The tire is the only part of the car that touches the road. Tires must strike a balance between traction, comfort, durability, energy efficiency and overall cost. As a result of these competing needs, tires are more complex to design and build than you might think.
Take, for instance, a smart phone. It seems far more complex than a tire. But actually, a similar amount of research and technology goes into every tire Michelin makes.
The steps of the tire making process
1- Understanding through research
We study peoples' tire usage and driving habits to make sure our tires meet everyone's needs.
2- Developing and mixing materials
Over 200 ingredients go into a tire. They play vital roles in safety, fuel efficiency, performance and eco-friendliness.
These components fall into five groups:
- Natural rubber: the main component of the tread layers
- Synthetic rubber: part of the treads of car, van and 4x4 tires
- Carbon black and silica: used as a reinforcing agent to improve durability
- Metallic and textile reinforcement cables: the "skeleton" of the tire, forming the geometric shape and providing rigidity.
- Numerous chemical agents: for unique properties like low rolling resistance or ultra-high grip
We create many different designs and use simulations to test and select the best tire concepts to be developed.
We expertly build each tire through both hand-made and automated processes. When necessary, we invent our own machines to reach our goals.
5- Quality control
Quality control is not only an end step. We measure quality throughout the process.
We do over 1 billion kilometres worth of tire testing per year – the equivalent of driving around the planet 40,000 times.
How does the design of a tire impact its performance?
A tire’s tread design – the grooves and patterns in the rubber on the top surface of the tire – is crucial to its performance. The tread design plays an essential role in your tire’s grip in different types of driving conditions and can impact both your safety and your driving pleasure.
Safety – wet road grip example
To understand the role of the tire tread on wet roads, it's useful to think of a water pump. The more channels in your tire's tread, the better it pumps water away from the tire and the road. Remarkably, it can displace water in just a few milliseconds. A 195/65R15 tire, for instance, can displace almost 3.96 gallons of water per second.
Design elements that impact wet grip:
- Groove ratio: The more/larger grooves a tire has, the better the tire pumps out water.
- Shape and layout: The shape of the tread patterns (symmetrical, directional, asymmetrical) contributes to how quickly water is drained.
- Sipes: These are thin slits in the rubber surface of the tread. They improve traction in wet or icy conditions. Acting like windshield wipers, sipes help the edges and grooves of a tire to drain away water.
Design elements that impact dry grip:
- The tire's profile (shape): A flat profile with square shoulders provides good support in turns.
- The amount of grooves: The smaller the percentage of grooves in the tread pattern, the more rubber there is in direct contact with the ground and the better the level of grip.
- Tread blocks: The larger the individual blocks of tread rubber in the design, the better the traction. But this can also generate more road noise.
- Self locking sipes: Tread blocks with many sipes will reduce the rigidity of the tread pattern. To counter this effect, we have introduced complex 3-dimensional sipes, which lock together under load.
What is the structure of a tire?
The typical radial tire consists of nine main parts.
1. Inner liner: An airtight layer of synthetic rubber (the modern equivalent of an inner tube)
2. Carcass Ply: The layer above the inner liner, consisting of thin textile fiber cords (or cables) bonded into the rubber. These cables largely determine the strength of the tire and help it resist pressure. Standard tires contain about 1,400 cords, each one of which can resist a force of 15 kg.
3. Lower bead area: This is where the rubber tire grips the metal rim. The power from the engine and braking effort is transmitted from the rim of the tire to the contact area with the road's surface.
4. Beads: They clamp firmly against the tire’s rim to ensure an airtight fit and keep the tire properly seated on the rim. Each wire can take a load of up to 1,800 kg without risk of breaking. There are eight of them on your car – two per tire. That’s a massive 14,400 kg of resistance strength. An average car weighs about 1,500 kg.
5. Sidewall: It protects the side of the tire from impact with curbs and the road. Important details about the tire are written on the sidewall, such as tire size and speed rating.
6. Casing ply: It largely determines the strength of the tire. It's made up of very fine, resistant steel cords bonded into the rubber. This means the tire can resist the strains of turning, and doesn't expand due to the rotation of the tire. It's also flexible enough to absorb deformations caused by bumps, potholes and other obstacles in the road.
7. Cap ply (or "zero degree" belt): This important safety layer reduces friction heating and helps maintain the shape of the tire when driving fast. To prevent centrifugal stretching of the tire, reinforced nylon based cords are embedded in a layer of rubber and placed around the circumference of the tire.
8. Crown Plies (or belts): They provide the rigid base for the tread.
9. Tread: It provides traction and turning grip for the tire and is designed to resist wear, abrasion and heat.
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