Norco has launched a redesigned and revamped version of the Aurum, with larger 27.5in wheels, for 2015. BikeRadar travelled to California to try out this new bike and do some launching of our own!
It may seem as though Norco is a little late to the 27.5in party, but it actually started developing this big-wheeled carbon downhill bike way back in 2012. The goals were clear: to make the Aurum lighter, faster and more efficient.
While other manufacturers have rushed to release their 27.5in-wheeled DH bikes to the World Cup circuit and the showroom floors, Norco riders Jill Kintner and Bryn Atkinson were quietly been racing this bike throughout the 2014 season.
Finally ready to unveil its creation to the world, Norco invited us to sunny California to sample the fruits of their labour. How could we refuse?
The sleepy, picturesque mountain town of Idyllwild played host to the launch. There, after an detailed presentation on the bike’s development and technology, a dusty, boulder-infested downhill track awaited. Furnished with loose corners, technical rocky lines, doubles and drops, it was an ideal testing ground for the new Aurum.
Once the dust had settled, these were the features that really stood out.
After settling on the 27.5in wheel size – not a decision taken lightly, given that development started long before 27.5in DH bikes became fashionable – Norco redesigned the bike around these new hoops. That included revised linkage geometry to ensure the axle-path wasn’t compromised.
With 27.5in wheels, the axle sits higher than the bottom bracket – this naturally gives the bike a more forward axle-path, so Norco has designed the linkage to compensate for this. The seat tube has also been brought forward to allow room for the bigger hoops, and the head tube shortened to compensate for the taller fork.
The forged aluminium rear linkage optimises axle path while maximising stiffness:
The forged aluminium rear linkage optimizes axle path while maximizing stiffness
Despite the increase in wheel-size, the head angle remains stubbornly slack at 63 degrees. All frame sizes have been made 10mm longer in the front-center and have a 5mm lower BB height, compared to the old Aurum.
The leverage curve has been tweaked, providing more support in the mid-stroke to cope with the demands of World Cup racing and aggressive riding.
Allied with a fairly firm base tune on the shock, this translates into a noticeably supportive and efficient feel on the trail. The bike was keen to pop and hop over the rock-strewn test course, and was resistant to wallowing when pushed in the corners. The Cane Creek shock on the test bike has the same base tune as the shocks on the production models will have. This has been tailored to the needs of the bike and felt nicely set up from the off.
As I became more confident on the bike, I sped up the low-speed rebound by one click to boost compliance, and added one click of high speed compression to cope with the bigger landings. These are simple adjustments, and were only necessary to suit my personal style of riding, rather than to compensate for any shortcomings in the bike. The stiffness of the frame added to the Aurum’s playful feel, helping it to stay on line while the suspension dealt with the terrain.
Gravity Tune geometry
Following feedback from a range of test riders, Norco concluded that the ideal rear center length is related to the rider’s height and chosen frame size. The rear center lengths on the new Aurum are proportional to the front center, helping riders of any size to achieve a similar weight-balance.
Bryn Atkinson was instrumental in this: as a taller rider, that he found overly short chainstays made the bike feel unstable at speed, and unpredictable in corners. “Like standing on the pegs of a BMX,” he said.
Slack and low geometry makes for confident cornering:
Slack and low geometry makes for confident cornering
From this experimentation, Norco decided on a 445mm chainstay for the size large bike (as tested). This fairly long rear center biases the rider’s weight further forward, aiding front-wheel traction. The downside of a longer chainstay is a longer wheelbase, which hinders maneuverability. The point is, though, that Norco has tried to strike the ideal balance between stability and maneuverability, tailored to each frame size.
At 6ft 3in, I found the 442mm reach on the size large bike a little cramped. I’d like to see an XL size become available for taller riders.
Despite being designed and tested in the crucible of World Cup racing, the bike is made with the rider in mind. External cable routing ensures faff-free fettling, so an amateur rider can swap out his or her brake with relative ease.
Burly frame protectors incorporate cable guides for the external cable routing:
Burly frame protectors incorporate cable guides for the external cable routing
The frame bearings are designed to be hard-wearing and easy to service, and a comprehensive suite of frame protectors shield the precious carbon from harm.
The Norco Aurum C1 model shown here features a SRAM X01 DH drivetrain, RockShox Boxxer WC fork, DT Swiss EX471 wheels and a Cane Creek Double-Barrel shock. It’ll set you back US$7,000.
The claimed weight on the size medium C1 model is (15.6kg) 34.4lb, which points to its race-winning intentions.
There’s also C2 and C3 models available, which sporting identical frames and more affordable kit for US$5,800 and US$4,230 respectively. A drool-inducing ENVE-wheeled build is also available, US$9,700.
The new aurum sports bigger wheels and a carbon front end, but that’s not all that’s new:
The Norco Aurum C1 will retail for US$7,000
Availability and pricing
The 2015 Aurum is expected to be available from April. Pricing is as follows: