Sonder Cortex Frame with DBIL Shock and Helm Fork
Fast and agile short travel full sus 29er mountain bike frame with Cane Creek Helm-Air fork and DBair IL rear shock
£1899.00
Available on finance, from per month*
Pictures are for illustration and some components and finishing kit of this build may be different. Please refer to the detailed spec sheet before placing an order.
How To Order
All our bikes are built individually to order. If you want to change any part of the spec to suit your needs then get in touch.
Please allow 20 working days for us to build, check, pack and despatch your Sonder.
Alternative payment options
Guide to paying with Cycle to Work Schemes

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Alpkit Ltd acts as a credit intermediary and offer credit products provided exclusively by Klarna Bank AB (publ). Klarna Bank AB (publ) is Authorised by the Swedish Financial Services Authority (Finansinspektionen) and is subject to limited regulation by the Financial Conduct Authority. Details about the extent of our regulation by the Financial Conduct Authority are available from us on request. Finance is only available to permanent UK residents aged >18, subject to status, terms and conditions apply. Registered office: Sveavägen 46, 111 34 Stockholm, Sweden. Corporation ID number: 556737-0431. |
At a Glance
Hand-welded from 6061 double butted aluminium frame for epic days over mixed terrain.
- Short travel 29er full suspension frame with 120 mm rear shock
- Front fork: Cane Creek Helm-Air with 130 mm travel
- Agile over mixed terrain perfect for full day epic rides
- Well behaved but comes alive on technical descents and UK trail centres
- 2.2” to 2.6” 29er
With bang up to date geometry, Cortex is confidence inspiring with a playful character. Stand up and mash on the pedals out of turns, manual sections of trail and pop off tree stumps, rocks and roots. Smash out short and loose technical climbs, flat out descents and tight techy singletrack sections. The harder you push the bigger you grin.
Cortex frameset is hand-welded from 6061 double butted aluminium with a tapered ovalised top-tube and large section down-tube for a stiff chassis with just enough compliance to get you out of trouble. 66 head angle, 74.5 seat tube angle, 40 mm bottom bracket drop and a 465 mm reach (size large). Cortex’s dialed in geometry and 2.6” tyre clearance offers a comfortable and efficient climbing position for big miles and a stable, spirited platform for smashing up descents.
Up to Date Trail Bike Geometry
Trail bike Agility with Enduro bike stability, the Cortex has a confidence inspiring, stable and forgiving ride.

Metric Shock Standard
Designed around metric shock sizing standard, with lengthened shocks and shorter strokes that increase bushing overlap for more smooth, supple, sensitive and reactive suspension action.

Horst link suspension design
The tried and tested Horst link suspension design allows the suspension to stay active when braking.

Tyre Clearance
Clearance for up to 29 x 2.6in tyres.

Internal Cable Routing
Internal routing in the front triangle for clean lines.

Frame spec
Alloy 29er short travel full suspension trail bike
Weight (kg): S: 2.73; M: 2.91; L: 3.05; XL: 3.11 |
Hydroformed and custom butted alloy frame tubing |
Internal cable routing |
Rear Shock: Rockshox Deluxe Select+ 190 x 45 mm |
Horst link suspension layout |
120 mm rear travel; 130 mm fork travel |
Clearance for up to 29” x 2.6 in wide tyres |
73 mm BSA threaded bracket shell |
148 x 12 mm rear thru-axle |
31.6mm seat tube, 34.9mm clamp |
ZS44/28.6| ZS56/40 headset (frame and rear shock does not come with headset) |
It is important to get the right size bike, if the bike fits it will be faster, more comfortable, and easier to handle. You can also take into consideration the standover height to ensure you pick a bike that will be a good fit. If you measure your inside leg and ensure there is a minimum of an inch from the toptube to your crotch this will give you enough seatpost adjustment to find your optimum saddle height.
Generally we recommend:
- Small
- Riders between 5ft 2in and 5ft 7in
- Medium
- Riders between 5ft 6in and 5ft 10in
- Large
- Riders between 5ft 9in and 6ft 2in
- X-Large
- Riders of 6ft 2in +

Cortex
Size | Small | Medium | Large | X-Large |
---|---|---|---|---|
ST - Seat tube | 400 | 425 | 465 | 485 |
TT - Top tube | 587 | 608 | 636 | 658 |
HT - Head tube | 100 | 105 | 115 | 125 |
HA - Head angle | 66 | 66 | 66 | 66 |
SA - Seat angle | 74.5 | 74.5 | 74.5 | 74.5 |
CS - Chainstay | 442 | 445 | 447 | 450 |
BB - BB drop | 40 | 40 | 40 | 40 |
FO - Fork offset | 51 | 51 | 51 | 51 |
WB - Wheelbase | 1169 | 1191 | 1220 | 1244 |
SO - Stand over | TBC | TBC | TBC | TBC |
RE - Reach | 420 | 440 | 465 | 485 |
SK - Stack | 602 | 606 | 615 | 625 |
Tyre Diameter | 755 | 755 | 755 | 755 |
Fork Axle to Crown | 540 | 540 | 540 | 540 |
Build | Sonder Cortex Frame with Cane Creek DBIL Shock and Helm Fork |
---|---|
Frameset | |
Frame | Cortex |
Rear Shock | Cane Creek DBair IL |
Fork | Cane Creek Helm-Air, 130 mm Travel, 29” Gunmetal Grey |
Weight | |
Frame (inc shock) | S: TBC M: TBC L: TBC XL: TBC |
Swapouts and Upgrades
You can interchange Love Mud components on this build at no additional cost. So if you want a different length of stem, a particular saddle or bar then let us know in the notes section in the checkout and we'll get in touch. We also hold big stocks of SRAM, Rockshox, WTB and regular build with Shimano, Hope, Cane Creek. We'll build your Sonder with any part that suits your needs. Give us a call, with the same experienced mechanic helping throughout your build you know who to call if there's anything you want to know.
Faqs
Support
- Visit the Support Centre
- Ring us on 0044 1773 417 007
- Write to us here
- Drop by our Factory Store : Open Mon-Fri 10am to 4pm or visit our stores in Ambleside and Hathersage which are also open at weekends.
Alpine Bond Warranty
We offer a 10 year guarantee on both our handmade titanium and Reynolds steel frames. Our hand welded 6061-T6 alloy triple butted frames and carbon frames come with a 5 year manufacturing defect warranty. All our bikes are built, checked and signed off by Cytech trained mechanics before being despatched to you in a custom-made bike box.