The stunning new Giant Propel Advanced SL aero road bike dissected in loving detail by’s James Huang.

Aero road bikes are booming at the moment and are especially of interest to triathletes wanting a bike for training and racing. After a sneak preview at Eurobike, Giant unveiled two new carbon fiber aero road machines just before the start of the Tour Down Under: the Propel Advanced SL and the women’s-specific Liv/giant Envie Advanced. Giant admits to being late to the aero road party but also says it’s gained from watching on the sidelines, supposedly offering a 12- to 36-second advantage over other top aero road bikes over a 40km time trial (at 40km/h) while also still maintaining a trim claimed weight of 1,675g for a medium frame, fork, integrated seatmast and clamp, front and rear brakes, and headset plug. Oh, and it looks good, too.

Wind tunnel and CFD-derived shape but with a (sort of) real person, too

Scott and Trek have popularized the use of truncated airfoil sections in an effort to boost aerodynamic efficiency while still maintaining good stiffness. In contrast, the shapes Giant uses on the Propel and Envie seem decidedly old school with their more conventional, teardrop-like cross-sections and sharper trailing edges. Giant has, however, abandoned its usual sloping top tube in favour of a level set up in order to reduce the frontal area.

Nonetheless, the devil is apparently in the details as Giant – once averse to making direct comparisons – now boldly calls out several key competitors as being not only less aerodynamic but heavier, too. According to Giant, the new Propel is 36 seconds faster in a 40km time trial (at 40km/h) and 458g lighter than a comparable Ridley Noah FAST, 32 seconds faster and 324g lighter than a Specialized S-Works Venge, 36 seconds faster and 233g lighter than a Scott Foil Team Issue, and even 12 seconds faster – and a whopping 546g lighter – than Cervélo’s ultra-slick S5 Team (not the top-end VWD).

Giant Propel Advanced SL aero road bike downtube

The Giant Propel Advanced SL down tube has a trimmed trailing edge designed to maintain good aerodynamics WITH a water bottle in place

Giant claims the Propel’s aerodynamic advantage extends to all yaw angles between 0 and 15 degrees, too, although it’s worth noting that it wasn’t a 100 percent apples-to-apples comparison. All of the bikes were tested with Giant’s relatively narrow P-SLR1 Aero wheels instead of wider-format models that are in favor these days. Also, wherever possible, Shimano Dura-Ace 7900 bits were used across the board.

Giant fitted the Propel with its own aero integrated cockpit, too, while the other bikes were equipped with their usual front end. According to Giant road category manager Jon Swanson, the aero cockpit only makes a slight difference at yaw angles between zero and five degrees, though, and didn’t affect the test overall. Likewise, while the data presented was done with Giant’s own wheels, Swanson says they did test the bikes with wide-format wheels and the resultant order was unchanged.

Giant has, however, impressively done that testing not just with a mannequin on board – Cervélo uses a model of David Zabriskie – but one that actually pedals. In this case, Giant took a laser scan of Blanco rider Grischa Niermann in his riding position, machined the model off of that, and then used that dynamic model across the board.

All of the testing was done with a single, round water bottle mounted to the down tube – a much more realistic configuration than with no bottles mounted, which is what is usually done.

One key component is the bike’s SpeedControl SLR front and rear carbon composite mini-V brakes. Although made by TRP like similar systems used on other bikes – including Giant’s own Trinity range – Giant says the SpeedControl SLR is a proprietary setup with cable pull ratios optimized for Shimano Dura-Ace 9000 and SRAM‘s latest Red group (which are now identical). Trailing edge shapes are supposedly specific to the Propel and they’re mounted behind the fork blades and seat stays to ‘hide’ them from the wind – which also makes them easier to service than something internally mounted or hidden behind a shroud.

Giant Propel Advanced SL aero road bike hidden brake

Giant worked with TRP to develop these brakes exclusively for the bike

Removable spacers behind the pads allow the use of wide-profile rims, too, and opening up the brakes for wheel removal is done V-brake style with easily removable cable noodles. Barrel adjusters are integrated into the noodles for quick on-the-bike adjustments.

Other aero details include a down tube shaped with water bottles in mind, aero-profile headset spacers, sleek carbon fiber dropouts, and fully guided Di2/EPS-compatible internal cable routing with derailleur housing that feeds into the top tube right behind the stem.

While improving aerodynamics was the priority for the new Propel, Giant says other performance metrics weren’t overly sacrificed to do so. Of the bikes Giant tested, front end stiffness on the new Propel is supposedly second only to the Foil, pedaling stiffness falls closely behind the Noah FAST and the Venge, and ride quality is a close cousin to the company’s venerable TCR Advanced SL.

“It had to be the fastest bike in the world but it also had to be lighter than every other bike in the world and as stiff as the TCR Advanced SL,” Swanson said. “We knew that last one would be pretty much impossible but those were our goals.”

Giant Propel Advanced SL aero road bike stiffness comparison

These are Giant’s measurements and claims, not those of TriRadar or BikeRadar

“We didn’t crush the world in terms of stiffness but I’m okay with that,” he continued. “At the top end of this, we’re all really close. We’re so close that so few, if any of you, would be able to pick out a difference between the top three.”

Scott in particular cites the Foil’s wider, truncated airfoil tube shapes as the key to that bike’s excellent stiffness. Swanson tells BikeRadar that Giant hit those stiffness numbers with the carbon fiber materials and lay-up schedules, and it was “by far the hardest project I’ve ever worked on in the bicycle industry,” he said, especially while staying within UCI guidelines. Swanson says most bikes require 3-5 iterations to dial in a new bike shape but it took a whopping 88 3-D models to finalize the Propel.

