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CFMoto, the Chinese motorcycle brand, is reportedly developing an all-new suspension setup similar to BMW’s Duolever. 

  • the new suspension system could be used on CFMoto upcoming touring and naked motorcycles.
  • the Hossack-style fork shows that CFMoto is exploring wider possibilities in creating a motorcycle that’s on par with established machinery. 

The setup is a girder-style fork suspension and is expected to be incorporated into the new CFMoto model. The suspension technology was first developed by British engineer Norman Hossack in the 1970s and has since been adopted by BMW and Honda for their touring bikes.

The use of the girder-style fork suspension on the 1250TR-G is intended to broaden the spread of suspension geometry and separate braking and suspension forces, allowing for relatively soft suspension without suffering from too much dive during braking. The use of a single shock absorber also makes it easier to adopt technology like adaptive damping or electronic control preload adjustment.

CFMoto’s new suspension setup is expected to narrow the gap in quality and technology held by more established Japanese, European, and American motorcycle brands. The company has already begun exporting 800cc models all over the world. The 1250TR-G uses a 140 hp, 1,279cc V-twin engine that is derived from a KTM design but heavily altered by CFMoto.

The new suspension technology is expected to form the basis of an upcoming 1250NK streetfighter model, which was inspired by the 2017 V.02-NK concept and first seen in patents filed earlier this year. While the 1250TR-G is currently only sold in China, its technology is already at levels that would be more than acceptable globally. 

BMW Motorrad always puts serious thought into developing front suspension.

  • BMW and ZF develop a new carbon fibre front end.
  • BMW won the 24-hour Spa of the EWC while testing the new carbon fibre telescopic fork. 

The R 1250 GS is fitted with a Telelever front end, the K 1600 GT Duolever suspension is innovative, while the S 1000 RR semi-active unit is an integral part of the superbike setup.

However, BMW has up the ante in its latest joint venture with suspension experts and partner ZF (Zahnradfabrik) to develop a carbon fibre telescopic fork.

 The collaboration is to develop the front fork for the BMW Motorrad World Endurance Team.

Firstly, carbon fibre front suspension is common in MotoGP, but it’s still a grey area for BMW as the House of Munich is not involved in the world championship.

As a result, the Endurance World Championship is BMW’s best bet to test out the new component.

The BMW M 1000 RR now features the said component, with the fork consisting of a carbon fibre outer tubed mated to a carbon fibre composite/metal inner tube. The metal fork legs slide within the carbon fibre tubes. 

The lightweight material not only helps to reduce weight and allows BMW to study the M 1000 RR characteristic.

According to BMW Motorrad Motorsport Director Mark Bongers, the main focus during the development of carbon fibre forks is to test the bending loads.

“Using this material and this technology allows us to shift the threshold at which body vibrations occur.

“One major focus during development was the design of the homogeneous bending loads. 

“The goal being for the throttle response for the rider to be extremely subtle, even under the most extreme strains. And feedback from the riders confirmed that the goal was achieved,” he said. 

In an exciting development, the number 37 BMW M 1000 RR fitted with the carbon fibre telescopic fork won the 2022 24-Hour Spa of the Endurance World Championship. 

Could the new component make its way to future BMW bikes? BMW certainly thinks so, but it will need to meet the strict homologation standards before that happens. 

(Source: webbikeworld)

  • Hydraulic forks have been around since 1935.

  • The springs provide the preload function.

  • Damping works by forcing hydraulic fluid through orifices or shims.

The hydraulic fork has been with us since the BMW R12 in 1935. Since then, forks have been revised to no end in the pursuit of excellence, giving rise to electronically controlled suspension.

But how do they really work? What goes on in there?

Basic principles

The most basic principle involves inserting a spring in each fork. For many years, the spring was the only component to play the role of preload (keeping the suspension from bottoming out) and damping (absorbing shocks).

The earliest form of damping came in more… springs. Yup, you’ve got one with larger diameter, surrounding another with a smaller diameter. The former is longer than the latter, so as the fork compresses more due to a larger bump or shock, the shorter, more tightly wound spring comes into play to put up more resistance. This provides a rising rate suspension, in effect.

Hydraulic damper rod

Next to arrive was the hydraulic fork.

When the hydraulic damper appeared, fluid is pushed through orifices on a damper rod to create damping. The rod is inserted into each fork leg, on top of the spring. The damping rate – how the quickly the suspension reacts – depends on the size or sizes of the orifice or orifices.

Cartridge forks

Fork cartridge – Credit JBI

Instead of using damper with orifices, a cartridge consists of different sized shims. Oil is then forced through. A soft shock will bend the weakest shim to allow oil through. Harder shocks will bend more shims to allow the wheel to move up at a faster rate. This means damping is more precise. One of the biggest advantages of the cartridge fork is that you can replace certain shims for different damping characteristics.

Separate function forks

As the name suggests, one fork leg holds the spring or springs, while the other size holds the damper mechanisms. The one with the spring controls preload, while the other checks damping. This way, the forks could be made to cater to their specific purposes. They can also be lighter as the components are not duplicated. Having different functions on each side doesn’t give off different feedback when the bike is turned to either side as the forks are tied to the same triple clamps.

Electronic suspension

These systems can control preload and damping, or separately depending on the bike. Instead of having the rider adjusting the parameters with tools (plus sweat), it’s all done through a button on the handlebar.

