Cervélo S3 Ultegra Di2 review

This article originally appeared on BikeRadar

Cervélo's S3 is a high performance hybrid that pulls front-end aero cues from its S series bikes but comfort-boosting rear features from the R series machines. The result is an effortless distance machine that's deceptively quick and closer cost competition to mainstream brands than you might expect.

• Highs: Impressively comfortable, efficiently fast aero all-rounder
• Lows: Low grade rolling stock, ugly Di2 installation
• Buy if: You want an ultra-efficient yet comfortable distance machine

While the sloped top tube and rearward diminishing tube tapers of the S3 create the appearance of a tall front end, it's actually very closely matched to most other aero road bikes in terms of head tube length in comparable sizes.

It's not as radically aero as Cervélo's P5 and S5 bikes: the seat tube just has a partial wheel hugger cut out rather than being offset back around the wheel, the down tube isn't ‘notched' behind the fork to drop it right on top of the tyre and you don't get top loading internal cable routing.

The main tube profiles – including bottle shrouding bulge and flush fit seat clamp for the same Cervélo aero seat post – are very similar though. Apart from a head tube that's 8-20mm taller than the S5, geometry is virtually identical too and the brakes are mounted front of fork and shrouded by shaped rear seatstays in the same way.

You get the same Cervélo developed BBright oversized, asymmetric bottom bracket design with reduced friction cable guides plus similar full carbon fork and full carbon dropouts too.

While the frame inserts are swappable for Di2 or conventional cables, the Di2 battery is just bolted to the belly of the bike rather than being mounted internally. It's because there wasn't an internal option that fitted when the S3 was designed, and Cervélo assures us it doesn't significantly affect aerodynamics, but it's definitely an eyesore on an otherwise very slick chassis.

We're used to seeing the boxy machined and hollowed out crank arms of long time collaborators Rotor on Cervélos though – so no surprise it's Rotor's 3DF crank and ‘pro compact' 52/36t rings turning the Ultegra Di2 gears. 3T supplies the well matched cockpit while Fizik sort the seating.

While the Mavic Cosmic Elite S wheelset looks poor value and less aero advantageous compared to Zipp and home brew carbon wheels on the S3's Boardman and Giant test companions, weight and responsiveness are surprisingly similar. The matching Yksion Comp tyres definitely feel dead compared to premium models though, so we'd recommend upgrading them before you even leave the shop.

Some bikes are ostentatiously outstanding in one particular aspect or another straight away, but the S3 is almost unassuming at first. The noticeably damped rear end created by the skinny seatstays hides the muscular horsepower of the BBright keystone and chunky chainstays when you're trundling through traffic.

The S3 powered up the steep gradients of our Majorca test ride

Despite relatively sharp feeling steep angled steering it feels similarly benign rather than belligerent through the bars too. In fact you could tour at tempo all day without really realising that you were on an aero optimised bike apart from the fact you would get to your destination significantly sooner than normal. In spite of the wheel hugger, it'll still take 25c rubber to put even more pneumatic anaesthetic between you and painful surfaces too.

Brace yourself between pedals and bars though and it becomes obvious why several Cervélo-sponsored pro teams use the S3 rather than the S5 for a lot of races as it surges up to speed regardless of gradient. While the 30mm deep Mavic hoops don't have the easy speed sustaining stride of deeper-section wheels, they are more responsive and agile once you've swapped the tyres.

The conventional brakes and carefully aligned cables give it real bite and power into corners too, so once you've realised what it's become capable of it's an absolute blast to throw around. In fact the more time we spent on the S3 the more we realised what an incredible balance of unthreatening user friendliness but effortlessly easy speed it delivers.

Whatever the ride on the menu or our mood on the day it always delivered a totally appropriate performance and we hung onto it long past our Majorca mission for evaluating deep section wheels (it'll happily take the widest HED, Zipp or Reynolds rims) and tyres for subsequent grouptests. The need to change wheels to get the best from it does mean we have to mark it down slightly on value though.