Expanding its range, sorting its sizing and making the best of Plus-size tyres — Genesis has been busy creating another trail-ripping hardtail, the Tarn.

Product Overview

Genesis Tarn 20


  • It has everything you need from a true trail ripper. Plus-size tyres deliver a surprisingly comfortable ride.


  • It’s not lightweight by any means, but going tubeless should drop the weight by almost 500g. With the refocused sizing, the 60mm stem seems too long for what this bike is capable of.


Genesis Tarn 20 (2017) first ride


Price as reviewed:


Need to know

Genesis has a solid footing in road bike design, building up a wealth of experience working with steel and other materials. In recent years it’s upped its game in the mountain bike world, with cutting-edge hardcore hardtails featuring relaxed geometry and generous sizing.

The Tarn 20 takes all that know-how and throws 27.5 Plus tyres into the mix.

This top-end version shares the same frame as the other models in the three-strong range. Crafted from doubled butted cro-mo tubing, it casts a very similar shadow to the 2016 High Latitude.

Thanks to Boost spacing front and rear, the Tarn 20 can fit both 29in and 27.5 Plus wheels — an added bonus of the wider hubs being improved wheel strength.

Huge clearance allows fitment of either 29er or 27.5 Plus wheels.

The main updates for 2017 have been to its components. To bring it in line with modern trail riding, these changes include the burly 120mm travel RockShox Yari fork coupled to a wide 760mm riser bar. Both changes hugely improve steering precision and control over last year’s bike.

The difference between the 29in wheels of the High Latitude and 27.5 Plus on the Tarn 20 was more noticeable than I anticipated. The Tarn 20 comes with the fast rolling/light casing versions of the WTB Ranger 2.8in tyres, with rolling speeds similar to its 29er counterpart.

With pressures set to 19psi in the rear and 17psi up front, losing grip and slowing down isn’t an issue, even with the harder compound rubber and low-end Shimano Deore brakes. Traction is simply on another level.

The biggest difference, though, is the extra suppleness of the 2.8in tyres that allow you to ascend out of the saddle, without bouncing over every rock and root. This, together with the inherent softness of the steel frame, means you can also spend a lot more time in the saddle, as it is noticeably less jarring on your lower back.

We don’t put much faith in the minimalist chain guide.

It’s on the descents, however, where the Tarn 20 really shines. It feels very stable for a hardtail, and it finds traction on rough off-camber sections where other non-Plus hardtails would struggle.

Occasionally the tyres felt as if they rolled around during hard cornering and through big compressions, even with the FatLab 40mm rims, but this is a small price to pay for all of the upsides of the bigger tyres.

Needless to say, the Tarn 20 is a well-rounded trail hardtail. The balanced and contemporary frame proportions inspire you to go fast, and the 2.8in tyres simply increase confidence further.

Spotlight on: sizing

Genesis has got the sizing spot-on with its latest range of mountain bikes. With generous frame proportions and a 470mm reach measurement, for once, this size L bike was actually too big for me. I’m not complaining though. At 5ft 10in tall, I consider myself an average guy, so it’s fitting (sorry) that a size medium Tarn 20 would have been a better option for me.

And, with sizes ranging from S all the way up to XL, this means that even the tallest riders can be accommodated on the Tarn 20. Couple this with a relatively slack 67.9° head angle, low 305mm BB height and the added traction and comfort of the Plus tyres, and the Tarn 20 can definitely charge.

Two-tone paintjob accentuates the shape of this British bomber


Frame:Genesis Mjölnir seamless double-butted cro-mo
Fork:RockShox Yari RL Solo Air, 120mm travel
Wheels:Shimano Deore hubs, FATlab 40mm rims, WTB Ranger TR 27.5x2.8in tyres
Drivetrain:Shimano SLX 1x11 chainset, r-mech, cassette and shifter
Brakes:Shimano Deore M506, 180/160mm
Components:Genesis handlebar 760mm, 60mm stem and saddle, KS Dropzone 125mm seatpost
Weight:14.18kg (31.3lb)
Sizes:S, M, L, XL
Size ridden:L
Rider height:5ft 10in
Head angle:67.9°
Seat angle:71°
BB height:305mm
Front centre:749mm
Down tube:730mm
Top tube:660mm