Sunweb’s sprinter Michael Matthews was on a new disc brake bike from team sponsor Giant for the road start of the Tour de France this week. It’s not the first disc brake Giant the we’ve seen Sunweb race, having detailed Bert De Backer’s Defy Disc in this year’s Spring Classics. This pre-production Giant Propel Disc not only suggests that a disc brake specific aero bike is on the way from the Taiwanese bike maker, but all new aero tube shaping could suggest that a full overhaul of the Propel line is imminent as well, with the carbon rim brake bike last updated in 2013 and an alloy version in 2015. Take a closer look at the bike, including the team’s thoughts on discs and fit…

The new Giant Propel Dic strikes a similar profile overall to the current Propel, but a closer look shows all new tubing shapes that for the most part are wider throughout. The downtube for example maintains a more constant depth from the headtube back to the even bigger bottom bracket and gets a chopped off aero Kamm profile for its full length.

Wider tubing also equates to wider tires, with plenty of space around Matthews’ unmarked 25mm Vittoria Corsa tubular tires.

The disc brake aero bike also gets an all-new fork shape, with a more straight and flat-sided set of legs, and an angular extension transitioning back into the downtube. As we can see here and in the photo at the top, the fork gets flattened and angular aero fork tips that extend below the axle.

The disc specific fork also gets a neatly integrated flat mount disc brake adapter that lines up with the fork blade while still offering 140 or 160mm rotor compatibility. We can also see pretty seamless internal routing for the front hydraulic line that enters the steerer tube inside of the stem and exits midway down on the inside of the fork leg.

Curiously like Kittel & Quick-Step, Matthews & Sunweb have ignore the UCI consensus for bigger rotors and have again opted for Shimano’s newest Dura-Ace R9000 series IceTech Freeza rotors in 140mm for both front & rear. While this Propel Disc was setup with a quick-release lever of the front 12mm thru-axle, the rear of the bike goes with a simple 5mm hex bolt interface.

The press fit bottom bracket stays the full massive width of the downtube with an angular transition from the Kamm tail shaping up front. The rear wheel tucks in nicely to the frame cutout, but there are still several mm left for a larger tire if needed. The frame still includes Giant’s Ride Sense speed & cadence sensor integrated into the non-driveside chainstay. And we can also see that Sunweb is one of the first teams to be racing on Shimano’s new R9000 Dura-Ace dual-sided power meter crankset. (It has the unique non-driveside axle cap here, and visible sensors in other photos.)

Of course the huge Giant steam and matching aero profiled carbon handlebar were eye catchers as well.

Matthew’s already long stem looks even longer due to the extended top and rearward covers that manage to completely hide all of the cables internally, including both Di2 shift wires and hydraulic brake lines. The stem uses a fairly standard removable faceplate to clamp the shaped bar, which means it is easy to interchange stem lengths, but has no means to adjust the bar angle.

Opening up the top cover’s four bolts allows access to all of the internal routing, with the rear brake and Di2 shift wiring entering the toptube just behind the stem. In fact the small segments on the rear sides of the steam are actually flaps (you can see the upper hinge element) that pivot up as the bar is turned to keep from binding on the rear brake hose. Presumably the same setup will work with mechanical shift cables and the cable actuated brake on a rim brake version.

Like the current Propel, this new bike uses an integrated seat mast with an alloy seat topper, and the extended lower clamping bolt makes for a tidy mount for that race number.

The seat cluster is a bit revised with a webbed section between the flattened toptube and aero seattube in what has been shown to reduce air turbulence. The end of the dropped seatstays also have a revised shape that is a bit more angular and flat-topped than the current Propel.

The UCI approved sticker number names the bike as the Giant “Propel Advance SL Disc MY18” with six sizes from XS-XL approved to race as of May 18th.

The last look at the front of Matthews’ Propel Disc has a fairly rigged together out front-style computer mount working off of extended faceplate bolts like the FormMount that we recently reviewed.

Giant has been tight-lipped on the official rollout of the new Propel Advance SL Disc, but the UCI approval from back in May also included a Propel Advance Pro Disc version as well, so expect to see at least that coming soon. Interestingly the UCI list does not have a new rim brake Propel listed, so Giant may be going disc-only with their aero bike from here forward.

As for the Sunweb team, for the most part they seem to be totally onboard with the move to disc brakes for improved stopping performance. Giant has worked with the to develop the new bikes, and they say they’ve been able to maintain the exact same racing geometry, fit, and handling with the added benefit of being able to race on wider tires as race surfaces dictate.


    • Yeah! How is it that the disc bike is the “aero” one when it has twice as many spokes on it’s front wheel?

      • Well, wheels aren’t the only thing…
        That said, I do think aero disc road bikes are stupid but I’m ok with people making them. I just think it’s extra stupid to only make them when a rim brake version will be faster…from frame to wheels.

        • Stupid? Why? Some people will prefer an aero bike due to the majority of their riding. The disc option will add better braking, especially in the wet, for minimal aero penalty versus a non-aero disc bike.

        • Stupid? “Faster” is always a trade off, even in aero optimised bikes. Sacrificing a small fraction on the aero side to achieve greater stiffness might turn out to be faster than purely optimised aerodynamics. Better braking can also be “faster” over the course of an entire ride/race. To determine what is “faster”, you have to look at the total package, not just one aspect.

          • The fastest riders brake the least. So yeah, it’s stupid to have this be the only option. I get why you’d pick this in the rain. But not at all in the dry.

            • Disk brakes are never about having the STRONGEST braking, but having the most CONTROLLED braking performance, so as not over compensate when pulling back the levers. Indeed, to precisely control your speed in turns without over braking is what makes disk brakes faster. As such, your point is moot.

  1. That stem looks the business, it’ll leave a mark if you ever hit it going over the bars. Then again, i suspect you’ll have other problems to attend to by then….

      • Because “aero” frame advantage is minimal at best at very high speeds.
        At those speeds, you’re better off on a tri bike and gruop riding removes the aero advantage.

        Ride position, comfort and power is far more important than any aero advantage frame can give you. Even wheels are an order of magnitude more important.

        If you’re looking for any advantage, it will matter only on long rides at which point more comfortable bike is going to be better.

        It’s ridiculous that 99.9% are getting aero bikes thinking they’re going to make them faster an if won’t beside they can’t maintain 45-55km average.

        • Specialized proved in their tunnel(comparing their own products against one another) that aerodynamics even matters on XC mountain bike and XC racing speeds which are not remotely fast. At least not fast compared to normal road riding.

    • Ideally, I’d like all my road bike aero, with the comfort of a “standard” bike. Over time, this will happen. Today’s aero bikes are often much more comfortable than standard offerings just 5-10 years ago.

  2. Cyclists need to take all the energy that they have for arguing about aero on forums and use it to maintain an aerodynamic tuck. They are going to need it.

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