Before rubber was invented, tyres were made up of a metal ring mounted on a wooden wheel. Today, we commonly recognise tyres as the black, round components mounted onto the bottom of each end of our cars. Yet we know that there is so much more to tyres than meets the eye. In fact, these hard-working circular rubber components can be rather fascinating! Here we take a slightly more technical perspective on those objects that make your wheels go round.
A tyre can be described as a thick rubber ring, often filled with air, that surrounds a wheel’s rim, to transfer a vehicle’s load from the axle through the wheel to the ground. It provides traction on the road or surface over which they travel.
Since tyres must carry a vehicle’s load at high speed, safety is a crucial consideration during their design process.
Tyre components & materials
Today’s modern pneumatic tyres consist of two parts:
- Body – contains compressed air
- Tread – provides traction to the vehicle
The raw materials of a tyre are made up of synthetic rubber (styrene-butadiene copolymer or SBR), natural rubber, fabric, and wire, as well as carbon black and other chemical compounds.
The materials are categorised into two groups:
- Cords – These provide reinforcement and used to maintain the shape of a tyre, providing the tensile strength necessary to contain the inflation pressure inside. Cords can be composed of steel, natural fibres (cotton, rayon, silk), or synthetic fibres (nylon, polyester, aramid). The rigidity of the tyre cords influences a car’s ride. For instance, more rigid tyre cords provide better handling and stability. Less rigid cords provide a more comfortable ride.
- Elastomer – Shorthand for ‘elastic polymer’, elastomers are composed of various composites of special polymers that are very elastic. A form of synthetic rubber, they form the tyre’s tread and encase the cords, helping to protect and hold them in place.
There are two main types of tyre structures: Cross-ply and radial.
- Cross-ply – The nylon cords cross diagonally over each other, then layered with rubber plies.
- Radial-ply – The plies of cord have been rubber-bonded, laid at 90 degrees across the circumference of the tyre, radiating out from the centre, then covered in a steel casing. These are the most common tyres produced today since they have numerous benefits including lower rolling resistance, better fuel economy, and less chance of blowout.
Key performance criteria
There are many performance criteria that design engineers aim for and test before introducing a tyre to the market, for example:
- Fuel efficiency
- External rolling noise
- Handling and braking
- Cornering grip
- Internal noise
- High-speed stability
- High-speed endurance
- Grip capability
- Puncture resistance
- Rolling resistance
- Electrical resistance
- Groove wander
- Air retention
Research & Development
The purpose of tyre research and development is ultimately for manufacturers to produce the best tyre for the market at the current time.
“Not only must fundamental tyre-development targets such as performance, safety, quality and processability be achieved, but new aspects must also be considered, such as recyclability, regulatory compliance and supply chain adequacy.” ~ Massimo Cialone
(Source: Automotive Testing Technology International)
Once the optimum design has been achieved, the manufacturer will then produce the tyre for testing in real conditions to ensure it will meet all its performance criteria. This can take many months, and sometimes years and many iterations to achieve performance requirements.
Amongst their many tasks, some of the main aims development engineers look to achieve in the building of a tyre are optimal handling, durability, and fuel efficiency. To achieve this, various factors are considered:
- Tread pattern
- Tyre contour
- Tread compound
- Tyre construction
Quality & performance testing
Testing of the tyre begins once the construction and development work has been completed. After the tyre is released by the experimental production team, it is ready for indoor and outdoor testing.
There are so many factors that can influence the quality and performance of a tyre, which makes testing during this process extremely important.
Test engineers conduct all the required testing and provide the performance results. Rigorous rounds of testing commonly include:
- Endurance testing to determine the loads and speeds a tyre can tolerate,
- Accelerated aging by increasing the temperature of a tyre before it’s mounted on the dynamometer to give a more accurate reading of how the tyre is affected by extreme conditions
- Measuring rolling resistance – the force required to maintain forward movement at a constant speed.
- The tyre’s performance, related to noise, tread wear, wet and dry traction, stopping distance, etc.
The data is analysed and depending on the results, the tyre may either need modifications or be released into production for the market. However, this is not the end of the test phase, as the tyre will continue to be monitored to ensure it meets performance expectations.
Tyre development and testing is one of the most complex mechanical design elements of your vehicle and can take years to complete. We expect a lot from our tyres – comfort, safety, and reliability – just a few important aspects we often take for granted.
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Disclaimer: This information is for educational, or entertainment purposes only. It must not be construed as advice, legal, financial, or otherwise. We do not make any warranties about the completeness, reliability, and accuracy of this information.