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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Hankook Tire has secured a new role as the Official Control Tyre Supplier for the 2026–2027 season of the Australian Production Car Endurance Series (APCES), following a partnership with the Australian Racing Drivers’ Club (ARDC). The APCES is a newly launched endurance championship created by the ARDC and Motorsport Australia, designed to continue the country’s legacy of production car racing. The series will feature production-based vehicles competing across eight performance-based classes, labelled X, A1, A2, B1, B2, C, D and E.

Hankook will exclusively supply its Ventus TD (Z221) R-Spec tyres to all participating teams, working alongside official trackside supplier Gary’s Motorsport Tyres. The control tyre format, which equips every competing vehicle with identical tyre specifications and performance, is intended to provide consistent racing conditions throughout the championship. The semi-slick tyres feature an optimised tread pattern and advanced compound technologies, delivering strong dry grip, stable cornering, excellent braking and superior heat resistance even under prolonged high-speed driving.

The championship will begin its opening round at Sydney Motorsport Park on 30 and 31 May, with additional races scheduled at Sandown International Raceway in August and Queensland Raceway in September. The final round is set for March 2027 at Mount Panorama Circuit in Bathurst, New South Wales, as part of the iconic Bathurst 6 Hour endurance race. The overall series champion will be determined at that concluding event.

Hankook has already built a strong reputation in Australian endurance racing as the official tyre supplier for the Bathurst 6 Hour, and it continues to sponsor other local events including the First Focus Radical Cup Australia Series, the Precision National Sports Sedan Series and the Hyper Racer Hankook Australian Drivers’ Championship. Moving forward, the company plans to strengthen its global premium brand position by using racing data from extreme motorsports conditions, combined with its global innovation R&D infrastructure, to develop ultra-high-performance tyre technologies.

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Bridgestone Corporation has extended its legacy of excellence with General Motors by securing a 2025 Supplier of the Year award, marking the company’s 11th consecutive win and 24th overall. The honour was announced during GM’s 34th annual awards ceremony in Austin, Texas. Out of a vast network exceeding 20,000 suppliers, Bridgestone emerged as one of only 103 companies across 14 countries to receive this distinction.

A global cross-functional team at General Motors determines the winners based on performance across key categories such as safety, innovation and resilience. The evaluation process considered each organisation’s results throughout 2025 alongside their alignment with GM’s fundamental values and ambitious future objectives. This rigorous selection method highlights the importance of consistent execution and shared strategic vision.

The recognition directly supports Bridgestone’s internal E8 Commitment, an ethos built around eight values beginning with the letter E, including Ecology and Extension. By crafting innovative tire solutions for GM, the Japanese company effectively advances its pledges on both ecological responsibility and technological extension. This synergy between corporate values and customer recognition reinforces Bridgestone’s position as a reliable partner.

David Colletti, President of Consumer Original Equipment Tires, North America, Bridgestone Americas Tire Operations, said, “This recognition reflects the strong relationship between Bridgestone and GM. Together, our shared dedication to innovation, quality and performance continues to fuel long-term success.”

Shilpan Amin, Senior Vice President, Global Chief Procurement and Supply Chain Officer, General Motors, said, “Supplier of the Year is one of those key moments our whole team looks forward to every year because it highlights the partnerships behind every vehicle we build. The results our suppliers deliver throughout the entire product development cycle are central to our ability to deliver world-class vehicles to our customers. When our suppliers, such as Bridgestone, lean in with us on new technology and flawless execution, we can move faster, compete harder and unlock more value across the entire supply chain.”

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Tyres Europe has joined a broad alliance of European industry associations urging the European Union to strengthen its trade defence policy. The coalition warns that unfair trade practices, combined with structural overcapacity and state-led market distortions worldwide, are intensifying pressure on local manufacturers. European producers must contend with high energy costs, strict environmental rules and complex regulations, placing them at a clear disadvantage compared to rivals benefiting from less transparent conditions.

The signatories have made clear that they do not seek protection from competition itself, only fairer conditions under which to compete. They argue that a truly global level playing field is essential to protect Europe’s industrial base, sustain competitiveness and allow EU companies to continue investing, producing and preserving jobs within the continent. Without such balance, the long-term viability of key sectors remains at risk.

As an immediate step, the coalition calls on the European Commission to assign more staff to the trade defence units within DG Trade. According to the statement, these services are severely understaffed in absolute numbers and relative to the EU’s main global partners. This shortage undermines Europe’s ability to respond effectively to foreign trade distortions in a timely manner.

Reinforcing DG Trade’s investigative capacity is therefore presented as a crucial short-term priority. Tyres Europe and the other associations contend that targeted staffing increases would significantly enhance the EU’s resilience against global market imbalances. Such a move, they believe, would help safeguard fair competition without erecting unnecessary barriers to international trade.

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Hankook Tire was conferred with the ‘Excellence in Quality and Delivery’ award during Japanese automaker Honda Motor Co., Ltd.’s ‘2025 Supplier Excellence Award’ ceremony, which took place in Columbus, Ohio, this past April.

Honda annually evaluates suppliers across North America based on criteria such as quality, delivery, value and innovation. Out of 56 honourees this year, Hankook Tire stood out due to its systematic quality management, stable supply capabilities and advanced product development competitiveness.

This latest accolade marks Hankook Tire’s fifth recognition from Honda, following previous wins for ‘Excellence in Value’ in 2016 and 2020, and ‘Excellence in Delivery/Value’ in 2018 and 2023. Since establishing a partnership with Honda in 2013, Hankook Tire supplies original equipment tyres for key SUV models including the CR-V, HR-V, Pilot and Passport, as well as global sedans like the Accord and Civic.

Building on this recognition, the tyre manufacturer aims to deepen its collaboration with Honda and expand its presence as a premier global brand in North America. Leveraging its integrated quality and technology system – supported by the Technoplex headquarters, Hankook Technodome R&D center and Hankook Technoring test track – the company continues to serve over 50 global automakers and plans to further enhance its AI-driven quality management through sustained R&D investment.

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