Understanding different tyres for construction equipment
Every construction equipment is unique and has specific demands related to productivity, performance and durability. These demands extend to the tyres the machine uses. For any mobile construction equipment, tyres are the singular point of contact with the road. Tyres support the weight of the equipment, absorb shock from the road surface, and change or maintain the direction in which the machine is heading.
As a rule of thumb, “construction machines meant to carry loads at speed need tyres designed for their maximum load capacity and speed and to handle heat dissipation,” explains Sang Jin Lee, GM - R&D, Hyundai Construction Equipment.“Rubber
Every construction equipment is unique and has specific demands related to productivity, performance and durability. These demands extend to the tyres the machine uses. For any mobile construction equipment, tyres are the singular point of contact with the road. Tyres support the weight of the equipment, absorb shock from the road surface, and change or maintain the direction in which the machine is heading. As a rule of thumb, “construction machines meant to carry loads at speed need tyres designed for their maximum load capacity and speed and to handle heat dissipation,” explains Sang Jin Lee, GM - R&D, Hyundai Construction Equipment.“Rubber is resistant to abrasion and cutting.” Machines meant to travel great distances with heavy loads need tyres designed for heavy loads and stability, and which generate the least heat during long working hours, he continues. “Machines meant to travel unlimited distances at speed needtyres offering traction and directional stability. Here, again, rubber proves useful. Also, the construction of the tyre tread, ply and material play an important role.” Tyres by machine Coming to specific machines, the needs of loaders are special because the machine can be deployed in a wide variety of conditions, ranging from normal road to severe muddy, rocky and sandy terrain, observes Lee. “Whereas the tyres of machines deployed in mines must withstand heat.” Machines used in underground mines need heavy-duty, solid, fire-resistant, cut-and-chip-resistant tyres capable of withstanding damage and side-cuts from the harsh terrain and narrow road widths, says Prasenjit Maity, National Head OE Sales, Underground Soft Rock, Komatsu. “Solid tyres have better tread depth and are safer, agile and long-lasting. From the angle of engineering, the type and size of the tyre should match the machine design and weight. Under-sized tyres may reduce expected life.” Choose well “We have cranes starting from two axles to nine axles; this means our cranes use anywhere between four and 18 tyres so it’s very important to choose tyres for a better lifecycle,” points out Subhajit Chandra, Divisional Head - Mobile Crane Division, Liebherr India. “Choosing the right tyre ensures safety, longevity and fuel savings, which increases with the fleet size and when tyres are used in tough conditions. Unfortunately, a few customers use low-quality tyres from China and end up increasing their maintenance cost.Usually, the performance of a tyre is determined by its fuel-efficiency, braking and wet grip and the level of emitted noise.” The cost of the equipment is not directly affected by the impact of tyres, according to Samaresh Mitra, General Manager – Surface, India, Komatsu.“However, the lifecycle cost depends a lot on correct tyre selection as the replacement or re-treading of tyres has a huge impact on cost. Breakdown due to tyre failure contributes to production loss.” As for a front-end wheel loader, many factors affect its fuel efficiency ,including poor maintenance, worn ground-engaging tools and operator inexperience, and the largest controllable variable, proper tyre selection, in Mitra’s view.“In loaders, improper traction due to wheel slippage is an energy waster. Both wheel spin and slippage reduce fuel efficiency and increase operating costs. Other simple steps you can take to cut fuel cost while maximising productivity include maintaining proper tyre inflation (under-inflated tyres increase rolling resistance) and properly matching the loader size to the application.” Radials vs. bias tyres In general, the construction of radial ply tyres offers better traction, better control and load-carrying capacity than bias ply tyres, says Lee. “Hence, radial tyres support better fuel economy, better maneuverability at high speed and, in the longrun, lower overall cost of ownership. As radial tyres feature a complex arrangement of rubber-coated steel wires and rubber-coated steel belts, they aremore durable against cut and punchers. Radial tires are best suited to applications where tread wear, distance and traction are important aspects.” Interestingly, Komatsu offers both radial and bias tyres in front-end wheel loaders. However, a few discerning customers prefer to use only radial tyres, points out Mitra. “Biasply tyres don’t shed heat quickly, which becomes a drawback at higher speed. Another problem is their stiff sidewalls, an outcome of their construction, as all the plies run from sidewall to sidewall. In contrast, the steel belts in radial tyres dissipate heat much better and as they have fewer layers of body cords on the sidewall, the sidewalls allow the tyre to flex more, provide a lot more feedback and increase the contact patch of the tyre on the ground. This design also allows the sidewall and tread to work more independently of each other, which is significantly different from what a biasply permits.” Tread patterns Tread