And yes, the new Propel is light. Claimed frame-only weight is 970g for a medium size – after backing out 144g for the integrated seatpost and clamp – plus 380g for the matching fork. Actual weight for a medium Propel Advanced SL 0 flagship is right at 7.0kg (15.43lb) with an uncut seatmast and without pedals.

Giant Propel Advanced SL aero road bike

Otherwise, the rest of the Propel and Envie frame features include the usual Giant hallmarks: the 1 1/4-to-1 1/2in OverDrive 2 tapered front end, an 86mm-wide PowerCore bottom bracket shell with press-fit bearing cups for use with standard 24mm-diameter cranksets, asymmetric chain stays, the RideSense wireless speed and cadence sensor that’s tucked into the non-driveside chain stay, a lighter and smoother-riding integrated seatmast, and T-800 carbon fiber composite that’s woven in-house.

Geometry is wholly carried over from the TCR Advanced SL, too.

Giant will offer three Propel Advanced SL models in March:

  • the $10,000 SL 0 with Shimano Dura-Ace Di2 9070 and Giant’s new Contact SLR Aero Integrated one-piece bar and stem
  • the $7,500 SL 1 with Dura-Ace 9000 and separate Giant Contact SLR Aero carbon handlebar and stem
  • the $7,000 SL 2 with the same bar and stem but a SRAM Red 2012 group

All three Propel Advanced SL machines will include Giant’s P-SLR1 Aero clincher wheels and the same SpeedControl SLR brakes.

Six sizes will be offered with effective top tube lengths ranging from 51.5cm to 60.5cm.

Nearly every feature of the Propel Advanced SL is carried over to the women’s-specific Liv/giant Envie Advanced, too, with similar shaping but specific geometry, a slightly softer bottom bracket, Advanced-grade composite material, and a telescoping seatpost. Claimed frame weight climbs to 970g for a size small.

According to Liv/giant’s Abby Santurbane, the Envie was designed using the company’s so-called ‘3F’ philosophy: Fit (geometry, sizes, components), Form (“we want the woman to walk into a bike shop and fall in love with the product”), and Function (technology, innovation, ride quality). Notably, all of the company people involved in Liv/giant bikes are women, including the marketing staff, engineers and industrial designers.

Giant Envie Aero Road Bike

Giant’s women-specific aero road bike, the Envie

Liv/giant will offer three different Envie Advanced options:

  • the $5,600 Advanced 0 with SRAM Red, Giant Contact SLR Aero Integrated cockpit, carbon composite Giant SpeedControl SLR brakes, and Giant P-SLR1 Aero wheels
  • the $3,500 Advanced 1 with Shimano Ultegra 6700 (compact chainrings), separate Giant Contact SLR Aero handlebar and stem, aluminum Giant SpeedControl SL brakes and Giant P-SL0 wheels
  • the US$2,550 Advanced 2 with Shimano 105 (compact chainrings), Giant Connect SL handlebar, Giant SpeedControl brakes, and Giant P-SL1 wheels

Five sizes with effective top tube lengths ranging from 50cm to 56.5cm will be available, intended to fit female riders from under 1.5m/5ft to over 1.8m/6ft tall.

Giant is anticipating March availability for both the Propel and Envie in the US, UK, Australia, Germany and “other select European countries.”

What about the TCR Advanced SL?

If the new Propel Advanced SL supposedly offers similar stiffness, ride quality, and weight characteristics to the current TCR Advanced SL flagship as Giant claims, it begs the question of where that model stands in relation to the new aero bike – and if it’s even still relevant.

As it turns out, “similar” is not the same as “equal” and Giant says the TCR Advanced SL still outperforms the Propel in terms of non-aero performance – but not by much. Riders who prioritize stiffness, ride quality and light weight will probably still want to go with the more structurally efficient TCR, but they should keep in mind that the aerodynamic gap grows even further with that bike’s more rectangular tube profiles.

According to Swanson, a rider on a new Propel will have a full 45 seconds at the end of a 40km time trial to contemplate their victory dance over a comparable racer on a TCR.

New aero cockpits

Going along with the new Propel and Envie are some new aero integrated cockpits and bars as well. As the name suggests, the new Contact SLR Aero Integrated bar and stem is a one-piece carbon fiber front end with an aero-profile top section and slimmed-down interface where a traditional clamp would normally reside. The huge, box-section stem is sized for Giant’s own OverDrive 2 steerer (although it’ll also work with 1 1/8in steerers with an adapter) and while the handlebar angle isn’t independently adjustable, Giant at least offers the Contact SLR Aero Integrated in twelve different sizes (four different widths), all with three degrees of backsweep on the tops plus dual-radius drops.

Giant Propel Advanced SL aero road bike cockpit

Giant’s new Contact SLR Aero Integrated bar and stem

Additionally, there will be a dedicated clip-on aero bar system option plus a bolt-on computer mount – a good thing since there is no way to install popular aftermarket Garmin mounts such as from Tate Labs or K-Edge. Brake and derailleur cables are routed internally.

Claimed weight is 395g (42cm x 110mm) and retail price is $549.

Riders seeking a little more adjustment can instead opt for the standalone Contact SLR Aero handlebar, which is still compatible with the dedicated clip-ons and uses the same overall shape but with a 31.8mm round center section for use with conventional stems – but again, not aftermarket Garmin mounts. Giant will offer the bar in four widths (38-44cm, center-to-center) with a retail price of $259.

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