother!!!!
  • + 3
 *reads article . .. . goes out goes for ride m.pinkbike.com/video/464169
  • + 4
 *just happens to be a 18year old thru shaft bike . . .
  • + 2
 Oh cool another proprietary shock that within five years shops will have now way to rebuild because the manufacturer discontinued the shock.
  • + 0
 FUX SUX if you don't believe me just buy a bike spect with Fox products then try to deal with their customer service. I'm so fed up with Fox customer service that I will not even purchase a bicycle specked with their components anymore.
  • + 1
 Have anyone of riders even had the feeling, the shock is not responsive or fast enough with modern (properly tuned/set) shocks? Must the be the suspension design what pushes Trek into these experiments ..
  • + 2
 What about oil quantity ? It seems way less oil in the reaktiv shock ,more, heating, more unstable comportment during long downhill ?
  • + 0
 The oil volume doesn't depend on the design of the shock. There should be the same oil volume in it compared to a standard shock if the shaft diameters are the same. Also overheating should be less a problem because there is no nitrogen wich gets hot and expands and makes the shock harder. With the shaft outside of the shock there is also a bigger surface to cool the shock down but I think it's not enough to notice it
  • + 2
 Mud and maybe a stone could get in to the area that the rod is poking in and out lol,not keen for a shock that moves a millisecond faster than normal.
  • + 4
 This comment section is going to be like 80% dick jokes.
  • + 21
 We can do better than 80%.
  • + 1
 if i wasn't currently at work it'd be 81%
  • + 3
 @sk133872: because work cares about the difference between dicking off while at work and talking about dicks while dicking off at work?
  • + 2
 @eswebster: sometimes
  • + 0
 I just finished my first ride on the new shock mounted to a fuel ex. It is the smoothest air shock I have ever ridden. I don't think I could tell the difference between a coil over or this shock. Amazing, they are totally on to something here. The rear suspension is actually smoother than the new pike that is on the front. Ray
  • + 3
 hhhmm... we'll see. Could just be another in a long line of marketing gimmicks
  • + 1
 I just got rid of a Trek with a faulty proprietary shock. Proprietary is alright if things work and the company supports it. I wasted a year and a half with that bike. Never again.
  • + 2
 A Lefty damper also works like this (and always has). So that's another point of reference for you.
  • + 1
 On the bright side - Everyone without a nitrogen compressor at home can home service this entire shock!! spares pending of course.
  • + 1
 I can clearly see air bubbles in the last 2 pics of the Fox shocks. Wow, can't wait to bleed that every week. Avid Juicy's anyone?
  • + 4
 That thing will cavitate like a blender at Mardi gras !
  • + 1
 So this is basically a pull shock without the eyelet on the main shaft. Aka R.S prodeluxe from a GT lobo or Schwinn straight 8
  • + 1
 Didn't Scott & Dt-swiss use a similar idea with the genius for years?? basically they all ended up with air/nitrogen migrating past the seals into the oil chambers.
  • + 3
 I really want one, for my hardtail...
  • + 1
 Hardtails are a weird phenomena, there's been so much time, and effort put into designing rear suspension, yet like half of people even care. Pretty much everybody in life recommends to, "keep it simple", so it's an interesting divide.
  • + 3
 I'm all AMPed up for this shock
  • + 2
 Wow more proprietary parts...no thanks I'll wait for a new standard next week
  • + 1
 interesting idea but i will let early adopters test this and see if its still about in a couple of years and only then will i even think of buying this.
  • + 1
 Uhm ... ok they do away with the IFP, but the "secondary shaft" is sealed by what - magic?
They replace one seal with another and the world becomes a better place?
  • + 1
 My opinion about this shock: mrblackmorescorner.blogspot.com.es/2017/07/amortiguador-trek-through-shaft.html

PD: sorry for Google translator Frown
  • + 1
 Wow, they reaktiv-ated the Lefty damper! This and Boost are the real deal!! Keep it coming Trek!
  • + 2
 Putting the shaft through results in smoother operation. Nice.
  • + 1
 Wonder if i'm the only one who saw this come up in their Facebook feed and thought it was an article about light sabres...
