Take a look into the crystal ball with us. We have dedicated the 12/2017 issue of BIKE to the future of mountain biking. A key question: "What will mountain biking look like in a few years?" Who's the best person to ask? The famous science fiction philosopher Stephen Hawking? No, we preferred to ask mountain bike visionary and design luminary Lutz Scheffer. His designs for Votec, Bergwerk and Canyon have set technology trends over the last two decades. He now develops for Rotwild. When we ask him to draw us a bike for the year 2037, but please without a motor, he has to laugh.
"Do you really think we're still biking ourselves? As a biological body? Our mind will have long since been transformed into a machine, or our brain will have shrunk because supercomputers will be able to do our job on earth much more sensibly," he jokes, but then adds in a matter-of-fact tone: "Despite all the e-MTB euphoria, there will certainly be a trend 'back'. A bike that is completely unproblematic and reduced to the bare essentials. Lightweight, low-maintenance, manageable, low-maintenance technology - these are the key points.
The red deer study that he drew for us actually looks like a real mountain bike. Quite unspectacular at first glance. But the bike is full of ingenious details: internal shock absorber with spring characteristics that adapt to the terrain and riding situation. Fully retractable seat post with automatic saddle tilt adjustment, depending on the gradient. Sensitive, light yet stiff upside-down fork - Scheffer believes this is the fork principle of the future. Another practical feature is the tool compartment in the down tube, which is somewhat reminiscent of the SWAT system from Specialized. However, Scheffer paid particular attention to the gearing.
BIKE: What are the considerations behind the study?
Lutz Scheffer: The future is usually less spectacular than you might think - it develops behind the scenes. Evolution takes place in small steps. Things that have not changed for a long time will probably remain very stable until a completely new basic technology appears. Then, however, there will be an upheaval with effects and products that no futurologist, scientist, visionary and so on has ever been able to predict and probably never will be able to. Perhaps philosophers would be the only and possibly more suitable candidates for predicting the basic principles of social and technological development.
Every significant invention that has changed society and opened up new fields of application or thought was neither conceived nor deliberately intended in this way. Some inventions will also return to age-old technologies. Cargo sailing boats, for example. The wind blows constantly across all oceans and could move huge ships with millions of tonnes of cargo without using a single drop of oil. Other inventions had a completely different intention. Similar to the evolution of the bird and the feather. It certainly did not come about with the intention of creating a living being capable of flight.
The chain is one of the things that led to today's original form of all bicycles. Since then, only details have been improved. I've thought of a few detailed improvements centred around the drive, suspension and ergonomics. All in all, they have to offer a real advantage: this is best measured in terms of efficiency for sports equipment. If the efficiency is poor, the invention will very quickly disappear by itself. Humans don't have much to waste with their limited performance.
What is important to be able to get around effectively on a bike?
On a mountain bike, the drive is one of the most important and elementary things. It is, so to speak, the essence of mountain biking. The muscle only works efficiently within a small window of force and contraction speed. Transferred to the crank, this means Pedal pressure and pedalling frequency must be right.
A gear change is therefore essential. Wind, gradient and rolling resistance must be overcome. Ergonomics, i.e. power generation, and traction, i.e. power transmission, must also be right. Key point: sitting position and posture. A gear spread of at least 600% is necessary to manage uphill and downhill sections with a favourable speed and power at the crank.
How can this be explained?
A simple calculation: Let's assume a 20% gradient and a system weight of 80 kg - i.e. rider and bike together. To ride the incline at a mere 6.5 km/h, you already need 300 W of pedalling energy. That is the endurance performance of a very well-trained athlete. On the flat, you can pedal at exactly 33 km/h with 300 W to overcome the wind and rolling friction.
Now I want to be able to pedal downhill, let's say on a 5% downhill gradient, with an additional 200 W to reach 44.9 km/h, for example. Within this speed range, I want to pedal at the physiologically ideal cadence. This varies from person to person, but is around 80 to 100 rpm. The necessary gear spread is then calculated from 44.9 km/h to 6.5 km/h. That makes 690 per cent.
Modern 1x12 circuits have 500 % ...
That's right. You can already see that a gearstick with a 500% gear spread is not enough to cover everything with a constant pedalling frequency of 6.5 to 44.9 km/h. You have to pedal slower on steep gradients and faster on descents to get by with 500%. That's not ideal. However, a 20 per cent gradient is not unusual for an MTB route in the Alps. There are many passages here that are significantly steeper than 30 per cent. What I want to say is that an MTB needs gears with a gear spread of at least 600 to 700 per cent.
From a muscular point of view, slow pedalling on inclines - at a 50 or 60 km/h frequency - is less efficient. It therefore limits the maximum possible inclines or long, sustained riding on inclines.
So what could be the solution?
This connection just described justifies the use of an additional two-speed planetary gear - a two-speed hub in combination with the derailleur. Well made, in the style of a Rohloff, it has an efficiency of 98%. It is important to know that pure derailleur gears with the lower number of teeth - 10, 11 and 12 sprockets - only have an efficiency of less than 95%. The reason for this is the so-called polygon effect and the strong bending of the chain under tension.
Therefore, a healthy number of teeth, with which you achieve 98 % efficiency, together with a planetary gearbox, which also has 98 % efficiency, is better than a poor chain transmission. Chain efficiency plus planetary gearing equals 0.98 times 0.98, so the bottom line is 96 %.
Conclusion: The interaction of hub and chain transmission in the fast gears results in better efficiency than a pure chain transmission with small sprockets. In the slow gears, the gear hub is directly bridged 1:1 and therefore does not generate any losses. The chain transmission then works alone with a healthy number of teeth.
The study is equipped with an 8-speed sprocket set in combination with a two-speed gear hub. So it remains exciting when it comes to shifting?
I think so. The two-speed gear hub in combination with the 8-speed derailleur in my study achieves a gear spread of around 60 %. The efficiency is high because I don't use the very small 9, 10 and 11 sprockets. The system has a low chain skew and therefore low wear. The narrow sprocket set enables a stable wheel with symmetrical spoke angles. The gears are shifted by an electrically shifted slider derailleur. This sits less exposed than today's derailleurs under the chainstay, which minimises the risk of defects. Due to the small tooth difference of the 2x8 drivetrain, a small chain tensioner would still be required.
The study has an upside-down fork. Why?
Ever since I started riding the Intend Edge upside-down fork from Cornelius (Kampfinger, editor's note), I've been completely convinced by this concept. It's the best fork I've ever ridden. It has 166 mm travel and weighs 1950 g. It could probably be up to 200 g lighter with 150 mm. The double bridge principle can in principle save additional weight, with even better stiffness, as the forces have to be carried less. During my time at Votec, I had already built an upside-down fork with 120 mm travel. I left out the steerer tube of the fork completely. Only a thin, hollow 8 mm aluminium rod preloaded the two headset bearings.
Lutz Scheffer, thank you very much for the interview.
Biking 3.0 - the 12/2017 issue of BIKE is all about the future. We have dedicated dozens of pages to the main topic and asked mountain bike experts for their visions: How will mountain biking change summer tourism? Will networked biking catch on? When will there finally be large single trail networks in Germany? Will there still be derailleur gears in ten years' time?
We explore these and other exciting questions. In BIKE 12/2017, on newsstands since 7 November. DK-Onlineshop and as a digital edition in the DK-Kiosk app for Apple iOS and Google Android available.
