SONDER FRONTIER NX EAGLE

Sonder offer a big hardtail range, from gravel-friendly expedition bikes, through trad XC machines, to slacked-out ‘all-mountain’ models. The Frontier sits somewhere in the middle, targeting ‘multi-activity’ riding, or everything from trail centres and bridleways to adventure riding.

The Frontier looks a little old-fashioned, with its high top tube, short reach (just 440mm on the large size we tested) and mid-length 445mm chainstays. Its geometry is designed around a 100mm-travel suspension fork, or a rigid one with the same axle-to-crown measurement. The BB shell is slightly higher than on most hardtails, for extra ground clearance, while the bearings themselves are housed in a practical threaded (rather than press-fit) unit, which shouldn’t creak and will be easier to fix or replace. Up front is an hourglass-shaped head tube, while the seatstays curve down to forged dropouts for a bolt-through axle. The latest Boost 148mm spacing spreads the hub flanges further apart for a stronger wheel. There’s clearance for a fat 27.5x3in or chunky 29x2.5in rear tyre.

Triple bottle mounts will hold enough fluids for out-there rides. There are eyelets for a mudguard or (if you fit a seat clamp with integrated mounts) a luggage rack. The gear cable and rear brake hose are routed internally, and there’s a port in case you want to upgrade to a dropper post in future.

THE KIT

This build is based around SRAM’s NX Eagle drivetrain, which boasts a big 50t cassette sprocket for easier climbing.

NX is getting on for feeling as solid and smooth as pricier SRAM kit these days, with its stiffer DUB axle and crisper shifting. The same brand’s Guide T brakes are plenty powerful enough for most, even with a smaller 160mm rear rotor. There’s no dropper, but the own-brand rigid post is well-finished, as are the stubby stem and wide bar, which sharpen up the steering. Sonder’s Nova wheels seem tough, but feel a little lethargic when accelerating, and are heavy. Quality WTB Ranger tyres in a 29x2.4in width provide decent cushioning and roll well, but the tread pattern and harder rubber aren’t that good under braking or in the wet.

This bike gets about efficiently, with nimble handling that makes it easy to thread along twisty trails and through tight gaps. With its stubby stem and relatively steep 68-degree head angle, it has a quick steering response, so you can pick precise lines at slower speeds up steeper climbs. On flatter terrain, the geometry puts you in a comfortable, upright pedalling position.

The frame feels stiffer and more direct than the smoother and betterdamped GT chassis, but lacks the punchy surge of the Kona under acceleration or uphill. One reason for this could be the heavier wheels ‘winding up’ under load; it appears some energy is lost through the spokes and there’s a big lag in freewheel engagement when stomping on the pedals. Once up to speed, it’s easy to maintain pace on the Sonder, with the Ranger tyres rolling fast, especially on gravel roads and trail-centre loops.

For aggressive mountain biking, the Frontier wouldn’t be our first choice. The Guide T brakes are dialled and the air-sprung RockShox Recon Silver RL fork irons out bumps effectively, but the Sonder transmits more feedback and trail vibrations to your hands and feet than the other bikes when the going gets rougher. At higher speeds, it feels a bit nervous, with a taller ride position and less assured feel than its rivals, particularly when faced with bigger trail features and small jumps.

It shares its fork with the Kona, where we had issues with it bottomingout. We didn’t have the same problem here, because testers weren’t prepared to ‘open the throttle’ on the Frontier to the same extent – in part due to the seat tube bottle mount restricting how far you can lower the saddle, but mainly because it doesn’t inspire confidence in even slightly technical terrain. This isn’t the Frontier’s specialisation, obviously, but the choppier ride won’t best suit bumpy adventures, either.

HIGHS

NX Eagle drivetrain shifts smoothly and cranks feel solid –Decent value LOWS

Handling doesn’t feel fully engaged on ‘proper’ MTB trails –Slightly undamped ride quality

Sonder Frontier SX Eagle £999

Essentially the same bike but with SRAM’s cheaper and flexier SX Eagle drivetrain and XC-rated Level brakes.

Sonder Frontier Deore £1,249

As well as the more solid-feeling, superior 12-speed Deore group, you also get a lighter set of wheels.

While the Sonder gets full NX Eagle, the GT comes with cheaper SRAM SX Eagle parts, including an older PowerSpline axle and internal-style BB

STRONG AND STABLE

Modern geometry makes the GT feel calmer and less hectic at speed, by dulling the way trail features might upset the ride

DROP IT DOWN

The Zaskar is the only bike on test with a dropper post, which lets you get the seat out of the way on the fly for more control on the descents

TRIPLE TRIANGLE

Trademark GT frame design where the seatstays overlap the seat tube and join the top tube under the nose of the saddle, forming an extra triangle.

TWITCHY STEERING

Some bikes can feel too reactive and responsive to handlebar inputs, making them harder to control at speed. The GT doesn’t fall prey to this.