The Cervélo S3 Disc is claimed to be better than the rim-brake version in pretty much every way. Most importantly, the loss of the rim brake calipers has resulted in a claimed saving of two watts over the standard model
The aero road bike market is being flooded with disc brake models, and on the Cervélo S3 Disc the more powerful stoppers compliment the frame excellently.
While some might argue they’re less aerodynamic, they certainly don’t make the bike feel any less fast but all that speed comes at a cost for comfort.
Cervelo S3 disc: Frame
Although disc brakes are traditionally less aerodynamic than their rim counterparts, Cervélo along with a number of other major bike brands, claim that its disc brake bike is marginally more aerodynamic than the non-disc version.
This, it claims, is because it has been able to improve the S3’s aerodynamics in other areas resulting in a net reduction in drag of a claimed two watts.
Alongside aerodynamics, the other biggest saving is weight, it’s a whopping 40g lighter than the rim-brake version.
The tube profiles have been tweaked slightly to improve aerodynamics, and the fork now features a higher crown to improve airflow behind the front wheel.
Happily, out on the road it doesn’t affect things much and the bike’s handling is still downright agile, and on the my local descents I certainly didn’t feel like I had to mince my way down. Pair these ride characteristics with powerful disc brakes and you’ve got yourself a grin-inducing combination.
The bottom bracket has been fortified and the frame is designed for 12mm thru-axles front and rear adding to the stiffness that can be felt through the frame and negating some of the additional braking forces created by those same discs brakes.
The frame also features Cervélo’s signature BBRight asymmetrical bottom bracket and lightweight, compression-moulded carbon dropouts.
SRAM Red eTap HRD makes up the beating heart of the Cervélo S3 Disc. The wireless shifting is different, and probably not quite as fast as Shimano’s, but it’s not difficult to grasp. Ergonomically, it’s not quite as up to date as Shimano’s Dura-Ace or Ultegra hydraulic systems.
The semi-compact chainset is bigger than the compact option most bikes come with nowadays. But once I adjusted to the difference, the 52 tooth outer ring felt like a good complement to the stiffness of the frame, really letting you turn out some speed on the flats. All of which is complimented by the Enve wheels, which hold their speed nicely.
Along with the flat-mount calipers, Cervélo has opted for 160mm rotors front and rear over smaller 140mm ones for superior heat dissipation and added stopping power. The power of the SRAM disc brakes is excellent, but the modulation and feel isn’t quite as good as Shimano’s newer models.
The tyres are 23mm tyres Conti Grand Sports – at this high price I would expect GP4000s and probably a 23mm tyre fitted up front for aero gains and a 25mm on the rear for comfort and traction.
In fact, I’ve no doubt these tyres play into the rigidity of the Cervélo’s ride with the unforgiving compound, and I’ve previously had to swap them off a Cervélo R5, and found that once replaced the bike’s ride quality improved significantly. It’s an underwhelming choice considering the price of both bikes.
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The saddle is a Fizik Antares with a flat profile lets you get low on the bike rather than being forced into an upright position. It’s not very forgiving though, and after 100km-plus days over the winter period you really notice it beneath you.
The Cervélo S3 Disc comes with its proprietary Aero AB04 bar, which is compatible with a normal stem. However, I found the bars, especially when partnered with the large hydraulic SRAM shifters, forcing me long and low on the bike. On particularly long rides, it’s a position I found difficult to maintain, with aching in my shoulders and neck.
However, the bars do have a nice shape, especially the round bend which is very comfortable to rest your hands on. Plus, through the use of a standard stem, the Cervélo S3 has the crucial advantage over many other aero bars, such as that on the Trek Madone and Canyon Aeroad, that you can adjust your stem length easily.
It’s worth pointing out that you will have to purchase a special out-front Barfly mount for this bar if you want to ride with your cycling computer in an aerodynamic way.
While aerodynamic advantage is very difficult to quantify in ride feel, the stiffness of the frame is very obvious. Every pedal stroke courses through the frame, pushed forward thanks to that stiff bottom bracket.
It really feels like every part of this frame is built to drive the bike forward. Very cliche I know, but nothing seems to be wasted here and I’d go as far to say that this is one of the fastest bikes I’ve ever ridden.
This is buoyed on by the Enve SES 5.6 disc-specific wheels which have a 63mm rim depth on the rear and 54mm on the front and they’re super stiff and feel very fast.
But with this stiffness does come rigidity and that means harshness is added to the ride which, to some extent, has come to be expected from aero bikes. The Cervélo S3 Disc is jarring on the rougher roads around London and the South East, especially in the winter time.
As with most disc brake bikes I use, I find they complement a fast bike, especially one with the handling characteristics of the S3 Disc, beautifully
As the smaller sibling to the Cervélo S5, the Cervélo S3 is designed to keep all the ride characteristics of its GC contending older stable mate and pair them with a more forgiving geometry. However, the geometry changes haven't made the S3 feel slow or cumbersome, and it's exceptional fast and seriously stiff. But this itself is an acquired taste, and there's a rigidity to the frame that would be tough to live with day in, day out.