Review: FiftyOne Bikes Assassin gravel bike delivers on versatility without sacrificing speed

For some time now, gravel bikes have been almost divided into two categories. You have the fast, light, race-focused bikes with smaller tire clearance and fewer mounts for accessories. And then you have the more adventure-focused set with room for massive tires, all the mounts, and often, a slightly more relaxed geometry.

But what if you want a gravel bike that can do both?

That seems to be the focus of the newest model from FiftyOne Bikes–the Assassin. It’s a bike that is fast and light enough to race your favorite gravel event without the bike holding you back. But it’s also just as eager to load up with bags and big tires to get out of Dodge on your next bikepacking adventure. It seems with the Assassin, you may not have to choose.

Before the Assassin showed up at my door, I wasn’t sure what to expect. As the first ‘production’ bike from FiftyOne Bikes, the Assassin is quite different than the custom tube-to-tube carbon creations the brand is known for. But that attention to detail that makes their custom bikes so incredible carries through on their new gravel bike as well.

Build Your Own Adventure

From front to back, the Assassin includes most of the details you could want out of a versatile gravel bike. One detail that sets the Assassin apart is the ability to adjust the dropouts at both ends of the bike. There are other bikes out there like the Otso Tuning Chip system at the back, and bikes with flip chips at the front, but bikes with adjustable dropouts front and rear are fairly rare.

Axle adjustment systems like the one found on the Assassin allow you to fine-tune the handling. In this case, you can adjust the wheelbase and chainstay length via the rear chip with three positions, and adjust the fork offset and head tube angle via the two-position chip on the fork. Admittedly, once I found my favorite position with 700c x 45mm tires, I kept it there and didn’t change it.

But the versatility of the chip system allows you to build the Assassin around your preferred wheel and tire size. The tire clearance is listed as 47mm in both 700c and 650b wheel sizes, and that’s with very generous mud clearance. Could FiftyOne have built a lighter frame and fork by sticking to one axle position front and rear? Probably, but it also would have been built around one ideal wheel and tire size. Given that the chip system seems quite robust (and quiet), it seems like a good addition even if most riders find their preferred position and keep it there.

While the bike camp equipped with Michelin Power Gravel tires in a 700c x 47mm size, they just seemed too wide for the 21mm internal width of the Campagnolo Shamal wheels. Since this bike was sent to me, Campy has introduced a more appropriate Levante wheelset with a 25mm internal width, that would clearly be the wheel of choice for this build. But free hub limitations kept me on these wheels (more on that below, so I opted for my trusted WTB Riddler setup in 700c x 45mm. Just that 2mm difference in tire size had a profound effect on the handling of the bike with these wheels.

Geometry

When it comes to the rest of the geometry, the Assassin is limited to four sizes for the initial run. Aidan Duff, the Managing Director of FiftyOne Bikes, tells us that he wishes they could have opened more sizes, but carbon molds are expensive. Very expensive if you’re taking a risk on a new bike that you don’t know how it will sell. So the decision was made to open four sizes–S, M, L, and XL.

That put me somewhere between the Small and Medium–with either a slightly shorter or longer reach and top tube than might be ideal. I ended up on the small which required a 90mm stem to get the reach dialed in. The medium has a longer effective top tube than all of the gravel bikes that I’ve ridden, though by height, I should be on the medium in the chart above at 5’7″. Even feeling completely comfortable on the Small, I would still like to try the Medium to get the benefits of a shorter stem, and slightly longer front center.

With that said, I’ve become extremely comfortable on the Assassin even after a recent back injury, and long days on the bike. The positioning feels aggressive, but still comfortable enough for big adventures. The main reason I would consider a slightly larger frame if it was offered, is that the Small has a bit of toe overlap for me with 700c x 45mm tires and my 41.5 shoes.

In the process of lining up the review, FiftyOne’s fit wizard Aaron Marsh dialed in my fit on the Small since it seemed like the best option, and the resulting fit was dialed right out of the box. They had even marked the seat post position for me. And based on my performance recently in the mountains of Alabama at Rocks, Roads, and Reggae V, it seems like it was just about perfect. I don’t know if I’ve ever felt so comfortable climbing on a gravel bike, and there was a lot of climbing.

A big part of that is owed to the compliance of the bike. It’s just so smooth over any surface. You can just focus on putting the power down while staying seated. At a point where I felt like I should have been feeling the miles, I was feeling exceptionally fresh. Back home, on a stretch of embedded, softball-sized river rocks that can be difficult to pedal through on a rigid mountain bike, the Assassin plowed forward with surprising ease.

Looking at the bike, you’d assume this is a result of the slender, curved seatstays with a bridge that’s only used while running full coverage fenders. Those features carry over into the overall design of the bike which looks quite stunning in person in the British Racing Green. Between the finish, the frame design, and the relative obscurity of FiftyOne Bikes in the States, curious riders asked what I was riding just about everywhere it went.

