A $5,250 mountain bike is worth being able to get to those priceless trail views.
A $5,250 mountain bike is worth being able to get to those priceless trail views.

Trek Fuel EX 27.5

Trek teams up with Penske Racing to make its already excellent trail bike even better.


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Last year, Trek rolled out the Fuel EX 29, which finally transformed its top-selling and most popular trail bike to a big-wheel platform. We found the bike so balanced and fun to ride that we held onto it for nearly nine months of testing.

Twenty-nine inch wheels seemed perfect for the Fuel EX, so we scratched our heads a bit when we heard that the company was also launching 27.5 versions of the bike for 2015. The new wheel size won’t replace the existing models—thankfully—but complement them for riders seeking a smaller-feeling bike. So in addition to seven models of the Fuel EX 29, there will now be two carbon and three aluminum Fuel EX 27.5s, ranging from the $2,630 7 up to the $5,250 9.8 (pictured here).

| (Aaron Gulley)

Wheel size isn’t the only story for 2015. Working with Penske Racing Shocks, which supplies custom suspension designs to top automotive race teams including Formula One, Trek has developed a new rear shock for the Fuel EX.

Dubbed RE:aktiv, the system places a spring-loaded valve inside the shock assembly that opens and closes based on the force of impact. With a big hit, the spring opens and allows lots of oil flow for soft, full travel. But under lighter loads, the valve stays closed, allowing the damper to provide better low-speed compression.

It’s similar in concept to an inertia valve, which is the basis for Specialized’s Brain technology, but Trek says that putting the valve inside the assembly (versus outside with the inertia type) makes the engagement more even. The upshot: RE:aktiv shocks should provide a more supple, supported ride feel at low speeds and small bumps, while still maintaining a linear, plush travel when the shock is fully engaged on bigger terrain.

The top three models of both the Fuel EX 27.5 and 29 (9.9, 9.8, and 9) will come equipped with RE:aktiv shocks. The new technology will also appear on comparable models of the 140mm Remedy, as well as on the women’s specific 120mm Lush SL.

Other than the new shock, our Fuel EX 9.8 27.5 tester is equipped with Trek’s proprietary DRCV Fox 32 Float fork up front, a complete Shimano XT group set, Bontrager Rhythm Comp wheels, and a Rockshox Reverb Stealth dropper post. It’s an excellent, hard-working spec, though as with last year’s bike, we’re not that keen on the wheels and feel that Bontrager’s meatier XR4 tires would be a far better choice for this bike than the XR3s that are supplied. Our size large tester weighs in at 27 pounds on the button. 

Having been so enamored of last year’s 29-inch version, we were skeptical of the need for a 27.5 version. But after time on the bike, we’re pleasantly surprised. The blaze of the Volt Green finish won’t be for everyone, but it’s definitely eye-catching and most testers have responded well to it. As for the new shock technology alone, it feels pretty similar to last year’s version, though the bike has a suppler, more fluid feel when climbing. It’s an incremental improvement, not a revolution, though that is testament to just how dialed-in the bike already was last year.

What about the 27.5 versus the 29-inch version? The smaller-wheeled bike is just as balanced and lively as the 29er, though littler wheels have a snappier feel, especially steering. So far, it has been a 50-50 split in testers who preferred one bike over the other, though everyone has said they’d be happy on either wheel size. Other than riding style preferences, the choice may simply come down to which bike fits you best. The 27.5 runs slightly smaller than the comparable 29—we were comfortable on a medium in the 29 but needed a large in the 27.5—which may make it a better option for shorter riders.

Like the 29, the Fuel EX 27.5 should be a good option for those seeking one bicycle that can manage pretty much any trail. And it continues Trek’s track record in recent years of producing high-quality mountain bikes across its entire range.

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