Giant Propel Disc 2018: aero road bike receives a major disc brake overhaul

We first caught sight of the the the pre-production Giant Propel Disc at this year's Tour De France, under eventual Green Jersey winner and Australian sprinter Michael Matthews. Having been three years in the making and much anticipated, the 2018  Giant Propel Disc is finally launched.

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It's the first time the Propel has had a make over since the launch of the bike back in 2013, and with competition from the Specialized Venge Vias, Trek Madone and Canyon Aero Road, the Giant was beginning to look a little left behind.

However, the brand hasn't spent these years idle. Instead of beating around the bush, it has gone in for a complete rebuild, with the 2018 Giant Propel Disc now claiming to have the highest stiffness to weight ratio of any of it's competitors.

Giant says it took three years of radical experimentation to deliver the Giant Propel Disc, as it was vital to ensure that the disc aspect of the bike was fully integrated and not an after thought or  just model variation.  The result is a bike that has new truncated ellipse shaped airfoil tubing on all tubes except the top tube, chain and seat stays.

The Giant Propel Disc uses flat-mount disc brake technology, a front (12 x 100mm) and rear (12 x 142mm) thru-axle which should offer exceptional stopping power. Interestingly, Giant also says that during aerodynamic testing its disc-brake integration produced less drag than traditional caliper brakes.

Giant says that the clean fork crown area, created by placing the disc-brake calipers down at the hub, makes the bike more slippery as the air hitting the new disc-brake caliper - that's mounted flat against the  bike - has already been disrupted by the leading edge of the tire/wheel.

Unlike the new design, the location of traditional calipers (either in front or behind the fork crown/legs) creates “dirty” turbulent air that slows a bike down.

As well as a chassis overhall, the Giant Propel Disc also has a new integrated Contact SLR/SL Aero handlebar/ stem unit, with internal cable routing. Also new is an integrated tubeless ready Giant SLR WheelSystem, coming with aero spokes.

The wheelset uses a taller 65mm rim depth on the back, which Giant says is proven in wind-tunnel testing to produce minimal drag, and a shallower 42mm rim at the front, which is less affected by crosswinds.

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There are three series in the Giant Propel Disc range, the Propel Advance SL Disc, Propel Advanced Pro Disc and Propel Advanced Disc, all of which feature the intergrated Contact SLR/SL Aero handlebar/ stem unit and SLR/SL Aero Wheelsystem.

The Propel Advance SL Disc is the flagship model with Giant's highest grade Advance SL carbon composite, and either a Shimano Dura-Ace Di2 or Ultegra Di2 electronic drive chain build option.

It's the same model we saw Matthews riding at the Tour de France and where the claim of highest stiffness-to-weight in its class comes from.

Giant says the total frameset (including forks, handlebars, seatpost, and bottom bracket) weight is just 2145g, only 45g heavier than the previous Giant Propel, and claim its nearly 500g lighter than the Specialized Venge Vias Disc, and nearly 300g lighter than the Trek Madone framesets.

UK prices to be announced on 5th September 2017.