Genesis Tarn 20 2017 first ride review

This plus-bike steals the limelight after an awkward start

GBP £1,799.00 RRP
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Last year the Genesis Tarn made quite an impression with its ‘from the future’ long front-end geometry and bulbous plus-sized tyres. The Tarn still stands out from the crowd and is built using Genesis double-butted Mjolnir tubing and is handily both 27+ and 29” wheel compatible.


Genesis Tarn 20 2017 spec overview

  • Frame: Genesis Mjölnir Seamless Double-Butted Cromoly
  • Fork: Rockshox Yari RL, Solo Air, 120mm
  • Shifters: Shimano SLX SL-M7000
  • Rear derailleur: Shimano SLX RD-M7000-11
  • Chainset: Shimano SLX FC-M7000-B 32T
  • Bottom Bracket: Shimano BB52
  • Cassette: Shimano SLX CS-M7000 / 11-42T
  • Rims: FATlab 40mm Tubeless-Ready, 32h
  • Hubs: Shimano HB-M618 / FH-M618 32h
  • Tyres: WTB Ranger 27.5+ x2.8″
  • Brakes: Shimano M506 180/160mmHandlebar: Genesis alloy / 760mm x 5mm rise
  • Stem: Genesis 60mm /+0deg
  • Saddle: Genesis MTB
  • Seatpost: KS DropZone 31.6mm / 125mm drop

The Tarn 20 is a lot of fun, but we’d recommend changing the tyres when the conditions get wet and loose
Russell Burton

Genesis Tarn 20 2017 frame and equipment

There are extra bottle cage mounts on the bottom of the downtube, and p-clips for Shimano’s side swing system paired with the traditionally placed cage mounts on top. The bike’s not cheap at a quid shy of £1,800 and is fairly hefty weighing in at 14.5kg.

Our test bike came with the wrong length stem. The supplied 65mm paired with the already long 465mm reach, made riding the Tarn feel like driving a limousine from the back seat. We reduced the stem to a 50mm and spent time fine tuning other areas. Getting the correct tyre pressure was key to the feel too, requiring plenty of time experimenting with what worked for us and our trails.

The Tarn is extremely comfortable on the rough stuff with minimal trail chatter due to the excellent performing Yari fork and volume of the huge tyres. On trail centre terrain you could easily forget that you were actually riding a hardtail.

The 2.8” WTB Ranger tyres roll surprisingly well and with the low pressure in them, there’s so much grip. When the back end does get unruly, sliding on roots, the wide width and volume of the tyres work wonders in giving you back lost control.

The Genesis Tarn 20 2017 hardtail
Russell Burton

Genesis Tarn 20 2017 ride impression

The Tarn is playful and the security of the big tyres helps increase rider confidence making you want to smash it into every corner you can find. That is until conditions get wet and loose where the Rangers had little to give — an issue found with many plus-bikes due to the current lack of aggressively treaded tyres available.

New 11-speed SLX running gear is slick in the speed of its shift and feels tight. The wide range of the 11-42 cassette works well with the 445mm chainstays and super long reach to get the bulky Tarn up hills with relative ease. On very steep climbs, the front wheel can want to lift but this was rarely a serious issue.

Early verdict

Reducing the stem length made a huge difference and a 35mm would be perfect. Once running super low tyre pressures the initial corpse-like ride totally exceeded our expectations. However, the tyres are questionable for UK conditions 11 months of the year.


‘Haters gonna hate’ but this plus-bike is one of the best steel hardtails out there.

Product Specifications


Name Tarn 20 2017
Brand Genesis Bikes

Available Sizes S M L XL
Rims FATlab 40mm Tubeless-Ready, 32h
Wheelbase (in) 47.13
Top Tube (in) 26.46
Standover Height (in) 30.9
Seat Tube (in) 19.02
Chainstays (in) 17.52
Shifters Shimano SLX SL-M7000
Seatpost KS DropZone 31.6mm / 125mm drop
Seat Angle 72
Rear Tyre WTB Ranger 27.5+x2.8"
Bottom Bracket Shimano BB52
Rear Derailleur Shimano SLX RD-M7000-11
Head Angle 68
Front Tyre WTB Ranger 27.5+x2.8"
Frame Material Seamless Double-Butted Cromoly
Fork Rockshox Yari RL, Solo Air
Cranks Shimano SLX FC-M7000-B 32T
Chain KMX X11
Cassette Shimano SLX CS-M7000 / 11-42T
Brakes Shimano M506 180/160mm
Frame size tested L