Giant Propel Advanced SL 1 Combining wind-beating speed with uncompromising stiffness and weight
Combining wind-beating speed with uncompromising stiffness and weight
Road bike design is frequently an exercise in compromise: light and stiff designs tend to be as aero as a brick; aerodynamic designs are often heavy or ride like a wet noodle, sometimes both. To paraphrase bike-design pioneer Keith Bontrager, “Light, stiff or aero – pick two.” So Giant’s claims for their new aero road offering, the Propel Advanced SL, seem quite bold. The company says the bike not only weighs less and tests better in the wind tunnel than any other aero road bike, but it also offers comparable stiffness to their top-end tcr Advanced SL, one of the best all-around road race bikes in our estimation.
Giant spent two years
developing the Propel, spending many hours at the ace wind tunnel in Magny- Cours, France. To ensure that the testing reflected real-life conditions as much as possible, Giant used a pedalling mannequin and reduced tunnel speed to 40 km/ h from the industry standard 30 m. p. h. (48 km/ h), a more realistic speed for the majority of cyclists. The result of that work can be seen in frame tubes that have been whittled into airfoil shapes; the seat tube cut- out that hugs the rear wheel; and the hourglass head tube that Giant’s road category manager Jon Swanson said, “leaves only a millimetre or two of clearance between the inside of the head tube and the steerer tube.” Giant says the fork weighs in at 380 g and the frame is 950 g.
Despite all the aero shaping and drag-saving features, the thing that most struck me during my test rides was how unlike a typical aero road bike the Propel felt. Part of that is the shared geometry between the Propel and the tcr Advanced SL, a bike on which I’ve had a lot of saddle time. But much of the ride quality is owed to the solid-feeling frame and fork, which uses Overdrive 2, Giant’s name for the oversize 1 ¼" to 1 ½" steerer. The wide bb86 bottom bracket allows the down tube to flare to nearly the full width of the bottom bracket, ensuring every watt from your pedal strokes goes to the rear wheel.
Climbing out of the saddle during my regular weekly hill loop and sprinting in the office throw- down, the Propel displayed no detectable flex. In fact, the Propel felt and reacted almost identically to the tcr, my regular machine. The only significant difference is that I felt the high-frequency- buzz road vibrations more on the Propel, something only noticeable after long hours in the saddle and alternating back-to- back rides. Descending with the Propel was a pleasure; the oversize front backed by the tcr- derived geometry makes for a confidence- inspiring experi-ence, whether I was descending the familiar switchbacks of Snake Road, or the back of Willunga Hill in Adelaide, Australia for the Propel’s launch.
The aerodynamic bona fides of the Propel are hard to verify without going to a wind tunnel, but there was a noticeable difference in how long and comfortably I was able to hold a turn at the front of the group on the Propel compared to the tcr or other non-aero machines from other manufacturers. Interestingly, during this year’s Giro, more than one Giant-sponsored Team Blanco rider, including general classification hopeful Robert Gesink, chose to ride the Propel with aero bars during the time trial stages, forgoing Giant’s own dedicated TT bike, the Trinity Advanced SL. A strong endorsement of the Propel’s aero credentials.
The test model was equipped with
the new Shimano Dura-Ace drivetrain, currently the best mechanical groupset in my opinion. The new hood ergonomics are a vast improvement over the previous model and the shifting manages to combine the smooth and light effort Shimano is known for with a positive click action. The only omission from the complete Dura-Ace group are the brakes, replaced here by Giant’s own SpeedControl slr. Essentially a V-brake design with aero-shape arms, the SpeedControl slr blends in nicely with the fork and seatstays and are designed to work with the leverage ratio of Shimano and sram levers. In use, they actually provide very good stopping power – close to Dura-Ace level, the current benchmark – but provide significantly less modulation with braking feel more of an on/off switch rather than the smooth progression of Shimano’s new Dura-Ace brake set.
In the cockpit, the carbon- fibre Contact slr aero bars and stem have compact- reach drops with a natural, comfortable feel. The shape of the bar top strikes a nice balance between aero and comfort. The enormous boxsection stem ensures that none of the steering precision from the oversize front end is lost.
Giant’s P-slr 1 aero wheels’ performance was the surprise of the test. The mid- depth 50- mm aero wheels, at 1,575 g, spun up easily and helped the bike hold its speed on the flats. The hoops were also solid laterally, even during low-cadence climbing out of the saddle. Although they don’t have the sophisticated blunt shape of the latest generation aero wheels, the P-slrs don’t come to sharp V and feature 23- mm wide rims, which provide a smoother transition for better aerodynamic performance with 23-mm and wider tires. The extra width also has the added bonus of creating a rounder tire profile, leading to better cornering and slightly improved ride feel.
With the Propel Advanced SL, Giant has very nearly created the no- compromise aero road bike. It’s something that matches their flagship tcr Advanced SL in every category save for comfort. Fast riders take note: the Propel bests the tcr in out-and- out speed. Great news, although you’ll have one less excuse when you shirk your turn at the front of the group ride.