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 S3 traces its lineage back to the Cervélo Soloist, a machine regarded as a pioneer in aero road bike design. The first S3 was launched back in 2009 and was famously ridden by Thor Hushovd en route to a green jersey in the Tour de France. The latest edition sees the S3 adapted into a disc-brake machine.
Although disc brakes are themselves less aerodynamic than their rim counterparts, Cervélo claims that the S3 disc is marginally more aerodynamic than the non-disc version.
The reason is that fitting disc brakes has allowed Cervélo to make the S3 more aerodynamic in other areas, resulting in a net reduction in drag of a claimed 2W.
Cervélo is also saying that its new bike is stiffer than the old model. The head tube and bottom bracket are apparently eight per cent and nine per cent stiffer respectively, hopefully improving handling and power transfer, while the frame is also 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.
The bottom bracket has been fortified and the frame is designed for 12mm thru-axles front and rear. A welcome addition, as although heavier than quick release skewers, the 12mm thru-axle is much stiffer, translating to less torque steer under the heavy breaking forces discs can exert.
The frame also features Cervélo’s signature BBRight asymmetrical bottom bracket and lightweight, compression-moulded carbon dropouts.
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The Cervélo S3 Disc comes with thru-axles (12mm front and rear) and flat-mount calipers, both of which are steadily becoming the standard for the disc-equipped road market. Cervélo has also opted for 160mm rotors front and rear for superior heat dissipation over smaller 140mm rotors.
Despite being named the ‘Cérvelo S3 Disc Ultegra Di2‘ this only really applies to the derailleurs and cassette. The chain is KMC, the chainset FSA. The disc rotors are the Shimano RT-86 and on a bike of this price and spec, I have come to expect Shimano’s higher spec and superior cooling RT-99 rotors.
The choice of FSA chainset is not to skimp – it is to enable the Cervélo S3 Disc to have 405mm chainstays. Shimano currently recommends disc-brake road bikes have chainstays of 415mm, which is longer than most race bikes. Longer chainstays creates more trail and can make a bike feel sluggish and less agile.
The FSA chainset allows Cervélo to have a 5mm offset, optimising the chainline and allowing for the shorter stay. It’s a good design feature that I would like to see in other disc brake bikes.
The tyres are 23mm tyres Conti Grand Sports – at this high price, these really are underwhelming and I would expect GP4000s and probably a 25mm width rear fitted.
The saddle is a Fizik Antares R5 – it’s good quality and nothing to complain about. Most people swap to their preferred saddle on purchasing, so I’m happy to see the spec budget spent elsewhere.
One of the coolest bits of kit on the Cervélo S3 Disc is the proprietary aero bar. It’s worth pointing out that you can purchase a special out-front Barfly mount for this bar too. I like the shape of the bar and the crucial advantage over many other aero bars, such as that on the Trek Madone and Canyon Aeroad, is that you can adjust your stem length. The Cervélo uses standard stems, making life much easier if you want to tweak your fit.
Adding disc brakes does not appear to have diminished the wind-cheating prowess of the S3. The Cervélo S3 Disc feels quick.
Those coming from non-aero bike with a standard round handlebar will instantly appreciate the watt-saving advantage on offer here. You can feel it. The ENVE wheels aid in this regard. However, I did detect significant flex in these wheels, especially in the rear.
Disc brakes haven’t muted the handling. A common problem with disc-brake equipped road bikes is the requirement for longer chainstays. Having a longer trail often results in the bike feeling a little sluggish, lacking a sense of urgency in the rear end.
By using the FSA chainset with a 5mm offset to ensure the correct chainline, Cervélo has engineered a 405mm chainstay rather than the 415mm recommended by Shimano. The result – the S3 Disc feels like an S3, just with far greater stopping power.
Comfort isn’t bad either. The S3 Disc doesn’t beat you up on long rides, which I am going to attribute to the redesigned seatpost and once-signature skinny seatstays.
Last year’s S3 and S5 featured a fully bladed seatpost, but the new S3 Disc has seen this updated to a design that can flex at the top, offering greater compliance.
A niggle I did encounter while testing was flex in the steerer tube, causing the stem to tilt slightly. This flex when pressing hard on the handlebars was disconcerting, but was instantly fixed by fitting a different expanding headset.
The ENVE wheels are decent and their aerodynamics certainly enhance the bike, but the hubs are noticeably inferior to the ENVE and Chris King hubs found on dedicated ENVE wheels.
Unfortunately, this is where the Cervélo S3 falls down. For £1,000 less you can get a Canyon Aeroad CF SLX Disc with the new Dura-Ace R9100 groupset. The equivalent Ultegra Di2-equipped Canyon will set you back £4,499.
An Ultegra Di2-equipped Specialized Venge Vias is cheaper too, at £6,000 RRP. Further comparison of the exact specifications of these competing bikes does not bode well for the Cervélo either. With the Canyon and Specialized you get higher-spec Shimano rotors and better tyres.
The Cervélo S3 Disc is a great-looking bike and Cervélo has done a brilliant job of retaining the short stays, handling and aerodynamic prowess of the original. Despite this, the price really is hard to justify when compared to offerings from rival brands and small details on the spec, such as the tyres, hubs and headset, let the overall bike down.