Giant Fathom 2 review

The attractively-specced Giant Fathom 2 looks like a hot ticket on paper, ticking almost all of the must-have boxes. It’s got a dropper post, a 1x Shimano drivetrain, big disc rotors and a 120mm travel fork. The fact that it also looks the part really is the icing on the cake.

The bike’s 650b wheels are clad in 2.4in-wide trail rubber that come setup tubeless from the factory – bridging the gap between plus- and standard-size tyres. Because the bike isn’t missing any key ingredients, I had high hopes for its on-trail performance.

Giant Fathom frame

The Fathom is built around Giant's own ALUXX SL aluminium tubing.

There’s provision for a front mech on the bike if you’d like to add more gears, and the cables are routed internally through the down tube, exiting just above the bottom bracket. Here, they continue their journey along the underside of the chainstays to the mech and brake caliper.

Unusually, the bike’s seatstays join the seat tube lower than the top tube, which Giant claims helps to increase the bike’s bump-absorbing ability and make the back-end feel smoother on rough terrain.

The rear wheel is attached with the Boost QR 141 axle, which replaces a standard 12mm Boost axle in favour of a quick-release system.

There are two bottle cage mounts — both inside the front triangle — but the stock dropper post on my large test bike fouled the seat tube bottle cage mount — stopping it from being fully inserted.

There's also a standard, tapered head tube and a tapered fork.

Crunch the numbers and it’s clear that Giant’s intentions are a little mixed. Giant states that the bike’s geometry is trail-friendly, but there are some measurements that surprised me.

For the size large, a 444mm reach is a little on the conservative side, as is the 1,153mm wheelbase. Likewise, the 425mm chainstays suggest that the bike is designed to be more playful than Giant initially let on.

Surprisingly, Giant has settled on a 67-degree head angle and a 45mm bottom bracket drop (with an off-the-floor height of 315mm), figures that I’d normally expect to be accompanied by longer reach and wheelbase numbers.

Giant Fathom 2 kit

The Fathom’s party piece has to be its headline spec.

The Maxxis Ardent tyres are setup tubeless from the factory and are wrapped around 30mm internal-width Giant AM 650b rims.

The bike has a 145mm travel Giant-branded dropper post, a 1x10 Shimano Deore drivetrain and Suntour SF19-Raidon 32 fork with 120mm of travel.

Although the Shimano drivetrain isn’t a range-topper, the Shadow+ Deore mech gets a clutch, and I know from experience that it’ll last.

The Shimano Deore 10-speed cassette’s gears range from 11 to 42 teeth which, when mated with the 30t narrow-wide-style chainring on the Praxis Cadet cranks, should offer a wide enough gear range for most trail scenarios.

Stopping is taken care of by Tektro HDM discs that run a 180mm front rotor and a 160mm rear.

Turning to Suntour for suspension duties probably saves Giant some cash over Fox or RockShox alternatives but, on paper at least, the fork doesn’t balk on features when compared to what the big brands can offer.

Giant Fathom 2 ride impressions

Excited by the spec and the bike’s overall look I hopped onto the Giant with lofty expectations.

The Fathom’s beefy construction made itself apparent fairly early on during the testing process. While the taut frame means you feel like you’re getting almost every watt of power you put in transferred to the rear wheel — and it accelerates rapidly when you really get on the gas — the stiff back-end can beat you up when things get bumpy.

Pedal into a rough section of trail — whether going up, down or along the flat – and the Fathom struggles to maintain its forward momentum, not absorbing the chatter or rolling over bumps as comfortably or as easily as some of the other bikes might.

That means more rider fatigue in the long run when you’re trying to maintain a decent pace, which is less than ideal on longer trail rides.

It's not all bad though, and, along with that super-efficient power transfer, the stiff frame also makes the Fathom feel relatively rapid and responsive when you’re letting gravity do the work. It reacts well to aggressive flicks and hard pushes in turns give a feedback-rich, accurate feel when you most need it.

The pin-point handling does mean you need to work relatively hard to keep the bike in check and under control when tackling really rough sections of trail though.

However, the Fathom’s overall comfort doesn’t just come down to the feel through the frame. The Suntour fork isn’t the most sophisticated unit out there and required more air pressure in the spring than prescribed to help it maintain its ride height when descending.

Run the fork too soft and it can dive through its travel too rapidly. With the extra air pressure added, the Fathom’s dynamic geometry is better preserved when it most matters.

The obvious trade-off for this increased mid-stroke and end-stroke support is a reduction in compliance and suppleness on a fork that’s already relatively reluctant to get moving into the beginning of its stroke anyway.

While the Fathom’s geometry is by no means extreme, it felt decently proportioned on the climbs and the descents. There’s enough room for things to feel stable while ascending, but the steeper 67-degree head angle and 625mm top tube numbers, when combined with a relatively short 444mm reach, didn’t convince me that the benefits they bring while climbing outweigh the pitfalls when you’re giving it some welly on the descents.

Once I’d accepted that it doesn’t provide an inherently comfy ride, I felt like I could happily ride this bike all day long over pretty much any terrain and without major issues.

The added flow a dropper adds (thanks to not having to stop to drop your seatpost manually) is a real plus on a bike of this price too. Over undulating terrain its movement is smooth and precise and the 145mm of travel proves to be more than adequate for pretty much all trail riding situations.

The Giant’s spec certainly stands out in a crowd of compromises. The Shimano Deore drivetrain proved to be faultless during testing and the 11-42t cassette, when mated with the 30t chainring, had more than enough gears for even the weariest of legs or steepest of climbs.

It’s an impressive feat that Giant has managed to use Shimano kit across the drivetrain (except for the cranks and chain), with other brands speccing cheaper cassettes to help reduce costs.

It’s also refreshing to see the bike come setup tubeless out of the box and the weight savings are noticeable – 12.76kg without pedals.

The Maxxis Ardent tyres also strike a good balance between grip levels and rolling resistance, particularly in their tubeless guise, but as soon as conditions become particularly extreme, especially very muddy, grip levels do significantly drop off.

The Tektro brakes were certainly the most lacklustre component on the bike, not bringing much power or bite.

If you’re riding gentle terrain, their performance isn’t terrible by any means, but as soon as the going gets a little steeper or the speed picks up, it’s possible to be caught off-guard when coming into turns that require serious speed to be scrubbed off relatively quickly.

The Giant is an impressively-specced ride with fewer compromises on paper than its competitors.

Hit the trails and the reality of its performance is slightly different to the numbers and parts written on a spreadsheet, thanks to the bike’s inherent harshness and overall geometry.

It’s a bike that’s comfortable almost everywhere though, and with a few choice upgrades – such as a new set of forks or brakes – it could be enhanced dramatically.

Giant Fathom 2 geometry

• Size tested: L
• Head angle: 67 degrees
• Seat angle: 73.5 degrees
• Top tube: 62.5cm
• Seat tube: 48cm
• Chainstay: 42.5cm
• Wheelbase: 1,153mm
• Bottom bracket height: 31.5cm
• Reach: 44.4cm

For a little more

Giant Fathom 1

• Price: £1,249 / US$1,470

Splash a little extra cash and you’re rewarded with Shimano brakes, an SLX drivetrain and an upgraded fork, which should perform better.

For a little less

Giant Fathom 3

• Price: £899

If you’ve got slightly less to spend the Fathom 3 isn’t a bad bike, but it does forego the luxury of a dropper post. You still get the same forks and brakes, though.