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Aero road bike has been redesigned with disc brakes

Giant has redesigned the Propel for 2018, introducing several new models including the Propel Advanced Disc we have here, priced at £2,999. Rim brake versions of the Propel have been in the Giant line-up for years but this is the first time that disc brakes have been added.

Check out our news story from when Giant first revealed its Propel Disc aero road bikes.

In Giant’s world ‘Advanced’ means that a frameset is made from carbon-fibre. The Propel Advanced SL Disc is the top-end platform, then you get the Propel Advanced Pro Disc, made from a lower grade of carbon, and then there’s this one, the Propel Advanced Disc, with carbon that’s different again. 

Giant Propel Advanced Disc.jpg

Giant Propel Advanced Disc.jpg

Giant says that the Propel Advanced Disc lineup had a development phase of three years involving its in-house engineers, Team Sunweb pro racers and aerodynamics experts at the Aero Concept Engineering facility in Magny-Cours, France. They used a moving mannequin on the bike in the wind tunnel, with spinning cranks and wheels, and they tested yaw (apparent wind) angles up to 30 degrees. They claims this results in the most accurate aerodynamic analysis possible. 

The results to the lineup are:

• New frame profiles
• An integrated disc-brake design
• New aero handlebar and stem system
• Internal cable routing
• Aero wheelsets with different rim depths front and rear (the idea being to reduce drag without compromising control or power transmission).  

Giant Propel Advanced Disc - down tube.jpg

Giant Propel Advanced Disc - down tube.jpg

One of the key features is a new truncated ellipse airfoil shape that’s used on the frame. The profile is designed to reduce drag at a wide range of wind angles, and it’s cut off square at the back to save weight, stick within the UCI rules, and make sure the bike doesn’t handle poorly in crosswinds. The idea is that, in terms of aerodynamics, the wind acts almost as if the tube profile tapered off gradually. Lots of other manufacturers do something similar with their aero tubes.

Giant Propel Advanced Disc - UCI sticker.jpg

Giant Propel Advanced Disc - UCI sticker.jpg

Interestingly, Giant says that with proper integration, a disc-brake design can actually improve aero performance over a rim-brake setup. That’s a significant claim in that one of the arguments often put forward against disc brakes is that they increase drag. 

Giant Propel Advanced Disc - fork detail.jpg

Giant Propel Advanced Disc - fork detail.jpg

“This is because the location of traditional callipers (either in front or behind the fork crown/ legs) creates 'dirty' air,” says Giant. “Opening up the fork crown area (by placing the disc-brake callipers down at the hub) means that the air hitting the new disc-brake calliper has already been disrupted by the leading edge of the tyre/wheel. This effect is further enhanced by an asymmetric fork that helps smooth out airflow over the calliper.”

Giant Propel Advanced Disc - rear disc brake.jpg

Giant Propel Advanced Disc - rear disc brake.jpg

Like most disc-equipped road bikes these days, all of the bikes in the Propel Advanced Disc range use Flat Mount disc brakes. The wheels are held in place by thru axles front and rear.

Giant Propel Advanced Disc - stem.jpg

Giant Propel Advanced Disc - stem.jpg

The new Contact SL Aero handlebar/stem system was designed with internal cable routing for better aerodynamic efficiency. 

Our review bike came fitted with a large stack of spacers, but you can reduce the height in the usual way by removing a few of them and chopping down the fork steerer. It’s only the leading part of that stack that’s actually made up of spacers, the rear part is a rubber shroud that hides the cables away.

The Propel Advanced Disc features Giant’s own SLR 1 Disc wheelset. The rear wheel has a 65mm deep rim, the idea being to provide of aero efficiency and power transmission, while the front wheel has a shallower 42mm rim for improved crosswind stability. These wheels are matched with Giant’s Gavia tubeless tyres.  

Giant Propel Advanced Disc - drive train.jpg

Giant Propel Advanced Disc - drive train.jpg

Giant Propel Advanced Disc is built up with Shimano’s Ultegra groupset with a 52/36-tooth chainset and an 11-28 cassette, which sounds like a setup that would suit this kind of bike. Everything else on the bike is Giant’s own, including the Giant Contact saddle.

Giant Propel Advanced Disc - bottom bracket.jpg

Giant Propel Advanced Disc - bottom bracket.jpg

An aero bike isn’t really about weight but our M/L model hit the scales at 8.48kg (18.7lb).

We’re really interested to find out how the Propel Advanced Disc bike performs on the road, and that’s exactly where we’re taking it. Look out for a review on road.cc soon.

www.giant-bicycles.com

Mat has worked for loads of bike magazines over 20+ years, and been editor of 220 Triathlon and Cycling Plus. He's been road.cc technical editor for eight years, testing bikes, fettling the latest kit, and trying out the most up-to-the-minute clothing. We send him off around the world to get all the news from launches and shows too. He has won his category in Ironman UK 70.3 and finished on the podium in both marathons he has run. Mat is a Cambridge graduate who did a post-grad in magazine journalism, and he is a past winner of the Cycling Media Award for Specialist Online Writer.