Trek Unveils Fuel EX 27.5, Partners with Fox and Penske for RE:aktiv Shock

They say good things come to those who wait, and in the case of Trek’s latest suspension project with Penske Racing Shocks, the new RE:aktiv rear shock is the product of 5 years of research and development. Offered on the brand new 27.5″ platform of the venerable Fuel EX, the RE:aktiv shock builds on Fox’s DRCV technology to offer a new level of suspension performance.

Already a leader in the custom shock absorber market for high performance vehicles such as Indy Car and Formula 1, Penske does not offer mass produced suspension. Instead they custom tailor each part to the needs of their customers and teams. A chance meeting between Trek’s Dylan Howes, the director of Trek’s MTB frame technology, and Jim Arentz, Penske Racing Shocks’ Technical director, led to the idea of a partnership to include Penske’s technology in Trek’s latest bike. Five years later, the new Trek Fuel EX 27.5 is ready for its debut, F1 technology and all…

The biggest difference that sets the RE:aktiv shock apart from the pack is the inclusion of what Trek and Penske refer to as regressive damping. Most mountain bike suspension is either progressive or digressive, while regressive damping is supposedly true F1 technology that has trickled down to Indy car, NASCAR, and now, well mountain bikes. On the track, regressive damping provides firm support on the straights and corners but as soon as it encounters a bump, the shock instantly opens up to plush, smooth progression. This all happens extremely fast and as Trek points out, “delivers on the unrealized potential of an inertia valve.”

Once Trek and Penske had worked out the damping they wanted to incorporate into the RE:aktiv shock, Fox was brought in to package it into a patent-pending exclusive design only for Trek bikes.

“The thing about Penske is they’re completely focused on being a racing company. So what we’re doing is leveraging their R&D resources and turning that into almost an extension of our own capabilities,” said Trek Director of Suspension Development Jose Gonzalez. “The combined effort with Fox providing the production expertise has produced just an outstanding shock.”

Trek Unveils Fuel EX 27.5, Partners with Fox and Penske for RE:aktiv Shock

As for the bike itself, the 27.5″ Fuel EX continues where the other Fuels have left off. In addition to the RE:aktiv DRCV rear shock, the frame includes Trek’s ABP (active braking pivot) and Full Floater suspension linkage with both OCLV carbon and aluminum frame options. Suspension is dialed in for 120mm of travel front and rear which mates to a 68 degree head angle and 73 degree seat tube angle. Other important numbers include a 142×12 rear end, ISCG 05 mounts, BB95 bottom bracket (carbon model), internal derailleur and dropper post routing, and E2 tapered head tube.

Trek Unveils Fuel EX 27.5, Partners with Fox and Penske for RE:aktiv Shock

Trek Unveils Fuel EX 27.5, Partners with Fox and Penske for RE:aktiv Shock Trek Unveils Fuel EX 27.5, Partners with Fox and Penske for RE:aktiv Shock

As of the launch, the 27.5″ Fuels will be offered in one carbon version – the EX 9.8 (with alloy chainstays), and three aluminum versions – the 7, 8, and 9. Pricing starts with the EX 7 27.5 at $2,629.99, up to the $5,249.99 Fuel EX 9.8 27.5. If you’re looking for the RE:aktiv shock technology however, you will only find it on the EX 9 and EX 9.8, the 7 and 8 models stick with the standard Fox DRCV technology.

Sold in the same sizes as the Fuel EX 29 with the exception of the 23″ frame, select models are available now from Trek retailers with the rest of the line available later this Summer.



  1. Sardus Pater on

    ok so why do they have to write “reactive” that way ? Cool bike anyway,it’ll give Specialized’s Brain a bit of a run. I wish I could try one.

  2. Eric on

    “On the track, regressive damping provides firm support on the straights and corners but as soon as it encounters a bump, the shock instantly opens up to plush, smooth progression. This all happens extremely fast and as Trek points out, “delivers on the unrealized potential of an inertia valve.”

