Decathlon’s in-house brand B’Twin offers a full-suspension trail bike for £750, which leaves it free to make its 900 series hardtails out-and-out cross-country (XC) race machines. If you’re after pure speed at the expense of technical trail confidence, the 900 is a proper bargain too.
A short head tube with internal bearings keeps the front end low. It’s tapered too, making future fork upgrades easier.
The tyres and rims can be turned tubeless easily if you’re looking for more smoothness and puncture protection
The down tube has a gently curved and deepened front end for maximum weld connection with the head tube, then squares off towards the reliable screw-in bottom bracket (BB).
Chunky rectangular chainstays carry power to the rear wheel, while the A-frame seatstays have flattened centre sections to allow some impact-reducing flex.
The external, mostly open cable routing is a blessing when it comes to easy servicing. Anti-paint-rub lagging on the cables is a nice touch too. The lack of rack mounts means any cargo will have to go on your back.
The big steel SRAM NX cassette is heavy but gives wide-range sequential shifting for less weight than a second chainring, front mech and shifter Steve Behr
The Manitou M30 fork, which has a distinctive reverse arch bracing its skinny legs, is as unapologetically race focused as the rest of the bike.
Fast-rolling Hutchinson Python tyres come fitted to the Mavic Crossride wheels and you can buy knobblier Toros on a £24.95 two-for-one offer with the bike — we ended up running one up front for extra grip on winter trails. The tyres and rims can be turned tubeless easily if you’re looking for more smoothness and puncture protection.
SRAM’s 1×11 NX transmission is an obvious highlight at this price, but the B’Twin/Tektro brakes are the most basic looking and feeling we’ve seen in a while, with 160mm rotors front and rear. They have to be pulled hard for a noticeable effect when things get steep or fast. The bar they’re sat on is super-narrow at 690mm and you know a bike is properly XC orientated when it comes with the stem inverted so it’s totally flat rather than slightly raised.
The sub-700mm flat bar confirms the Rockrider’s race-focused character and the bike comes with its stem inverted for a super-aggressive ride position Steve Behr
Courtesy of the short head tube, 100mm fork and flat bar, the Rockrider has a classic head down, arse up race character.
The sub-700mm bar keeps elbows in and, combined with the 80mm stem, makes this a bike that you have to lean round corners in a committed arc, rather than one that you can flick into and out of turns.
If you’re all about flat-out speed on smoother trails it’s a high value, high velocity bargain
While that’s a world away from the latest trail bike geometry, it’s still the way most XC riders like their bikes to behave. That’s because the committed straight-line focus and low-leverage steering mean the bike isn’t constantly needing corrections, particularly when you’re climbing. Instead, it just ploughs straight on while you concentrate on the serious business of getting the power through the wide-range NX gearing.
While the hefty cassette makes the rear wheel heavy on paper, the extra mass is all at the centre where it has the least effect on responsiveness. The B’Twin however always felt eager and punchy, with a clear acceleration and altitude gain advantage over the other bikes on test.
The twist-grip lockout on the fork maximises out-of-the-saddle sprinting efficiency on smooth surfaces. Even with the lock off, it’s a naturally stiff rather than soft-feeling unit, just the way racers like it.
The smaller 650b (rather than 29in) wheels and stiff tyres, plus the clanking inability of the fork to cope with bigger multiple hits, outweigh the slight forgiveness of the frame on rougher terrain. That means a potentially jarring, speed spilling ride if you feed it too many roots and rocks in one go.
The numb-feeling brakes don’t inspire confidence in challenging situations either and the steep 69.5-degree head angle and low BB mean it’s more than a stem flip, bar swap and fork upgrade away from ever being a confident trail bike. If you’re all about flat-out speed on smoother trails, though, it’s a high value, high velocity bargain.