After years of sitting on the sidelines, Giant has dived head-first into the aero road game with two all-new frames, the Propel Advanced SL and women’s-specific Envie Advanced, as well as a crop of wind-cheating components.
“Late to the party” is a highly tempting cliché given Giant’s slow hop onto the aero bandwagon, but doesn’t really describe the company’s entry into to the market; if we’re sticking with worn-out phrases, let’s go with: “all good things come to those who wait.” With the Propel and Envie, which share the same aerodynamic attributes and essential design, Giant has nimbly and effectively grabbed key features from the best the market has had to offer, reworking and improving on them before adding a bit of its own secret sauce to the mix. The result is a frame that, at least on paper, looks to challenge anything currently available.
Think of aero road bike design as a sliding scale, with aerodynamics on the left and stiffness on the right. The tube shapes required for either extreme are fundamentally at odds with each other — aero likes skinny, stiffness digs fat. The design teams behind every aero road bike have to make a crucial decision: where on that scale do they want their bikes to land?
On the far left is Cervélo’s S5, an incredibly aerodynamic and shamelessly skinny frame saved from complete lateral complacency only by a set of wide hips; nothing keeps a bike riding true like a massive bottom bracket section. Opposite are the Scott Foil and Trek Madone — boxy, utilizing Kamm-tails exclusively in place of traditional NACA profiles. Sitting in the middle are Specialized’s Venge, Lightspeed’s CR1, BMC’s new TMR01, and numerous others. A bike’s position on this scale is a measure of intent, not execution, of course. Some frames aimed towards stiffness are still very quick in the tunnel, and vice versa.
On this scale, it appears that Giant has skewed just to the left, to the aero side, of the Venge. Tube shapes are skinny and carry Kamm-tails only out of necessity. The use of an oversized head tube keeps it well out of S5 territory, but the overall package is one more tuned into pure aerodynamics than absolute stiffness.
The world’s best time trial bikes all share essentially the same ingredients, just mixed together in slightly different ratios, and if the new Propel and Envie are anything to go by, that trend looks to be heading into the road world. In both frames we see a cleverly shaped, water-bottle-ready, half-Kamm-tailed downtube very similar to Cervélo’s S5, another, smaller Kamm-tail on the seat tube, integrated brakes that mix the best attributes found on Ridley’s Noah FAST and BMC’s TMR01, and wide headset bearings to maintain front end stiffness, à la Scott and Trek.
Integrated aero cockpit
Nothing is to be overlooked in the quest to reduce drag, and Giant honed in on the handlebar and stem as an area ripe for improvement. The top-tier builds on both the Propel and the Envie will come stock with the Contact SLR Aero integrated stem and bar combo.
The integrated cockpit weighs on 395 grams (claimed) and is designed to eliminate the often clunky interface between bar and stem, replacing it with a sleek, sharp connection. The tops are wing-shaped and sweep back three degrees for improved ergonomics. The bars feature a recessed top cap, dual-radius drops, 12 length/width size options, an optional computer mount and integrated Di2 junction box for exceptionally clean Di2 routing, and an OverDrive 2 steerer clamp with titanium hardware. The stem is fixed at negative eight-degree drop, and the whole integrated combo will set you back $550.
If bar/stem integration doesn’t work you you, Giant will also sell the Contact SLR Aero handlebar without accompanying integrated stem. The bars feature a standard 31.8mm clamp, and maintain the rest of the tech found in the integrated version — dual radius drops, three-degree top sweep, and aerodynamic wing tops. Weight is claimed at 230g for a 42cm width, and the price is $260.
Giant’s lab testing
Included in press materials for both the Propel and Envie are a number of lab tests, including head tube and bottom bracket stiffness and wind tunnel results.
Incredibly, Giant’s testing has shown that the Propel Advanced SL is actually faster in the wind tunnel than Cervelo’s S5, which is the fastest aero road frame we’ve ever tested at VeloLab, and is commonly considered to be the aero benchmark.
The rest of the data matched up with what we have seen ourselves: the S5 is very quick, followed by the tightly-packed Scott Foil and Specialized Venge. Just as we have seen, Giant’s data places the S5 considerably faster the rest of the frames currently on the market. Amazingly, the data shows the Propel taking another massive leap forwards, testing well over five watts faster than the S5 at both zero and 10 degrees yaw.
Without having been present for the testing, or seeing a full protocol, it’s impossible to say whether the data is valid; although it is unlikely that in today’s world of independent wind tunnel testing, including our own, a company would simply lie through their teeth.
There are a few things Giant did differently than we do in our VeloLab aerodynamics testing, the most obvious of which is that company performed its testing with a dynamic dummy — a mannekin shaped like pro rider Grischa Niermann that actually pedals as the test is performed — in order to more closely simulate the real effect of two churning legs on each bike’s aerodynamics. That could have some effect, particularly since Giant used this same dummy during the development phase.
However, a more likely source of some of the Propel’s incredible wind tunnel performance comes down to something much less dramatic than a robotic mannekin. Giant tested its own bike with the Contact SLR Aero integrated bar and stem, and tested all the rest with a standard round handlebar and stock stem. This likely skewed the results slightly in Giant’s favor — the bar and stem form a leading edge of the entire system, and considerable drag can be reduced through their refinement. However, these gains would likely only be in any way dramatic at close to zero degrees yaw, where the Propel does indeed have a decent lead over the S5, and do nothing to explain the incredible performance near at the higher yaw angles.
An intergrated bar and stem are certainly not the sole reason why the Propel tested so well, then. Given the sorts of gains we’ve seen are possible with a more aerodynamic cockpit setup, it’s safe to say that the Propel would likey fall quite close to the S5 if tested with identical cockpits. So, it’s still incredibly fast.
