First Look: Giant Propel Disc Road Bike 2018

Words by Aaron Scott

on 29/08/2017 15:40:23

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When Giant launched the Propel in 2013, it was lauded as the �world's fastest� aero road bike, and while it wasn't the first aero-dedicated model to reach the market the extra time that Giant committed to its development resulted in a bike that swerved many of the compromises usually associated with that particular niche of road bike. Since then, the popularity of the Giant Propel has been hard to miss - from Sunday runs, to the start line of amateur criteriums, and on to the world's biggest professional events, the Propel's distinctive silhouette can usually be spotted.

Since that launch in 2013 there has been little change to the Propel besides some updated specs and a fresh lick of paint. Until, that is, the Tour de France this July when eagle-eyed viewers will have spotted something a little different between the legs of eventual green jersey victor, Michael Matthews. And so, after three years of development with their own engineers, the professional riders from Team Sunweb, and aerodynamics experts at the Aero Concept Engineering facility in Magny-Cours, France, Giant have lifted the lid on the brand new Propel Disc.

Total Control

Let's start with the obvious - the new Propel comes with disc brakes and, at the time of writing, there is no rim brake model. A bold move, yes, but one which Giant believe is justified by the higher level of aerodynamic efficiency displayed by the new model along with the superior braking power and greater modulation in wet or dry conditions that disc brakes offer. After all, you can't win a sprint if poor braking has cost you your position on the final bend, or you've been dropped on a technical descent.

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One of the arguments often levelled at disc brakes is that their addition to an otherwise aero-optimised frame negates any of the benefit of those hours of design tweaks - this isn't the case with the Propel Disc. Designed from the ground up with disc brakes in mind, Giant found that with proper integration, a disc brake design can actually improve aerodynamic performance, and so the frame and fork are engineered specifically for flat-mount disc brakes, with the mount tucked neatly in behind the fork. This integration combined with an extra clean profile around the fork crown and an asymmetric fork design which helps shield and push air around the front disc-brake caliper has resulted in a front end that's performance outweighs any aerodynamic impediment associated with discs.

Ultimate Speed

So how do you make a fast bike even faster? Giant have started pretty much from scratch with the Propel Disc - the new model doesn't share a single tube shape with the previous generation - and they have taken a holistic view of the bike as a complete system, including the rider. Working firstly through the typical bike design rigours of computational fluid dynamics, prototypes were then taken to the wind tunnel and aerodynamics experts at Aero Concept Engineering (ACE), a former FI aerodynamic testing facility, to be refined further.

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To more accurately replicate real-world riding, a moving mannequin is saddled up, with a rolling system which turns the legs over - an exclusive testing protocol used only by Giant which can imitate on-road conditions and overcome any inconsistency issues found when testing with real people. Once aboard, the Propel Disc was tested at speeds of 40kph and yaw angles between 0 and 30 degrees, with testing showing on average a 15-watt saving over the old Propel. Besides the work on the fork, where does this saving come from? The Propel Disc uses a truncated ellipse airfoil shape which lowers drag at a wider range of wind angles compared to traditional teardrop frame tubing.

Unrivalled Efficiency

Alongside all of the aerodynamic artistry on display with the Propel Disc, Giant have set off in pursuit of a class-leading combination of weight and stiffness to make this the most 'efficient' bike available. Although the new frameset is 45g heavier than the previous generation at 2,145g, it weighs in lighter than other high performance aero bikes such as the Specialized Venge ViAS Disc (2,559g) and the Trek Madone (2,374g) - and bear in mind that this includes the weight associated with producing a frame which can handle the additional forces created by disc brakes. To top it off, these competitors are thoroughly thumped when it comes to stiffness and stiffness-to-weight ratios according to Giant's testing regimen.

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Contributing to the Propel Disc's excellent aerodynamic performance (and the other feature which jumps out on first viewing) is the integrated bar and stem, which have become almost ubiquitous on aero bikes. Rather than using a one-piece system, Giant uses its own two-piece design with all cables completely hidden from view. A clever stem cover slots into place to cover the cables as they exit the bar and keeps them hidden from the wind until they drop into the frame behind the head tube, keeping everything tidy while still allowing a degree of flexibility in terms of stem lengths and customisation. All the bikes come with an optional out-front mount computer mount which can house a Garmin or Giant's own new Neos Track. This new stem is part of Giant's 'system' approach which extends to the choice of wheels and the new SLR Aero WheelSystem, which features a 65mm rear wheel for its superior aerodynamic performance alongside a 42mm front wheel for added control in crosswinds. Interestingly, Giant also specs the entire range with tubeless tyres.

Giant NeosTrack GPS Computer

Giant NeosTrack GPS Computer

At £149.99 and with all the connectivity you could need, the new NEOS Track looks set to be a cyclists best friend.

  • ANT+ and Bluetooth connectivity
  • 30+ hour battery life
  • 80 grams
  • 2.6in screen
  • Giant Lab mobile app
  • RRP £149.99

Product Featured

Giant Propel Advanced SL 0 Disc 2018 Aero Road Bike

Giant Propel Advanced SL 0 Disc 2018 Aero Road Bike

An aero rocketship! Possible of propeling you to exhilarating speeds with the added control of disc brakes to create the complete eero bike.

  • Frame - Advanced SL-grade composite carbon fibre with Integrated Seatpost
  • Fork - Advanced SL-grade composite with Full Composite OverDrive2 steerer
  • Groupset - Shimano Dura-Ace Di2 2x11 speed
  • Wheels - Giant SLR 0 Aero Disc Wheel System

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