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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Ecolomondo Corporation, a Canadian leader in scrap tyre recycling technology, has finalised a joint venture and engineering agreement with Spanish renewable energy firm Alternativas Riojanas Eolicas y Solares S.L. (ARESOL) to construct four Thermal Decomposition Process (TDP) facilities across the European Union. The partnership follows a non-binding letter of intent signed in December 2024 and subsequent technical evaluations, culminating in a definitive agreement in July 2025.

The first facility will be established in Valencia, Spain, processing 20,000 metric tonnes of end-of-life tyres annually. Three additional locations will be selected based on feedstock availability, tipping fees, offtake agreements and government incentives. ARESOL brings four decades of renewable energy project expertise, including engineering, procurement and construction (EPC) capabilities, to support the deployment of Ecolomondo’s proprietary TDP pyrolysis technology.

Under the agreement, a joint venture entity will be formed, with Ecolomondo holding a 51 percent stake and ARESOL 49 percent. Governance will include two directors from each company and one independent member. This initiative aligns with Ecolomondo’s global expansion strategy, following the successful ramp-up of its Hawkesbury TDP facility and recent shipments of recovered carbon black (rCB) to key clients.

Eliot Sorella, Executive Chairman, Ecolomondo Corporation, said, “We are excited about this important partnership, and we look forward to working with the ARESOL team as part of our European rollout. We will enter the European market with a JV partner that is based locally, understands the European market and has the experience to build plants in selected sites in any city in the EU. This agreement is exactly in line with the Company’s long term strategic objective to become a global industry leader, creating sustainable products from end-of-life tyres.”

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Goodyear India said its first-quarter profit nearly tripled, boosted by higher revenue and improved margins as the tyre maker benefited from steady demand in the commercial vehicle segment.

Net profit for the three months ended 30 June surged to INR 1.41 billion from INR 487 million a year earlier, the company said in a regulatory filing.

Revenue from operations rose 8.7% to 655.2 billion rupees, driven by volume growth across passenger and commercial vehicle tyres despite competitive pricing pressures in the market.

The Ballabgarh-based company saw its operating expenses rise 7.6 percent to INR 641.9 billion during the quarter. Cost of materials consumed, the largest expense component, increased 4.4% to 267.4 billion rupees.

Employee benefit expenses climbed 12.7 percent to INR 50.5 million, whilst finance costs jumped to INR 1.3 million from INR 1.2 million in the corresponding period last year.

The company’s earnings before interest, tax, depreciation and amortisation margins improved during the quarter, reflecting better operational efficiency and pricing discipline.

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 TVS Srichakra, India’s tyre manufacturer, reported a 61 percent surge in first-quarter profit after receiving a government grant, though operating performance remained subdued amid challenging market conditions.

Net income rose to INR 181.2 million in the three months ended 30 June from INR 112.6 million a year earlier, the Madurai-based company said in a regulatory filing. Revenue from operations increased 3.1 percent to 76.17 billion rupees.

The profit surge was primarily driven by an exceptional income of INR 1.76 billion from a government grant. TVS Srichakra received an interim eligibility certificate for investment promotion capital subsidy sanctioned by the Tamil Nadu state government in November 2021, to be paid over 12 years in equal annual instalments.

“Grant income of 18.81 crores attributable towards completed useful life of eligible assets up to 31st March 2025 recognised under exceptional item,” the company said, referring to the accounting treatment of the subsidy.

Excluding the exceptional item, the company’s operating profit before tax fell to INR 67.4 million from INR 160.8 million a year ago, reflecting pressure on margins. Total expenses climbed 4.6 percent to INR 75.75 billion, led by higher material costs and other expenses.

The company, part of the TVS Group conglomerate, also incurred costs of INR 12.5 million during the quarter under a voluntary retirement scheme for employees, compared with INR 53 million for the full previous fiscal year.

TVS Srichakra’s consolidated revenue rose 3.6 percent to INR 81.94 billion, while consolidated net profit increased 93 percent to INR 128.3 million, again boosted by the exceptional income.

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Brown & Brown Dealer Services (BBDS), a division of insurance brokerage leader Brown & Brown, Inc., has acquired the assets of Tire Shield, Inc., a Las Vegas-based provider of administrative services for tyre, wheel and GAP protection products in the automotive, RV and power sports industries.

Founded in 1997, Tire Shield will continue operations from its Nevada headquarters under BBDS, with its team reporting to William Kelly, President of BBDS Administrative Services. The acquisition strengthens Brown & Brown’s portfolio of specialised insurance solutions.

As a global firm with over 23,000 professionals across 700+ locations, Brown & Brown has delivered tailored risk management and insurance strategies since 1939. This move reinforces its commitment to scalable, innovative services for clients’ evolving needs.

Mike Neal, president of BBDS, stated, “We are excited to welcome the Tire Shield team and their valued customers to Brown & Brown Dealer Services. The addition of Tire Shield allows us to broaden our offerings to include GAP waiver administration services in addition to our vehicle service contract administration services. We look forward to continuing to service and grow these businesses.”

Mark Otto said, “We are thrilled to be joining the BBDS team. This marks a new chapter for us, enabling broader capabilities and opportunities to serve our customers. Together, we look forward to accelerating innovation and delivering even greater value.”

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