K-FACTORY Swingarms: Flexibility hidden beneath solid and sturdy looks!

K-FACTORY is well known for their exhausts, but let's take a look at their swingarms, which are just as impressive. From the appearance, one can imagine that it grips the rear wheel firmly, but in fact, K-FACTORY is most particular about the balance. Their swingarms are designed to be supple and flexible, so that the rider can enjoy the feeling of pushing the throttle when cornering.

Rigidity and weight that have no effect on function are not necessary!

K-FACTORY started manufacturing swingarms around 2005, and over the past 18 years the main base material, the square pipe, as well as the chain tensioner parts have evolved greatly in pursuit of flexibility and light weight with the theme of "pushing the throttle on corners".

"If you look at the two types of reinforcement, you can see when viewed from the top that the swingarm with two reinforcing walls (rather than one) has a narrower base material and the wall thickness of each part is also thinner. At first glance, this two-wall reinforcement may look stiffer, but actually it is more flexible. Also, since it is an unsprung part, we wanted to make it lighter. We don't want meaningless weight or rigidity, but actually making it lighter is the most difficult thing," says Nobuhiko Hirose, who is in charge of development at K-FACTORY.

Indeed, looking at the cross section of the base material, you can see that the thickness has been adjusted very precisely, and when you actually hold it, you can tell that the two-walled is lighter than the one-walled reinforcement. Of course, this square pipe was developed by K-FACTORY exclusively for swingarms. When development first began, a pentagonal base material was used, but it has been replaced by lighter and more flexible material over the years.

Vertical rigidity is more important than lateral rigidity

"The first swingarm we made was quite rigid. We kept testing and changing it to be lighter and more flexible, thinking each time that we could push it just a little bit further. For swingarms, vertical rigidity is more important than lateral rigidity. It was just at the time when the swingarms on supersport models were becoming wider when viewed from the side, but thinner when viewed from the top. Swingarms were being made to be more rider-oriented, to pursue total balance, rather than to ensure rigidity," says Hirose.

"With the GPZ900R, just by installing the two-walled swingarm, the weight was greatly reduced and the feeling definitely changed. It's really flexible. If the swingarm is too rigid, the ride is rough, and there is also thrust, so you can't trust the tires. But this swingarm can bring out the individual characteristics of both touring tires and high-grip tires. This is because a good swingarm allows you to do a lot with the suspension. Also, though it's just for the looks, you can use 200-size tires," says Michihiko Ishida of MC GEMMA.

Mr. Ishida has been using K-FACTORY swingarms since the beginning and has seen their evolution throughout the years. He says that the suppleness of the two-wall reinforced swingarm has made it easier to set up the chassis for both street and racing.

Another of K-FACTORY's strengths is their ability to design and develop axle shafts and chain tensioners in-house. Comparing the earliest with the latest models, the details are quite different, and the latest models have that balance of both light and strong. K-FACTORY's swingarms have continued to evolve the concept of "pushing the throttle on corners" from the rider's point of view. Why not take this opportunity to change the way you ride with the flexibility that resides within that solid and sturdy look?

New two-wall reinforced swingarm for the popular Z900RS/CAFE

K-FACTORY's swingarms are made of 90 x 30mm big size square pipe. The standard mono suspension version shown in the top photo is buffed aluminum and costs 249,073 JPY. Anodized aluminum finish can be ordered as an option (plus 22,000 JPY). The bottom photo shows a version for the Z900RS that can be converted to dual suspension and is made to order.

A new base material manufactured exclusively in pursuit of flexibility

As a test, we measured the weight of the two square pipes, and found that the 70 x 35mm one-wall type weighed 87g, while the 90 x 30mm two-walled type weighed 84g. The two-walled type is 5mm smaller in width and the thickness of each wall is also thinner. As a result of the pursuit of rigidity balance, the excessive thrust from the road surface and the rough feeling were gradually eliminated.

In the image above, the end block in the front and the one on the left side of the back row are of the latest design. The newest model weighs 394g, while the previous one weighed 414g; the newer the generation, the lighter the weight. The part that holds the dual suspension was machined from a single piece to ensure rigidity and the axle shaft diameter has also been changed.

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