First Ride Review: Is The Sonder Cortex The 120mm Travel Trail Bike You Should Be Riding?

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Andi gets an exclusive first ride review of the latest 120mm travel full-suspension bike from Sonder. Meet the 2020 Sonder Cortex.

Sonder, the bike brand of Alpkit, has been making waves in the British mountain bike world for a couple of seasons now, and with the recent launches of the Signal Ti hardtail, all-new Transmitter and now the 120mm travel Sonder Cortex, they aren’t showing any signs of slowing down.

The Sonder Cortex is a designed from the ground up, 120mm travel full-suspension bike, but while this final production bike we have before us here is new, the Cortex has been spotted before.

sonder protobike 29er
Remember seeing this?

The original prototype Sonder Cortex featured a swoopy hydroformed mainframe, but the final model uses straight tubes which we think actually suits the Sonder brand identity a little better.

Neil Sutton, Sonder’s bike designing wizard, has designed the Cortex with 120mm of travel and 29in wheels, but don’t be fooled into thinking this is simply a cross country whippet, the Cortex might be short on travel but it’s full of fun and packed with full-throttle beans.

Like all Sonder bikes the Cortex is available via the Alpkit website, and in Alpkit stores dotted around the country. Customers have a few build options to choose from with prices starting from around just £1500, but as each bike is built to order there are options to tweak the specifications here and there and add a few upgrades to get the bike how you want right out of the box.

Sonder Cortex Review: The Bike

sonder cortex review 1
The all-new Sonder Cortex

The original prototype Sonder Cortex was first spotted back in January of 2018, and since then it has undergone a major makeover and now sports a tubeset that is more in line with the rest of the Sonder bike family. It’s also had a geometry tweak here and there and the final production bikes will be available in brown, green and a rather natty bone white finish.

After well over a year of development and ride time, Neil finally came to the decision to build the Cortex with a 66° head angle, 74.5° seat tube, and as we’ve witnessed before on Sonder bikes, varying chainstay lengths which increase slightly with each frame size. This makes a lot of sense, as a tall rider won’t have the same central position as a short rider and just as we need to increase reach we should really look at increasing the rear too.

In this case, reach figures range from 420-480mm across the 4 sizes, while the chainstays increase from 442-450mm.

Full geometry details for the Cortex can be found below;

Seat tube length400425465485
headtube length100105115125
head angle66666666
Seat Angle74.574.574.574.5
BB Drop40404040
Tyre Diameter


Fork Axle to crown


Fork offset51515151
Effective Toptube587608636658

Sonder Cortex Review: The Ride

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Review Info

Price:From £1500
Tested:by Andi Sykes for 1 day

Comments (12)

    Yes please. This sounds like the perfect successor to my favourite bike of all time – Orange ST4. A bit nippier, lighter, more engaging ride than a hulking long travel bike. But beefy enough, geometry for smiles and miles and just all-round balanced.

    Now to start saving…

    I can see a frame only in my future…. This looks perfect for most of my riding! Love my Intense Spider, but I do miss 29 inch wheels on my trail bike.

    why does it have to have all those bendy tubes? Gopping.

    @peteimpreza the bendy tube model was the proto.

    Uuuuuu excited…

    That might be actually something to look into.

    2.6 rear clearance I can probably live with 🙂

    When are they going to be available for demoing?


    Checking the prices on their website, the full GX / Cane Creek front and rear is only £2600! If that is correct then there’s a hell of a lot of bike for the money.

    The website spec list does however say that the fork is 130mm travel. Wonder if they’ve changed the specs slightly for the final release?

    Looks great, except… that seat tube length grows inconsistently as the sizes go up:

    Small 400 – pretty good for riders 5’2″ to 5’7″ (reach 420)
    Medium 425 (+25) – reasonable for 5’6″ to 5’10” (reach 440)
    Large 465 (+40) – why the big jump? 5’9″ to 6’1″ (reach 465)
    X-large 485 (+20) 6’2″ upwards (reach 485)

    If you had thoughts of sizing up to get more reach (and 465 is hardly super-long for the large) you’re not gonna get much of a dropper in place.

    At 5’10” i’d still get a 150mm dropper (maybe a 170mm) in that large frame so it’s not really that long.
    I agree shorter would have been sensible though, with the options for 200+ droppers increasing significantly.

    Brown model has a seat gusset but green does not… size specific or another proto…?

    The original prototype Sonder Cortex featured a swoopy hydroformed mainframe, but the final model uses straight tubes which we think actually suits the Sonder brand identity a little better

    Errr…. In the new version, only the top tube isn’t swoopy and hydroformed – the bottom tube and seat tube are pretty much as curvy as ever.

    @peteimpreza the bendy tube model was the proto.

    Seriously. Look again.

    What does it weigh? Sonder won’t say yet. Looks quite lean and rapid, a build with the new hunt xc wide may be on the cards

    what do you think, frame will accept 140mm fork?

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