Bike of the Week | FiftyOne Assassin gives you six geometry settings

Irish brand’s first off-the-shelf gravel bike makes a bold statement

FiftyOne Assassin against a pink background

Gravel bikes continue to diversify, with machines tailored to racing and others that encroach on mountain bike territory. However, the FiftyOne Assassin looks as if it could excel in all gravel sub-disciplines.


FiftyOne is revered for its custom geometry, one-off paint schemes and tube-to-tube carbon construction, but the Assassin bucks convention for the Irish brand. It’s the brand’s first production gravel bike, with a monocoque carbon frame manufactured in Taiwan.

With two flip chips and plenty of mounting points, the gravel bike can be adapted to a wide range of needs. However, going by its spec sheet, this particular model seems to be aimed more at the go-fast crowd than the bikepacking fraternity.

A frame ready for anything

FiftyOne says the Assassin’s frame uses a mixture of Toray T700, T800 and T1100 fibres. The brand says the frame weighs 1,245g, including hardware, in a size medium. The Trident fork adds another 540g.

The head tube has a reasonably stout profile and the thin seatsays wave as they head towards the seat-tube junction.

The chainstays are dropped, enabling the Assassin to accept up to 47mm-wide gravel bike tyres in 700c and 650b wheel sizes.

There are also rack and mudguard mounts, and the fork has mounts along the length of its blades to mount luggage.

The cables are routed internally, but the Assassin eschews integration. FiftyOne has also stuck to convention with the round 27.2mm seatpost, which you could upgrade if you wanted greater compliance.

The frame can accept either 1x or 2x drivetrains and there’s also a moulded bash guard underneath the down tube to protect against rock strikes.

The bike is compatible with a dropper post. There’s even storage for a Shimano Di2 battery inside the down tube if you want to run the bike with this groupset and a dropper post.

The Assassin uses a T47 threaded bottom bracket.

What is Bike of the Week?

Every fortnight, we’ll bring you a detailed first look at one of the latest bikes (or framesets) to arrive at BikeRadar HQ – from road to commuting, gravel to enduro, and anything in between.

This is our chance to introduce the bike and everything that makes it unique before hitting the road or trails.

Head to our Bike of the Week hub for previous editions.

Six bikes in one?

There are three positions at the rear to choose from.
Oscar Huckle / Our Media

The FiftyOne Assassin has adjustable geometry thanks to flip chips at the front and rear dropouts. While an increasing number of gravel bikes use flip chips, such as the Giant Revolt, Berria Belador Allroad and Windover Bostal, it’s rare to see a frame with two.

The flip chips provide three positions at the rear and two at the fork.

This means there are six setup permutations – and that’s before you consider changing the wheel size or tyre width, which can alter the geometry and ride of a bike even further.

You’ve then got two positions to choose from on the fork.
Oscar Huckle / Our Media

The fork has high and low settings. The high setting allows for 53mm of fork rake and a 75.95mm trail. The low setting reduces the fork rake to 45mm and increases the trail to 87.49mm.

The short, mid and long rear dropout options enable you to alter the wheelbase of the bike by 5mm each time.

FiftyOne says you don’t need to realign the brake caliper when changing between settings because there will still be sufficient rotor height.

A Campagnolo build

Campagnolo Ekar is a fitting groupset choice.
Oscar Huckle / Our Media

Our test bike is equipped with a Campagnolo Ekar groupset and retails for €6,499.

This smokin’ colourway is called Rothmans Blue, but there are also British Racing Green and Black Ops / Raw Carbon options.

Complete bikes start at €4,500 for a Shimano GRX800 build and rise to €7,499 for Campagnolo Ekar with ENVE finishing kit. There is also a frameset option at €3,499.

The 9-42t cassette will get you up most climbs.
Oscar Huckle / Our Media

The 9-42t Ekar cassette is paired with a 38t crankset. There are 160mm disc brake rotors specced front and rear.

Campagnolo also provides the Shamal wheels. These were Campagnolo’s first gravel wheels and are constructed from carbon fibre with a 21mm internal rim width. The brand has since launched its Levante wheelset with a greater 25mm internal rim width.

The Shamal hubs use cup-and-cone bearings.
Oscar Huckle / Our Media

On this bike, the Shamals are shod with 700c x 45mm WTB Riddler tyres.

The bike uses Zipp’s aluminium Service Course stem and seatpost.

There is an Easton EA50 AX aluminium gravel bike handlebar with a moderate 16-degree flare and a WTB SL8 chromoly saddle.


All-in, the bike weighs 9.18kg without pedals, but including a bottle cage and seat pack.