Trail Testing a Rocket: The GT Helion Carbon Pro

The not-so-minor details


GT Helion Carbon Pro


Monza Bicycle Imports






Faster than a hardtail.
Fantastic rear suspension.
Holds momentum through singletrack like you've got a strong tailwind.
Climbs trails with rapid pace.


The trade off for climbing speed, is a nervous descender.
We missed a dropper post at times.

Gone are the days where you needed loads of suspension travel to let you go bloody fast off road. A bike with top quality short-travel suspension, dialled geometry in a stiff and responsive frame is so incredibly capable of a fast ride. The GT Helion is one bike that knows its place: it’s not a do-it-all, one-bike-wonder kinda thing, this is a cross country weapon.


From afar, the Helion looks so simple with its straight carbon tubes creating a clean and angular looking frame, plus the way the top tube and chainstay both follow a parallel path gives the Helion an uncluttered and traditional appearance. But tucked away underneath out of sight is effective technology that’s far from traditional, more on that soon.

The Helion Carbon Pro is of course a carbon frame; all tubing is made from the fantastically stiff, responsive and lightweight wonder material. The wheels are 650B, which is not such a common sight in such a short travel machine – we would usually expect to see the bigger 29” wheels with shorter-travel bikes of around 100-120mm of travel.

GT Helion 2
Set the trails on fire, on this rocket ship.

A new generation RockShox Maxle (found and loved on the Pike fork) fastens the rear wheel in tight, and all the cables are externally routed down the underside of the frame. External cable routing may not be the flavour of the times, with many brands boasting internal routing as a feature, but gear cable and brake line work is far easier like this. GT prove that routing externally can be as neat as internally routed frames, and the way the rear derailleur cable goes internal just towards the rear is a nice way of keeping the cable away from the slapping chain.

GT handle the task of directing the cables with real class, especially with the tricky task of navigating a clean path around the suspension linkage.

GT Helion 30
That silver linkage delivers on what many bikes fail to do: offering great suspension, but with minimal drivetrain feedback.


GT use a suspension design called AOS, Angle Optimised Suspension. The whole idea behind this system is to have the rear suspension pivot around a very high main pivot – note how far above the bottom bracket the main pivot is. This all adds up to a rearward axle path that helps the rear wheel can move up and over impacts, helping maintain your momentum. Confused? Watch this video from GT.

But that’s not the end of it, having such a high pivot means that the chain length will grow dramatically as the suspension compresses, which creates hectic pedal feedback. The solution was to de-couple the cranks from the frame, isolating any tension added to the chain from the rear wheel moving away from the frame. The bottom bracket is housed in an independent section of frame, which retains the optimal location as everything compresses and rebounds.

GT Helion 10
From the drive side, the Helion hides all its trickery.

This system is not new, we’ve just seen it in many variations over the years, and even the old GT i-Drive from the 90s was achieving similar results. GT also uses the AOS system across their entire dual suspension range, from this short travel Helion up to the massive GT Fury which Gee Atherton rode to victory in the Cairns World Cup Downhill this year.

This all might sound like a lot of complication, but in fact there is no more moving parts than your typical Giant, Specialized or Santa Cruz. All the bearings are large, and held together with solid hardware and not once during our testing were any concerns of increased maintenance raised.

The rear shock is protected from any mud or debris from the rear tyre by a nifty guard, so that solves any of those issues nicely.


Geometry wise, the Helion errs on the sharp and racey side of things. Not only does the short travel lend itself to cross country, the frame’s geometry, too, is clear about its intentions. Our medium frame has a long 606mm top tube, a sharp 69.5-degree head angle, and behind you are long 438mm chain stays. These numbers combine to give the Helion a very stong personality, and a distinct place in the lineup of offerings from GT.

During our testing time aboard the Helion, we were also ripping around on a Trek Fuel EX 9.8 and a Specialized S-Works Enduro 650B, so when it came to throwing a leg over the Helion it sure felt racey! Setting up the suspension on the Helion is a little different to most bikes as the rear shock is hidden away out of view, making sag measuring the traditional way with the rubber o-ring a bit tricky. GT incorporate a sag indicator into the frame. Some bikes do sag meters better than others, and we found this one a bit hard to gauge precisely where we were at. We went out a couple times with not enough sag, eventually dropping the shock pressure to find that sweet spot, which just required a bit of trial and error.

Immediately we noticed the bike’s length: it’s a big one! The long top tube allows you to really get out of the saddle and put the hammer down with enough room to keep your hands away from your knees. And not having such a short rear end is a blessing on the climbs, you don’t need to put in any effort to keep the front wheel from lifting up uncontrollably like you do on your typical all-mountain bike.

The Helion really does fly up the climbs, it’s bloody fantastic at gaining traction and transferring your hard efforts into lightning fast motion.

When the trails get tight and twisty, the length is a bit of a handful, but we got used to it quickly, drawing wider lines and keeping a consistent pace rather then throwing ourselves into turns like we have been doing on the Enduro or Fuel EX. But as soon as the trails open up, you’ll be hard pressed finding a bike that takes off and holds its speed as much as this one.

