The Sonder Cortex is a trail-ready 29er that starts at just £1,499

Sonder's budget-friendly 120mm 29er is said to come alive on technical terrain

Sonder Cortex pack shot

Sonder, sibling brand to Alpkit, the outdoor clothing and kit company, has added to its bicycle range with the Cortex trail bike — a 120mm travel full suspension 29er that starts at £1,500 and is designed, it seems, to do just about anything.


2020 Sonder Cortex 29er trail bike key specs

  • 120mm do-it-all trail 29er
  • Builds start at £1,499
  • Frameset available for £999
  • Up-to-date geometry
  • Size-specific chainstay lengths

The Cortex frame is built from hydroformed aluminium, with a 4-bar linkage suspension system. The horizontally mounted short-ish stroke shock sits under the top tube and is driven by a short link to help manipulate the suspension’s feel.

The rear end of the frame is asymmetrical, with the driveside chainstay dropping lower than the non-driveside.

The main pivot sits just above the bottom bracket. Cable routing looks to be fairly maintenance-friendly, with internal routing inside the down tube, but external for the mech and brakes along the chainstays.

sonder cortex rocker link
This little rocker drives the shock, as part of the 4-bar suspension linkage

While many smaller brands seem to go fairly progressive with their geometry, Sonder has kept things up-to-date without pushing any boundaries; a size large Cortex has a reach of 465mm, a 66-degree head angle, 447mm chainstays and a 51mm offset fork, combining to give a 1,220mm wheelbase. The seat tube is 465mm long and sits at 74.5 degrees, while there’s 615mm of stack and 40mm of BB drop.

There is an increasing number of brands giving size-specific chainstay lengths, with larger bikes getting longer stays to balance out the weight distribution of the bikes, thanks to the associated longer front triangles. Sonder is one of those, with the chainstays varying from 442mm to 450mm, corresponding to reaches varying from 420 to 485mm over the four sizes on offer. Have a listen to our latest Tech Talk podcast, for our take on mountain bike geometry.

Sonder Cortex Kirroughtree
Sonder says the Cortex is designed to do just about anything

Go anywhere, do anything, seems to be the message from Sonder with the company choosing to pair the 120mm frame with a 130mm fork. While 120mm at the back doesn’t sound like a lot of travel for a go-anywhere, do-anything trail bike, Sonder claims the bike is “for epic days over mixed terrain. It comes alive on long technical descents.”

If Sonder has done its homework, there’s little reason to believe it wouldn’t be capable — with 29″ wheels and a nicely progressive suspension kinematic, shorter travel bikes have no reason to shirk bigger terrain.

Following trends for burlier bikes, the Cortex is designed to run tyres up to 2.6″ wide for additional grip and confidence on tough tracks.

sonder cortex cane creek
The top-end bike comes with Cane Creek suspension front and rear

2020 Sonder Cortex range overview

Sonder will be offering the Cortex in six standard builds. These start at £1,499 for a build with SRAM’s new SX Eagle groupset, a RockShox Recon RL Silver 130mm fork and a RockShox Deluxe shock.

cortex nx eagle revelation white
This SRAM NX Eagle, RockShox Revelation model comes in at £1899

Prices then rise, with SRAM NX Eagle and GX Eagle groupsets, and RockShox Revelation and Pike builds. The range is topped with the £2,599 SRAM GX Eagle Cane Creek build, which comes with a Helm fork up front and DB Inline shock at the back.

sonder cortex frame only
Frame only options will be available, with RockShox Deluxe or Cane Creek shocks

Sonder will also be selling the frame on its own for £999 including the Deluxe shock, or £1,099 with a DB Inline. You’ll also be able to purchase it bundled with a Helm fork plugged in up front for £1,899.

While not unique, it’s good to see some level of customisation available, too. Buyers can pick and choose from a range of components from the likes of RockShox, WTB, Hope and Cane Creek to get a bike that suits preference and pocket alike.

sonder cortex bike
Three colours will be available – green, ‘crayon’ and brown

While Sonder’s bikes are primarily sold online, they can also be viewed, and purchased, at Alpkit’s stores, located in Hathersage, Ambleside and Keswick. The Cortex is available for pre-order now.