Gearing up

The bicycle as a design was essentially perfected more than a century ago. Despite myriad improvements that have optimised the machine over recent years including pneumatic tyres, derailleur gears, ski binding-inspired safety pedals and suspension systems for mountain bikes, the basic concept has remained the same.

While telescopic front forks first appeared about 15 years ago and are now standard, more extreme riding demands rear suspension for which there is no widely accepted solution. Simple systems fail because riders cannot tolerate pedal feedback through the chain and although elaborate linkage and pivot systems can help minimise this problem they demand lots of maintenance. However, there is one novel attempt to solve this problem that may just bring about the next great step forward in bicycle design.

The iT-1 from Southern California-based GT Bicycles looks at first glance like any other top-end full-suspension mountain bike, with high ground clearance to allow around 9in of suspension travel, hydraulic disc brakes and huge tyres. But on closer inspection two features stand out: no rear derailleur and a £4,000 price tag.

GT has also done away with the front derailleur, as well as the cluster of up to nine sprockets at the rear wheel, by building the bike around an enclosed eight-speed planetary gearbox mounted above the cranks. Critically, the output sprocket is coaxial with the pivot for the rear suspension arm. It is the world’s first complete production-model bike with an internal transmission.

According to iT-1’s product manager Mark Peterman, this bike was built for downhill racing and was inspired by motocross bikes, where the chain follows the arc of the swing arm. Moving the transmission out of the rear wheel also slashes unsprung weight, further enhancing suspension performance, and improves front-rear weight distribution and handling.

The concept was first shown at the 1998 Interbike industry exhibition in Las Vegas ‘to great fanfare and lots of head-scratching’, he said. GT had already distinguished itself with probably the first four-bar rear suspension linkage available on mass-market bikes, but, said Peterman, these were difficult to manufacture and maintain. Then, he said, came an ‘epiphany’ when Japanese cycle components giant Shimano introduced its Nexus eight-speed rear hub. GT built the iT-1’s transmission around that component.

In addition to suspension performance, the iT-1 was designed to help downhillers actually make it through their events, which last three or four minutes at speeds up to around 50mph. Exposed rear derailleurs are easily broken on rocks or branches.

Andy Kyffin is a mechanic at the North West Mountain Bike Centre in Cheadle, Cheshire, and has supported world-class downhillers. He worked with GT on the iT-1 project and said another motivation for developing a gearbox bike was to eliminate the rear derailleur’s sprung jockey wheels, which are needed to shorten or lengthen the chain when shifting gears but also allow it to bounce off the sprockets.

The later introduction of supplementary chain retention devices means chain loss is no longer a major problem, but he remains enthusiastic about the gearbox concept. ‘A motocross bike without the engine could be a good thing for the downhill,’ he said.

That notion is being taken almost literally by Honda, which got into downhilling in 2003 apparently to develop suspension and gearbox technology for motorcycles. The firm is highly secretive about its design, but one of the bikes was ridden to a silver medal in last month’s world championships, in New Zealand.

Unfortunately, said Peterman, in 1998 Shimano ‘put a knife in the heart’ of the project by refusing to certify the Nexus hub’s external housing for use in downhill racing. Shimano subsequently redesigned the Nexus hub shell and, as fortune would have it, the market also moved in GT’s favour. By 2003, when the bike was shown again at the Eurobike exhibition in Germany, so-called ‘free-riding’ had become a major market.

This non-competitive mix of kamikaze downhilling and extreme stunt riding in remote locations demands great suspension performance and supreme reliability. Weight is not an issue, and in any case the iT-1’s 45lb is middling mass for a freeride bike, said Peterman.

But when he adds that sales last year were only 200 units worldwide it is hard to conclude that the iT-1 represents the future of bicycle design, even in its speciality niche. Even if Peterman’s forecast of a 50 per cent rise in 2007 to 300 units comes true, the bike still looks like a curiosity.

Further restricting this bike to specialist applications is the fact that, while eight gears may be enough for what Peterman describes as a ‘gravity bike’, they aren’t enough for ordinary cross-country use. The range of gears compares to a typical 24-speed derailleur system, but the spacing between them is far larger, even considering that the 24-speed bike has maybe only 16 or so distinct ratios. Another downside, added Kyffin, is that planetary gear systems offer some drag and don’t always change gears crisply.

However, the concept remains immensely appealing for cyclists. British Cycling Federation spokesman Philip Ingham said the iT-1’s price wasn’t ridiculously expensive for professional downhillers who go to extremes for a winning edge, as races are decided by thousandths of a second.

Andy Kyffin is even less bothered by the price. North West Mountain Bike Centre sells a few all-out downhill bikes for as much as £5,700, and there are many models in the £3,000-4,000 range. If mass production brought prices down, he said, sales would soar; riders would eagerly buy a bike in the £700-1,000 range just to spare their transmission from exposure to British weather.

Moreover, while derailleur gears can only be shifted during pedalling, planetary gears can be shifted at any time, even when coasting or standing still. As there is no changing between gear ranges at the front derailleur, shifting is also simply a case of ‘up’ or ‘down’.

Even more exotic than the iT-1 are the G-Boxx bikes handcrafted by Karlheinz Nicolai in Germany and sold — in single-figure volumes in the UK — for prices upwards of £5,000. These are built around a 14-speed planetary gear hub mechanism from Rohloff of Germany. Nicolai may seem an unlikely catalyst for a mass-production revolution, but he is confident his patented system will be chosen by many bike makers who want to get into gearbox bikes. His strategy is to promote an open-standard interface between the gearbox and the frame, and to license G-Boxx technology to rival bike builders and to SR SunTour, a Japanese components maker that makes him, in effect, a mass producer.

At last month’s Eurobike exhibition in Friedrichshafen, British mountain bike maker Orange — which supplies 2006 junior world downhill champion Tracey Hannah, of Australia — showed a G-Boxx concept bike. Nicolai said other brands have approached him for gearboxes and he is certain that, with a standard interface, gearbox bikes will eventually take an important percentage of the market for mountain and city bikes. He believes in two or three years G-Boxx bikes will be available for around £2,500, and said the current weight penalty of about 1kg over a derailleur bike can be cut to 500g with designs he is working on.

GT, meanwhile, is preparing to launch a less advanced version of the iT-1 for half the price in 2008. Peterman said GT’s objective is to push Shimano to make a dedicated gearbox that could be slotted into a standard shell design. He added that so far GT’s suggestions have been met by polite nods from Shimano. But the Japanese company has huge influence in the bike business and if it decides to push gearboxes then GT will soon have competition.