Cyclist
Aero vs lightweight vs all-rounder: which is the fastest road bike?
Aero kit is fastest on the flat; lightweight kit is fastest on steep climbs – we all know that. But what if you’re doing a long ride such as a gran fondo, with flat sections, climbs, descents, the full works? Is an aero, lightweight or all-rounder setup faster overall?
The answer isn’t obvious, so to find out we brought together three bikes and three corresponding sets of kit and tested them all on a 100km loop in the French Pyrenees, including an ascent of the mighty Col du Tourmalet. In total, the ride has 2,000m of ascent and is dominated by that famous climb, but it’s worth remembering that the Tourmalet accounts for only a fifth of the full distance, with much of the rest of the route looking like happy hunting ground for aero gear (for details of the route, see the map further down).
‘Performance over the full course should always be the focus, so this is a great test,’ says Simon Smart of Drag2Zero, consultant to several top brands and WorldTour teams. ‘It can be tempting for riders at all levels to focus their kit choices on an obvious highlight in a route, such as the Tourmalet in this case.
‘For the past 14 years, my work in bike and kit development has been all about finding that sweet spot between aero and weight.’
The bikes and kit
For our aero bike we chose the BMC Timemachine Road 01, which isn’t outrageously heavy at 7.9kg but is designed to be all-in aero. The exception is its 50mm wheels, so we swapped them for a set of super-deep 82mm Zipp 808 Firecrest wheels. They weigh a beefy 2,015g, pushing the overall weight up to 8.2kg, but should make the BMC a missile on the flatter roads.
Likewise, the Giro Eclipse Spherical helmet and Suplest Aero shoes promise real aero gains in return for some extra grams. Castelli’s Sanremo speedsuit was the original one-piece road skinsuit, and version 4.1 is faster than ever. Completing the outfit, Rule 28 socks save a few watts with their ribbed fabric. The whole setup is primed for speed and weighs a combined 9.46kg.
For the lightweight bike we plumped for the Specialized S-Works Aethos at just 6.19kg. Its round tubes shun aero entirely as part of its extreme diet. The Poc Ventral Lite helmet and Giro Empire SLX II shoes are the perfect featherweight complement, while the Assos Superleger bib shorts and socks are made for tackling big climbs on hot days. The matching jersey has only one pocket, with indoor training in mind, so for this test we used a Dhb Aeron Lab Ultralight jersey, which is incredibly light yet still includes three pockets to get you round a longer ride. At a combined 7.16kg, this setup is a climber’s dream.
Our all-rounder bike is the Factor Ostro VAM, which the company calls an ‘everything bike’, combining low drag and low weight at 7.21kg. The Met Trenta helmet and Lake CX302 shoes, like the bike, split the weight difference of the lightweight and aero setups, with the helmet adding some aero too. The Sportful Bomber jersey is a close aero fit while remaining, like the Total Comfort bib shorts, wearable all day. The bike and kit come in at 8.4kg, which is almost exactly halfway between the other two setups.
The testing method
Controlling such a long test with runs on different days is obviously very challenging, but there was still a lot we could do to make it a fair and representative test. First, I rode to power, using the same Favero Assioma Duo power pedals on each bike. The first run set the pace, then I repeated the same power for each sector of the ride on the subsequent runs, with a list of sectors and target power numbers taped to the top tubes (see the map for details of each sector).
While it’s impossible to do this blind, by closely watching live power and lap (sector) average power on a screen it’s straightforward to control both the overall average power for the run and smooth power distribution. It does take a lot of concentration, though.
Second, I used the same riding position in each sector – hoods on gentle climbs, tops for steep climbing, drops on the descents and flats – and the bikes were set up identically. Third, I carried the same spares, food and bottles with me, using two one-litre bottles so that I wouldn’t have to stop and refill. I even ate in the same places on each run.
Fourth, to eliminate any differences in rolling resistance, the bikes were each fitted with Pirelli P-Zero Race 26mm tyres with Maxxis Ultralight inner tubes, all inflated to 90psi front and 95psi rear.
While test repeats are a good thing, for a test this long that isn’t viable. It took a lot of planning and no little luck to get a week of consistent, high pressure, calm and sunny weather into which to pack all three runs, riding on alternate days. I rode non-stop and without donning a gilet or jacket on the descents, which would have ruined the aero comparison.
Even with all that effort, there remain vulnerabilities in the method. Air pressure won’t have been identical and there’s no way to control for the aero effect of passing traffic on the flats nor delays caused by cars needing to be passed on the descents. If a particular delay arose – sheep in the road, for instance – Strava data could be used to identify the time loss. Also, the two towns on the route – Lourdes and Bagnères de Bigorre – were impossible to ride through at constant power so have been neutralised, with all three bikes given the same averaged time.
