As a rule, aero road bikes have never rated among our favorites. Sure, they might slice through the wind with the greatest of ease and provide an eye-catching profile, but their tendency to be on the heavy side without much compliance has always held them back compared to road bikes.
It’s been about four years since Giant last did a serious upgrade to their long-serving aero race bike with the addition of disc brakes. In addition to a host of smaller refinements, the new Propel line has gone on a serious diet, and Giant claims it has also gotten more aero. The refined tubing brings it closer to the all-rounder TCR line but retains the aero-enhancing teardrop tube shaping. Our first question was whether this could be the perfect balance of aero and tube refinement we have seen from Giant.
The Propel has been in the giant catalog for many years now and has gotten a few redesigns, but none as significant as this. The new Propel Advanced 0 went through extensive CFD analysis and dynamic wind-tunnel testing. The truncated ellipse airfoil tube shapes are optimized at every real-world yaw angle. This is in conjunction with the new composite layup that reduces the overall weight of the frameset.
One of the most noticeable changes is the use of a smaller aero seatpost, similar to the one found on the TCR. The Propel fork is full carbon and actually uses the lighter and stiffer Advanced SL composite. Giant still uses the oversized carbon steerer, so if you want a different stem, remember it needs to be 1 1/4 inches, not 1 1/8 inches. The Propel frameset is built to route the hoses and wires internally, but Giant has put a little twist on this, making it easier than ever to adjust or swap stems and position.
Giant has maintained the race-oriented geometry for the Propel, and our size M has a wheelbase of 98cm with 40.5cm chainstays. The frame fits a size 30mm tire max, which is a bit smaller than we would prefer for a modern road bike. Our bike has a stack of 54.5cm and a reach of 38.8cm. There is a 14.5cm head tube at 73 degrees for a responsive but stable ride.
Giant offers two Propel Advanced Pro 0 models, one each in a SRAM or Shimano build. Our test bike featured the new semi-wireless 12-speed Shimano Ultegra Di2 drivetrain with a 52/36 crank paired with an 11-30t cassette and a mismatched set of brake rotors (160mm in the front and 140mm in the rear).
Our test bike hit the scale at 16.25 pounds, which is impressive for an aero bike with 50mm-deep wheels. The Giant SLR 1 50 wheels have a hookless bead and 22.4mm internal width. They are matched with 25mm Cadex Race tubeless tires.
All the rest of the build is self-branded with a Giant Vector composite seatpost, Contact SL Aero stem with OverDrive Aero internal routing, and a Contact SLR Aero handlebar and Fleet SL saddle. Overall, the build is solid and leaves very little need for an upgrade. Giant even provides a composite computer mount that integrates with the stem, as well as position-specific composite water bottle cages.
Setting up and building the Propel with its completely internally routed cockpit was one of the easiest experiences. The cable routing through the handlebar and what we are calling the hollow cutout stem makes it quicker and easier to adjust. The bottom of the stem is open, allowing you to pull the stem off the steerer and the hoses, then have slack to move.
Unlike the top-tier Advanced SL, which uses an integrated seatpost that needs to be cut to length, the Advanced Pro has an adjustable seatpost with a wedge to secure it. Compared to the previous version, the slimmer and shallower seatpost provides much better in-saddle compliance, something that almost all aero bikes lack.
On the road, the Propel has the same performance geometry you get on the TCR, making it fun, predictable and responsive. The Propel feels like it is fast and does offer more front-end road feedback than the TCR, but it isn’t overwhelming. For us, it only took a few rides, and we were feeling at home and willing to push the bike deep through corners.
Speaking of cornering, the Propel feels like it is at home going up a climb as it is racing down them. Out of the saddle, the Propel is responsive, and the cockpit is impressively stiff laterally. Even in heavy winds, the Propel seemed stable and unphased.
If there was one thing that left us scratching our heads and wondering what the team at Giant was thinking, it was the 25mm-spec’d tires. Sure, they are on a modern hookless rim and the quality is not in question, but 25mm is so dated. They do measure out to 26.8mm, but even for our fairly slim test riders, the recommended tire pressure is 70–75 psi. We did drop below that and had no issues, as the Cadex tires are fairly supportive yet supple. For us, a 28mm tire is the spec that should ship stock for all bikes.
The carbon Giant SLR 1 50 wheels have a claimed weight of 1518 grams, but the biggest complaint for some (and beloved feature for others) was their 30t ratchet-driver rear-hub engagement that is loud out of the box. Similar to DT Swiss hubs that also use a ratchet, the addition of a bit of grease to the engaging surfaces will quiet them down. For us, 12 degrees of engagement is fine on a road bike, especially an aero road bike.
As the world’s largest bicycle manufacturer, we have always been impressed with the value Giant offers. With that said, we are a bit disappointed that a race bike with so much refinement and race potential doesn’t come with a power meter. To get a Shimano drivetrain with power, you need to jump all the way up to the SL 0 with a hefty price of $12,500. So, for us, the SRAM Force version of this same bike is the real winner, as it carries the same $8000 price tag but comes with a Giant Power Halo power meter stock.
As always, the new 12-speed Shimano worked flawlessly, and our 11-30t cassette is essentially the 11-speed, 11-28t cassette but with an extra climbing cog. Overall, the Propel performs above our expectations and has us thinking that the TCR might be a rare sight in the pro peloton. Our Propel only comes in one color—dark purple—and while we like it, it was the most debated part of the bike in our weekend group ride.
• Aero with less weight
• Needs a power meter
• Tubeless tires that are too small
Weight: 16.25 pounds
Sizes: XS, S, M (tested), ML, L, XL