BUYER'S GUIDE: Aero bikes – Bike Magazine Australia

They’re fast: Leading bikes in the aero category make sacrifices for speed – including rider position and total bike weight. If you’re after something more upright for long rides, you’ll be best served looking elsewhere.

They’re hi-tech: By utilising integrated components and internal cable routing, aero road bikes help you cheat the wind. But it does mean you might be calling on your local mechanic for more tasks than before.

You’ll have a target on your back: If you’re riding something built for speed and cheating the wind, be prepared for others to stick it to you!


The Giant Propel Advanced SL Disc 0, $11,999

The new Propel Disc shares no tube shapes with the previous generation Propel. Its truncated-airfoil design is similar to what is used on other aero-road bikes: a rounded leading edge with flat back. The shape – Giant calls it a truncated ellipse – was developed over three years by Nixon Huang, Giant’s senior global category manager, and Xavier Gergaud, director of Aero Concept Engineering, an independent company that helps Giant with aero designs.

Huang says the shape works better overall at wind angles from zero to 30 degrees than a traditional teardrop shape. The Propel shares other details with its competitors as well, including dropped chain stay attachment and a rear wheel cut out.

“It’s not just the frame anymore, it’s not just the fork anymore, that makes an aero-road bike an aero-road bike; it’s every single component and how they affect each other,” says Andrew Juskaitis, Giant’s senior global product marketing manager.

Consequently, part of the Propel Disc’s aerodynamic benefit comes from the frame-specific bar and stem with hidden derailleur and brake lines. Wheels are also part of the story, with a 65mm-deep rear wheel coming on all models. Up front, Giant uses a 42mm deep wheel to balance aerodynamic benefits with cross-wind stability.

Unsurprisingly, all the newness results in a bike that Giant claims to be more aerodynamic that the previous generation. Compared to the old Propel with rim brakes, the new Propel shows about a 10 watt improvement (206.9 watts for the new Propel Disc versus 217 watts for the old Propel with rim brakes) at 40km/h. And while Giant did not provide specific data on the competitors it tested, Juskaitis says that the new Propel Disc’s aerodynamic performance equals the best-selling aero bikes on the market.

Though the Propel Disc (982 gram claimed frame weight) is about 45 grams heavier than the previous generation, the Disc version’s improved stiffness gives it a better stiffness-to-weight ratio than the old Propel. Giant has also presented data that shows that, according to its tests, the Propel is stiffer and has a better stiffness-to-weight ratio than the Canyon Aeroad CF SLX Disc, Specialized Venge ViAS Disc, and Trek Madone (rim brakes).

Why Discs?

Giant says its testing showed that it could make large aerodynamic improvements by improving air flow though the fork crown. “That really was the quantum shift for us. If we keep the air going through the fork crown as cleanly as possible, that makes significantly more difference than keeping the air clean down at the caliper,” Juskaitis explains.


I tested the Propel Advanced SL 0 Disc over the course of two days in central France. The first ride was spent lapping the Magny-Cours motorsports race track where ACE is based. And though it was fun to make engine noises and zip around the traffic free-circuit, the perfect tarmac and its wide, sticky, turns, with mild elevation changes didn’t reveal much about the new bike.

However, the second ride in the hilly countryside of central France was quite eye-opening. What most struck me was how the Propel felt like a normal race bike. Aero frames, disc brakes, aero wheels, aero-shaped handlebars — these things usually work against a bike’s handling. But the Propel felt like a good modern race bike. It was lively, compliant, precise, and fast. That it also has (claimed) class-leading aerodynamics and disc brakes is some sweet, delicious, cream on top.

Punching hard up a rise, the frame’s bottom bracket stiffness and power transfer felt excellent. Giving everything in a flat sprint, the bar and stem yielded little, the front wheel tracked true, and there was little discernible wind up in the front triangle. Handling was sharp and fast – never darty or unpredictable – and the Propel Disc was not unsettled by rougher corners. Neither ride was particularly windy, so I wasn’t able to evaluate the bike’s cross-wind stability. 

The frame did an admirable job of both dulling normal vibrations and sucking up bigger impacts, but enough rumble and grit filtered through to prevent a flat feeling, and remind you that, yes, the Propel Disc is a race bike.

The only complaint I can muster about the Propel is that it lacks jump. Though very stiff and reactive – this bike certainly goes – it doesn’t telegraph the feeling of explosive quickness, that fiery crackle and pop, that I associate with the very best race bikes. To be fair, no aero road bike (and very few disc-equipped race bikes) have this trait either. That the Propel Disc comes close is noteworthy.

Though I’ll say the Propel Disc is the most impressive disc equipped, aerodynamic road race bike I’ve ridden, there’s still a gap between it and the top race bikes. Giant’s non-aero TCR Advanced with rim brakes, for example, is one of the best race bikes available, and is smoother, lighter, quicker, and more lively than the Propel Disc.

But the Propel Disc is within striking distance of those leading race bikes – many of which are still non disc, and not fully aerodynamic – and it offers the control of disc brakes, and the efficiency of a fully aerodynamic frame. It’s almost game changing, and definitely class leading. – Matt Phillips


Specialized Venge ViAS Disc Ultegra, $4,500

World Tour performance at enthusiast pricing. Specialized claim a 116 second advantage over the Tarmac at 40km/h in their Wind Tunnel. The Aerofly Bar and negative 17-degree stem find a compromise in aero efficiency and rider comfort. With Shimano Ultegra hydraulic disc brakes, coming to a stop fast is just as easy.

Ridley Noah SL Disc, $10,999

With a design that takes everything, including the surface of the frame, into consideration for a slippery and stiff build, the Noah SL Disc has all the features you want and the frame uses a variety of carbon fibre to get the precise weight and build Ridley wanted.