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Canyon is the first manufacturer in the world to develop a road race bike which features hydraulic disc brakes that are controlled by the brake/shift levers. Thanks to this technology the safety of bike racers is significantly raised as disc brakes clearly function better than traditional brake systems on wet courses and on long descents. They also radically reduce the wear on the rims. The weight of the complete bike – despite being extremely robust – is still under the UCI limit of 6.8kg.
What makes this technology possible is the patented brake/shift levers which for the first time allows the hydraulic fluid reservoir to be contained inside the shift levers.
The Project 6.8 was developed together with Hans-Christian Smolik.
The technical background of a road bike disc brake.
Hydraulic disc brakes have become standard on high-end mountain bikes because of their good braking performance and reliability. So far, road bikes have continued to use rim brakes to stop. On long descents the heat generated by the rim brakes leads to a reduction in their effectiveness. This reason alone makes heavier riders wish for a workable and more reliable braking system.
Another advantage of disc brakes is that their performance does not suffer in the wet. In contrast to a disc brake, a rim brake – because of its position and greater surface area – collects a lot more water and dirt when used in bad weather. Disc brakes can displace the dirt on the braking surface a lot more quickly and then put their higher stopping power to use.
Sporadically, disc brakes have been mounted on road bikes in the past. However when this was done, it did not take into full account the specific requirements of a road bike. The rigid road bike fork is relatively elastic in its conception so that it can provide a certain level of riding comfort. When equipped with MTB rotors a road bike fork would be overwhelmed with just 160mm discs and plastic deformation or breakage would result. Additionally under braking the elasticity of the fork leg would cause it to twist. This would cause the bike to turn every time the brake is applied and force the rider to steer accordingly in the opposite direction. In critical riding situations this can compromise control of the bicycle.
Additional consideration must also be given to ensure that the center of gravity of the bike is further from the contact point of the front wheel than that on a MTB (because of a smaller front triangle). The braking performance for this reason must be correspondingly reduced so that there is no danger of going over the bars.
A further problem would also be the heat generated which would be transmitted through the caliper to the thin leg to the fork. Here it would not be dispersed as well as on larger diameter (bigger volume) MTB forks. As alloy and carbon fork stability suffer at temperatures over 150 degrees, this could cause permanent damage.
These problems were considered when developing our study. The result is the Project 6.8.
The solution to the problems… and the path to Project 6.8.
The problems encountered at the fork can be solved with dual rotors with a diameter between 120 and 125mm. The shorter leverage between the brake pads and the middle of the hub also reduces the braking force for road bike use. An additional adjustment can then follow with the effective length of the road bike brake levers. The master cylinder can then have double the effective diameter, however it must provide for two slave cylinders; correspondingly only half of the oil pressure is used.
In this way the fork legs only experience half of the braking force of a single disc brake and thus deform less – but in a synchronised fashion – so that the tracking will remain positive. Our test rides have shown us that an elastic road bike fork, such as our SL fork handle these forces well.
As each brake disc must only generate half of the braking performance, less heat from the each brake occurs and can be dispersed on each side of the fork. Therefore the danger of damaging the material of the fork is considerably reduced. The spoke/rim loading is also reduced, as the spokes on both sides of the wheel only have to carry half of the braking force. Four cross lacing gives further reduction in the spoke loading.
The unification of existing mechanics such as fitting the master cylinder and fluid reservoir into the brake levers creates space problems, as the traditional existing mechanisms take up too much room. This was solved by a modified and space saving version of the mechanics that Smolik had been developing on his own since 1980.
So that the fluid reservoir could be accessed without having to remove the brake lever, it has been equipped with a dome-formed cover which is placed on top of the brake lever.
Smolik further proved his immutable power for innovation with Project 6.8. His courage to try new methods and his immense technical knowledge brought about Project 6.8’s sensational outcome. It is a race bike with two hydraulic disc brakes that has actually been proven in practice.