3 things you need to know about aero bikes

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!


OUR PICK

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.