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Cannondale F-Si Carbon 3 review

Fast, composed and damn-good looking, Cannondale's F-Si Carbon 3 proves the hardtail concept is anything but dead

Cannondale F-Si Carbon 3
(Image: © Desmond Louw)

Our Verdict

The Cannondale F-Si Carbon 3's stealthy looks and impressive trail manners make it a great choice for anyone looking for a dust-busting hardtail


  • Stealthy aesthetics
  • Impressive ride quality
  • Telepathic handling dynamics
  • Decent spec level


  • Could be lighter

The rise of the lightweight full-suspension mountain bike - and gravel bike to a certain degree - has quickly placed the hardtail under threat. In fact, at one stage, many pundits predicted a full-scale mass extinction but the hardtail has managed to hang on, albeit it’s now on the endangered species list. Fact is, there is something intrinsically pure about riding a hardtail mountain bike - perhaps it's the unsullied, feedback-rich riding experience or the lively trailside manners? 

In recent years, the hardtail has become a far easier bike to live with and tame, boasting improved refinement levels thanks largely to contemporary frame design and advances in carbon fibre layering techniques. We've even seen a resurgence on the UCI Mountain Bike World Cup stage where certain professional riders are eschewing the full suspension in favour of a hardtail - track dependent, of course. 

We recently spent a month putting Cannondale's F-Si Carbon 3 hardtail through its paces in the Western Cape, South Africa. Considered by many as the mountain bike trail mecca of the world, this would prove the ideal setting in which to test its mettle and put its trailside manners to the test.

Design and geometry

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Cannondale F-Si Carbon 3

If Darth Vader bought a bike it would undoubtedly be this Cannondale F-Si (Image credit: Desmond Louw)
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Cannondale F-Si Carbon 3

A collection of gloss-black decals offset the matte paint finish to create a more dynamic and complex package (Image credit: Desmond Louw)
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Cannondale F-Si Carbon 3

A Fabric Scoop perch ensures comfort when things get rowdy (Image credit: Desmond Louw)
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Cannondale F-Si Carbon 3

An integrated seatpost binder helps reduce trail chatter and improve ride quality (Image credit: Desmond Louw)

It's difficult to dispute the stealth, almost Darth Vader-like visage of the Cannondale F-Si. Onlookers will find it hard to tell it apart from the range-topping World Cup model such is its refinement and pomp - it really is an impressively designed machine. We quite like the way Cannondale has played with the balance between gloss and matte paint surfaces - not only has this added a touch of complexity to the visual package, the subliminal monikers make it look more like bonafide trail weapon and less like a rolling billboard.

In terms of geometry, the F-Si represents a bold move by Cannondale to make it more focussed and easier to tame on the trails than its predecessor. As such, it utilises a 69-degree head angle complete with 55mm fork offset, shorter 427mm chainstays and an integrated seatpost binder which helps reduce trail chatter.

Cannondale’s Ai asymmetric frame design utilises a 6mm drivetrain offset which helps promote not only a truer chain line but also caters for 2x chainring configurations and improved tyre clearances. Those with a keen eye will also notice the revised frame design. Here thinner seatstays and tapered chainstays form part of Cannondale's 'Proportional Response' tubing philosophy - this blueprint has allowed Cannondale to keep the ride quality uniform across the sizing spectrum.

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Cannondale F-Si Carbon 3

The new Lefty Ocho fork utilises a standard, single-crown tapered steerer which means a conventional stem can be used. Ride quality is naturally plush and tunable (Image credit: Desmond Louw)
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Cannondale F-Si Carbon 3

A mixed 12-speed SRAM Eagle (NX/GX) rear assembly (10-50T) and Truvativ Stylo 6K DUB 34T crankset make up the drivetrain (Image credit: Desmond Louw)
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Cannondale F-Si Carbon 3

Stopping power is taken care of by SRAM's Level T hydraulic brakes (Image credit: Desmond Louw)

Components and build

The Cannondale F-Si Carbon 3 pictured here is constructed from the brand's standard-modulus carbon fibre so while it's not as light as the 900g Hi-Mod World Cup frame it still weighs in at a paltry 1100g.

In terms of specification, there's an array of mouth-watering kit on display - most notable of which is Cannondale's new 100mm Lefty Ocho fork. Unlike the previous-generation Lefty 2.0, the Ocho utilises a standard, single-crown tapered steerer and conventional stem. There's also a less-complicated cable-operated lockout system which trumps the hydraulic versions of old based purely on the ease of which it can be tuned and maintained.

Despite its positioning in the lower rungs of the carbon range, it still comes specced with a full SRAM Eagle groupset - in this instance, an assortment of NX (cassette) and GX (derailleur, chain and shifter) bits. These parts - while heavier than their more expensive silver-, gold- and oil-slick-coloured siblings - provide just as much precision and reliability on the trails. 