    ….so it’s a new version of the Brain?

  3. M on


    The other carbon on the website is just a computer generated pic. If the 9.9 looks like that they should be shot

  4. Adrian on

    Eric, looking at some other Penske products, it just seems to be a valve and shim stack.

    Sounds like Trek is criticizing Brain and other inertia valve systems.

  5. i on

    “On the track, regressive damping provides firm support on the straights and corners but as soon as it encounters a bump, the shock instantly opens up to plush, smooth progression. ”

    without exception, that’s what the ad copy for every bike suspension product ever made has said.

  6. Jason on

    @aaron – you are correct in that Team Penske/Penske Racing only raced F1 in the 70’s, however Penske Racing Shocks is currently a shock supplier to several current F1 teams.

  7. ron on

    I see a new market of lower travel bikes (120-130mm of travel), but with geometry that lets you jump/drop and corner like a crazy person(low BB and 67 degree head angles) sparked by bikes like the Kona Process 111(w/29), Santa Cruz 5010, etc. I’m doing my own version by throwing a 1.5 degree angleset in my new Blur TrC and putting a lowered Pike on it.

  8. Padrote on

    yeah I can really see how F1 cars and mountain bikes share the same suspension needs.

    also congratulations trek on your late entry onto the hi-ves yellow bandwagon

  9. bob on


    all ready done, 2009 trek fuel with works components -2º head set, off set shock bushings from burgtech, fork lengengthened an extra 10mm and bigger from tyre than the back i’ve takene the stock 71º head angle to a measured 67º and a BB bang on 13” :o) had to fit an non setback seat post to maintain a usable climbing angle. 165 26-38 xt crankset help with peddle strikes but are tough with my 11-28 cassette. filed the fork damper with 12.5 wt and it’s like a new bike, super stable even when landing off the side of the trail it just keeps tracking where i want it.

  10. Jason on

    @Padrote – Pretty much any form of vehicle racing requires suspension to do basically the same thing – keep the chassis stable and provide adequate traction and feedback to the rider/driver during low-speed events like braking, cornering, and accelerating while still being able to respond to high-speed events like an F1 car hitting a curb, or a MTB hitting a rock. F1 is at the pinnacle of racing, so why not use a technology/design that works in that application?

  11. kc on

    Le histoire se repete. Didn’t Paul Tracy ride a Penske suspended thermoplastic Yeti somewhere in the early nineties? Nice to see Trek is working with them now.

  12. goridebikes on

    Like all 27.5″ flagship bikes from big brands, this one also features the “tennis ball” color in an attempt to make you think it’s as cool as the SantaCruz Bronson…

  13. Seraph on

    The RE:activ shock can also be found on the EX 9.9, whose existence on this mortal plane as of right now is awaiting the delivery of the new XTR 11 speed components.

  14. compositepro on

    Ah the old F1 tie in

    I worked in F1 iirc at this moment in time caterham are running penske shocks

    depends what and where you read it but it initially sounds very inerter like in its description of function though very doubtful it is anything like that n reality however as far as brain shocks go that would be next evolution before MR fluids and penske were involved from around 2008 with inerters

  15. JB on

    I had a chance to ride the carbon version over the weekend at a Trek demo day in Bellingham. Although the sizing was wrong, I found it to be an awesome bike. I had no idea about the new shock, but felt that it was XC efficient while climbing, yet felt very plush and controlled on the way down. I also demoed a Fuel ex 29er and didn’t get along with it as well. The 27.5 bike was noticeably slacker and more playful. That neon green color is even more shocking in person. Despite that, I’d strongly consider getting one once they come out with a carbon 1 x 11 version.

  16. Dirty Sanchez on

    “Inspired by a Kona process”…. That design was outdated 10 years a go. Good to see all the big company lame a** bashers on bikerumor comment befor they’ve ridden it. Why even come to this site if you hate EVERTHING new? (deleted) Some of us come here to see ACTUAL new info, embrace new technology and, if you pull your head out of your a** realize this is probably a pretty damn cool bike no matter who’s logo is on the side. Kudos to Trek for actually researching and designing instead of ripping off and duplicating. Except the color of course, why would anyone paint a new bike in a popular color. That’s crazy talk.

