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

sonder cortex review detail
Also available in green or bone white

I arrived with Neil at Lady Bower reservoir as this is where I tend to ride in my free time, and it’s also not too far from the local Alpkit store in Hathersage, this was pretty lucky really as I had totally forgotten to bring my pedals with me. Once pedals were rustled up though, we both headed straight-up, and when I mean ‘straight-up’ I mean we took the steepest climb we could find that gained as much altitude as quickly as possible. Of course, it’s a matter of our ultimate fitness and an insatiable appetite for climbing which drove us to hit slippy moss-covered rock climbs and steep root riddled inclines, and nothing to do with the fact that time was ticking on due to my pedal mishap.

Spinning along at a steady pace you soon come to realise that the Sonder Cortex is a pretty nice place to be. The cockpit on my size L brown test bike measures up with a reach of 465mm with a seat-tube angle of 74.5°, not the steepest seating position but an efficient and comfortable place to be none-the-less.

Our test bikes were fitted with Cane Creek rear shocks which have a million and one different settings plus a climb switch, although I found climbing with the switch wide open preferable. Small bumps and light trail taps are transferred from the 29in wheel, through the slender top-tube mounted links and despatched quickly by the rear shock, while all the power you produce from your meat motors is transferred down to the ground with little fuss but plenty of efficiency.

sonder cortex review detail
Super compact linkage

Once at the top we enjoyed the view before heading back down again picking up speed and switching lines as we hopped from rock to drop. Gapped natural grass doubles hit steep technical chutes, and played my most favourite game of all “huck and hope” where you hit a blind jump or drop and hope the bike carries you through.

It’s a pretty standard day of riding for a 150mm travel 29er, except Andi you have forgotten something else, haven’t you? As well as forgetting your pedals you’ve gone and forgotten how much travel this bike actually has! All those gaps, and rocks and games of “huck and hope” weren’t played out on a big travel EWS machine. No, that was all done with ‘just’ 120mm of travel front and rear!

sonder cortex review detail
Just 120mm travel

Sure when the going get’s really tough and the speeds reach Tesla Roadster levels of lunacy, 120mm of travel does start to feel a little firmer and you’ll bottom out now and then, but WOW 120mm of travel can do quite a lot really can’t it?

Sonder Cortex Review: Overall

sonder cortex green
Also available in Hulk green

While riding the Sonder it felt just as fast as my big bike but sharper to corner, easier to hop and overall a hell of a lot of fun to ride, and I cannot wait to get on it again.

As we only had 1 day on the Sonder Cortex for this first ride review, we have requested a long-term test bike so that we can really put it through its paces, so keep an eye out for the complete review coming soon.

Review Info

Brand: Sonder
Product: Cortex
From: Alpkit
Price: From £1500
Tested: by Andi Sykes for 1 day

Andi is a gadget guru and mountain biker who has lived and ridden bikes in China and Spain before settling down in the Peak District to become Singletrack's social media expert. He is definitely more big travel fun than XC sufferer but his bike collection does include some rare hardtails - He's a collector and curator as well as a rider. Theory and practice in perfect balance with his inner chi, or something. As well as living life based on what he last read in a fortune cookie Andi likes nothing better than riding big travel bikes.

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Comments (14)

    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?

    Yes havvi!… I was thinking about fitting 140mm pikes, it should be ok but i’m checking with the guys at alpkit so will let you know.

    I’m considering the frame for my own build, not many reviews on these and the only other write up I have found online (by Guy Kesteven) is saying the default Rockshox Deluxe Select+ shock didn’t work too well for them, they ended up setting 20% sag to not blow through travel then it lacked plushness – anyone got any more time on this bike with that shock and care to comment?

    If it makes any odds I’m circa 95kg, 6’5″ and would be riding an XL so I’d presumably be running a fair bit of pressure. My old 20″ 2008 Orange Five used to blow through it’s travel easily, I ended up swapping for a coil shock and mostly riding hardtails more for years and have finally sold the five and looking at modern 29er trail bikes, I’d like more rear end support this time…

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