Cube Reaction GTC Pro 27.5 – first ride review

How dynamic is this 650b racer?

Our rating 
2.5 out of 5 star rating 2.5
GBP £1,399.00 RRP

Our review

Great-riding frame and decent transmission let down by under-controlled fork and wheels
Skip to view product specifications

Hardtails are in a weird place as we head for 2015. On suspension bikes the 650b or 29in wheel size debate seems to be sorting itself out into a ‘more fun’ or ‘more fast’ split.


There’s no doubt 29er wheels have a more pronounced proportional effect on the overall speed, control and smoothness of a hardtail than a sprung bike. There’s also a sense of pressure to apply the new wheels to every category, and it’s been interesting to watch how different manufacturers have gone about it.

Frame and equipment: design differences

Some designers, such as Whyte, have gone for a clear ‘29er is for XC racing, 650b is for technical trail fun’ route. Others have followed the path of Giant, which dramatically ditched its top line XtC Advanced 29 in favour of an all-new XtC Advanced 27.5 range. Many though are following the same strategy as Cube, keeping a strong 29er range (Cube has two carbon 29 frames and one alloy frame in its race range to give 19 bike options) but adding two carbon-framed bikes and two alloy 650b bikes.

It’s Cube’s more affordable carbon mid wheel bike we’re testing here, but the ‘cross-country race configuration’ decals make it clear that it hasn’t relaxed the speed focus. There’s no missing the big lockout lever for the 100mm travel Manitou fork either – in any case you have to position it carefully so it doesn’t get in the way of the shifters.

Cube’s carbon knowhow is in full effect here:
Russell Burton

Cube’s carbon knowhow is in full effect here

The frame is a really nice unit whichever way you look at it. As you’d expect for a bike costing this much it’s built from Cube’s Pro composite series material rather than the Super HPC Advanced mix of its top 29ers. It’s still laid up using its two halves Twin Mould process, which lets it put solid formers inside the frame junctions to eliminate fibre wrinkles. Its smooth flowing lines have a clear stiff front, springy rear bias too. The short tapered head tube lifts up into the big down tube, which expands and flattens into a full width rectangular section at the press-fit bottom bracket. The top tube starts similarly deep, and finishes flat and broad with a smooth curving ‘shelf’ past the seat tube into triangular seatstays that flatten around the tyre.

Carbon qr dropouts feature a threaded gear hanger to aid crash proofing:
Russell Burton

Carbon QR dropouts feature a threaded gear hanger to aid crash proofing

Super-deep flat top triangular chainstays kick up at the far end to mount the chainstay brake and the full carbon QR dropouts use a replaceable threaded gear hanger (rather than threaded frame) for crash proofing. The rear brake hose is kept external for easy servicing but it’s got internal down tube gears plus plenty of mudroom and a side slotted seat tube.

Ride and handling: practical performance

It feels similarly practical when you first hop on thanks to generous (for XC at least) 720mm bars and 80mm stem. While overall weight isn’t particularly impressive, low tread tyres and smaller wheels mean it’s noticeably keener to get moving than a similar priced 29er. The fat front end and deep chainstays let you put plenty of grunt into the back wheel through grips and pedals. The sculpted rear stays and flex from the long 27.2mm seatpost help it shrug off and skim over rocks and roots, so it’s noticeably smoother than a 26in bike. While some cost conscious carbon bikes can feel worryingly brittle and skittish or dull and over damped, the overall lay-up has a really well balanced and positive – not punishing – character.

A skinny 27.2mm post takes some of the sting out of the back end:
Russell Burton

A skinny 27.2mm post takes some of the sting out of the back end

The geometry follows similar lines with the 70-degree head angle naturally putting the front wheel where you need and the short back end whipping the rear out at speed or tucking it neatly into slow turns without having to take the long way round. The fact we know it wheelies and drops off rocks okay shows it’s a naturally enjoyable frame to ride – not just a single-minded fast one.

The reaction gtc frame could definitely build a really fun, dynamic and quick bike…:
Russell Burton

The Reaction GTC frame could definitely build a really fun, dynamic and quick bike…

We have specifically used the word frame rather than bike there because there are several component elements of the Reaction Pro that definitely compromise rather than complement the frame.

The most obvious is the Manitou fork. We can’t fault it for colour coordination, and the ABS+ damped mid-stroke is reasonably smooth. The start of the stroke is notchy though and we had regular undamped top out clank that got worse after a small oil leak started after just a couple of rides. The bulky remote switch needs careful positioning to stop it obscuring the shifter. The rebound dial at the bottom end of the leg is a tiny plastic switch that looks more suited to a Christmas cracker and is awkward to adjust consistently.

…but ultimately the fitted fork and wheel spec hold it back:
Russell Burton

…but ultimately the fitted fork and wheel spec hold it back

The skinny fork stance and QR front axle mean noticeable twang and twist once you start pushing the bike hard through corners or hauling on the anchors. This makes the already slippery hard compound Active Line Schwalbe tyres even harder to control if the trails get damp. From experience the flexy-feeling Manitou Radium wheels don’t last that long in the wet without regular TLC either. Between them the wheels and forks negate most of the sharper, stiffer, more dynamic edge that 650b potentially gives over 29in wheels in race or fun trail terms.


So, we’ve certainly no complaints about getting SLX and XT on a carbon frame for the money, and the Cube branded finishing kit is all really good gear. We would definitely recommend saving for the next model up – the Reaction GTC SL – rather than buying the Pro and upgrading. That’s because the GTC SL solves a lot of the issues with a 15mm axle Fox fork, DT Swiss wheels with top spec Schwalbe Evolution series tyres.

Product Specifications


Name Reaction GTC Pro 27.5 (14)
Brand Cube Bikes

Brakes Shimano Deore M615, 180/160mm
Shifters Shimano SLX
Top Tube (in) 23.35
Seat Tube (in) 17.72
Chainstays (in) 16.69
Bottom Bracket Height (in) 11.61
Weight (lb) 25.6
Year 2014
Wheelset SUNringlé Radium MA wheels
Weight (kg) 11.6
Stem Cube Performance, 80mm
Seatpost Cube Performance
Cranks Shimano SLX
Seat Angle 73.5
Saddle Selle Italia X1
Rear Tyre Schwalbe Rapid Rob Active Line 27.5x2.25in tyres
Rear Derailleur Deore XT
Head Angle 70
Handlebar Cube Race Flat Bar Pro
Front Tyre Schwalbe Rapid Rob Active Line 27.5x2.25in tyres
Front Derailleur Deore XT
Frame Material GTC carbon
Fork Manitou Marvel TS Air, 100mm (3.9in) travel
Wheelbase (in) 45.6