The History involved:
The first front suspension in bikes was adopted before 1914 but many manufacturers didn’t use proper rear suspension until 1945. Amongst the earliest were Indian, BMW, BSA, Aerial and Norton. In 1913 The Indian consisted of a swing-arm suspended from a leaf spring. These earlier swingarms have evolved so much over the years that if any rider, who is very much interested in vintage bikes, only knows that these type of setups actually existed long ago.
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The modern day everyday bike consists of a twin shock setup at rear with regular swingarm which is pivoted at the front to the bike’s frame. This too was soon replaced by a mono-shock suspension. In the earlier days, mono-shock appeared only on the niche motorcycle market but its appearance on motorcycles from popular companies such as Yamaha and Suzuki led to its commercial dominance.
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The primary goal while installing Monoshock suspension was to save weight as bike manufacturers removed one of the suspension and redesigned the swingarm to fit the single shock centrally to it. But companies were still not satisfied with the performance so they tried to change the design of the swing arm. This time the swing arm evolved to be known as “single-sided mono-shock swing arm”, the design was made possible by light weight and strong material as the swingarm bears all the stress from the rear axle offset to one side.
The setup and its requirement: Contrary to the double-beam swingarm which needed to have longitudinal stiffness, the single sided design needs to have the torsional stiffness to prevent it from twisting when offset load is applied, as a result, single sided swing arm were made bigger with a lot amount of cross-bracing inside them.
In 1980’s BMW introduced the offset monoshock setup, where the shock unit was mounted to one side of the bike instead of the centre. The driveshaft ran down inside the single sided swing arm and into the rear drive. This removed the need to make swingarms which were heavily engineered at the front, which was earlier needed to resist the torsional load of mounting the wheel to a single sided swingarm. This is how its requirement came to be. Final thoughts:
Over the years since 1980, the design has significantly improved. The reduction of heavy engineering at the front of swing arm also allowed single sided swingarm to lose more weight and become more performance oriented. Nowadays such a design can be seen on popular like Benelli TNT 300, 899, Ducati scrambler Desert Sled, Ninja 650 etc. In the end, the offset setup is just one of the ways how a monoshock suspension can be mounted on a bike, there isn’t enough scientific evidence to know exactly how much this setup improves the performance but everyone on God’s green earth is learning and figuring out new cool stuff as they are going. Do give us your thoughts about this article and for everything related to motorcycles, stay tuned to BikesMedia.
By: Yetnesh Dubey