If you’re into the new-school enduro bikes, or even take downhill racing seriously this style of bike would be the ultimate training tool to sharpen your handling skills and appreciate the feel of a razor sharp bike again.

GT Helion 4

It’s an engaging ride, the stout 110mm of travel is firm and supported, so you’re really able to work the terrain to your advantage, pulling on the handlebars out of turns and pumping it into undulations in the terrain. Add the light and fast wheels into the mix, and we found ourselves ripping through our local singletrack with less pedal stokes than we’d usually need to keep the bike moving.

Our medium frame came with a 80mm stem, and 740mm wide bars, and we appreciated the way that the wide-but-long cockpit helps to counteract the bike’s razor sharp head angle. We wouldn’t suggest going any shorter in stem length on the Helion, it may make the handling a touch too quick and quite a handful.

Where this bike doesn’t exactly shine is no surprise the area that you’d expect such a fast and efficient climber, steep and challenging descents.

It requires a composed pilot to make the most of the stiff and sturdy frame when the trails start turning up the pace and pointing down. Maybe the lack of dropper post that we are so used to using contributed to that nervous attitude on steeper trails, but it didn’t like to be jumped or lofted off drops. But in fairness to the Helion, this is simply just the trade off you pay for with a bike that is so strong in other areas.

GT Helion 11
The front end of the frame is long, and also incredibly precise when steered through twisty trails.

With remote lockouts on both fork and shock, you have immediate control of compression adjustment, and on this type of bike, the remote lock outs are a good fit. The FOX lever might be a little clunky in appearance, and adds cables into the mix, but at least the GT is without a front derailleur, so that’s a bonus. A little time and a pair of cable cutters would be worth it, trimming the cable a bit shorter would reduce the spaghetti mess. Activating the remote lever with one click puts both the fork and shock in ‘trail mode’, great for climbing trails, or when the terrain is buffed. One more click and both end lock out firmly for tarmac jaunts. If it wasn’t for the remote lever, a traditional lever on the shock would be a stretch to reach do to when riding, as it’s a long way down.

GT have nailed it, the balance between suppleness, comfort, control and traction is spot on.

Even without the use of the remote lever, the rear suspension remains firm and supportive under pedalling, resisting bob or unwanted compressions leading to energy loss. This is about as good as it gets, GT have nailed it, the balance between suppleness, comfort, control and traction is spot on. The FOX CTD shock is tuned to perfection, the 110mm travel is delivered in a plush yet efficient manner.

The whole AOS thing works a treat, the efficiency is really noticeable in reducing those mushy moments you don’t want from a dual suspension bike. We did notice the bottom bracket back and forth in relation to the main frame when the suspension was cycling through its motion, especially when seated, but only ever so slightly and didn’t bother us one bit.


GT do it differently when it comes to speccing parts and they’re not afraid to mix it up – just take a look at the drivetrain for example. A Shimano XT 10 speed drivetrain is mixed with a RaceFace crankset with their take on the narrow/wide chainring, first pioneered and proven in SRAM’s single ring drivetrains.

To keep the gear range low enough, an e*Thirteen sprocket is retro fitted to the cassette by removing the 17 tooth sprocket and adding the large black 42 tooth cog.

To keep the gear range low enough, an e*Thirteen sprocket is retro fitted to the cassette – the  17 tooth sprocket has been ditched at the large black 42 tooth cog fitted. The range of gears is actually pretty good – whereas a single ring conversion with 10 speed Shimano loses a bit too much on one end of the range, the Helion’s e*Thirteen conversion works a treat. Shifting into the low gear is fine, perhaps not as seamless as with regular Shimano cassette, but it’s worth it for the extra climbing gear. A chain guide is fitted for extra security, though perhaps not really necessary, and we’d happily ride the bike without it.

GT Helion 23
Note the big black sprocket? That’s the e*Thirteen 42 tooth that gives the Shimano 10 speed drivetrain a lower range of gears. Nifty!

FOX take care of the bouncy bits in excellent fashion and we especially love the custom coloured decals on the forks. The fork felt smooth and supple, once again re-affirming that FOX are back on their game for 2015. All the cockpit parts are great, even if the Tundra saddle is a bit firm. Did we miss an adjustable seatpost? Yes, even on this type of bike an adjustable post would widen its abilities, the weight penalty is always worth it in our opinion!

The wheels were fine, and the refreshingly quiet DT rear hub was a nice change after riding some seriously noisy Specialized and Bontrager wheels. The tyres however were not tubeless ready, and are best suited to softer soils, so buyers beware. A tackier set of rubber sealed up with a tubeless valve would have taken the bike to the next level of awesomeness.

A highlight of the parts were the Shimano XT brakes, with 180mm rotors at both ends, they simply can’t do any wrong.


The GT really grew on us! We really appreciate the way that its geometry and efficiency combines all the things we like about hardtails, but with what we love about a dually! The long and roomy frame puts you in a seriously powerful position to sprint through singletrack and fly up climbs, and the unique gear components and sharp appearance give the Helion that feeling of riding something special, and different.

A short travel dually of this quality in the hands of a skilled rider can really show up any slack trail bike or enduro weapon on calmer trails, or if you’re seeking a fast bike for marathon events or taking on a cross country race, you’ll be well served with this one.

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