However, the principles remain the same. What’s different is that sensors on the fork and swingram provide real-time ride height and damping data to the suspension ECU. The ECU then determines the correct strategy i.e. setting, depending on the selected mode. The ECU then sends signals to servos to alter the parameters.

Fork oil


Damping works by converting kinetic energy (moving fluid) to heat. This is why oil is commonly used as it could absorb the heat plus has low flow resistance. Changing the oil to difference viscosities or amount alters the damping characteristics.

But bear in mind that it must be replaced at every 20,000 km.

  • In this Suspension Explained series, we will unravel the “mysteries” of your bike’s suspension

  • Although the suspension is now very advanced, the basics remain the same

  • As the prologue, we touch on preload, compression damping and rebound damping

Suspension technology has progressed by leaps and bounds over the years. The motorcycle started out as a little more than an engine stuffed into a bicycle frame, hence the only suspension was the rider’s bum and his resolve to withstand the hammering.

Since then, motorcycle suspension evolved into simple underseat springs to sprung struts to hydraulic and gas damping to electronic self-adjusting marvels.

Regardless, the principles of the suspension remain the same. There are a number of parameters that govern how your bike behaves whether on the road, track or off-road. However, only three parameters are adjustable on a motorcycle (without further modification), namely preload, compression damping and rebound damping.

Adjusting the suspension best requires a bit of background knowledge, because whatever adjustments that may have you feeling right may not be exactly right for the bike’s dynamics. A wrong adjustment may mask itself as another problem, causing you to go around in circles. Oh yes, we’ve been there.

We’ll discuss one topic per week. We’ll also speak to the experts on aspects of suspension technology, adjustments and modifications, while dispelling some myths along the way.

Hope this series will be beneficial to all our readers.

 

PRELOAD

Any discussion about suspension has to start with preload. Preload is of course related to spring rate, but since most riders don’t change the springs in their suspensions, we’ll just stick to preload.

To put it in simple terms, preload means the amount the springs are compressed when the suspension is fully extended.

Front preload adjuster – the blue bolt

For illustration purposes, take a valve spring and stand it on your desk. Now add some weight to the top so that it compresses a little. That’s preloading the spring. Adding more weight means adding more preload, while taking some off means reducing preload.

When you increase the preload by turning on the preload adjuster on the forks, or collar on the rear shock, suspension sag is reduced; and vice-versa. The spring pushes back against the adjuster collar, lifting that end of the bike up. So, if you increase (by turning clockwise) your rear suspension’s preload, the seat goes up higher, and similarly for the front.

Rear preload adjuster

Therefore, adjusting the preload DOES NOT change your spring rate. If someone comes up to me and say I’d make the spring stiffer by adjusting the preload… well, I’d tell him to go fly a kite. But that’s just me.

We’ll leave this subject here. More on this in latter instalments.

DAMPING

If a bike’s suspension depends on the spring along, it can leave itself prone to oscillations. A compressed spring stores kinetic energy. When it’s released, it may extend to more than its resting length. The load on top of the spring has now received this kinetic energy and unleashes it back downwards, compressing the spring. This goes back and forth until that kinetic energy is transformed to heat (absorbed in the shock absorber’s oil).

Courtesy of motorcycle.com

Have you ridden on a bike that “pumped” up and down or wallowed like a sampan in stormy seas? (My bike does that.) Yes, it’s due to the lack of damping.

Damping is divided into two: Compression damping and rebound damping.

COMPRESSION DAMPING

Compression damping (or just compression) determines how fast the wheel move upwards when it contacts a bump. Correct compression damping will allow the suspension to absorb bumps and road irregularities better.

The damping adjusters on the BPF fork are all on top. Compression is marked as COM

With more compression dialed in, the suspension, hence the wheel, is more resistant to moving upwards and vice-versa. Dialing in the correct amount will also deal with fork dive to a certain amount during hard braking, although that depends more on the spring rate and preload.

Compression damping is adjusted by the screw in the middle

Too much compression damping will cause the shock of the bump to be transferred directly to the chassis and rider. (That “BLAM” feeling when you hit a bump.) Consequently, the wheel will skip across the bumps, or cause the brakes to lock up easily as the suspension resists being compressed.

On the other hand, too little will have the wheel kicked up quickly, which will also cause it to lose touch with the road. Hitting corners at high speeds will cause the suspension to “squash” down, reducing ground clearance.

REBOUND DAMPING

Rebound damping is the opposite of compression damping. Rebound determines how smoothly and controlled the suspension re-extends to its proper state, after it has been compressed.

Rebound damping is marked at TEN (for spring tension)

Without or too little rebound damping will cause the spring to re-extend quickly, or in simple terms, bounce back. The rider will feel as if he’s being kicked out of the seat after the initial bump has been absorbed. It’s like squeezing a spring between your fingers and letting it go abruptly, or like a Jack-in-a-Box.

Rebound adjuster on the rear shock is usually underneath the shock body. Here it is the screw surrounded by the red collar

Too much rebound damping will cause the wheel to “pack up.” That means the wheel will only come back down too slowly, causing the bike to feel “loose.”

CONCLUSION

That’s it for this week. This is just basic knowledge. We’ll touch on more next week, so stay tuned!

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