The balance of the build is made up of a carbon seatpost, an alloy handlebar and stem, a Fabric Scoop saddle, SRAM Level T hydraulic brakes and Stans Crest Mk 3 rims shod in Schwalbe Racing Ray (F)/Racing Ralph (R) rubber. The total weight of this particular build is 11.08kg with Shimano XT pedals.

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Cannondale F-Si Carbon 3

It's a case of point, shoot, repeat - the Cannondale F-Si is up for anything (Image credit: Desmond Louw)
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Cannondale F-Si Carbon 3

Stiff and relatively light, it makes quick work of the climbs and does a decent job eating up the miles on the flats (Image credit: Desmond Louw)
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Cannondale F-Si Carbon 3

The relaxed geometry has transformed the Cannondale F-Si into a willing and appreciably agile trail slayer (Image credit: Desmond Louw)

Ride, handling and performance 

It's fast, no question. Whether it's hammering up a climb out of the saddle, cruising along gravel roads or sending it down hair-raising descents, the Cannondale F-Si is up for the task. Much of the bike's newfound trail prowess comes as a result of a complete design overhaul. Using the contemporary long, low and slack geometry blueprint and combining it with the company's new carbon layup techniques - the F-Si has come out the other end a far more accomplished bike than before.

The most notable improvement is without a doubt the ride quality. Thanks to a new integrated seatpost and SAVE 'Micro-Suspension Flex zones' Cannondale has managed to weave together one of the most impressive-riding hardtails on the market. 

In this guise, it's obviously not the lightest model in the segment but it's still feathery enough to attack the climbs - especially when you consider throwing rider weights and the 34 x 10-50T gear ratios into the mix. Power transfer is immediate, whether you're seated or out of the saddle, which heightens the sense of speed. At 62kg, I was able to out-climb better specced - read lighter - full-suspension bikes regardless of the terrain and, while I thought I'd be on the receiving end come the technical descents, the plush Lefty Ocho fork, relaxed geometry and grippy Schwable tyres gave an added sense of composure and assurance to push just that much harder.

Speaking of tyres, the standard-issue 2.25in Racing Ray/Ralph front/rear combo offered a superlative mix of pliancy, grip and performance across all terrain types. And, despite lacking dedicated SnakeSkin sidewall protection, no punctures were had, and this in Cape Epic country.

The only area that could be better - and this is nitpicking - is the stopping power. Don't get me wrong - the SRAM Level T brakes are powerful, responsive and modular but on longer descents that require trail braking and regular inputs, they have a propensity for fading. Trading the standard 160mm front rotor for a bigger 180mm disc should solve this.

Cannondale F-Si Carbon 3

Apart from the SRAM Level T brakes that have a tendency to fade on really long descents, the Cannondale F-Si Carbon 3 is hard to fault  (Image credit: Desmond Louw)


Cannondale's F-Si Carbon 3 proves there is still space for a hardtail mountain bike in a full-suspension-obsessed world. The F-Si is a lively bike - it's tame enough to rein in when things get rowdy but there's still a sense of ferality which keeps you on your toes.

Of course, you can never ignore the fact a full-suspension bike will always be notably faster on bumpier, more corrugated terrain as well as over multi-day stage races such as the Cape Epic where body preservation is the name of the game - but for single day assaults, there's nothing more liberating than threading the F-Si through a ribbon of sphincter-clenching singletrack.

Add to that its superb ride quality (for a hardtail), drop-dead gorgeous looks and a handsomely appointed component list and the Cannondale F-Si makes a serious case for itself. Especially when you consider the cheaper upkeep thanks to a paucity of pivot bearings, bushings, and a rear shock.

The Cannondale F-Si Carbon 3 will suit anybody from the semi-competitive mountain biker to the roadie looking at crossing over to the world of gravel and dirt. Heck, it could even double up as a pseudo-gravel bike if you fit a larger chainring, drop bars and narrower tyres.

Test conditions

  • Temperature range: 25-35 degrees 
  • Weather: Hot, windy
  • Trail: Tygerberg Mountain Bike Club Trails, Cape Town, South Africa
  • Route:  Singletrack, gravel roads 
  • Mileage: 511km 

Tech spec: Cannondale F-Si Carbon 3

  • Price: £3,099
  • Frame: BallisTec Carbon
  • Size: Medium
  • Weight: 11.08kg 
  • Groupset: SRAM Eagle GX/NX
  • Crankset:  Truvativ Stylo 6K DUB 34T, 10-50T SRAM NX cassette
  • Pedals: Shimano XT
  • Wheels: Stans Crest MK3 29
  • Tyres: Schwalbe Racing Ray/Ralph front/rear (2.25, 29er)
  • Brakes: SRAM Level T, 160mm front/rear rotors
  • Bar/stem:  Cannondale 2, 760mm bar/Cannondale 3 31.8mm, 7-degree stem
  • Seatpost:  Cannondale 2, Carbon, 27.2 x 400mm
  • Saddle: Fabric Scoop Flat Elite

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