- Brief excursion on the motorcycle chassis
To shed more light on this topic, here follows a brief excursion into the motorcycle chassis. Spring preload changes the vehicle height as well as the steering axis angle and trail. In terms of the laden motorcycle, this means: To ensure that the motorcycle runs the same as when in normal use, it is necessary to increase the spring preload. This is usually done using hexagon slotted nuts or a practical hand wheel. It is similar with the fork. The level of the fork should also be adjusted - where possible - to the increased load. The compression and rebound values are also similar. The rebound spring movement controls the rebound stage. What does this look like? Simply push together a spring on a ballpoint pen and then let go. No motorcyclist would like to experience these uncontrolled vibrations, or wobble, on a motorcycle. A damper and its rebound settings are used to avoid these vibrations. Last but not least, the compression stage. It is designed with a considerably lower effective range and assists the springs to compress.
A good feelingCDC in the biker's test
The advantages of CDC in the motorcycle can be easily summarized on paper. But how can you feel the difference when you are riding the motorcycle? A report from an experienced biker.
The weather forecast promises sunshine for the whole weekend. The bikes are ready and waiting in front of the garage. There is nothing stopping us taking a relaxing weekend trip along small and narrow country lanes. Or is there? The motorcycles appear to be heavily laden at the back. The immediate thought is that this will become worse when the biker gets on. What is the word that springs to mind here – spring preload?
And again we reach for the screwdriver
When everything has been tuned, we are ready to go. Once the adjustments have been made, the bike has good contact with the road surface and you can feel the potential level of tire friction underneath. This gives you confidence in your own driving ability and is thus an important safety feature. Following an enjoyable trip, you have reached the end of the first stage. And now? Take off the luggage and take another spin to enjoy the winding roads once more with considerably less load at the rear. But wait a minute, the chassis settings are no longer correctly tuned! So now we have to unpack the screwdriver and reset everything for a "solo ride without luggage". There must be another way of doing this?
Yes there is! CDC from ZF is the answer. CDC stands for Continuous Damping Control. Sensors record in real time the bike's chassis movements and immediately adjust the damping to every situation. Sounds ingenious, and it really is. In everyday situations, all you have to do is adjust the spring preload according to the load you are carrying on the bike before you set off - this is done by the push of a button - and you are ready to go. However CDC is not just a comfort feature. The balance between excellent damping characteristics and stable feedback on even the poorest road conditions ensures not only comfort but safety as well. If you have ever had to perform full braking under these conditions, you will know the scenario all too well: the chassis is pushed to its damping limit. Full braking completely compresses the spring on the fork. The tires are then responsible for damping. In the best-case scenario, it becomes uncomfortable and it takes longer to brake the motorcycle. In the worst-case scenario, the wheel locks up and the motorcycle will inevitably crash.
The solution: Continuous Damping Control (CDC)
CDC automatically identifies a situation. And can reinforce the spring compression in a fraction of a second. The fork does not lock up, the tire can transfer far more braking power – and the motorcycle comes to a safe stop. This is an important safety feature in conjunction with ABS components. The brake releases as soon as the front wheel locks up. This will happen faster when the damping is not correctly tuned than with an optimally adjusted chassis and which is why the braking distance is far shorter.
"Magic" at work in the bike chassis
The greater the load on the bike, the more significant the advantages of "comfort" and "safety" become. The spring elements always have to be adjusted when additional weight is loaded on the bike. Or to explain it differently: if you add your weight to a 200 kilogram motorcycle, you will be transporting approximately 280 kilograms along the country roads. If you then add a passenger and luggage, you will soon reach 380 kilograms. This corresponds to a plus of 36 % of the overall weight! It is almost a miracle in itself that the suspension elements withstand this weight – it would be magic without the adjusted suspension elements. CDC from ZF automatically waves its magic wand.
The advantages of CDC are demonstrated in another everyday situation encountered in the life of a biker - a biker whose main objective is to have fun. Bikers talk of the ultimate lean angle experience, the pure enjoyment when cornering. For many bikers it is the real essence of motorcycling. When it comes to taking on the corner, approach the turn at speed, keep on the outside, gently apply the brakes, decide on the curving line to follow, lean your body into the turn, dive into the lean angle, release the brake, focus on the end of the turn, and then accelerate. What could be more rewarding? Probably nothing if the bike rear did not sag under the engine power like dead wood. Or if the front wheel cannot decide between feedback and stable guide when braking into a turn patched up with tar. The turn is then used to randomly try out various radii – and the line is lost.
CDC can conjure up a smile underneath the helmet
ZF's CDC identifies the optimum damping settings for every - yes every - situation. This ensures perfect turn-in ability and precisely the right traction when accelerating out of the turn.
Traction on modern 150 + X PS class bikes is undoubtedly the responsibility of traction control. Traction control regulates the power output if the spinning rear wheel is pushed to its limits. As you can guess, traction control - just like ABS mentioned at the start and many other electronic advanced driver assistance systems – essentially depends on the chassis. If the rear shock absorber fails, the rear wheel will also quickly reach its limits. It cannot distribute enough power to the road and is decelerated sooner by traction control. Everything stays on track with CDC.
CDC is not an instrument that defies the laws of physics. This chassis solution designed by ZF gives motorcyclists the ability to gain the most out of the entire motorcycle - in terms of comfort, safety, and riding fun.
More information on CDC for motorcycles
With CDC on tour
The damping on the motorcycle chassis is adapted to every riding situation.
CDC Product Information
Available in the motorcycle since 2014: the CDC electronic damping system.