Nearly every company going has an aero bike somewhere in its range. And for good reason. Our independent testing shows that the difference between a good aero bike, and a climbing bike, could be as much as 25 watts at 45kph. It’d take a lot of training to gain 25 watts.
Aero bikes are characterised by:
- Wide tube shapes designed to reduce drag
- Integrated cockpits
- Hidden, or disc, brakes
- Hidden seat post clamps
While it’s all well and good having the fastest possible aero bike, you won’t want to ride it very far if it’s uncomfortable or too heavy. Happily, the new generation of aero bikes launched for 2019 have improved vastly in those areas that they were traditionally weak. Weights have come tumbling down and ride quality and comfort are much improved, making these bikes you would happily use in a sprint or a long day in the saddle.
We’ve tested the latest and greatest models, with prices ranging anywhere from mid-level to the top-end, and as a testament to that, all of the aero bikes listed below earned a spot on our Cycling Weekly’s Editor’s Choice list.
Best aero bikes 2019: Our favourites
Scott Foil 10 Disc
Read the full review: Scott Foil 10 Disc
£5000 will get you the Scott Foil 10 Disc, which sits third in the Swiss brand’s aero range, below the Scott Foil RC Disc and the Scott Foil Premium Disc. It comes equipped with a Shimano Ultegra R8070 groupset and a set of Synchros Meritt 1.0 Disc wheels.
The Scott Foil 10 Disc remains one of the most comfortable aero bikes on the market, featuring compliant dropped seat stays, seat post and the wide 28mm tyres. The use of disc brakes improves the bike’s handling characteristics and does away with our one gripe on the rim brake model, where the calliper was located down by the bottom bracket.
At 7.95kg, it’s not as light as some of the more recent aero bike models, but its fast (the old model was one of the fastest we’d tested) and comfortable.
USA buy now: Scott Foil 10 Disc at Scott
Cannondale SystemSix Carbon Dura-Ace
Read the full review: Cannondale SystemSix Carbon Dura-Ace
The SystemSix is Cannondale’s first ever dedicated aero road bike, and the brand has come out swinging. It looks the exact way you’d expect an aero bike to look, it’s all stark angles and chunky tubes and because of this you’d be forgiven for thinking it’d be uncomfortable, but actually the SystemSix has a comfort that belies it’s chunky nature.
It’s also a very fine handling bike, with a geometry that almost matches the Cannondale SuperSix Evo and hydraulic brakes that instil confidence on descents.
The SystemSix rolls on the Cannondale’s Knot 64 wheels which are tubeless ready, very stiff and spin along excellently. It weights 7.8kg and sits 4th in a range five, coming with Shimano Dura-Ace R9120 groupset. The three high end models all come with a Power2Max power meter, although it costs extra to activate it.
Giant Propel Advanced SL 1 Disc
Read the full review: Giant Propel Advanced SL 1 Disc
If you’re looking for raw performance above all else in your aero bike then the Giant Propel Advanced SL 1 could be for you. It’s seriously stiff, and on the flats it rolls very well feeling like a rocket ship when you’re stamping on the pedals. However, this raw stiffness does compromise handling, and it’s not as comfortable to descend on as, say, the Cannondale SystemSix or the Specialized S-Works Venge.
It also has one of the more sophisticated (read difficult to work on) front ends and the bike has the most striking looks of any aero bike on the market. This particular model sits one from the top of Giant’s Propel range, coming with Shimano Ultegra Di2 hydraulic groupset and Giant’s own SLR wheels.
USA buy now: Giant Propel Advanced SL 1 Disc at Giant for $7665
Trek Madone SLR 9 Disc
Read the full review: Trek Madone SLR 9 Disc
The Trek Madone SLR 9 Disc was the first Madone to come with disc brakes, although unlike a lot of other aero bikes, a rim version is still available. It’s also the first Madone to come with Trek’s IsoSpeed Decoupler, the same system that’s found on its Domane endurance bike, fitted to the top tube. According to Trek, this yields 17 per cent more comfort than the old Madone and in its firmest setting it’s 21 per cent stiffer.
Despite the added comfort, the Trek Madone still offers excellent power transfer out on the road and it’s clearly a racing bike. It’s stiff enough as is that we found we didn’t want to ride it with the IsoSpeed Decoupler in the harshest setting. At 7.5kg it’s middling weight for the latest aero bikes, but the performance and stiffness of the frame helps it feel agile.
