A tiny New Zealand outfit are taking on something just about every big bike brand has considered, prototyped and then shelved – the internal gearbox bike. It’s been one of the holy grails of bike design for a while. Just as we were starting to accept that it would stay in the realms of fantasy, along came Zerode and the G-1.
The performance benefits of an internal gearbox are numerous and easy to understand. For a start, the gears and the parts used to shift them are packed away in a weatherproof housing. Mud and water can’t get at them, wear is reduced and there are no fragile bits of metal to snag and break on rocks. Shifting is smooth and consistent – smashing in another cog under maximum exertion over the finishing line will feel exactly the same as your first shifts of the day rolling around the car park.
The downsides of previous designs have been weight and a loss of pedalling feel as the directness of the traditional setup is lost. But that’s not the case here. An eight-speed Shimano Alfine touring hub is the heart of the gearbox. It’s a sealed unit, which weighs the same as the sum of the parts it replaces. Positioned snugly above the shock in the mainframe, the gearbox moves the weight of the transmission from its traditional position at the end of the chainstays to the front triangle.
As a result, Zerode have increased the sprung weight (the rider, frame…) and reduced the unsprung weight (the rear wheel, brake…) so the back end is more sensitive over obstacles. This in turn offers greater suspension performance throughout the G-1's huge 235mm (9.25in) of travel. Moving the weight inboard also improves handling. The main mass of the bike is centralised and where you want it for the best manoeuvrability – between your knees.
Path of least resistance
Zerode weren’t content with ‘just’ producing a gearbox bike though. They also addressed what they saw as a glaring omission of many suspension designs. With the transmission gubbins out back, many manufacturers focus their efforts on achieving a vertical wheel path (where the rear wheel travels up and down). Zerode reckon that hits on the trail rarely come in a linear fashion, instead reasoning that having a more rearward path enables the wheel to flow over obstacles, as opposed to bouncing out of the way.
By reducing the slowing effects of hits, the Zerode can carry more speed. Moving the gearbox inboard added to this improved responsiveness – so much so that the Kiwis claim impact stresses are reduced to the point where you can run lighter wheels. When it comes to geometry, Zerode have decided to keep things long, slack and low. The G-1 has a 64.5-degree head angle, a 355mm (14in) bottom bracket height and will be available in short and long (562 or 602mm) top tube lengths.
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Anything is possible
The Zerode G-1 is available as a frameset (comprising frame, Fox DHX RC4 shock, shifter, gearbox, tensioner, rear sprocket, spacer kit and axle) from £2,700, and as a custom build to whatever spec your wallet can handle. They’ve even got an all-mountain version in the pipeline for those who want to take the G-1’s bold performance on all-day jaunts.
It’s hard not to admire the plucky blokes at Zerode – they’ve taken on the perceived rules of downhill frame design, chewed and digested them, and then still decided to chuck them out of the window. Without forward-thinking manufacturers like Zerode making rule-breaking bikes, the market would stagnate. Watch this space to see if their bold promises for the G-1 add up to a ride as revolutionary as they claim. For more details, visit www.zerode.co.nz or www.prestige-cycles.co.uk.
This article was originally published in Mountain Biking UK magazine. The latest issue, #274, is out now and includes a look at dirt jumper Sam Pilgrim's NS Majesty.