Specialized Crux
Specialized has launched a new Crux, turning the former cyclocross bike into a fully fledged gravel racer with improved aerodynamics, tyre clearance and handling.
Once called the gravel Aethos for its resemblance to Specialized’s round-tubed climbing bike, the fifth generation Crux mimics watt-saving tricks from the Tarmac, the brand’s all-round road race bike. These changes reflect the diminished importance of cyclocross and the increasing professionalisation of gravel racing – the winning speed of Unbound 200, the world’s most prestigious gravel race, has gone up by an average of 6kmh in four years.
Although heavier than before, the S-Works Crux remains very light for a gravel race bike. Specialized claims 800g for a frame and 7kg for a complete build. Despite the introduction of internal cable routing, the frame is still compatible with mechanical groupsets, but only 1x single chainrings up to 52 teeth. Specialized had added UDH compatibility to the outgoing model mid-cycle, which the new bike retains.
‘We had three main priorities with the project,’ says road and gravel category leader Alex Jerome. ‘We wanted to make the bike faster, focused on aerodynamics and weight, while retaining the ride quality and compliance of the Crux 4.’
Beneath the range-topping S-Works Crux at £11,999 / $14,000 / €13,999 / AU$19,500, Specialized has introduced a new build tier called S-Level. Costing £8,799 / $10,500 / €10,499 / AU$14,900, the Crux S-Level features a heavier frame, lower-spec wheels but identical groupset and finishing kit. The rest of the range hierarchy is as before, starting with the £3,999 / $4,500 / €4,499 / AU$6,200 Crux Comp. An S-Works Crux frameset costs £5,249 / $5,800 / €5,799 / AU$8,500.
What’s changed?
- Every tube shape for 15.2 watts greater efficiency at 45kmh
- Weight is up slightly
- Tyre clearance is now 55mm
- Longer, slacker geometry
- Integrated and internally routed front end
- What hasn’t?
- Overall stiffness and compliance
The standout claim Specialized makes about the new Crux is that it is 15.2 watts more aerodynamically efficient than its predecessor at 45kmh over a spread of wind angles. The brand measured this in the wind-tunnel using a moving leg mannequin, similar to Giant’s Grishcha 2, a method it says produces the most accurate and repeatable aero data.
Had Sofia Gómez Villafañe ridden the Crux 5 instead of the Crux 4 at the 2025 Unbound 200, Specialized says she would have finished 9min 58sec faster (assuming the same course, conditions and power output). Specialized male gravel pros, including Ian Boswell and Mads Würtz Schmidt, would have saved less time (in the region of seven minutes) due to shorter race durations.
Specialized made these calculations using its race simulation tool, having also collected data on gravel 'surface roughness', which it says affects rolling resistance, energy loss, fatigue and speed, from black boxes placed under racers' saddles. These simulated time savings are impressive on the face of it, but the Crux 4 was not aero-optimised. It's also likely that Specialized's competitors have progressed too.
Nonetheless, Specialized claims the new Crux is faster in its simulations than its closest competitor, which has 45mm tyre clearance. It wouldn't name the bike, but it sounds a lot like the Cervélo Aspero-5, an aero gravel bike styled on the brand's S5 aero bike. If true, that's no mean feat. Specialized hasn't had the opportunity to test the Crux against fast-looking prototypes from Ridley and Factor.
Half of the Crux's improvement in aerodynamic efficiency comes from the frame, fork and seatpost, 30% from the new Roval Terra Aero CLX wheels and 20% from the new Roval Terra cockpit, according to Specialized.
'Every tube on this bike is completely different from the more traditional round tube aesthetic of Crux 4,' says Jerome.
In general, Specialized has squashed the round shapes into D-shaped, truncated airfoils, albeit relatively shallow ones. The fork is now bladed and the new head tube uses a version of the Tarmac SL8's 'Speed Sniffer', a stretched, lipped leading edge.
'It's less pronounced than on the Tarmac to save weight,' adds Jerome. 'That's a critical piece for us, as are the airfoils on the fork legs, seatstays and chainstays.'
From a separate handlebar bar and stem and exposed cables, the S-Works Crux and S-Level move to the integrated Roval Terra bar-stem and internal cable routing. Identically to the Tarmac SL8, this passes cables into the frame through the upper headset bearing. This isn't the most user-friendly way of hiding cables, so some may be pleased that it doesn't trickle down to the cheaper Crux builds, which have two-piece cockpits.
Claimed to be the lightest gravel cockpit at 298g, the Terra features a five-degree backsweep to help you tuck in your elbows while holding the tops, a shallow 107mm drop and 12° flare for easier transitions between the hoods and drops. It's said to be 78% less stiff than the Rapide cockpit designed for the road.
Still lightweight
The new aero profiles bring extra surface area, potentially equalling more material. Specialized says it succeeded in minimising weight gain – a painted size 56cm S-Works Crux frame without hardware weighs 789g up from 727g previously and a complete bike with the lighter Roval Terra CLX wheelset comes in at 6.9kg, according to the brand. The rest of the range uses the second-rung Fact 10R frame. This is now claimed to weigh 897g, 72g heavier than before.