  17. Charlie Best on

    I’m currently riding a 2011 Fuel Ex 9.9 which I couldn’t see any reason to upgrade in the near future, but this has made me rethink, TREK’s decision to drop 26″ Fuel Exs from their range shows commitment and confidence in the new wheel size. I’m heading to TREK World at the start of August, hopefully I’ll get a chance to spend some time on one of these.

    For those saying they copied the colour of the Bronson, well, the bike is actually quite green, not tennis-ball yellow at all.

  18. josh on

    Come on, Stop all the Trek bashing guys. Most of you would ride the fool out of this bike if you actually gave it a chance. No Trek is never going to be the niche brand that only the cool kids ride, but as a guy that sells multiple brands, they put a hell of a lot more R/D in their bikes than most other brands.

    IE. You are not Cool just because you think your bike is the coolest. Don’t be a “Joey” from the how to be a mountain biker video.

  19. greg on

    this has nothing to do with an inerter. inerter only belongs in f1, or any other vehicle that uses extremely high spring rates coupled with extremely tall, soft tires.
    5th element shocks, and all that followed, have been some form of digressive damping. at low shaft speeds, damping is relatively heavy, getting heavier with faster shaft speeds roughly linearly… until you cross a threshold, in which the damping force increases with shaft speed at a much slower, still roughly linear rate. digressive damping still has a faster shaft speed equaling higher damping force, no matter what.
    regressive damping (and inertia valve shocks) do what others cant: past a certain shaft speed, the damping force is LESS than at slower shaft speeds.
    funny thing, and im not suggesting we use it, but you know what kind of damping is regressive and dirt cheap? friction damping.

  20. 'Ol 'Shel on

    Handling and comfort would be a lot better if the industry demanded that riders adapt to plush, working suspension, rather than reinforce the misconception that crappy small-bump compliance = efficiency. But, you can’t give people what they need; you have to give them what they think they want.

  21. Jason on

    @’Ol ‘Shel – RE:aktiv/regressive damping does NOT necessarily hinder small-bump compliance. Small bumps still create high velocities, which is where the regressive damper ‘opens up’ and lets the suspension move.

  22. MulletRacer on

    Hmm. I have ridden a few epics and the brain is not for me. The klunky on off feel is a major turn off. Since the Brains introduction, it has been redesigned a million times. Im not even sure Specialized believes in it yet.

    I look forward to riding Treks version. Its a great concept, excited to see the execution.

  23. greg on

    since specialized revised the fundamentals of the brain action in 2009, it’s been fantastic. completely unobrrusive. old ones had the brass mass as a hydraulic timer, staying open for a defined time after first hit. 2009 on the circuit closes upon rebound every time. it took specialized to notice what fox overlooked- the fact that for the second hit, the circuit would reopen before the shock was even done rebounding. no need for the timer.

  24. tigen on

    Trek’s website lists a crazy high stack height on the 17.5″ model for some reason.

    120mm is weak vs. the Santa Cruz Solo 130mm with similar geo. And alloy chainstays vs carbon on the Solo. Fixed Trek build kits with choices you don’t want vs many choices on the Solo. And coming out like a year later.

    But they have a new proprietary shock! Not gonna get excited just yet.

  25. singlespeedminded on haters should ride one..I rode one at a trek demo and was blown away by the new shock(I already have a 29er Fuel EX and love it) ReActiv hooks up almost like the rear end is locked out. I will say that I lock out my rear shock with a remote on most climbs anyway, but this technology is a spot on upgrade to what has existed until now….I call the 27.5 wheel “cute” because 29ers roll better anywhere! but thats been settled(or argued to death)…this bike is a winner and I’m sure we’ll see ReActiv in the 6 inch bike next year which will be one hell of an all around “trail” bike.


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