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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Infiniteria has appointed Proman as its Engineering, Procurement and Construction partner for a circular tyre recycling facility in Uddevalla, Sweden. This collaboration marks a decisive move towards establishing what the company describes as Europe’s leading circular tyre recycling business, with the Uddevalla site serving as the cornerstone for a future network of industrial-scale plants across the continent.

The company specialises in transforming end-of-life tyres into high-value recovered materials, aiming to accelerate the transition to a more resilient circular economy. The Uddevalla facility stands as Infiniteria’s flagship project and represents the initial phase of a broader European expansion strategy.

Committed offtake agreements are already in place with major customers including Preem, Nokian Tyres and Michelin, underscoring strong industrial demand for the recovered materials.

Kajsa Ryttberg-Wallgren, CEO, Infiniteria, said, “Bringing Proman on board as our partner is a major step forward for Uddevalla. They have a proven track record in delivering complex industrial plants, and the discipline and capability they bring mark a decisive step towards starting operations. We are fully committed to Uddevalla as the long-term home of our flagship facility, to our customers and to building Europe’s leading circular tyre recycling business.”

Francisco Carlos, Managing Director, Proman Portugal, said, “We appreciate the confidence and trust placed in Proman by Infiniteria as we take on the role of Engineering, Procurement and Construction partner in the Uddevalla project. Proman brings strong global expertise and experience to the project, including project management, engineering, procurement, construction and commissioning of complex industrial facilities. We look forward to working with Infiniteria to progress the Uddevalla project towards successful completion.”

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Tyres Europe has released replacement tyre sales data for the first quarter of 2026, with the industry showing early signs of recovery according to an assessment by Secretary General Adam McCarthy. The figures from member companies reveal that consumer tyre segments, including passenger car, SUV and light commercial vehicle categories, rose by one percent compared to the first quarter of 2025. This modest growth follows a weak performance across the previous year.

McCarthy noted that the recovery was uneven across different tyre types. All Season tyres continued their strong momentum with a five percent increase, driven by consumer demand for year-round versatility, while summer tyres slipped by one percent as they lost further ground to all season alternatives. Winter tyres posted a sharp decline of 14 percent, which the Secretary General attributed to mild weather conditions across much of Europe. Members’ sales significantly outpaced imports, which were impacted by European produced tyres and possible regulatory action. Travel demand remained subdued during the quarter, with higher fuel prices linked to the Middle East conflict affecting the market from March.

Other segments reflected a mixed landscape. Truck and bus tyres edged up one percent, supported by improved freight activity and business sentiment before recent geopolitical developments and rising fuel costs created uncertainty. Agricultural tyres declined 11 percent amid continued caution in farm investment. In contrast, the moto and scooter tyre segment recorded a more positive six percent gain, according to the Tyres Europe report.

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Hankook Tire & Technology reported a sharp rise in first-quarter operating profit, supported by stronger sales of electric vehicle tyres and replacement tyres across key markets including Europe, Korea and China.

The South Korean tyre maker said consolidated revenue for the three months to March reached USD 3.63 billion, up 7 percent from a year earlier, while operating profit rose 42.9 per cent to USD 345.9 million.

Sales in the group’s tyre business increased 9.3 percent year-on-year to USD 1.75 billion. Operating profit in the division rose 31.1 percent to USD 298.6 million, representing an operating margin of 17.1 percent.

The company said demand for original equipment tyres supplied to electric vehicle and hybrid models, alongside higher replacement tyre sales, supported performance despite continued uncertainty linked to tariffs and elevated oil prices.

Hankook Tire said tyres measuring 18 inches and above accounted for 49.1 percent of total passenger car and light truck tyre sales in the quarter, up 2 percentage points from a year earlier. Electric vehicle tyres represented 29.6 percent of original equipment passenger car and light truck tyre sales, an increase of 6.6 percentage points year-on-year.

The company expanded original equipment tyre supply during the quarter for both internal combustion engine and electric vehicle models produced by Mercedes-Benz, BMW and Ford.

Hankook Tire said it currently supplies original equipment tyres to about 50 automotive brands across roughly 300 vehicle models, including Porsche.

The company also continued to expand its iON electric vehicle tyre range, which now covers about 300 specifications from 16-inch to 22-inch tyres.

Its thermal management subsidiary Hanon Systems reported first-quarter sales of USD 1.88 billion, up 5 percent year-on-year, while operating profit rose more than fourfold to USD 66.3 million.

Hankook Tire said it continued to expand production capacity at its Tennessee plant in the US and its Hungary facility in Europe as part of efforts to strengthen global supply capabilities.

The company said it aims to raise the proportion of high-inch tyres to 51 percent and electric vehicle tyres to more than 33 percent of passenger car and light truck original equipment tyre sales.

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Hankook Tire, the exclusive tyre supplier to the ABB FIA Formula E World Championship, supported all competitors during the 2026 Hankook Berlin E-Prix. The double-header at Tempelhof Airport Street Circuit featured Hankook’s iON Race tyre, which was pushed to its limits by the venue’s rough concrete surface and a fast, 15-corner layout. Rounds 7 and 8 of Season 12 unfolded across two days on the 2.374-kilometre anticlockwise circuit, where tyre preservation and energy efficiency became critical success factors.

The abrasive concrete apron at Tempelhof forced drivers to carefully manage degradation, while the Turn 2 ATTACK MODE zone added a recurring strategic puzzle. Hankook’s iON Race rubber delivered steady grip and predictable handling as track conditions shifted between Saturday and Sunday. The double header demanded consistent tyre behaviour, with teams adjusting to changing rubber build up and surface temperatures over the two race days.

Nico Müller secured his first Formula E victory in Round 7, holding off Nick Cassidy and Oliver Rowland through disciplined energy management. In Round 8, Mitch Evans produced a remarkable comeback from last on the grid, passing Oliver Rowland and Pascal Wehrlein with a late decisive move to take the win. Both performances highlighted the tyre’s balance of durability and performance under racing stress.

Off track, the Berlin weekend drew large crowds to Hankook’s Fan Village, where interactive displays featured iON tyres on electric vehicles. The brand also partnered with DS Automobiles to debut the DS N°7 model. Following the Tempelhof races, the Formula E season now heads to Monaco for the next rounds on 16 and 17 May.

Manfred Sandbichler, Senior Director of Hankook Motorsport, said, "The Berlin double-header confirmed the resilience of the iON Race under some of the most demanding surface conditions in Formula E. Running two races at Tempelhof provided valuable insight into how the tyre responds to sustained abrasion across a full race weekend. The competitive racing and strategic variation across both days reflected the tyre’s ability to operate within a broad performance window, and these insights will support ongoing development alongside the championship."

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