In vehicle dynamics, slip angle (also known as sideslip angle) is the angle between the actual direction of travel of a rolling wheel and the direction towards which it is pointing. Slip (usually described as percent slip), is the relative motion between a tyre and the road surface on which the tyre is moving on. This slip can be generated either by the tyre’s rotational speed being greater or less than the free-rolling speed, or by the tyre’s plane of rotation being at an angle to its direction of motion. Fig.1 shows a top view of how slip angle occurs when the vehicle is turning right.

It is called slip angle, because the part of the contact patch that is to the outside of your turn is moving faster than the wheel itself is in the direction it (the contact patch) is pointing , while the part on the inside is moving more slowly. Since the outside part is moving faster than the tyre it must be slipping and hence is the name of ‘Tyre Slip’. The inside part is gripping better than it would if moving in a straight line. For this reason, the contact patch ‘walks’ itself into the turn.

Mathamatical model of slip angle

The slip is generally given as a percentage of the difference between the surface speed of the wheel compared to the speed between axis and road surface. Fig.2 shows that slip angle is the vector sum of wheel forward velocity and lateral velocity. Mathematically, slip could be represented, as:

where , w is rotational speed of the wheel, r is wheel radius and v is vehicle speed. This indicates that a positive slip means the wheels are spinning and negative that they are skidding. Locked brakes, wr = 0, means that slip is -100% and spinning on the spot, v = 0 and wr ≠ 0, means that ∞.

Slip angle , therefore, is the angular difference between the direction the tyre contact patch with the road is pointing and the direction of the wheel (Fig.3). In actual case, the tyre tread does not point in the same direction as the wheel. This is because a tyre is being made of rubber, the sidewalls deform, and the tread pattern itself can ‘squirm’ when the wheel is turned from the straight-ahead.

In fact, modest slip angles are ‘good’ as tyres generate progressively more grip with increasing slip angles (Fig.3).For every type of vehicle and tyre the modest slip angle or the good slip angle is different and for all the tyres in your car, the slip angle might be different at any point of vehicle dynamics.When the limit exceeds, where after no further grip is generated. Thereafter, increasing slip angles are ‘bad’, and the tyre will tend to lose grip. Because of the slip angle, the contact patch of the tyre (Fig.3) need not be in the same orientation as the whole wheel, often lagging a few degrees behind. Greater the slip angle will obviously mean that the larger portion of the contact patch is slipping (Fig.3). At some point there is so little part of the contact patch that there is no slipping, which means that traction is lost and the tyre begins to slide. As the tread element moves through the contact patch it will be deflected further from the wheel mid-plane(Fig.3). This deflection gives rise to the slip angle, and to the cornering force.

Tyres seem to operate at their peak performance when they are under a few degrees of slip angle, they generate the most grip at that particular slip angle. For race and high performance tyres this optimum slip angle is around 6 to 10 degrees while this number is a little lower for street tyres (Fig.4).

Measurement of slip angle

There are two main ways to measure slip angle of a tyre: on a vehicle as it moves, or on a dedicated testing device. There are a number of devices which can be used to measure slip angle on a vehicle as it moves; some use optical methods, some use inertial methods, some GPS and some both GPS and inertial.

Various test machines have been developed to measure slip angle in a controlled environment. Sensors measure the force and moment generated on a dynamic vehicle, and a correction is made to account for the curvature of the track. Other devices use the inner or outer surface of rotating drums, sliding planks, conveyor belts, or a trailer that presses the test tyre to an actual road surface. These days computer simulation models are available for measuring tyre slip angle. Technicians can use a simple tyre finite element model to generate lateral, tangential and radial tyre accelerations for a fixed load and slip angle. The profiles are validated by using experimental data. The simulated acceleration profiles are used for the estimation of slip angle and tyre/road friction coefficient.

Effects of slip angle

Each tyre will have its own slip angle. A tyre that is not slipping has a slip angle of zero degrees. The ratios between the slip angles of the front and rear axles will determine the vehicle’s behavior in a given turn. If the ratio of front to rear slip angles is greater than 1:1, the vehicle will tend to understeer, while a ratio of less than 1:1 will produce oversteer (Fig.5).

Actual instantaneous slip angles depend on many factors, including the condition of the road surface, but a vehicle’s suspension (Fig.6) can be designed to promote specific dynamic characteristics. Incidentally, a vehicle suspension system may include; Coil spring, Leaf spring, Hydraulic and Air Spring or their combinations. This is very important for racing car as they need to take sharp turns on high speeds.

A principal means of adjusting developed slip angles is to alter the relative roll couple (the rate at which weight transfers from the inside to the outside wheel in a turn) front to rear by varying the relative amount of front and rear lateral load transfer. This can be achieved by modifying the height of the roll centers, or by adjusting roll stiffness, either through suspension changes or the addition of an anti-roll bar. Because of asymmetries in the side-slip along the length of the contact patch, the resultant force of this side-slip occurs away from the geometric center of the contact patch, a distance described as the pneumatic trail, and so creates a torque on the tyre.

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TyresNmore, the automotive aftermarket e-commerce platform owned by RPG Group, has promoted Rakesh Tatikonda to Chief Executive Officer and announced the change with immediate effect.

Tatikonda, who previously oversaw business operations at the Mumbai-based firm, will spearhead the organisation’s expansion and innovation strategy. The appointment advances RPG Group’s ‘Talent First!’ policy, which rewards internal promotions and develops employees.

