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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Birla Tyres has officially joined the Automotive Tyre Manufacturers’ Association (ATMA), becoming the newest member of the leading industry body. The company, with its registered office in Kolkata, operates a large-scale manufacturing facility in Balasore, Odisha, which spans 195 acres and is dedicated to producing a diverse range of speciality tyres.

Based in New Delhi, ATMA represents major tyre manufacturers that account for more than 80 percent of domestic production. The association serves as a vital link between the government and the industry while also engaging with media, opinion leaders and international trade bodies to advocate for the sector’s perspectives.

ATMA actively participates in policy formulation and regularly consults with government departments on economic challenges affecting the industry. Its existing membership includes prominent firms such as MRF Tyres, JK Tyre & Industries, CEAT Ltd and Bridgestone India, the local subsidiary of the Japanese tyre giant.

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Bridgestone has reported a significant shift in UK consumer sentiment regarding electric vehicles, with new data indicating a sharp rise in drivers who reject the technology. The tyre manufacturer's survey reveals that 26 percent of motorists now declare they will never purchase an EV, up from 17 percent in 2025, while only 16 percent plan to acquire one within the coming year.

Persistent operational anxieties continue to overshadow the market. Battery durability and replacement costs trouble 55 percent of respondents, half worry about charging expenses and 44 percent express unease over range limitations and high sticker prices.

Infrastructure inadequacies further compound hesitancy, as 43 percent feel public charging stations remain insufficient and 41 percent are deterred by prolonged recharging times. Despite these barriers, 53 percent anticipate purchasing an EV within five years, while seven percent remain undecided.

Bridgestone is reinforcing its commitment through 'EV Ready' tyres like the Turanza 6, engineered for efficiency, safety and wear life across electric and combustion vehicles. These innovations align with the company's E8 Commitment and Ecology pillar, advancing sustainable tyre technologies and mobility solutions.

Drew Chapman, North Region Consumer Sales Director at Bridgestone, said, "Electric vehicles are becoming an increasingly familiar sight on our roads, but our research shows that many drivers still have genuine questions and concerns about making the switch. While some of the barriers are gradually reducing, issues such as battery life, charging costs and infrastructure remain front of mind for many motorists. The industry has made significant progress, but it's clear there is still work to do in building confidence among consumers.

"Whether drivers are behind the wheel of an EV, hybrid or conventional vehicle, they want products they can trust. Our focus is on helping motorists get the very best from their vehicles today while supporting the mobility solutions of tomorrow."

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The Yokohama Rubber Co., Ltd. has secured its place in three major global ESG stock indexes, marking over two decades of sustained recognition in sustainable investing. The company’s inclusion in the FTSE4Good Index Series now extends to 22 consecutive years, while its presence in the FTSE JPX Blossom Japan Index has reached a 10th year and the Sector Relative Index a 5th year.

Developed and administered by FTSE Russell, a London Stock Exchange Group subsidiary, these benchmarks serve distinct investment purposes. The FTSE4Good Series is widely utilised by international investors as a reference for responsible portfolios. Meanwhile, the two Japan-specific indexes, designed to highlight domestic firms with exemplary ESG performance, have been adopted by the Government Pension Investment Fund to steer its own sustainable asset allocation.

Under the corporate sustainability motto of caring for the future, Yokohama Rubber continues to integrate social problem-solving into core business operations, thereby generating shared value. This longstanding index qualification reflects the firm’s consistent commitment to transparent governance, environmental stewardship and social responsibility, reinforcing its strategic focus on long-term value creation through ethical business conduct.

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Apollo Tyres Ltd has launched the Apollo Altrust Winter van tyre, a new addition to its commercial vehicle lineup engineered to deliver extended durability alongside reliable snow and wet-weather traction. Scheduled for European release in July 2026, this winter variant finalises the Altrust family, which already includes the popular summer and all-season iterations.

Developed entirely within Europe, the tyre achieves a top wet grip classification of ‘A’ and a noise rating of ‘B’ at 72 decibels. Offered in 15 size options across 15- to 17-inch rim diameters, the Altrust Winter is designed to accommodate a broad spectrum of vans and light commercial vehicles, including contemporary models such as the Ford Transit, Mercedes Sprinter and IVECO Daily.

Superior handling on snow, ice and rain-soaked roads stems from several engineering innovations. A multi-pitch tread pattern optimises block sizing and spacing for consistent performance, while three-dimensional sipes enhance road biting capability. Additionally, the centre and shoulder lateral grooves have been strategically configured for swift water dispersal, which bolsters wet grip and lessens aquaplaning risks.

For fleet operators, longevity and reduced wear are critical to lowering total cost of ownership. Apollo’s research division formulated a compound with a balanced polymer-and-filler mix to boost abrasion resistance and curb material degradation. Reinforced shoulder tie-bars preserve a stable contact patch under heavy use, promoting even tread wear and sustaining all-weather effectiveness over the tyre’s lifespan. Noise management was also prioritised, with careful tuning of pitch sequences and shoulder block bridges to minimise acoustic output.

Udyan Ghai, Group Head – Marketing, Apollo Tyres Ltd, said, “Our research and development team in Enschede, The Netherlands, spent over two years exploring the needs of van owners and users, creating a winter van tyre that delivers an optimal balance of performance and value. They focused on those attributes that matter most to fleet operators and van drivers: safety, durability and low operating costs. We know that wet-weather performance is becoming increasingly important for operators across Europe, so we are particularly pleased to see the tyre secure an A rating for wet grip.”

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