First Look: Trek Fuel EX 27.5 with RE:aktiv suspension

27.5 All Mountain Trail

Trek Fuel 27.5 Rear Quarter Shot

Editor’s Note: Mtbr was invited to the launch of the new Fuel EX 27.5 and RE:aktiv suspension near Ashville, North Carolina. We’re here to relay what we learned as we talked to the product managers and engineers. We got to ride the bike for two days and can give initial impressions. As we get the bike for a longer term test, we’ll give a more detailed review.

Trek released their Fuel 27.5 today and instead of just releasing this popular bike platform in the new wheel size, they went deep into the R&D lab to improve the suspension of the bike. They tapped in to Penske Racing for new ideas and technologies for the rear shock.

What they came up with is called RE:aktiv and it is a shock that automatically stiffens up when you’re climbing and opens up when you’re descending rough terrain. Sounds familiar right? Many have tried before with mixed results in the marketplace. The most widely known are the old Terralogix Fox fork, White Brothers Magic (magnetic valve) and the Brain shock and fork by Specialized.

RE:aktiv Damping Rates Compared to Other Designs

The RE:aktiv damping curve has a bump shown in the yellow line, that resists pedaling forces and small bumps. But past that, it opens up into a fairly linear rate of damping.

Trek aimed to one-up all the past comers by delivering a better platform and improving the transition between platform and wide open. This is the critical area where most other shocks before it have had a knocking or clicking sensation that could be felt by the rider. In short, the quality or plushness of the travel was never on par with normal shocks.

RE:aktiv is compatible with CTD modes. The descend mode is not affected much but the Trail mode is very useable now for pedaling and descending. The Climb mode is firmer but it has a linear damping curve too once over the hump.

Why Penske Racing?

Trek worked with Penske to develop regressive damping technology for bikes. Regressive damping is a patent pending technology that has been used by Penske in the highest levels of Motorsports including F1 racing and MotoGP. It generally refers to a set-up that limits shock movement due to small bumps or pedaling forces, then breaks away to allow travel on bigger hits.  This is accomplished with a spring-loaded valve that opens when there is enough pressure built up by the force induced by a shock. It is tuned to stay closed during pedaling forces and open up when a bump force is detected. The key here is the transition between closed and open is smooth so the quality of the suspension travel remains plush. Trek has worked hard to eliminate any knocking, clicking or any noise made by the shock. And while they looked to Penske to develop the shock, they worked with Fox to make the shock easy to manufacture in mass quantities and serviceable by shops and consumers.

Trek Fuel EX 27.5 in Dupont Forest Cornering

Does RE:aktiv work?

We got to try the RE:aktiv equipped Fuel 27.5 bike in the Pisgah and Dupont forests of North Carolina. First impressions are the rear shock is indeed a better platform shock. Trail mode is more useable since it feel stiffer under pedaling and plusher once the rocky descents get going. There is no knocking, clicking or noise whatsoever coming from the shock. Descend mode on the CTD is about the same as old shocks. 

We are pretty excited about this new technology and can’t wait to try it in our local trails.

Does it work with DCRV and CTD?

Yes, DRCV continue to be the shock’s air spring technology to deliver a more linear rate. RE:aktiv is only compression damping technology and the two are designed to interact together. CTD is still part of the equation as well to give the rider three choices on suspension modes. The rear shock is a bit overloaded with acronyms and overlapping technologies that that have been introduced over the years to achieve a plush descender that pedals well on climbs. We anticipate a merger of some these technologies in the future.

Trek Fuel EX 27.5 in Dupont Forest Jump

The front fork is left hanging as well as it does not have RE:aktiv technology. It can benefit as well and we can see Trek adding this to their forks in the future. At the end of the two days of riding, were fascinated with how well the ‘Trail’ mode worked. No longer did it just feel like an overboost of low speed compression that made the rear less active. It really felt like a better pedaling platform and when rough descents came, the rear was definitely more active and supple than the old ‘Trail’ mode. We left North Carolina feeling that this was a meaningful advancement in shock technology and not just a mere partnership gimmick or buzz word. We can’t wait to see it in other bikes and on the front fork.

Continue to Page 2 to see stunning photos from North Carolina’s Dupont State Forest »
About the author: Francis Cebedo

The founder of mtbr and roadbikereview, Francis Cebedo believes that every cyclist has a lot to teach and a lot to learn. "Our websites are communal hubs for sharing cycling experiences, trading adventure stories, and passing along product information and opinions." Francis' favorite bike is the last bike he rode, whether it's a dirt jumper, singlespeed, trail bike, lugged commuter or ultralight carbon road steed. Indeed, Francis loves cycling in all its forms and is happiest when infecting others with that same passion. Francis also believes that IPA will save America.


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  • SteveB says:

    Really curious to hear how this new Fuel compares to the 29er?

  • Francis Cebedo says:

    >>Really curious to hear how this new Fuel compares to the 29er?

    It really is a more playful version of the 29er. Easier to manual and easier to whip are cliche’s but they are true for the 27.5

    The bike does seem lower to the ground with more top tube clearance.

    And the rear suspension seems a little more active on the 27.5

  • Bikethrasher says:

    Really glad to see Teek rework the Fuel EX. It’s one of my favorite trail bikes. I’m also glad to see it offered in the smaller wheel size this year. I was concerned they were going to make it niner only

  • John says:

    DW-link relies on chain tension, so it is “deficient” and compromised when pedaling. There is no perfect system despite the marketing. However, it’s nice to get more crossover tech from motorsports, where there is a lot more money for R & D. I look forward to trying this.

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