Getting to grips with the “ins and outs” of a tyre’s make-up is an important part of understanding this essential “no-nonsense” part of a vehicle which is where the rubber literally hits the road! While it’s something many of us don’t give a second thought to, tyre companies around the globe make considerable ongoing investment in time and resources to keep researching, innovating and improving on the tyre components and technology needed to meet the constantly evolving needs of modern lifestyles and vehicle performance.
Tyres specific to certain industries or applications (such as those fitted to earthmoving or road-building machinery for example) often have components distinctive to that task. That said, the majority of latest tyres used on- and off- the road for daily work, leisure or transportation use are all generally comprised of common types of components. Understanding what these tyre components are, what they do and how they fit together, is not only interesting but can also be useful (sometimes even vital) information when it comes to tyre choice and maintenance. Let’s dive in and take a look starting on the inside with the tyre’s Inner liner…
THE INNER LINER
As its name suggests, the Inner liner is the lining on the inside of the tyre which is used as an all-important air seal. Its function is similar to an old-fashioned inner tube, but technologically improved and using latest materials. One of the most critical components of a tyre, the inner liner is something that the tyre needs in order to continue operating and performing at its peak level. If punctured, the inner liner must be repaired correctly to maintain its integrity.
The next tyre component is the bead. This component is instrumental in holding the tyre onto the rim, and also provides an anchor for the casing (which we will talk about next). The bead ensures an airtight seal between the rim and the tyre.
The casing makes up the bulk of the tyre, with the primary task of holding the air in. Another key role it plays is flexing to provide shock absorption.
Polyester is the most popular material used for casings in latest model car, performance SUV and light-truck radial tyres, with nylon and rayon also sometimes used. Meantime, truck and bus tyres (which obviously require an extra level of robustness when it comes to their design and construction) generally use a mono-ply steel casing construction. Tractor tyres’ casings are textile in most cases – generally nylon or polyester, while some special applications will also utilise Kevlar (a lightweight, yet extremely strong and durable fibre) for added reinforcement and puncture protection.
Belts on a tyre have the very important task of stabilising and supporting the tread, providing lateral and circumferential stiffness as well as protecting the casing. Belts can’t be physically seen as they are embedded into the structure of the tyre, but they are always there under the surface performing three key overall functions including:
- Providing casing protection from penetrations
- Providing lateral and circumferential stiffness for cornering, braking and acceleration, and finally
- Stabilising and supporting the tread by controlling the tyre’s diameter, the tread arc radius, its footprint shape and any tread squirm (tread squirm is excess movement sometimes felt on new tyres caused by flexibility in the rubber between the tread surface and the tyre’s carcass).
Moving on now to the tyre’s Overlay, this is a tyre component that is typically made of nylon. Covering the steel belts, the overlay acts to provide greater stability and durability, and increase ride comfort. There are two main types of overlay – continuous spiral overlay and sheet overlay. The difference between these is shown in the image here.
Modern tyres typically use the continuous spiral overlay method, as it has a number of key advantages that meet the needs of today’s drivers, vehicles and modern-day driving surfaces. These benefits include a uniform shape of contact patch and enhanced steering response as well as improved high-speed stability and cornering ability.
The tyre’s tread is the most prominent and visible part of the tyre (and the aspect of a tyre that many of us probably think about when we think of a tyre), so it stands to reason it gets the lion’s share of attention when people are shopping for tyres or checking for wear and tear. However, it’s important to note that the tread is not merely created for its good looks, it also serves a number of very important functions, with different tread patterns relating to the tyre’s intended use and driving conditions. In 4×4 mud tyres for example the “aggressive” tread pattern may be specifically designed to drive in muddy (and other) off-road terrains – geared for traction, self-cleaning and reduced stone retention in such conditions. Conversely, some treads are much smoother – such as those used for lawn or golf-course maintenance, where minimal damage to sensitive turf surfaces is required.
The tread (on any vehicle) primarily serves the vital purposes of:
- Providing traction
- Dispersing water from the contact area
- Resisting abrasion
- Transmitting forces to the ground – including thrust, steering, braking and acceleration, and
- Protecting the casing against impact damage.
Last but not least there is the Sidewall, which literally holds the tyre together and provides lateral stability and impact absorption. The Sidewall provides a fantastic (and useful) surface to display all of the necessary information you see on the side of a tyre, including size, service descriptions, load and speed ratings, and other important facts such as where it was manufactured. Although you don’t need to understand all these markings, they can be of great assistance to tyre professionals assisting you with the maintenance of your tyres – as they can help determine the age of a tyre and other information to assist with decisions about the best time to replace.
As with anything, it’s important to remember that while components may be similar in name, not all quality is created equal and safety can be compromised — so in choosing a tyre always take the time to do your research or find a tyre professional in your local area to assist. Maxxis Tyres are renowned for their value combined with superior quality underlined by world-class R&D design, manufacture and testing in state-of-the-art facilities — with warranty all part of the deal.