'Lightweight bikes don’t actually get you to the bar any quicker' – Andy Turner explains why climbing bikes aren't dead yet and it's not for the reason you're thinking

This month saw the launch of the new Cervelo R5, a climbing bike so inconspicuous in its new design, it hid in plain sight in the pro peloton for weeks. Journalists finally cottoned on to its existence in a car park in Lille at the Grand Depart of this year’s Tour de France.

What no one expected was that that would be the last time we’d see it in competition, such was the dominance of the recently updated S5.

Cervelo’s R5 wasn’t the only bike shut out from the action, and left in the back of the team truck. Colnago’s V5RS hardly got its tyres dirty either, upstaged by the whackier, slipperier design of the Y1RS. Jayco Giant ran the Propel for the entire event, leaving the excellent TCR in the back of their wagon too.

At the time, whilst trying to get to the bottom of the team equipment strategies, we and others reported that at speeds of over 26kmph, bike weight could be heavier by significant amounts (1-1.5kg in some circumstances) with no disadvantage if it was more aerodynamic.

As speeds increase, aero advantages increase exponentially, and that blows any weight-weenie argument out of the water. So does it mean light bikes are no longer relevant in the pro peloton unless they’re light and aero? Not necessarily.

Whilst aero bikes proliferated in the men's race, the Tour de France Femmes was very different. The race was in fact won on the new 5.97kg R5. So why didn’t race winner Pauline Ferrand-Prevot opt for the aero bike? I questioned our resident aerodynamicist, Andy Turner to see what he thought.

“The answer is she did optimise her setup for a balance of aero and other preferred factors like spending her weight savings on deeper wheels, then choosing to position any unspent grams low in the frame. This would have afforded more speed in the flat sections from the deeper wheels, but more confident descending in the mountains with the lower centre of gravity from positioning the ballast low in the bike. We saw Sarah Gigante Putting in more effort to make up ground she lost to Ferrand Prevot in the corners. This could have been down to those changes.”

Asked whether or not the smaller frontal area afforded by a smaller frame, made any difference, and could be the reason why they chose the climbing bike, Turner was emphatic:

“The S5 is always going to be faster in pure aero terms, regardless of the smaller head tube length. But with the deeper wheels on the R5, there’s not a lot in it, and other advantages can trump the S5 as a strategic choice, all things considered.”

If aero gains are available, it seems, within a kilo or so of the UCI weight limit, the aero optimised approach will usually deliver more returns than weight saving. But there is more than one ‘right’ answer.

“Aero supremacy doesn’t mean weight isn’t a non sequitur. It’s just not the only game in town, especially where strict limits are imposed.” Turner explained. “What’s new, or at least challenging for some, is that weight is not as important as we all think it is, when set against aero performance.”

Turner thinks consumers worry too much about weight in the bike, when system weight - the bike and rider combined - is more important:

“Aero bikes aren’t ‘heavy’ bikes anyway, with most under 8kg, and weight saving measures on even the heavier aero bikes, can get them to near parity, or close enough, leaving the aero bike with a stonking advantage over the climbing bike, especially as speeds on less hilly Tour stages climbed as the event wore on.”

Mountain stages were also proven to be aero first too, with even the mighty Ventoux mountain stage, falling to the aero bike.

So does this mean the lightweight bike, the climber, is dead?

“Lightweight has often been overegged. The vast majority of us can’t discern any difference in a few grams, and it can cost an absolute fortune to play the weight-weenie game. We all do it occasionally, and it’s part of the fun, but the physics also tells us that the advantages we often pay thousands for give little more than pub bragging rights. They don’t actually get you to the bar any quicker.”

“Consumers aren’t restricted by the UCI weight limit, and it doesn’t matter how many times I tell someone that lightweight bottle cages aren’t going to make a difference, people still think they will. Why else would you buy a Dura Ace groupset over the Ultegra version when it’s functionally the same shift? Plenty do. I think consumers will still be seduced, just on the headline weights.”

Whilst we tend to instinctively think that climbing is the hardest part of the sport, and the less weight we’re shifting up a hill must be a benefit, the main reason to buy a climbing bike might not be lightweight at all.

Discussing his theories about why Pauline Ferrand-Prevot of Visma Lease-a-bike might have opted for the R5 over the S5, Turner thinks it likely comes down to a benefit that gets traded off easily, and rarely finds it’s way into ‘race-bike’ marketing, and that’s comfort.

“Whilst the new S5 shares the same stack height as the new R5 for the first time, Pauline is riding hers with around 35mm of spacers. In pure aero terms, a lower position would test faster in a windtunnel, but could be a disaster for Ferrand-Prevot’s power output. The same can be said of a bike that’s overly stiff.

The seatpost on the S5 is not as forgiving as the R5, neither is the main frame or rear triangle. A bayonet fork will, all things being equal, never deliver the feel of a less aero model. There’s just too much material in it for it to be as comfortable. A well made climbing bike will usually have a better balance of stiffness and compliance than a bulkier aero equivalent. Add to that Ferrand Prevot’s smaller frame will have less seatpost exposed than bigger riders like Matteo Jorgenson. Her smaller bike will therefore have less compliance so the difference between the R5 and S5 is exaggerated.”

From a consumer point of view, an aero road bike offers far too extreme a position for a Sunday club run as the front end is usually dropped lower.

Whilst the R5 bucks this trend, matching stack height to the more aero S5 in the new model, the comfort argument is still relevant, even in the pro ranks. Evidenced by Ferrand Prevot’s choice to stick with the R5.

Aero, and even standard road bike positions, are generally designed for pros – people who have are folded in half for a living. The majority of us sit at a desk, and no matter how fit we get, our physiology is different.

Still, consumers and industry both follow the pro scene, meaning comfort is traded out for aero performance. But climbing bikes, often afford considerably more comfort, and that is key to physical performance when it comes to endurance activities.

For you and me, that means the climbing bike is going to be the best option nine times out of ten. Comfort and compliance, will increase your ability to stay on the bike for longer, and should also boost your confidence in corners.

We’re a long way away from the extreme discomfort afforded by the early aero bikes – the new S5 I’ve been riding recently is exceptional in comfort terms, for the type of bike it is – but the R5 and bikes like it will remain a far more pleasant ride.