by James Love
April 12, 2017
Ah the British steel hardtail. Classic! Quintessential! Tough, durable, simple, and fun. The ever-reliable companion for those who like to ride all-year round. In the case of the Genesis Tarn, chubby 27.5+ tyres give an old favourite a new twist…
British bicycle brand Genesis offers four different models in its mountain bike range. There’s the Caribou and the Longitude for off-road bikepacking, the Core 27.5in hardtail, and the Tarn 27.5+ hardtail. Equipped with with the in-vogue 27.5×2.8in tyre standard, the Tarn range offers a long and low chubby option for hardtail riders who are looking for more comfort, more traction and more capability without having to resort to the complexity of a fully suspended frame.
Within the Tarn range, there are three models: the Tarn 10, Tarn 20, and the Tarn 29. All models are built with the same steel frame, which can also be bought on its own for £599.
The Tarn 10 is spec’d as a fully rigid bike for those who want to ditch the suspension all together, while the Tarn 29 (obviously) utilises 29in wheels. In comparison, the Tarn 20 features 27.5×2.8in chubby tyres with 120mm of air sprung travel. It’s pitched as a versatile, go anywhere, velo tout terrain bike. And with an impressive parts spec on paper, this could definitely be the hardtail that many UK riders are looking for.
“The quintessential steel UK trail hardtail – redefined. Tarn is our dedicated 27.5+ offering, designed from the ground up around the new Boost axle standards, wider chainline and new-school progressive geometry. A beautifully crafted steel frame and an enviable part spec with the new Shimano SLX 1×11 drivetrain, Rockshox Yari RL Solo Airfork, FATlab 40mm rims, KS dropper seatpost and tubeless-ready WTB Ranger 2.8″ rubber will happily handle anything and everything the UK’s trails can throw at you.” – From Genesis.
2017 Genesis TARN 20 Features
- Trail hardtail that’s long and low slung
- Made from seamless double-butted steel tubing
- 120mm fork travel
- Dedicated 27.5+ wheel model (TARN 29er also available)
- 68° head angle
- 72° seat angle
- 445mm chainstay length
- Dropped toptubes – generous standover
- Boost 148x12mm rear thru-axle
- No less than three x water bottle mounts
- Available sizes: Small, Medium, Large, X-Large
- RRP: £1799.99
With the chunky RockShox Yari fork up front, the Genesis Tarn 20 looks the business. 120mm of travel and a 68° head angle to strike a balance between nimble steering and descending capability.
As all proper British hardtails are, the Tarn 20 is made from steel. Double-butted cromoly to be specific, with loads of gentle curves bending this way and that to offer more ‘give’ where it’s needed.
To keep that toptube low-slung, Genesis support the seat tube with a curved brace that looks dead lovely. I’m riding the XL frame size, but there is masses of standover height.
Short, but not too short. A 445mm rear centre length offers a metric shit-tonne of mud clearance around the chubby 27.5×2.8in tyres, while giving stability to the handling overall. The rear end is Boost’d, and is also 29in wheel compatible.
I’ve already discovered the virtues of that mud clearance around the chainstay yoke, with the slender steel tubes allowing gloopy mud to slip and slide past.
The upper seatstay assembly is reinforced with a subtle gusset to help increase lateral rigidity, whilst still maximising tyre clearance. I haven’t tried it yet, but there is easily room for 3.0in wide tyres in the frame.
A Shimano 148x12mm thru-axle offers tools-free removal and installation of the rear wheel.
Up front is the RockShox Yari, which is proving to be a popular OEM choice through 2017. Coming into the line as a cheaper alternative to the Lyrik fork, the Yari uses a similarly beefy 35mm chassis and a Boost 110x15mm thru-axle, but specs a simpler RC damper inside the right-hand stanchion to help get the price down.
With basically the same chassis as the Lyrik, the Yari is a suitably tough fork to deliver front-end control on the Tarn 20. Solo Air spring offers quick and simple setup of air pressures for your riding weight, and Bottomless Tokens can be utilised to increase or decrease spring rate progression.
40mm wide (internal) rims come courtesy of Fatlab, and feature a tubeless ready rim profile with 32 spoke holes.
Tyres are supplied by WTB, who kinda kicked off the whole 27.5in plus movement just a couple of years ago. The tyres are the Ranger model, which we have plenty of experience with. Not ideal for mud, but much better suited to trail centres and hardpack surfaces. Also tubeless compatible.
Nice to see some name-brand hubs at the centre of the chubby wheels, with Shimano Deore units taking care of rolling duties. User-serviceable bearings and all that.
Likewise, there’s a set of Shimano M506 hydraulic disc brakes, which we have very little to worry about. 180mm Centrelock rotor up front, and a 160mm rotor out back.
The brake levers don’t get tools-free reach adjusters, so you’ll need a 3mm hex key to adjust the lever reach. That said, once you’ve got it set you’re unlikely to need to play with it again.
Tidy 1x cockpit with a Shimano SLX M7000 right-hand shifter firing off up and down shifts with its dual-paddle trigger design. Neat and slim lock-on grips too.
With the exception of the KMC chain, the entire drivetrain is from the Shimano SLX M7000 catalogue, with a Shadow Plus rear mech keeping the chain bounce low. There’s a 32t chainring up front, while an 11-42t cassette delivers the gear range on the back.
Genesis has also equipped the Tarn 20 with an additional inboard chainguide to help prevent the chain from bouncing off and slipping down in between the frame and the crankset. Simple, but a nice detail.
Further aiding simplicity is the use of fully external cable routing for both the rear brake and rear derailleur. The Tarn 20 can be setup with a front mech, and there’s routing options for that as well.
Genesis has also been able to squeeze a dropper seatpost into the price of the Tarn 20, though to keep things tidy and simple, it’s a crotch-grab unit from KS. A small lever underneath the saddle allows you to raise or lower the saddle height without having to resort to a hex key or a quick release on the seat collar.
As of now I’ve taken it out into the hills on a spin or three, splattered mud on it and used the crotch grab actuator yeeow up ‘n’ down seat post. Have left the wheel reflectors on. Review to follow. Stay tuned…
2017 Genesis Tarn 20 Specifications
- Frame // Genesis Mjölnir Seamless Double-Butted Cromoly
- Fork // RockShox Yari RC, 120mm Travel
- Hubs // Shimano Deore Centrelock, 110x15mm Front & 148x12mm Rear
- Rims // Fatlab 40mm Internal, Tubeless Ready, 32h
- Tyres // WTB Ranger TCS Light, Tubeless Ready, 27.5×2.8in Front & Rear
- Chainset // Shimano SLX 32t Chainring
- Front Mech // N/A
- Rear Mech // Shimano SLX, 11-Speed
- Shifters // Shimano SLX, 11-Speed
- Cassette // Shimano SLX, 11-42t, 11-Speed
- Brakes // Shimano M506, 180mm Front & 160mm Rear
- Stem // Genesis Alloy, 31.8mm, 60mm Long
- Bars // Genesis Alloy, 31.8mm, 760mm Wide, 5mm rise
- Grips // Genesis Lock-On
- Seatpost // KS DropZone, 31.6mm, 125mm Travel
- Saddle // Genesis MTB
- Size Tested // X-Large
- Sizes available // Small, Medium, Large, X-Large