Sonder Frontier NX1 Rigid Rumpus Bike Review

Sonder Frontier NX1 Rigid Rumpus Bike

The aluminum Frontier is Sonder’s multi­activity MTB. Ride hard at the trail center, load it up for a midweek bikepacking trip, or pocket your passport and ride around the world. With full rack mounts at the back and multiple bosses on the fork, the brand bills it as an adaptable off-road explorer. Designed for long day comfort but promising not to be too slouchy, it comes with 27.5+ wheels, but can also be set up with larger diameter alternatives.

First impressions

Often ridden by people who take an excessive interest in the origin of their coffee beans, received wisdom dictates that adventure bikes should be made from steel, preferably of a single origin, However, a first smash around on the aluminum Frontier had us questioning this.

Weighing around a kilo less than a more rust-prone alternative, it’s light, stiff, and possesses manners that are fully-caffeinated. But is the Frontier just a mountain bike with a bunch of tabs welded on, or a proper ends-of-the-earth adventurer? We loaded it up with bikepacking bags and headed for the hills to find out.

On the road

Left unencumbered, the Sonder is a riot to thrash about on. With large and gently radiused tires, it feels as if it can be leaned over through the corners until the bars almost clip the ground. At the same time as imparting grip, the tires’ huge volume allows them to be run as low as the mid-teens.

Giving several centimeters of squish, their suspension-like characteristics help the Frontier float over rough terrain. With big handlebars, an upright position, and loads of stand-over, the Frontier is great for roistering about on, and could certainly serve as a regular mountain bike if you don’t mind the rigid fork.

With a short-length reach and medium headtube, it’s comfy, but not so high at the front as to feel ponderous. Loaded up with bikepacking bags, it remains equally competent.

Still exhibiting little in the way of flex, the aforementioned qualities pair with its slack steering to keep everything steady, even when the line on your OS map turns out to be a goat track rather than a 4×4 route. Just be careful that the straps don’t accumulate too much grit and start eating into the softer-than-steel tubing.


Pushed into the ground by the weight of extra luggage, the Frontier’s more rigid aluminum frame is just noticeable. But with the tires interceding between the bike and trail it never feels uncomfortable. Similarly, the tough aluminum fork keeps the steering sharp but doesn’t possess the filling-loosening harshness you’d expect from its brutish appearance.

Light overall, and in particular when it comes to rolling mass, the Frontier doesn’t hang about, either. Compatible only with the single-chainring gearing you’ll find fitted to most modern mountain bikes, the Sonder employs a 32t chainring and 11-42t cassette.

This provides an equal span of gears to those on the Genesis, but with bigger gaps in between, In most situations, this works well. Although on steady gradients you might find yourself wanting to sit between gears more regularly than you would with a narrower cassette. If you know your next holiday will involve grinding up lots of big hills, a smaller chainring to swap-in would be a clever purchase. We’ve no qualms about the braking though. Taken care of by SRAM’s Level hydraulic brakes, these are excellent, especially given the price-point.

The spec

The frame Slightly harsher than a steel alternative but around a kilo lighter, we can forgive the Frontier’s frame its somewhat agrarian looks, Hell, at this price, we’ll even forgive it its weird 141 mm rear hub spacing which could make finding replacement wheels tricky.

Like the Genesis, it does without bolt-through fixings, although if this leaves it a little more flexy we weren’t able to discern it. Versatile enough to later accept 29er wheels or a suspension fork if you wish, in either configuration the Frontier provides an abundance of mud clearance.

Using a solid plate on the drive-side stay to accommodate the chainring, and a barely-there seatstay bridge, there’s simply nowhere for muck to accumulate. It also retains the good grace to route its cables through the top tube, and even includes a routing port for a dropper post.

With most of the fixing points you might want, these include full rack mounts and multiple boss mounts on the fork. The lack of a third bottle mount on the underside of the downtube seems odd, however, as many riders will want to pop a frame bag inside the main triangle.


SRAM’s NX1 group has a feature-set that’s bonkers to find on a bike costing this little. First, there are its 11 gears. Each of these shifts rapidly, and with an instant thwack that leaves you in no doubt that the sprocket is engaged. The gears themselves also span a good range thanks to the 11-42t Cassette, while the single-ring chainset allows you to shift sequentially through them.

Making do without a front derailleur and shifter keeps things looking neat, although the flip-side is bigger jumps between each sprocket. Finally, there’s the clutch on the rear mech that stops the chain flapping about. Hauling up the Fortitude, SRAM’s hydraulic Level brakes provide lots of direct feeling power and feature an adjustable lever reach.

Frame and fork of Sonder Frontier NX1 Rigid Rumpus Bike

Finishing kit

Sonder’s Love Mud branded kit is all solid stuff. The huge 780 mm Aspect riser bars have come straight off an MTB, and so might get cut down by some riders. The Membar seatpost has a robust twin-bolt clamp, and comes in a 31.6 mm diameter, which will make swapping in a dropper post easy should you so wish. Sitting above it, the saddle is a pleasantly neutral shape. Its seamless covering won’t soak up water, deans easily, and is unlikely to rub anyone up the wrong way.


Using Sonder’s own Love Mud Rumpus wheels, these sport humongous45mm rims that’ll support tires up to 3,5-inches wide. Wrapped in slightly more conventional 2.8-inch WT8 Ranger tires, these are a fast-rolling general-purpose trail option.

Relatively light, they’re OK on smooth surfaces and speedy as you like off-road. Like the rims they sit on, they’re also ready to be set up tubeless. With an obscure 141 mm width to the rear axle, the quick-release hubs spin on sealed cartridge bearings.

While their freewheel is pleasingly quick to engage, its loud ratcheting can be somewhat abrasive when one is trying to commune with nature.


Frame: Sonder 6061 aluminum with matching fork

Groupset: SRAM NX1 11-speed

Brakes: SRAM Level hydraulic disc

Chainset: SRAM NX1 single-ring 32t

Cassette: SRAM PG-1130 11-42t

Bars: Love Mud Aspect Riser 780mm

Stem: Love Mud Piskie, 60 mm

Saddle: Love Mud Abode

Seatpost: Love Mud Membar 31.6

Wheels: Love Mud Rumpusf

Tires: WTB Ranger Comp 27.5×2.8


Size tested: MChainstays (C): 435 mm
Weight: 12.10 kgHead angle (HA): 68°
Top tube (TT): 602 mmSeat angle (SA): 73°
Seat tube (ST): 430 mmWheelbase (WB): 1127 mm
Stacks (S): 595 mmBB drop (BB): 50 mm
Reach (R): 420 mm 

Rating: 8.2/10

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