patterns or tyre designs should allow as much material as possible to exit thetyre groove so that the vehicle gets more traction to move with stabilityin muddy conditions, advises Lee. “The tyre tread pattern impacts the productivity and heat generated by an equipment as well as the running cost,”adds Sakthikumar VG, Managing Director, Schwing Stetter (India). “While common wheel loader applications such as operations in sand and soft conditions need more basic tread designs (called L2), general loading application srequire more resistance to scrapes and impacts (L3), and the toughest applications such as quarries need deeper and tougher treads (L5),” explains Lee. Each successive tread design is deeper than the lower level; an L4 is generally 50 per cent deeper than itsL3 equivalent while the diameter of the casing is the same.” Limited availability Some manufacturers are importing tyres for their products. Others aren’t satisfied with what’s available locally. “As we are only dealing in high-capacity, front-end wheel loaders with a bucket capacity beginning at 15 cum and increasing upto 50 cum, our tyre sizes start from over 120 inch in diameter,” shares Mitra. “However, such tyres are mostly imported from the US or Japan and most manufacturers are reluctant to give a concrete lead time commitment in advance.” “Our hydraulic tyre-mounted mobiles cranes commonly use tyre sizes 14 R 25 /16 R 25 that are manufactured in Europe, and supplied all over the world,” says Chandra. “In India, high-quality tyres aren’t easily available.” “At present, our underground haulage machines in India are fitted with foam-filled tyres and we face issues with gripping and tyre slippage from the rim,”reveals Maity. “We are looking to work together with tyre manufacturers to engineer solid tyres to suit our machines. In general, the lead time of tyres is high in India and it is also difficult to procure tyres in small quantities.” What other tyres is India missing? Introducing tyres for higher capacity equipment like wheel loaders and maintenance-free tyres, both of which are available in developed countries, would be helpful for the industry, responds Sakthikumar. “Currently, customers are guided on tyre maintenance but not every customer follows those recommendations. Maintenance-free tyres would ensure that customers get the desired outcome from the machine even when they don’t follow the tyre guidelines.” In the mining sector, the size of trucks is increasing and hauls are getting longer and, so, manufacturers will have to develop products that withstand these increasingly intense conditions, says Lee. “New technological trends include compounds that are more heat-resistant and tread patterns that dissipate heat for longer hauls.” For shorter hauls requiring tight operations, better compounds are being developed to resist severe tyre cuts while in operation, he adds. “Matching the tyre to the task is becoming more challenging.” Service gaps Tyres need to be in continuous good working condition to ensure machine safety. However, V Srinivasan, Partner, 6T Services, a tyre consultancy, believes “the technical servicing of off-the-road tyres, which are predominantly used in construction equipment, is not on a par with the quality one gets in the West; consequently, the ‘ton-kilometre’ capacity of a tyre is not optimally exploited. Any downtime immobilises the asset.” To improve this situation, he recommends that tyre manufacturers repeatedly conduct ‘tyre clinics’ to educate driver-operators and the management on the need to choose the most appropriate tyre for an application. Also, users should ask the tyre manufacturer’s technical servicing team about the suitability and applicability of a particular tyre for the intended use. For short hauls where tyres are subjected to very harsh conditions, the possibility of replacing pneumatic tyres with more puncture-proof and longer-lasting (although more expensive) solid tyres should be considered, suggests Srinivasan.Ultimately, it’s about boosting longevity as well as performance. Maintain your tyres The basic tasks include maintaining the appropriate tyre pressure based on the manufacturer’s recommendations; discarding old, unevenly worn, bulging and cracked tyres; attending to punctures; and checking the alignment, advises Subhajit Chandra, Divisional Head - Mobile Crane Division, Liebherr India. “Unevenly worn tyres impact the axle of the crane, which can misbalance the entire superstructure. Significant tread wear can reduce the weight and increase tyre rigidity.” Off-the-road tyre customers must go beyond basic servicing; predictive analytics would help minimise downtime and maximise safety and productivity, suggests Sang Jin Lee, GM - R&D, Hyundai Construction Equipment. Manufacturers’ preference Manufacturers and discerning end-users choose tyres that can perform well in the worst types of weather or roads. Liebherr India’s Mobile Crane Divisionoffers eco-friendly as well as economical tyres. “Eco tyres have less rolling resistance, which may lower the fuel costs in the long run,” says Subhajit Chandra, Divisional Head - Mobile Crane Division, Liebherr India. “However, these tyres don’t suit every mobile crane, driving style and needs. Schwing Stetter (India) looks for application-specific tyres and tyres with rims that are compatible with our equipment (self-loading mixers, wheel loaders, motor graders, truck mixers, and stationary and mobile concrete pumps). “In general, we prefer tubeless tyres suited to rough terrain applications,” says Sakthikumar VG, Managing Director, Schwing Stetter (India).