However, that smooth ride does not come at the expense of explosive sprinting power. Step on the gas and the Assassin just gets up and goes. The Assassin balances compliance and pedal efficiency exceptionally well. Fittingly, this seems like a bike that you could comfortably race Unbound on, then throw some bags on the next month and shift gears towards a bikepacking adventure.

Carry It With You

On the opposite side of the go-fast spectrum, the Assassin offers a number of options for bolt-on accessories. There is a removable seatstay bridge which allows for full coverage fenders to be run front and rear. The frame and fork also have bosses for racks, with the rear capable of carrying up to 15kg, and the front up to 5kg. Add in the two-bolt mounts on each fork leg which can carry another 5kg each, top tube mounts, and three water bottle cage mounts, and you are left with plenty of cargo-carrying abilities.

And if you’re carrying all that cargo, you’ll probably also need some lights–which is why the fork is internally routed to be dynamo hub compatible.

Threaded BB, Dropper Post & Di2 Compatible

Additional frame details extend the bike’s capabilities with optional internal routing for a 27.2mm dropper post, and battery storage for Di2 systems inside the downtube. Both a dropper and Di2 can be run at the same time. You’ll also find a removable front derailleur hanger which allows for 1x or 2x drivetrains and up to 50/34t chainrings up front. A threaded T47 bottom bracket is used, along with 12mm thru axles front and rear.

Campagnolo Ekar Review

This was my first long-term test of Campagnolo Ekar 1×13, and initially, I had mixed feelings. The gear range is just about perfect. With a 38t ring up front and a 9-42 cassette, I was well equipped for some steep climbs in Alabama. There’s even a 10-44t option for even lower gearing which I think would be welcomed by some.

Annoyingly, the current cassette does not play well with certain wheels from other brands–even if you have the right freehub body. This was brought to my attention by Industry Nine after requesting an N3W freehub body so I could run the Ekar Cassette on a pair of Atomik Carbon wheels. The cassette did not work with the Atomik wheels which were built with Berd spokes, though I did just recently test a set of Reynolds G700 wheels with an N3W freehub that worked perfectly with the original cassette. So it can be done, it just depends on the wheelset in question–a safe bet seems to be wheels with straight pull spokes.

The first gen Ekar cassettes have button head bolts on the back of the cassette that will interfere with the spokes on non-Campy wheels. Apparently, there will be a second gen cassette with flat counter-sunk bolts that should remedy the issue, and there will also be an update kit available from Campagnolo to remedy existing cassettes (Campagnolo USA tells us the part number for the update kit will likely be CS-EK100 when available).

The shifting is typically Campy with very a positive feeling and loud clunks for downshifting (loud enough that other riders commented on it, there’s no hiding downshifts to sprint here). Overall, the derailleur seems to be more sensitive to cable tension than its competitors, though it could be just how this bike is cabled.

I initially expected the beautiful carbon cranks to quickly show wear, but in spite of many muddy and icy rides, they still look great.

The brakes have impressive power and modulation, though the lack of much free stroke at all may take some getting used to.

The Shamal wheels are gorgeous and feel surprisingly aero with big tires, but I can’t help but feel that the 21mm internal width keeps the tires from reaching their full potential. I had hoped to try out a wheel with a wider rim to compare, but that’s when I ran into the cassette issue mentioned above. Now that Campagnolo offers the Levante gravel wheel, it seems that it will probably be the option for those wanting to run wider tires on Campy wheels.

Ekar Shift Lever Jamming? Use the Campy Ekar Shift Paddle Reach Adjustment

Initially, I had issues with the shift lever jamming up on the brake lever–you’d shift, and the lever wouldn’t return to its home position. But what started as a major annoyance turned out to be a simple adjustment. There is a hole for a tiny 1.5mm allen wrench on the shift paddle, which allows you to adjust the fore/aft position of the paddle itself. I simply needed to adjust it back a bit to provide some room between the shift paddle and the brake lever, and the jamming issue was solved.

The other concern I have comes from the shape of the hood. For my hands, it leaves something to be desired since there is a pronounced lump right under the base of my palms. After a lot of creative bar tape wrapping with my favorite wide and cushy WTC Supple Lite bar tape, it’s much better. But still not as comfortable as the hoods on SRAM AXS, or Shimano Di2 or mechanical. Depending on your own hand shape and size though, you could have a different experience. But it’s probably worth trying before you buy just in case.

Riding Away

I came away from this review very impressed with the bike overall. I always ask myself during the process if this would be something I would buy with my own money. During the last ride, I was already thinking about which bikes I could sell to make room for the Assassin, so the answer is yes. I would definitely buy this. I would want to test ride the medium beforehand, but I would definitely buy one of the two.

The Assassin isn’t your average gravel ride, and that’s the point. If you want to go fast but still have plenty of room for tires and accessories, the Assassin is up for the job. Just don’t expect to go unnoticed.

As reviewed, the FiftyOne Assassin Ekar 1x build retails for €6,499 (~$6,923). A 2x Shimano GRX build is available for €4,999, and the frameset sells for €3,499.

For the complete tech breakdown of the FiftyOne Assassin, check out our first post here.

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