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    Cracking the motorcycle code: 5 types of steel used in two-wheelers

    In 2021, the two-wheeler industry in India was ranked 1st globally in terms of unit production, ahead of China. While the industry has been around since 1955, it was only in the 1980s that the segment rose to prominence, owing to the relaxation of foreign investments in the sector (starting in 1981), and the introduction of the New Economic Policy (NEP) in 1985.

    With the demand for motorcycles and scooters (conventional and electric) growing by an average of 7-8% every year, India’s domestic production has kept pace, with over 190 million two-wheelers rolled out annually. This represents nearly 7% of the country’s GDP. Four major categories of two-wheelers account for the bulk of the sales -

    • Motorbikes

    • Scooters(petrol & electric)

    • Quad bikes

    • Mopeds

    Of these, motorcycles and scooters make up more than 80% of the total sales.

    For MSMEs in this space, the future – particularly in the two-wheeler segment - does look bright. But as competition grows and production costs continue to rise, auto firms are under pressure to continuously innovate or perish. With several new models launched every year by flagship brands, there is a remarkable array of two-wheelers in all shapes and sizes on offer.

    And nowhere is this variety more evident than in the heart of every motorcycle - its chassis, or motorcycle frame.

    Motorcycle design has seen significant changes over the years, and bikes produced today are substantially different from those designed just 40 years ago. In tandem, the materials used for motorcycle manufacturing have also undergone several changes over the years. While steel remains the gold standard, advances in steel grades in the last few decades have seen increased adoption of alloy steels, high-strength tensile steels, and Advanced High Strength Steels for motorcycle chassis production.

    Let’s now take a closer look at commonly used types of two-wheeler frames – and the type of steel used in each.

    Types of motorcycle frames and the steel used

    Backbone frame:

    This is one of the most basic and cost-effective varieties of motorcycle frames, where the engine is supported by a single spine.

    Stainless steel is the most commonly used material for making backbone frames because it has excellent structural properties and can withstand high temperatures without becoming brittle. Among stainless steel varieties, AISI 4130 (American Iron and Steel Institute) grade steel is the most popular choice. For higher-strength requirements in heavier two-wheelers, structural stainless steel grades are viable alternatives.

    Single cradle frame:

    It is one of the most popular types of frames in India in which the engine is held in place using a single cradle with a single spine.

    The steel used in the single cradle frame is high-strength low-alloy (HSLA) steel that is not only strong but also lightweight and weldable. HSLA steel is used in chassis components, body-in-white, seating components, and suspension assemblies.

    Double cradle frame:

    This type of frame is also widely used in India. It has two tubes that support the engine, offering greater strength and rigidity, but the added weight makes it less optimal for performance-oriented motorcycles. It is commonly used in touring and long-distance bikes.

    The two most popular types of steel used in the double-cage frame are:

    High-alloy steel: This type of steel is known for its high strength and excellent corrosion & fatigue resistance

    Galvanised steel: This type of steel is well known for its corrosion resistance, making it ideal for motorcycles that will be exposed to rain or snow regularly.

    Perimeter frame:

    The perimeter frame, also known as the twin-spar frame, is less rigid than the other types of motorcycle chassis, making it a popular choice for high-performance sports bikes.

    Perimeter frames are manufactured using a combination of carbon steel, high-strength steel (HSS), and various alloy steels (titanium, magnesium HSS alloys) depending on factors such as cost and the weight of the bike.

    When weight is not a concern, stainless steel and its alloys are employed as they are corrosion-resistant, hard, durable, and ductile. SS can be machined to very high levels of precision, making it a practical and cost-effective option for fine detailing work on sports bikes.

    Monocoque frame:

    The monocoque frame is built with a single metal piece (hence the name). Though typically used in cars, monocoque chassis is used in the manufacture of certain types of motorcycles. In a monocoque, the entire skeletal structure is produced from a single sheet of steel or other material, using robotics.

    Modern two-wheeler monocoque designs employ a combination of steel and carbon fibre or alloyed steel aluminum. Steels used in monocoque production include -

    • High-strength low alloy steel (HSLA)

    • High-tensile strength steel (HTST)

    • Carbon steel

    • Alloy steel

    • Trellis frame:

    Known for its simple construction, and lightweight strength, the trellis frame is another popular type of chassis in motorcycle manufacturing. The biggest advantage of using a trellis frame is its lightweight construction.

    The main material used for manufacturing trellis frames is mild steel, which is made up of iron and carbon. Furthermore, steel alloys such as chromium steel alloy, and stainless steel are also used to complement the central steel structure.

    As we can see, over a dozen varieties of steel and steel alloys are used in the construction of a two-wheeler chassis. Here’s a quick look at the 5 most popular ones -

    Stainless steel

    Due to its lightweight nature, corrosion resistance, high tensile strength, and resistance to wear and tear, stainless steel can endure heavy loads without breaking. This makes it a good choice for the production of robust, durable motorcycle components.

    Advanced high-strength steel (AHSS) –

    These materials offer exceptionally low weight, high strength, and optimised formability, allowing manufacturers to utilise less material and significantly lowering a vehicle's weight. Their tensile strengths are higher than those of traditional high-strength steel. Nearly all new motorcycle designs now use AHSS.

    Low-carbon, or mild steel –

    It is the most frequently used metal in the manufacture of commuter motorcycles because it has lower production costs and greater durability than other easily available forms of steel. Except for high-performance sports bikes, all two-wheelers utilise mild steel to varying extents depending upon weight, chassis type, and overall design.

    Galvanised steel

    Galvanised steel is less expensive than stainless steel but more efficient than aluminum. It’s the perfect alternative to high-carbon and AHSS steel grades that provide long-lasting protection for every component of the vehicle they are utilised in.

    The lower cost, enhanced durability, good surface finish, and availability of galvanised steel are a few of its advantages.

    If you’re a two-wheeler manufacturer, or an MSME supplying the auto industry, look no further than JSW One for all your steel buying needs. JSW One MSME is committed to helping small and medium-sized steel businesses with all their procurement needs under one roof, without having to compromise on quality, speedy delivery, and price. Visit our portfolio of certified automotive-grade steel products here - JSW One.

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