The new chief executive brings over 15 years of industry experience, having worked across multiple sectors with companies such as telecommunications giant Reliance Jio and IT services provider Infosys. Before joining TyresNmore in 2022, Tatikonda held senior positions at tyre manufacturer CEAT, where he developed expertise in strategy, operations, marketing and digital transformation.

“My aim is to transform automotive aftercare in India by offering seamless, tech-driven, end-to-end mobility solutions delivered with trust, transparency, and convenience right at the customer’s doorstep,” Tatikonda said in a statement.

TyresNmore operates a doorstep service model for tyre and battery replacement across six major Indian cities: Delhi NCR, Mumbai, Bangalore, Hyderabad, Pune, and Chennai. The platform represents RPG Group’s entry into the growing automotive aftermarket sector, which has seen increased digitisation as consumers seek convenient maintenance solutions.

During his tenure in operations, Tatikonda scaled the business and improved profitability while driving digital transformation initiatives. His track record shows he strengthened operational efficiency and enhanced customer experience in the mobility convenience sector.

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Vaculug, Europe’s largest independent retreader producing high-quality OTR and truck retread tyres for fleets across the UK and Europe, has expanded its UK presence by acquiring Tyrefair in Kinross, Scotland.

This strategic acquisition extends the company's award-winning service further north, ensuring Scottish customers receive the same high-quality OTR and truck retread tyres Vaculug has supplied for 75 years. Since the purchase, the Kinross location has already grown by 25 percent, with an ambitious target to double its business within a year and then double it again.

This move is a key part of Vaculug's 2026 growth strategy, focused on strategic acquisitions that enable better, faster and more sustainable customer service. The acquisition reinforces Vaculug’s long-standing environmental mission, marking a new chapter of sustainable growth with a strengthened Scottish operation.

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Nokian Tyres is expanding its US presence through a new nationwide partnership with American Tire Distributors (ATD). This agreement provides Nokian access to ATD’s vast network of over 110 distribution centres, serving roughly 80,000 customers.

The collaboration will efficiently supply tyre shops with Nokian’s complete product lineup, enabling dealers to broaden their inventory. Both companies bring 90 years of experience and a shared dedication to innovation, safety and sustainability. This partnership will offer drivers more choices, supported by Nokian’s award-winning Tennessee factory and ATD’s technology-driven logistics.

This enhanced distribution capability ensures that consumers will have greater access to a full spectrum of high-performance tyres, meeting diverse driving needs and conditions. The alliance strengthens both brands' market positions by combining premium products with an unparalleled delivery system, ultimately improving service for dealers and drivers alike across the country.

Chris Ostrander, SVP, North America, Nokian Tyres, said, “The partnership with ATD enables us to reach more tyre shops and more drivers than ever before. ATD’s robust distribution network, customer service and responsiveness strengthen our agility to serve both new and existing customers.”

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The U.S. Tire Manufacturers Association (USTMA) has announced a new webinar series designed to advance the circular economy for end-of-life tyres (ELTs) in collaboration with the Tire Recycling Foundation. Titled ‘The Road to 100% Tire Circularity: ELTs Going Full Circle’, the initiative aims to foster the development of scalable and profitable markets for recycled tyres. The series will launch in September 2025 and continue through February 2026.

Hosted by John Sheerin, USTMA’s Senior Director of ELT Programs, each session will convene industry experts, recyclers and state policymakers. Their discussions will focus on the latest research and real-world applications that transform waste tyres into valuable resources, thereby diverting them from landfills and generating environmental, industrial and economic benefits.

The programme will explore three of the most promising markets for end-of-life tyres. It begins on 23 September 2025 with a session on tyre-derived aggregate (TDA), examining its use in civil engineering projects like structural fill and stormwater management. A subsequent webinar on 30 October 2025 will cover the growing market for moulded and extruded products made from recycled rubber.

A significant portion of the series will be dedicated to rubber-modified asphalt (RMA), a material known for creating longer-lasting and more sustainable roadways. An introductory session on 20 November 2025 will review the overall performance and benefits of RMA. This will be followed by two regional deep dives: one on 14 January 2026, focusing on practical applications in Midwestern states like Michigan and Ohio, and another on 28 January 2026, exploring its adoption in Southern states including Kentucky and Georgia. The series will culminate on 24 February 2026 with a capstone session providing a comprehensive overview of grant and funding opportunities available to support the growth of these ELT markets.

This initiative addresses a critical need. While tyres are one of the most recycled products in US, and stockpiles have been reduced by 94 percent over the past three decades, the generation of end-of-life tyres continues to outpace their consumption in recycling markets. The webinar series is presented as a strategic pathway to bridge this gap by promoting innovative and sustainable end-use applications.

Those interested in shaping the future of tyre management are encouraged to register for any or all of the webinars through the USTMA website. Attendees will receive a resource kit after each session to help facilitate further discussion and action.

Anne Forristall Luke, President & CEO, USTMA, said, “We view these webinars as a crucial opportunity to connect key leaders across the country and show them that sustainability and economic growth go hand-in-hand. By showcasing proven applications and providing the tools to act, we can collectively turn ELTs from a waste challenge into an economic engine.”

Sheerin said, “As we look to expand ELT markets and unlock the full environmental and economic potential of end-of-life tyres, collaboration is essential. And no one can do it alone. State DOTs, regulators, recyclers and manufacturers must work together to help grow ELT markets through targeted investment, supportive policy and continued research.”

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  - CNJ SUPPORT September 11, 2025 15:03 PM

  How can we enroll on this Webinar

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