  • + 1
 This looks like a sooper cool idea. When I need to replace it in a few years i know it will be very easy to find a new one.
  • + 1
 Seems like Middle Out compression. Wonder what kind of angles it takes to work properly.
  • + 2
 How is cavitation dealt with?....
  • + 1
 Cavitation has nothing to do with this. Cavitation happens when the pressure of a fluid is lower than the boiling point of that fluid, which is basically impossible in a well designed damper.
  • + 2
 @shredteds: So you are Fox engeneer? That would explain a lot...
  • + 0
 @shredteds: how could cavitation not have anything to do with this? There is no pressure on the fluid to raise the boiling point!
  • + 1
 @MX298: The length of the reservoir cap on the RS shock suggest it will have air valve.
I'm guessing Fox could have floating piston inside the shaft and rubber pellet at the end.
  • + 4
 Until it ingests air from the air spring side, cavitation won't be any issue on that shock as it runs positive pressure gradients in both rebound and compression - it can't draw a vacuum anywhere.
  • + 1
 @VorsprungSuspension: had to look that up Smile
  • + 1
 @dhfool: No, I'm an engineer somewhere where the first gen CTD would have been my last project.
  • + 1
 @MX298: Well, that's not exactly how it works but I understand what you're talking about. If the shock is fully bled, then the pressure (negative gauge) required to boil pure damper oil is lower than will ever occur in the shock. Therefore, there cannot be cavitation until the damper is compromised. Besides, Navier-Stokes dictates that the fluid can't boil any more volume than the remainder of the fluid can compress, and the fluid is essentially incompressible. If both of those points are true, that means the volume that could boil is essentially zero, so caviation shouldn't be an issue until air is introduced. Math is fun!
  • + 2
 All this talk about "shafts" got Waki all excited!
  • + 2
 Re:aktiv - Trek
R3act - Marin, Polygon
  • + 1
 I'm with you.... so stupid. Lemmings.
  • + 3
 Neat.
  • + 2
 More bike porn from people who don't ride enough..
  • + 2
 What a crock of shit it's just oil flowing through a valve.
  • + 1
 I see air bubbles . Not good ...
  • + 1
 100% hella not an improvement over a nice twin tube design.
  • + 1
 Or a nice any design using a bladder.
  • + 1
 Well done, this looks good.
  • + 1
 Ughh another stupid standard. FFS Trek!!!!!
  • + 1
 Will this work with 26" wheels?
  • + 1
 yeah, I need mostly like 27 seconds too.....
  • + 1
 Wonder if they'll fit into metric specd bikes of other brands.
  • + 1
 So rear shocks will come with boners now?
  • + 1
 Drcv was total crap let's see how this goes
  • - 1
 Pisses me off how new stuff always goes on the high end bikes first You would think they would make it available at every price point To target a larger group.
  • + 0
 That isn't how things work. New products and new tech generally always go on higher end models and then trickle down. Often times just parts of the tech trickle down right away. It's like that in ALL industries. Not just bike.
  • + 1
 The good news is their old 2017 Remedy 9.8 with 150mm Pike, Al wheels and old shock is $5300 and the 2018 Remedy with this new shock and upgraded 160mm Lyrik and Carbon wheels is $300 cheaper
  • + 1
 @mikeyin19: 5 grand seems like a lot. If you buy a frame online and put your own parts on it you can do maybe $3500 for a really nice bike, easy. But that depends on your definition of "really nice bike." For me that's like zee brakes, DVO suspension, Spank wheels, Revive dropper, and whatever's cheap for the rest.
  • + 2
 or just buy a coil.
  • + 1
 There's no protection for this rear erection!
  • + 1
 @paulaston what's the deal with the lower mount offset?
  • + 1
 do you not get more stiction from the shaft seals?
  • + 1
 No cavitation for FOX?
  • + 1
 Interesting, but it
  • + 7
 well said
  • + 2
 Life happended. What I meant to say was twice the wear surfaces now. Interesting idea, though.
  • + 1
 Rigid is sick
  • - 2
 Shocking.
  • - 2
 I wonder how the industry will reakt to this shocking news?

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