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Teton Tested: GT’s Snappy Helion Carbon Pro XC Bike

GT sent us two bikes to bash around at the Big Sky Bike Test: The mountain-masher Force and the whippet Helion Carbon Pro. The Helion, given its XC-race market alignment, was an odd choice for Big Sky's mostly lift-service runs. It can drop your friends on climbs, and have some serious fun, but would it be outgunned on out-of-the-box big mountain riding? Given GT's gravity pedigree—as well as a now-legendary low center of gravity and capable spec—we were very interested to see how the Helion stacked up.

One caveat: we're reviewing Helion's platform and overall build more than its wheel size, as GT will be pushing the 29er version and a "women's specific" 27.5 with a slightly different spec for 2017. Though suspension and characteristics will remain the same as our 27.5 tester.


A really clever OEM package, the hallmark of GT. Ryan Dunfee photo

Fork: 120mm Fox Factory 32 Float 27.5 Remote FIT4 damper
Shock: 110mm Fox Factory Float DPS w/Remote Lockout
Crank: RaceFace Turbine SL 36/26T
Derailleurs, brakes and shifters: Shimano XT
Wheels: DT Swiss 350 hubs with Stan's NoTubes Crest ZTR, 32H
Handlebar: RaceFace Turbine 35, 740mm wide with 10mm rise
Head Angle: 69.3 degrees
Seat Tube Angle: 70.5 degrees
Chainstay: 438mm
BB Height: 325mm
Wheelbase: 1118mm
BB drop: 26mm
Top Tube Length: 634mm
Reach: 425mm


Throwing in a few hip-turns is no problem on the Helion. Ryan Dunfee photo

Helion's shock is nestled deep within the bike's AOS/Pathlink suspension, making it slightly harder to set SAG exactly. Fortunately, even if you err on the stiff side, your ride won't feel harsh. Fox float suspension front and rear keeps everything nice and easy otherwise.

I appreciated having a remote lockout on this bike, which is not usually the case for me. Mostly I hate them. But one drawback to having suspension, and center of gravity, so low on a frame is; you can't reach down and flick the shock's lever with your hand. The Helion is such ann efficient climber, it would be a shame not to have full use of both climb and descend modes. So the lockout is appropriate here.

Doesn't mind a boost or two. GT photo

I'm also not a huge fan of a double chainrings and a front derailleur. Not that a double chainring makes a bike less good, but it's just another thing to think about, it adds weight and crowds the handlebars. In this day and age, dump it. 

GT could maybe simplify the Helion's cockpit a little. Ryan Dunfee photo

And, if you were so inclined, with no front shifter you could add a dropper lever on the left side. The Helion is capable of shredding a diversity of trail environments—you might pick your lines a little more carefully than on a deeper travel bike, but it’s a GT—so charge it downhill.

Stan’s Crest wheels roll on a Maxxis Ikon(r) and Ardent(f) tire combination. Very light, race-able, yet session-able choice of rubber.

XT and Raceface, and a wider-than-your-average bar. What's not to like? Ryan Dunfee photo

An XT and Raceface cockpit, drivetrain and cranks round out the solid build. Todd Seplavy, GT’s product manager, always makes good choices that optimize build for your money. Nothing to really pick at, other than my standard front derailleur gripe. It feels exactly as feathery as an XC bike should when you pick it up (maybe a pound over).


Note the high pivot and tucked away AOS/Pathlink box and shock. Ryan Dunfee photo

Because GT's Angle Optimized Suspension is not your average horst-link, DW or VPP design, it's worth going through a few specifics.

AOS was developed with feedback from the Athertons a few years back, when they were still racing for GT.

AOS delivers a high main pivot point, allowing your bike’s back axle to travel rearward, as well as up, when it encounters trail features. High pivot designs, usually great for DH, usually come with a fair amount of pedal feedback. But the AOS design mostly de-couples pedaling forces from suspension travel with a lower pathlink suspension unit.

The AOS pathlink unit and all its touch-points. GT Photo.

GT’s AOS pathlink unit—a CNC’d aluminum box which houses the bike’s bottom bracket, shock bushing, chainstay pivot and downtube/mainframe pivot—does that de-coupling. It's kind of the special sauce of the whole design.