USA buy now: Trek Madone SLR 9 at Trek from $11,799
Ridley Noah Fast Disc Ultegra Di2
Read the full review: Ridley Noah Fast Disc Ultegra Di2
This latest iteration of the Ridley Noah Fast has had a re-design, saving the frame 250g over the previous iteration. Like the Trek Madone, there’s both a rim brake and disc brake version available. In the UK There are two models available: one with Ultegra mechanical and the other with Ultegra Di2.
It’s worth noting that Ridley’s bike sizes run large, with the small frame having a 54.5cm top tube length which is the equivalent of a medium for many bike brands.
Specialized S-Works Venge
Read the full review: Specialized S-Works Venge
The Specialized S-Works Venge takes quite a different shape from the old Venge Vias, and it now has an uncanny resemblance to the Specialized S-Works Tarmac SL6 Disc. Like the Cannondale SystemSix, the Venge is disc brake only, but it takes an even more elitist approach by being compatible only with electronic gearing.
The design update improved the bike’s handling, which now feels lightening fast. It has also improved the bike’s ride quality, and it feels more plush and comfortable compared to the old model. At £9,750 for the full build, the Venge has one of the more expensive price tag. But for the money you get Roval’s exceptional wheels and the very good S-Works Power Crank, too. Alternatively, you can stump for a frameset only at £3,700.
UK buy now: Specialized S-Works Venge at Tredz for £9,750
USA buy now: Specialized S-Works Venge at Specialized for $12,520
Best aero bikes 2019: Why would you buy one?
Well that’s a very good question that, with the Cycling Weekly wind tunnel still seeking funding from the powers that be, we can’t answer with complete scientific accuracy. However, we have conducted a couple of past experiments that have compared the performances of aero bikes with non-aero bikes.
In the first of these, we put the two bikes to the test in what should be the aero bike’s home turf: the velodrome. We rode each bike (a now outdated Cervélo S5 and Canyon Ultimate CF SLX) for 10 minutes at 200W and 10 minutes at 300W, with the aero bike being 275m ahead and 1.7kph faster when ridden at 200W, and 435m ahead and 2.6kph faster when ridden at 300W.
In the second experiment we pitched an aero bike (again the Cervélo S5) against a lightweight bike (a Focus Izalco Max) on a climb, tackling Box Hill in Surrey twice on each bike, again at 200W and 300W, to see if the aero bike would still be faster even in the hills despite the Cervélo S5 being 800g heavier.
However, this time it was the lightweight bike that came out on top. At 200W, it took our test rider 9:24 to tackle the 2.5km climb on the aero bike at an average speed of 15kph, while the lightweight bike was 18 seconds faster with an average speed of 16kph.
At 300W, the lightweight bike was still faster, but the gap between the two was reduced, with the aero bike only being seven seconds slower with a 0.4kph difference in speed. This shows how much more important aerodynamics become at higher speeds, while weight is more of a factor at lower speeds.
The take home message then, is for most riders over most terrains, an aero bike will be faster than a lightweight bike. The only case where weight begins to become more of a factor is on steeper climbs where you’re travelling more slowly, and even then any time gains could well be balanced out on the descent, where the high speeds are going to make aerodynamics a factor again.
What features should I look out for in an aero bike?
At a most basic level, all aero bikes should come with tubes that have been shaped to smooth airflow, meaning that they will have a slender front profile but being extended rearwards. However, manufacturers can’t go crazy if they want to see their bikes used in races, with the UCI’s 3:1 rule restricting the ways in which they can shape the tubes.
This rule means that the depth of a tube’s profile (or indeed any other part of a bicycle) cannot be more than three times its width. So if a bike’s down tube is two centimetres wide when viewed from the front, then it cannot be more than six centimetres wide when viewed from the side.
In an attempt to continue to improve the aerodynamics of their bikes while staying within this rule, many manufacturers now use kamm-tail tube profiles. This means that the tube retains a traditional aerofoil shape at the front, but with the back half lopped off to give it a flat back.
A lot of people say that aero bikes now all look the same and a possible reason is because of the use of popular dropped rear stays, which the industry has collectively decided is the most aerodynamic shape. Helpfully, it’s also comfortable, too.