R&D aerodynamics engineer Lio Bardina says low weight is even more important on gravel than on the road due to rolling resistance: 'It is almost an order of magnitude higher on gravel than it is on the road. Your force to overcome rolling resistance is multiplied by the weight of your system. So system weight actually has a much larger impact on gravel bikes than it does on road bikes because that coefficient of rolling resistance is much higher.'
And although gravel is getting faster, it's still slower than road cycling, making aerodynamics a bit less influential.
'That is not to say aero still isn't the biggest force, because it is, but not by nearly as much,' Bardina says. 'When we talk about how many grams we're willing to accept on a chassis for each watt improvement, that grams-per-watt number is much lower on a gravel bike than a road bike.'
To achieve this, Specialized employed what it calls flow state design.
'It's a process of iterating circularly between aero performance, FEA [finite element analysis – a way of virtually stress-testing a frame] and ply-by-ply analysis,' says Doug Russell, the head engineer on the Crux.
'We then feed that back into subtle shape changes to ensure we're not making a geometry, frame layout or tube junction that's going to cause a high-stress zone requiring reinforcement or pose manufacturing challenges. It helps achieve a frame that's super-lightweight and aero at the same time.'
In the early concept phase, Russell says his team made three or four hybrid frames, comprising parts of the old Crux and Tarmac SL8, to isolate different parts. One was a Crux 4 frame with a Tarmac SL8 seat tube and seatpost to examine their aero benefit. Another had a mainly SL8 front triangle bonded to the Crux's chainstays and bottom bracket area, so he could test it with gravel wheels and tyres to discover their effect on drag.
The Crux's minimalist frame would have also aided Specialized's weight target. It gains a few mounting points on the top tube and fork legs, yet it lacks internal frame storage, a feature even some gravel race bikes now incorporate.
As comfortable as possible
Gravel race bike designers appear to be acknowledging that stiffer isn't always better off-road. Specialized is no different.
'When people are doing 8- to 10-hour gravel races, we want to make sure they're as comfortable as possible,' says Jerome. 'We wanted to retain the Crux 4's compliance.'
The switch from the more structurally efficient (in terms of stiffness-to-weight ratio) round tubes posed problems here. Cylindrical seat tube and seatposts, for example, flex more than the aero shapes Specialized wanted to import from the Tarmac SL8. To compensate, Specialized added compliance to the frame.
'We still achieve the same amount of deflection and compliance at the saddle with a more aerodynamically beneficial shape,' Jerome says. 'For every single size, we do the same amount of detail work in terms of ply-by-ply, ensuring the ride characteristics and compliance and stiffness numbers feel really similar in each frame size.'
Slacker and longer
Specialized has also squarely focused the new Crux's geometry on gravel racing. Before, it doubled up for cyclocross. The front end remains aggressive, and it's now longer, lower and slacker for better handling on technical terrain.
'We lowered the bottom bracket by six millimetres to account for the fact that when you're riding gravel, you've got bigger tires, you want to sit in the bike a little bit more,' Russell says.
'Compared to a cyclocross bike, which has a historically pretty high bottom bracket, as the Crux 4 still had, we wanted to bring the bottom bracket down for more stability when you're on long, fast gravel descents or any kind of rough terrain.'
The seat tube angle is also steeper by half a degree on every frame size. 'That gives you that more racy position that most people are trending towards now, a little bit more forward for aerodynamics and power,' he says.
The larger frames are longer too. Reach increases by 3mm in size 56, 7mm in size 58 and 10mm in size 61.
'That's where the increased wheelbase and stability are coming from,' Russell says. 'On the smaller ones, we didn't want to increase the reach at all because we do still see a fair number of riders at the smaller end of the spectrum running a pretty short stem to get their fit right.'
'But we did see many of the riders on the bigger frame sizes still opting for quite long stems for a gravel bike, say 120mm or 130mm. So giving them a little bit more reach helps keep the stem length shorter for better handling.'
The Crux's tyre clearance has stepped up significantly from 47mm to 55mm, the equivalent of a 29x2.2in mountain bike tyre, as requested by the Specialized Off-Road racing team. Although Jerome expects the team to ride the 700x50c Specialized Tracer most of the time, they and consumers have more choice.
Making space around the front wheel was relatively easy. Unofficially the old Crux fork could accommodate a 29x2.1in tyre. Slightly widening and slimming the fork legs was all that was required.
Broadening rear wheel clearance while keeping chainstays to 425mm for reactive handling was more difficult. It required 'countless hours' of work on the bottom bracket area of the bike.
'It is one of the more technically challenging areas of the bike if you want chainring clearance up to 52 teeth, 55mm tyre clearance and to maintain our stiffness targets,' says Jerome.
The smaller bottom bracket area Specialized has used since the Tarmac SL6 did help, according to Russell.
'The curved walls of this compact shape are less likely to flex inwards than flat walls of an oversized, square shape, requiring less material to reinforce them. That saves weight and makes more room for the tyre and chainring,' he adds.
In addition, the dropped chainstays run straight for as long as possible to keep weight to a minimum before curving outwards around the widest point of the tyre. The carved-out seat tube also wraps around the rear wheel.
