Cube Reaction GTC SL review£1,699.00

Does Cube’s 29er have the trail reactions we’re after?

BikeRadar score4.5/5

Cube’s carbon Reaction GTC range starts at £1,249 but the SL is where the well-balanced frame actually gets the fork that it needs to really shine.

The ‘Grand Tour Composite’ frame may be affordable but it’s also really well put together, from the tapered head tube to the 142x12mm rear axle. A broad, rhomboid down tube keeps the press fit bottom bracket well supported, while the seatstays and top tube both taper towards the seat tube, where they sync in a wide wraparound ‘shelf’.

The slim seat tube uses a 27.2mm seatpost and a side, rather than rear, slot to prevent rear wheel spray seeping into the frame.

Gear cables are piped internally for clean lines, while the rear brake line is external for easy servicing. The brake itself is mounted on the chainstay and dropout, to stop it compromising the seatstays’ ability to flex, and the XT rear mech uses a direct-mount hanger.

The frame comes in six closely spaced sizes for an accurate fit, but check their dimensions carefully because each is smaller than average. Overall, the weight is relatively hefty for a carbon bike.

Shimano’s 2x11 XT transmission feels even sharper thanks to direct-mounted front and rear mechs
Shimano’s 2x11 XT transmission feels even sharper thanks to direct-mounted front and rear mechs

The £1,249 Reaction GTC has a Manitou M30 fork, the £1,399 GTC Pro a RockShox Recon Silver and the £1,599 GTC Race a Manitou Minute, but the GTC SL benefits from the extra sensitivity and control provided by a Performance series Fox 32, with its 15mm thru-axle and handlebar lockout lever.

The GTC SL carries its enthusiastic acceleration right through the gear range

Impressively, all the Reaction series bikes, apart from the GTC, which has a Race Face crankset, get a 2x11 Shimano XT transmission that includes a switchable clutch rear mech to keep things quiet.

The fact that the SL also has XT brakes isn’t the bonus it might first appear to be, though, because, yet again, we had unpredictable bite point issues with one of them.

The Fulcrum Red 66 wheels are light and the LiteSkin versions of Schwalbe’s Rocket Ron tyres are crazily so, at just over 500g, even in a generous 2.25in-wide guise. They’re super-supple for smooth riding, but extremely fragile in terms of puncturing and don’t convert to tubeless very well, as the sealant can leak through the sidewalls.

The smooth application of power really comes into its own when the trail starts to get rougher
The smooth application of power really comes into its own when the trail starts to get rougher

For the price, the overall weight is OK rather than impressive but the hyper-light tyres help give the Cube an immediately responsive and race-eager feel.

You do have to be careful of the delicate tyres on rocky terrain — save the LiteSkins for race day and fit something tougher for everyday blasting

The GTC SL carries its enthusiastic acceleration right through the gear range. But what’s interesting is that it doesn’t do that with ostentatious stiffness. Instead it just gets on with the job very efficiently. This smooth application of power really comes into its own when the trail starts to get rougher, yet life in the saddle doesn’t get uncomfortable.

The combination of a skinny 27.2mm seatpost, supple tyres and careful carbon lay-up sucks up a surprising amount of speed-killing stutter over bumps, roots and rocks so that you can keep pedalling without worrying about kickback or sporadic traction.

The further we rode the bikes on test, the more we appreciated the GTC SL’s forgiving and friendly character. While it may not feel shockingly stiff through the cranks it consistently pulled away from the other two carbon bikes on test.

The 70-degree head angle could feel twitchy on a stiffer bike, but again the frame and fork damping means the GTC SL stays on line well and descending drama is minimal unless you’re pushing silly-fast. You do have to be careful of the delicate tyres on rocky terrain — save the LiteSkins for race day and fit something tougher for everyday blasting.

Also check the XT brakes before buying and make sure the shop bleeds them so they work consistently. Otherwise, there’s little to note, apart from the overall weight being a tad high and the compact sizing needing double checking. The GTC SL is the clear team favourite for kick-ass competitive speed or just ripping up the trails in super-fast, hardtail style.

Guy Kesteven

Freelance Writer, UK
Guy started filling his brain with cycle stats and steaming up bike shop windows back in 1980. He worked the other side of those windows from '89 while getting a degree in “describing broken things covered in mud" (archaeology). Dug historical holes in the ground through the early '90s, then became a pro bike tester in '97. Guy has ridden thousands of bikes and even more components the world over since then and can remember them all in vivid, haunting detail. Can't remember where the car keys are, though.
  • Age: 45
  • Height: 180cm / 5' 11"
  • Weight: 68kg / 150lb
  • Waist: 76cm / 30in
  • Chest: 91cm / 36in
  • Discipline: Strict sadomasochist
  • Preferred Terrain: Technical off-piste singletrack and twisted back roads. Up, down, along — so long as it's faster than the last time he did it he's happy.
  • Current Bikes: An ever changing herd of test machines from Tri bikes to fat bikes and everything in between.
  • Dream Bike: His Nicolai Helius AM custom tandem
  • Beer of Choice: Theakston's Old Peculier (not Peculiar)
  • Location: Yorkshire, UK

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