We’ve already been impressed by the C and R series disc bikes, but with the S3 this is the first time we get to see how discs have been integrated into a pure aero race bike.
Cervélo makes some bold claims that during wind tunnel testing, into a 40kph headwind, there’s no difference between the rim-braked S3 and the S3 Disc. When the wind comes in from the side, where rivals see a loss in power, Cervélo recorded a 2-watt gain.
Now, 40kph wind tunnel tests are fine for a minority of elite riders, but some of the other stats are of more use to us mere mortals. The frame is 40g lighter over the standard S3, the fork is down 50g, head tube stiffness has increased by eight percent and bottom bracket stiffness by nine percent. As disc groupsets are heavier, this all evens itself out.
I first tested the S3 Disc on Spain’s super-smooth blacktop — aside from a 10km gravel diversion after relying too heavily on my Garmin’s directions. The 23mm Continental tyres felt great, especially when spread out closer to 25mm on the broad ENVE SES rims. Back home, the 23s underwhelmed on our not-so-well maintained roads. The advent of discs has freed up space for bigger tyres, so I wish Cervélo had used it.
The ENVE rims are oblivious to forces from crosswinds, giving confidence at speed Robert Smith
Ultegra Di2 performs as it should — smooth, accurate and chatter free — the compact 52/36 FSA chainset and 11-28 cassette offer a wide, usable range, and at the top-end the 52/11 gives you plenty of scope to exploit the S3’s speed potential.
The bike feels lively and responsive and the short, 100cm wheelbase keeps it agile. Yes, it’s firm, but never wearing. Good contact points such as Fizik’s Antares saddle and the buzz-killing, deep-winged aero bar help counteract the firmness.
The Shimano 805 brakes offer excellent control. They suffer from occasional noise due to the downgrade from IceTech rotors, which cope with heat better than standard Shimano rotors.
FSA SL-K stem holds the own-brand aero handlebar Robert Smith
Climbing is usually where you lose out on an aero bike, but the S3 feels as capable as its R series siblings, despite carrying more weight. The stiffness in the chassis, bolstered by thru-axles and stiff hoops, makes the S3 feel great when attacking out of the saddle, and longer in-the-saddle climbs are rewarding thanks to the lightness of responses needed.
The S3 Disc shows promise, but on a bike costing over £6,000, there are a couple of downgrades too far, with the lower grade tyres and big standard rotors looking out of place on what is a well-sorted bike.