We don’t think about what goes into an off the road tyre very much, but they’re actually fairly complex pieces of technology. While there are many types of off-the-road (OTR) tyre, we’re going to look at the standard parts of a common air-filled radial tyre shared by most.
OTR Tyre Parts
Working from the outside in, we start with a well-known part – the tread. This consists of rubber tread blocks separated by grooves. The blocks can then be divided by finer grooves known as sipes for extra grip. Along the edge of the tread is the shoulder, where OTR tyres can often be distinguished by buttresses, or high blocks around the outside of the tread.
Beneath the tread and top layer of rubber come protective layers known as the breakers, belts and cap plies. These are heavy-duty layers of rubber, steel and textile designed to protect the more delicate layers beneath. They are more common and thicker in radial tyres but can often be found on the outside of bias tyres for extra protection, too.
Main tyre plies
Beneath this protective layer are the main plies. These layers are made similarly to the belt plies, but are generally finer and more flexible, they also wrap around from one inner rim of the tyre to the other, forming its main internal structure.
Around the vertical edges of the tyre runs the sidewall, which is made of thick rubber. This is designed to keep the tyre sturdy while allowing a degree of lateral movement and deformation when turning and loading.
The part of a tyre that touches the wheel is called the bead. It consists of several steel cables that wrap tight around the inner rim of a tyre. These are coated in rubber that is fashioned to fit into a grove inside the vehicle’s wheel, forming an airtight seal.
Finally, inside the tyre is a rubber sheet known as a liner deigned to prevent air permeating through the tyre itself.
More to come
There you have it. We’ll be looking at each part of a tyre, as well as its function, variations and the science behind it in more detail in future blogs.