Cube Reaction GTC SL review

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

Our rating 
4.5 out of 5 star rating 4.5
GBP £1,699.00 RRP

Our review

A great-value example of exactly how fast and much fun an XC hardtail should be
Buy if, You're looking for a fast, fun cross country ride
Pros: Excellent balance of efficiency and speed sustain over rough terrain; smooth, remote control Fox fork and full Shimano XT spec
Cons: Slightly heavy frame, fragile tyres and temperamental XT brakes
Skip to view product specifications

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 2×11 XT transmission feels even sharper thanks to direct-mounted front and rear mechs
Russell Burton

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 2×11 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
Russell Burton

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.

Product Specifications


Name Reaction GTC SL
Brand Cube Bikes

Available Sizes 16in 17in 18in 19in 21in 23in
Rear Tyre Schwalbe Racing Ralph LiteSkin, 29x2.25in
Wheelbase (in) 44.09
Top Tube (in) 24.61
Seat Tube (in) 19.69
Chainstays (in) 16.93
Bottom Bracket Height (in) 12.2
Spoke Type 28 Fulcrum Red
Weight (kg) 11.85
Stem Cube Performance Pro, 100mm
Shifters Shimano Deore XT M8000 (2x11)
Seatpost Cube Prolight (rigid)
Seat Angle 73
Saddle Selle Italia SC1
Rims Fulcrum Red 66
Rear Wheel Weight 2340
Rear Hub Fulcrum Red 66
Bottom Bracket PF
Front Derailleur Shimano Deore XT M8020
Brakes Shimano Deore XT M8000, 180/160mm rotors
Cassette Shimano Deore XT M8000, 11-40t
Chain Shimano HG600
Cranks Shimano Deore XT M8000, 36/26t
Fork Fox 32 Float FIT4 w/ remote lockout, 100mm (3.9in) travel
Frame Material 'GTC Twin Mold' carbon fibre
Front Hub Fulcrum Red 66
Rear Derailleur Shimano Deore XT M8000
Front Tyre Schwalbe Rocket Ron LiteSkin, 29x2.25in
Front Wheel Weight 1790
Grips/Tape Cube Race lock-ons
Handlebar Cube Flat Race Pro, 720mm
Head Angle 69.5
Headset Type FSA Orbit I-t
Frame size tested 19in