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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Smithers, a renowned provider of testing, consulting, information and compliance services, has announced that its proving ground at Treadwell Research Park in Pearsall, Texas, has achieved ISO 17025 accreditation.

Operated on behalf of Discount Tyre, the facility’s accredited scope currently covers wet grip testing and tyre buffing, with plans to expand accreditation to include rolling resistance and pass-by-noise testing. The site boasts diverse paved and off-road test surfaces for comprehensive tyre performance validation. Additionally, it complies with UNECE Regulation No. 117 for Wet Grip and Pass-by Noise standards. This accreditation underscores Smithers' commitment to delivering high-quality testing services in the tyre industry.

Sean Connolly, Director of Test Track Operations at Smithers Winter Test Centre/Pearsall Test Track, said, “The tyre industry is currently focused on a variety of sustainability initiatives, such as reducing the rate of tread wear to extend the life of the tyre. Understanding tyre performance at varying levels of tread wear is critical for tyre manufacturers looking to get the most out of their designs.”

Jim Popio, PhD, Vice President, Smithers Materials Science and Engineering Division, North America, said, “We’re incredibly proud that our existing processes and procedures meet the rigorous requirements of ISO 17025 accreditation. Accurate data, on time, is central of the Smithers promise on a global scale, and we strive to go above and beyond our clients’ expectations with exceptional service as well.”

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Michelin, a leading tyre technology company, has launched its first Michelin Experience Store in India, in partnership with Bharat Tyres. The facility spread across 25,000 sqft is located in Adgaon on the Mumbai-Agra highway, Nashik and is Michelin’s largest store in the country.

It is designed not only to provide a premium experience, but also showcases the company’s global legacy through the Michelin Wall. Customers will also be to experience the Heritage Wall that visualise the heritage of both Michelin and its local dealership partner.

The Michelin Experience Store also has a Display Zone that showcases Michelin’s innovations in electric mobility, materials science and environmental responsibility.

The dealership also includes service areas for cars and trucks, PPF coating, precision wheel alignment, advanced balancing services, innovative puncture repair solutions, professional car detailing and a wide array of car accessories. 

Shantanu Deshpande, Managing Director, Michelin India, said, “We are proud to unveil Michelin’s first Experience Centre in India. The sole purpose of this store is to go beyond traditional tyre retail and provide customers an immersive experience of the brand, of our dealer partners and of the technological prowess of our tyre solutions that are safe and sustainable. Nashik, a key hub with growing premium vehicle ownership, is the first of many such centres that will further strengthen our footprint in the western region while providing state-of-the-art experience and services to evolving customers.”

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Radar Tyres, the flagship brand of Omni United, has appointed Sami Jauhojärvi, Olympic gold medallist and one of Finland’s most celebrated cross-country skiers, as its official brand ambassador.

Jauhojärvi's sporting excellence – built on resilience, performance and a profound connection with nature – mirrors Radar Tyres' commitment to delivering premium-quality tyres across all seasons and terrains at accessible prices. The brand's comprehensive range includes Summer, All Season, Winter and specialist Ice tyres, designed to meet diverse driving needs with reliable performance.

This collaboration represents a strategic alignment as Radar Tyres expands its European and UK presence. Jauhojärvi will serve as brand ambassador, featuring in marketing campaigns, digital initiatives and local events while sharing his expertise to support Radar Tyres' mission of making high-performance tyres available to all drivers.

G S Sareen, Founder and CEO of Omni United, said, “We’re excited to welcome Sami to the Radar family. Sami’s authenticity, credibility and strong connection with his audience make him an ideal partner for us. He embodies the spirit of perseverance and performance – the same qualities we build into every Radar tyre. As we continue to grow our brand across Europe, partnerships like this play a key role in building deeper connections with consumers. We’re excited to build on this momentum with more such collaborations in the near future.”

Jauhojärvi said, “I am thrilled to represent Radar Tyres, a brand that has a remarkable mission to make premium quality and performance accessible to all and also has deep-rooted values of giving back to society via various initiatives it has undertaken over the years such as supporting breast cancer research. I’m sincerely surprised about the performance and silence of my Radar Tyres and happy to deliver this feedback to all the people.”

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Kenda Tires is celebrating Dan ‘The Flying Dutchman’ Vanden Heuvel's nomination to the Off-Road Motorsports Hall of Fame's Class of 2025, recognising his legendary 49-year career as both a champion racer and community leader.

Since entering his first race at age 15 in 1977 at Crandon International Raceway, Vanden Heuvel has become one of off-road racing's most respected figures. His aggressive driving style earned him 20+ Pro-Class wins, five Crandon World Championships and a PRO-2 title. As owner of Flying Dutchman Racing, he mentored numerous drivers including his son Mikey, who secured Kenda Tires' historic first PRO-2 victory.

Beyond competition, Vanden Heuvel's greatest impact comes from his tireless community work. He co-founded the Midwest Off-Road Racing Association, created the Short Course Kart Series for young racers and established the MORR Injured Driver Fund with his wife Nancy. His hands-on approach – from building tracks to mentoring drivers – has shaped generations of off-road enthusiasts.

Now as Kenda Tires' Product Display Manager, Vanden Heuvel continues supporting the sport, assisting drivers across multiple series while representing Kenda at events nationwide. His dedication embodies the brand's values of community and passion for motorsports.

The formal induction ceremony will be held on 2 November 2025 in Las Vegas. This honour celebrates not just Vanden Heuvel's remarkable racing achievements but his enduring legacy as an ambassador who has profoundly influenced off-road culture.

Brandon Stotsenburg, VP of Automotive Division, Kenda Tires USA, said, “Dan is more than a legend – he is a mentor, a servant-leader and the beating heart of the off-road community. He helped deliver Kenda’s first PRO championship and still shows up for others every single weekend. We are honoured to have him represent Kenda and even more proud to call him family.”

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