That fact is made even more impressive by the other data sets Giant included in its launch, most notably its stiffness testing. Giant’s testing shows the Propel’s front-end stiffness to be considerably higher than the Venge, Noah FAST, and S5; it loses out to the Scott Foil, which remains one of the stiffest frames we’ve ever tested.
In pedaling stiffness it again does quite well, sitting closely in line with (but just behind) both the Noah FAST and Venge, and ahead of the Foil. More importantly though, it once again trounces the S5.
If all the testing is to be believed, and these days that’s a matter of personal faith, it paints a picture of an exceptionally well-rounded frame. Without the integrated cockpit, it likely sits close to the S5 in the wind tunnel, but defeats it handily in all the stiffness tests. At the same time, all the bikes that we’ve proven more rigid than the Propel in BB stiffness are signficantly slower in the tunnel.
The Propel Advanced SL
At a claimed 950g frame weight, and 1,675g total module weight (frame, fork, brakeset, seatpost, seatpost clamp, and headset plug), the Propel Advanced SL is in with a fighting chance at being the lightest aero road frame on the market, an honor currently bestowed upon the Scott Foil. Giant claims its frame is eight grams lighter than the Foil, and when the rest of the module components are included, it claims the Propel is a whopping 233 grams lighter.
Geometry is the same as on the non-aero TCR Advanced model, except the Propel gets a horizontal top tube.
Some aero frames are simply assumed to be a sum of their parts — place an aero tube here and another there and voilà, aerodynamics. But true refinement, squeaking out those last marginal increases, comes from a system-wide approach. Giant calls these aerodynamic developments AeroSystem Shaping Technology, placing a focus on both tube and joint shapes, which have been nailed down only after hundreds of hours of Computational Fluid Dynamics (CFD) research, as well as wind tunnel testing.
The proprietary integrated brake system, dubbed SpeedControl SLR and built by TRP, is the most visibly notable drag-reducing feature. Both front and rear brakes are linear, like the v-brakes on your old mountain bike, and are designed to tuck in neatly behind the fork and seatstays. Giant has carefully shaped the trailing edges of each brake arm to keep airflow as smooth as possible.
The brakes feature the same leverage ratio as both new SRAM Red and Shimano 9000, and are adjustable for both wide and narrow rims with a small spacer. The brakes have a quick release and built-in barrel adjuster as well, so useabilty doesn’t appear to have been compromised.
The Propel has an integrated seatpost (ISP), similar to that found on the non-aero TCR Advanced, and features internal routing that can be easily swapped between mechanical and electronic groups. The company’s PowerCore bottom bracket area technology — a marketing term for a drastically oversized BB86 press-fit bottom bracket — and OverDrive 2 1¼”-to-1½” tapered head tube carry over from the TCR as well. The Propel will also be compatible with RideSense, an ANT+ speed and cadence transmitter integrated into the left chainstay, similar to Trek’s DuoTrap.
Wind tunnel testing was performed with a single bottle, and the downtube is shaped to better incorporate a bottle, tapering quickly from a traditional airfoil into a chopped off, Kamm-tail like shape.
The Propel is set to hit local shops this spring, sometime around March, and will be available in the following builds:
Propel Advanced SL0: Shimano Dura-Ace Di2 9070, Giant PSLR-1 wheelset, Giant Contact SLR Aero integrated cockpit. $10,000 MSRP.
Propel Advanced SL1: Shimano Dura-Ace 9000 mechanical, Giant PSLR-1 wheelset, Giant Contact SLR Aero bar and standard stem. $7,500
Giant Propel Advanced SL2: SRAM Red, Giant PSLR-1 wheelset, Giant Contact SLR Aero bar and standard stem. $7,000
The Envie Advanced has the distinction of being the first aero road frame purpose-built for women, and comes out of a development group that is entirely female, from designers to engineers to marketers. This is no shrink-and-pink job; Giant hasn’t simply downsized the frame and added feminine graphics. Both geometry and layup were designed from the ground up for female athletes, with input from Olympic and world champion Marianne Vos.
The essential design features remain the same as the Propel, though. The Enve uses the same tube shapes and has the same integrated brakeset, maintaining the oversized bottom bracket area and the stiff tapered head tube. The only bit of tech that is lost is the integrated seat post, as Giant chose to use a neatly integrated, proprietary-shaped seatpost instead.
With the Envie, Giant maintained the same women’s fit concepts used in the rest of the Liv/Giant line, notably the company’s 3F (Fit, Form, Function) design philosophy. The Envie gets a slightly shorter top tube and slightly taller head tube than the Propel, and is built with a completely different carbon layup schedule designed to deliver “optimized pedaling stiffness and efficiency as well as a smooth ride” — what exactly this means we’re not sure, although it’s safe to assume that the stiffness has been decreased and compliance increased with an eye towards smaller, less powerful riders.
“The geometry ensures that women are not just efficient while pedaling, but are also balanced for improved bike handling and performance,” said Abby Santurbane, head product developer for Liv/Giant. “The result is a unique aero bike that is amazingly fast on the flats, yet is still efficient while climbing, and easy to handle on descents.”
The Envie is also slated for mid-March availability.
Envie Advanced 0: SRAM Red, Giant Contact SLR Aero integrated bar/stem, Giant P-SLR1 Aero wheelset. $5,600.
Envie Advanced 1: Shimano Ultegra, Giant Contact SLR Aero bar with standard stem, Giant P-SL0 wheelset. $3,500
Envie Advanced 2: Shimano 105, Giant Connect SL bar, Giant P-SL1 wheelset. $2,550.