Helion loves the fast, smooth downs. GT photo

The pathlink drives the shock's travel and also allows the free-floating bottom bracket to pivot rearward in tandem with the back axle and chainstays as the suspension travels. This rearward travel maintains a constant distance between bb and rear axle and negates the chain growth and pedal feedback usually found on high pivot bikes.

The Helion's shock rate (the distance a shock compresses in relation to how much the entire suspension travels) is linear at the start, and then turns slightly progressive as you get deeper into the travel. So, if you were inclined, you could run a coil shock, though you’d have to get a really narrow one to fit in the housing.

I’m actually a big fan of how AOS performs. I love that the shock, pathlink unit and most of the suspension stuff are at the very bottom of the bike’s frame, lowering the center of gravity and giving the bike a remarkably planted, maneuverable feel. And it feels plush. I’m not an engineer so I’ll shut up now about any further design thoughts, for fear of getting in trouble.


Flip the lockout, push the pedals, and it jumps. Ryan Dunfee photo

This was the best climber in the test. Of course, it was the only XC bike, so that was to be expected.

The IBIS Ripley and Trek Fuel EX were also great on the ups. Ryan Dunfee and Regan Christian-Frederick were fans of the Devinci Django for climbing, too. No slouches with any choice, but I felt the Helion had that slight purpose-built competitive advantage on this facet.

And the lockout helped—flick the switch and boom, instantly there’s no energy wasted on suspension movement front or back.

A snappy geo goes round the corners really well. GT photo.

Helion's tight geometry (compared to a trail bike) allows you to pick lines quickly, and change your pick if necessary. 740mm Race Face handlebars were a nice touch for a bike like this.

Even locked out, the Helion never felt harsh. The carbon frame, decently sized handlebar, and Stans wheels kept the overall ride quality very comfortable.

You could see long climbs on this bike, in a race or an all-day ride, not being much of an issue. It's one of those bikes that doesn't sacrifice a whole lot of fun for its climbing performance.


Perfectly happy. Ryan Dunfee photo.

Here’s where the bike has a bit of a secret. Because it’s a GT, you know they thought about how it performs downhill. In fact, without knowing for sure, I’d guess this suspension design was driven by descending performance and then had climbing engineered in—rather than the other way around.

Helion had a light, nimble quality. Picking and executing precise descending lines came easily. It’s not a slacked-out mauler, but it’s not supposed to be.

The 120mm Kashima-coated fork pushes its way through most reasonable requests. The low bb and AOS suspension make the most of the bike's rear travel. Its initial bump compliance is comfortable, not harsh like some XC bikes.

Playful and light. GT photo.

Because it’s light, it’s also playful. You bound from one section of trail to another, boosting a little here and there, leaning it quite easily this way and that because of the low center of gravity.

The Helion felt quite at home on the fast, flat tracks Big Sky had to offer. You definitely want to make SURE you release the lockout and open up the suspension on the downs, of course. But whip the thing through successive left, right, left berms and have a lot of fun. If you were only going to ride trail with this bike, you might move the Ardent tire to the back and get something burlier for the front, but the spec'd Ikon and Ardent combination rolled fast and were plenty grabby.

The Bottom Line

GT's Helion is a really nice all-around bike with XC DNA. Ryan Dunfee photo

For 2017, GT will be pushing a new 29'er version and using the 27.5 wheels for the women's version. I'm a little sad, because I felt that the light weight and 27.5 wheels of our tester kind of set the bike apart from the crowd. BUT, I can only imagine the 29'er will perform similarly with even greater rollover. Or GT just found a way to optimize the platform for height using wheel-size specific geo. Which is smart.

Whatever you end up with, the Helion XC bike is remarkably refreshing and more playful than your average race rig—hey, the platform is good, the specs are good so give it a whirl.

From The Column: TGR Tested

About The Author

stash member Gunnar Waldman

Editor-at-Large, IMBA instructor and east-coaster. Raced Trans-Savoie in France, SoCal Enduro and Endurance in Temecula and is psyched for all the great new races in the east. Article Ideas:

The attack left her without an arm but with an insane determination to return to professional surfing which she has steadfastly accomplished even through recovery and a busy family life. -