How it went
All three runs went well, with near-identical weather and no delays or disruptions, meaning the power readings for each sector were virtually identical. In places, such as the uphill drag for the first 11km, it was hard to feel a difference between the bikes in terms of speed. And surprisingly the same was true on the ascent of the Tourmalet, albeit to a lesser extent. The weight differences were perceptible but it certainly didn’t feel like one setup was like dragging an anchor while another seemed to float.
The descent was a different matter, but it was handling, not aero and weight, that split them. The Specialized felt brittle and almost too light, skipping off bumps and denting confidence. The BMC on the Zipp 808s was even more of a handful. Such deep wheels really don’t belong in the high mountains, where the wind comes from all over the place.
The Zipps are very stable for their depth in a crosswind on the flat, but they got nudged around to a disconcerting extent on the upper slopes of the Tourmalet. The Factor showed how it should be done: stable, planted, precise, assured… and was faster for it.
The long false flat descent that followed had a slight headwind each day and here the aero setup was in its element, while the Specialized felt limited in this environment. The all-rounder Factor, true to type, felt somewhere between the two.
The results
And the winner is… the all-rounder setup with a time of 3h 19min 37sec. In second place, 2min 46sec back, is the lightweight setup with a time of 3h 22min 23sec. Third is the aero setup on 3h 24min 41sec, a full 5min 4sec behind the all-rounder.
The all-rounder won four out of seven sectors and was second in the other three. Of particular note is that it lost only 15 seconds to the lightweight setup on the ascent of the Tourmalet. Perhaps most compelling is how it set fastest times on a range of terrain: the draggy climbs, the big descent and the flat section.
The lightweight setup placed second, winning on the Tourmalet but unable to make its advantage there count enough to stay in contention. In short, it’s only the most effective when climbing steeply and it pays dearly on the faster sections.
The aero setup was a distant third, with totally polarised results: it won the two sections that suited it and was last on the others. On the Tourmalet, its weight cost it nearly two and a half minutes going up and then poor handling cost it a further 43 seconds going back down.
‘These results are fascinating,’ says Smart. ‘The all-round setup gives away some aero and some weight but it does the best job of hitting that sweet spot, plus it was the most stable and confidence-inspiring bike. The overall time difference is massive.’
• Want a full run-down of the data from our aero vs lightweight vs all-rounder speed test, including comparative times and power data for each sector of each ride, as well as links to the rides on Strava? Click here
Conclusions
Aero is everything and weight is… most things too. Combining these attributes into all-rounder products can achieve a best-of-both-worlds that out-performs dedicated light or aero gear.
So, when I next sign up for a gran fondo, will I simply be taking the all-rounder setup seen here? Not quite. I’d want the all-rounder Factor Ostro but I’d pair it with the aero Giro helmet, Castelli Sanremo speedsuit and Rule 28 socks with the super-light Giro shoes. That would work out both lighter, by 44g, and more aero. I’d guess that would be worth about another minute.
Test route
Lots of up, lots of down, and everything in between
The contenders
Aero setup
BMC Timemachine 01 Two 8.18kg (7.9kg stock)
Wheels Zipp 808 Firecrest (our addition, model year 2021)
Helmet Giro Eclipse Spherical: 308g
Glasses SunGod Airas: 33g
Speedsuit Castelli Sanremo Speedsuit: 256g
Socks Rule 28: 56g
Shoes Suplest Aero: 626g
Kit weight 1,279g
Total equipment weight 9.46kg
Lightweight setup
Specialized S-Works Aethos 6.19kg
Helmet Poc Ventral Lite: 210g
Glasses Poc Elicit: 23g
Jersey Dhb Aeron Lab Ultralight: 83g
Bib shorts Assos Equipe RSR Superleger S9: 129g
Socks Assos RS Superleger: 30g
Shoes Giro Empire SLX II: 498g
Kit weight 973g
Total equipment weight 7.16kg
All-round setup
Factor Ostro VAM 7.21kg
Helmet Met Trenta Mips: 287g
Glasses Rudy Project Spinshield: 28g
Jersey Sportful Bomber: 111g
Bib shorts Sportful Total Comfort: 168g
Socks Rule 28: 56g
Shoes Lake CX302: 540g
Kit weight 1,190g
Total equipment weight 8.40kg
Thanks
Thanks to Simon Smart at Drag2Zero (drag2zero.com) for his expert insight; Billy at Specialized France for the loan of his personal S-Works Aethos; Favero for the excellent Assioma Duo power pedals (cycling.favero.com); Pirelli (pirelli.com) for supplying the P Zero Race control tyres. Ride this Col du Tourmalet circuit and much more with Escape To The Pyrenees (escapetothepyrenees.com).
• This article originally appeared in issue 150 of Cyclist magazine. Click here to subscribe
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