OEMs Explore Options For Optimised Ride And Handling

When we speak of two-wheeler technologies these days, more often than not, discussions are focused around engine development, electronics and suspension. Chassis – that bunch of steel tubes and/or aluminium plates –tends to get ignored. These days, when new bikes are launched, OEMs’ press releases are often filled with details of how engineers extracted every last bit of horsepower from the engine, details of every conceivable electronic rider aid and details of adjustable/active suspension. The chassis? Not so much. And yet, a bike’s chassis,even though it remains hidden under bodywork and lets the engine be the centrepiece in terms of style, remains one of the most important components of a two-wheeler. Chassis design and construction defines the way in which a bike rides and handles, and over the last many decades, OEMs have continued to experiment with various types of construction, all of which have their own positives. Here, we take a look at some of the more recent developments in two-wheeler chassis design.

- Sameer Kumar

THE EVOLUTION

Chassis design for powered two-wheelers (motorcycles and scooters) evolved from bicycle chassis about a century ago. Early efforts were pretty basic, with engines being bolted on to beefed-up bicycles frames. Of course, as motorcycle engines became bigger and more powerful, manufacturers felt the need to develop proper chassis that could keep pace with power output. From there, development branched off in various directions, with OEMs experimenting with multiple permutations and combinations of materials, arrangement and construction. The basic purpose remained the same – the chassis would act as the base for mounting a bike’s engine, fuel tank, handlebars and suspension (including the swingarm) – but the ways in which this could get done invited experimentation, which continues to this day.

Over the years, types of two-wheeler chassis used by OEMs includes the steel single or twin downtube cradle-type frame, steel tube perimeter chassis, aluminium twin-spar frame, steel tube trellis frame, hybrid (steel tube trellis section combined with aluminium side plates) frame and aluminium/carbon fibre monocoque chassis. Surprisingly enough, almost every single type of frame mentioned in the list above is still in use today, on modern motorcycles, depending on price, positioning and intended usage. While more basic, commuter-spec two wheelers are often fitted with single or double downtube cradle-type frames, more expensive, higher-end bikes usually get steel tube trellis or aluminium twinspar chassis. Some manufacturers are also using carbon/aluminium monocoques, which do away with steel tubes and/or aluminium spars, thereby reducing weight and complexity.

CHALLENGES IN DESIGN