Integration is the latest big trend when it comes to aero bikes, with the latest aero bikes such as the Trek Madone aiming to hide as much hardware as possible within the frame.
Key to this is cable routing. The sleekest aero bikes keep the gear and brake cables hidden for as long as possible, routing them through the handlebars, stem, and frame before they emerge close to their partner components, usually on the backside of the tubes to keep them out of the wind. At the next level down from this the cables are not routed through the handlebars and stem, but do at least enter the down tube behind the head tube to keep the cable entry out of the wind.
Integrated rim brakes used to be very common on aero bikes and when the first models emerged a few years ago most manufacturers decided that the optimum aero position to stick the rear brake was by the bottom bracket, although the aerodynamic benefit of this was questionable.
Now, however, the market has moved a long way from integrated brakes, and disc brakes are the most common stoppers that you’ll find on aero bikes, with some models even being disc brake specific. The bike brand’s argue that they’ve managed to design the latest models around the rotors, or generate more aero savings across the frame.
However, possibly the most important part (or parts) of a seriously sleek aero bike are the wheels. According to Kevin Quan of Knight composites, a 95mm deep rim (which is admittedly incredibly deep) will save a typical rider 35 watts compared to a standard box section wheel at time trial speeds.
While 95mm is probably a little deep, most aero bikes do come with chunky rim profiles, typically between 50 and 65mm deep. Other than aero benefits, deep wheels are stiffer and faster rolling as a result. Oh, and they look amazing, too.
There are, of course, other areas that aero bikes can maximise efficiency. Nearly all models now come with either an integrated bar and stem that are designed in an aerodynamic shape, or ones that are capable of running cables internally.
How easy are aero bikes to live with?
Yes, for most people on most terrains, an aero bike will be faster, but if you’re considering buying one, you also have to weigh up what day-to-day life will be like with your new pride and joy.
It used to be the case that the more aerodynamic the bike, the more difficult it was to live with, mostly because of complicated internal cable routing. This does make altering cable length or raising and lowering stack height a bit of a pain because it involves cutting cables to do so. However, many modern aero bikes now come with split spacers, which makes this process a lot easier.
Traditional integrated brakes used to be a bit of a faff, too, but this nuisance is now transferred to disc brakes. While sitting in a more accessible area, the more power brakes have a new complication depending on how au fait you are at bleeding a hydraulic system.
Finally, if you’re going to get the most out of your aero bike, then you might occasionally find yourself riding in the dark. In this case, aerodynamic seatposts and handlebars can make it a little tricky to fit lights, while the seatpost design may also limit the saddle bags you can use.
How else can I be more aero?
Before you rush, wallet open, to your local bike shop in search of the latest aero bike, it’s worth considering that there are plenty of other much cheaper ways to make some aerodynamic gains.
The vast majority of the wind resistance that you have to overcome while cycling is caused by, well, you, so your position and clothing choice can make a big difference to your speed. Riding in a low, crouched position with your hands on the the hoods is roughly 20 per cent more aerodynamic than riding upright with your hands on the tops.
Similarly, tight-fitting aerodynamic clothing and an aero helmet can also make a significant difference. The benefits might not be as stark as with changing your position, but if you’re riding along with a baggy rain coat unzipped and flapping in the wind, then you can wave goodbye to any gains that you might have got from your expensive aero bike and flash deep sections wheels.
How much should I pay for an aero bike?
With aero bikes now being available at almost all price points, it’s more a case of how much can you afford to pay rather than how much do you need to pay.
At the top-end of the scale, it’s not unusual to see aero bikes pushing hard against the £10,000 barrier, which should be enough to get you a cutting-edge frame matched with some pretty tasty components and deep section wheels for a seriously aero machine.
However, for a fraction of this price, you will often be able to pick up a bike with a frame that might not have the same high-quality carbon-fibre (so will be usually be less stiff and heavier), but will at least have the same shape tubes which will still be subject to the same laws of physics.
Wheel choice is also important when considering how much to pay for an aero bike. If you already have aerodynamic, deep section wheels, then there’s no point in paying more money for an aero bike that comes with similarly posh wheels. Instead, buy the bike with the cheaper wheels, take these off to use as training wheels, then put on the deep section wheels that you already own for race days.