Tour Tech 2011: Tyler Farrar's Cervélo S5

Tyler Farrar is on a brand new Cervélo S5 for this year's Tour de France and we had a good look at it when we visited the Garmin-Cervélo hotel in Truffauges just before the race started.

The S5 is one of the new breed of aero road bikes – you get the geometry and handling of a road bike with low-drag features borrowed from the world of time trialling/triathlon thrown into the mix. We featured it when it was launched last week. 

The most obvious aero feature is the seat tube that comes with a cutout for the rear wheel to smooth the airflow through the centre/rear section of the bike. Virtually every TT bike these days comes with something similar, Cervélo themselves having popularized the concept with their P3.

The seatstays kink out sharply from the seat tube to provide shelter for the rear brake calliper and, moving forward, the down tube is dropped so that it sits really closely behind the front wheel. This is designed to smooth the airflow from the fork to the frame and to reduce turbulence behind the fork crown. Check out the area where the fork and the frame meet: the two are really neatly integrated.

The head tube is interesting too. We didn’t get the chance to check inside – we couldn’t see the mechanics letting us loose on Farrar’s bike with a set of Allen keys – but Cervélo tell us that it uses two walls: an internal one to provide the stiffness and an outside one to improve the aerodynamics and provide reinforcement.

All the tubes are designed to be as aerodynamically efficient as possible – they’re ultra-narrow, keeping the frontal area to an absolute minimum. The S5 almost disappears when you look at it head on.

The head tube, for example, with 1 1/8in headset bearings top and bottom, is a really cinched in hourglass affair with a painfully-skinny waist and the down tube is incredibly narrow – you could chop onions with it… If you found yourself needing to chop onions and couldn’t find a knife, like.

The only area that isn’t slender is the bottom bracket. It’s built to Cervélo’s own BBright standard and it’s a bulbous piece of work. Both the BB shell and the axle are oversized for added stiffness when you pedal. And yes, it’s supposed to be asymmetric – they’ve not just taken it out of the mould too soon. Those little holes on the left hand chainstay (right handside of the picture), by the way, are for mounting a Di2 battery.

The cables take the internal route towards the back of the bike, the two gear cables looping over the stem and ducking inside the top of the top tube and then down through the head tube.

Another little wind-cheating feature is the seat clamp or, rather, the lack of one. The aero seatpost is held in place by a wedge recessed into the top tube. Speaking of the seatpost, it comes with a two-position head that allows you to alter the seat angle; you can move it forward if you want to fit clip-on aerobars, for example.

You get two different positions for your water bottle cage on the down tube too. Cervélo reckon that using the lower one improves the slipperiness just a touch.

They say the S5 is 12% stiffer than the existing S3 and significantly more aerodynamic. They’re claiming that over 100km it is a minute and a half quicker than an S3 were both bikes to be ridden by identical riders putting in identical efforts – they also say that it offers a whopping 30 Watt advantage over a standard road bike.

Tyler Farrar is one of three Garmin-Cervélo team members riding the S5 for the Tour de France, chosen not because he was expected to do big things but simply because his ride position fitted the new bike best. If you’re interested in getting an S5 for yourself, it’ll be available soon, prices for the frameset starting at £2,499.99.

Farrar’s bike is built up with a mainly SRAM Red groupset but with a Rotor 3D+ chainset. That little red gizmo, by the way, is simply a chain catcher – a length of anodized aluminium that stops the chain overshifting inward.

The wheels are Mavic Cosmic with full-carbon deep-section rims and bladed alloy spokes. That isn’t a combo that’s in the current Mavic range.

It’s pretty hard to see but there’s a band between the carbon rim and the tyre: the narrow strip between the top of the brake shoe and the tread. It looks like the sidewall of the tyre, but it isn’t. That’s actually a little flap of rubber that’s attached to the rim. What’s it doing there? Well, it smoothes the line between the top of the tyre and the rim so we’re saying it’s an aero feature… although we’re prepared to be shot down in flames if anyone knows any different.

We've spoken to Mavic and their basic response goes along the lines of "we could tell you but then we'd have to kill you kind-of-a-thing" except more polite. Our Mavic source confirms our theory is correct though this is an aero enhancing feature that they are currently testing and developing in the race and the returned aero figures are "beyond our expectations"… I'm strapping my Kevlar vest on now. Only two teams at the Tour have 'em, Garmin Cervelo and Liquigas Cannondale. Currently they are the wheels with "no definitive name" and Mavic has no plans to give them one just yet, nor are they giving out any further technical information because "they are likely to be changed during the development process".

Farrar opts for an alloy cockpit rather than carbon – lots of pros do for extra rigidity. The bar is a 3T Ergonova Pro and that looks like an ARX Pro stem in a whopping 140mm length – the Garmin Transitions branding is sooo last year. Farrar is old-school in his pedal choice too. Those are Shimano Dura Ace 7810s. The current 7900 model comes with a carbon composite pedal body.

Naturally, Garmin Cervélo use Garmin computers. This is the Edge 500 which is GPS based so there’s no need for a speed sensor to be fitted to the bike – all the info comes from the sky.