Tires are, without a doubt, indispensable parts of a road vehicle or automobile. In fact, they perform multiple functions in the overall operation, performance and safety of all sorts of vehicles – from bicycles, automobiles, trucks and even aircrafts. They keep the wheels in close contact with the ground for traction while providing for a flexible cushion that absorbs shock and makes riding comfortable.
Tires, as practical components of transportation technology, trace its early beginnings in Scotland. The first to invent it was Robert William Thomson, in the 1840s, and then used in the wheels of a bicycle by John Boyd Dunlop more than 30 years later. In the early twentieth century, they were mass produced by tire manufacturing companies which strategically partnered with the automobile industry.
Parts and Functions
Tires are commonly made of rubber, which is flexible and elastic. They are further reinforced by steel, fabric or wire for strength and durability. There as are many types as there are kinds of vehicles that they may be used on. Their use determines the kind of materials they are made of, their manner of construction and their overall design.
To better understand them, it is basic to first identify to be able to appreciate how these parts contribute to accomplish their functions.
The tread is that portion which touches the road surface. A contact patch is that portion in the thread that comes in contact with the road at any given time. The thread is made up of rubber, or any rubber composite material, that is both elastic and can stand the wear and tear of rubbing with the ground due to resistance, traction, and environmental factors.
On the tread itself are geometrical patterns that are called grooves, lugs, voids and sipes. The grooves, voids and sipes are practically spaces which allows for the passage and release of water encountered on the road. They are not just designs, but they serve the purpose of preventing hydroplaning – which is a dangerous condition when a tire steps on water and loses its contact on the ground resulting in the vehicle going out of control. The lugs on one hand are the protrusions in the threads that serve the purpose minimizing tire noise.
The bead is the part that keeps the tire safely fixed to the wheel rim. It is made of high-strength steel cable loop and enclosed by low flexibility rubber. This part adds more to tire strength and has to be perfectly fitted in the rim so that the air inside will not leak out. It is a very tough portion so that it can handle the pressure from tire mounting machines in the process of mounting the tire into the rim.
The body is the main part of the tire. It is made up of layered plies or fabrics, which vary in terms of material, placement and orientation according to the use and application of the tire. The fabric used may be of polyester cord. The orientation of the fabric may be at certain angles to the thread to achieve different results. They are primarily classified according to the orientation of the ply in relation to the thread. These fabrics are non-extendible and are embedded in rubber in order to achieve a perfect balance of both flexibility and stability, in the midst of the pressure accompanying its pressure.
The fabrics used may be cotton, rayon, nylon, polyester and Kevlar. The number of plies a tire has also varies. In effect, the overall measure of tire strength is determined by the number of plies it is built with. In effect, most car tires have 2 plies, and the number of plies is raised as the vehicle size and weight increases calling for more strength from the tire for performance and support.
The belt is the area under the tread which helps resist tire puncture. They are usually made of steel which makes the tire stay flat and make good road surface contact. Belts may also consist of different number of layers of steel. Passenger vehicles usually have two or three belts in their tires.
The sidewall joins the tread and the bead. As it still requires strength and flexibility, it is also made of rubber and reinforced with fabric or steel cords. Together with air inflation, it supports the weight of the vehicle. This is the part where government required prints and all other prints with regard to tire specifications are found. The sidewalls bear the markings on tire type, tire width, aspect ratio, tire construction, rim diameter, uniform tire quality grading, and service description.
It is now time to get to know the markings on the sidewall to understand them even more. The letters P, LT, and T represent the tire type. P stands for passenger vehicle tire, LT stands for light truck and T stands for temporary or spare tire. A three digit number represents the tire width in millimeters, when the tire is already fixed on the rim. A more common tire width is 235mm. A two digit number is for the aspect ratio.
The aspect ratio is the height of the tire, measured from the bead to the tread and is expressed as a percent of the tire width. For example, the number 75 means that the height of the tire is 75% of its width. A lower aspect ratio means a wider tire. A wider tire means higher lateral stability and enhances tire performance. The letter R, D or B stands for the type of tire construction. R is for radial, D is for diagonal or B is for Bias. The rim diameter is specified in inches, which states the measurement of the rim for which the tire would fit.
The uniform tire quality grading is the rating given by the US National Highway Traffic Safety Administration. Only passenger cars are rated and the ratings indicate the tread wear, traction and temperature. The service description consists of two things: load rating and speed rating. The load rating is equal to the maximum load by the tire, and the speed rating also corresponds to the maximum speed allowed for the tire.
According to their construction types, they may be radial, solid, bias, and belted bias and semi-pneumatic. The most dominant modern tire construction is the radial type. In this type of construction, the plies are positioned at 90 degree angles with regard to the centerline of the tread. This type of tire has longer tread life, better steering control, improved vehicle handling and efficiency. This is the reason why it the most commonly used type of tire today.
The solid types do not need to be inflated. They don’t have a hollow space inside, which makes them stronger and extremely capable of carrying heavy loads. This type of tire is ideal not only for industrial vehicles such as trailers and forklifts, but for special types of vehicles such as golf carts, scooters, lawn mowers and even skateboards.
A bias tire is constructed with the plies at 30 to 40 degrees relative to the tread centerline, laid down alternately opposite each other. The plies are crisscrossing and overlapping. This is sometimes referred as the cross ply. This design allows for maximum tire flexibility ensuring a smooth ride. The catch in this type though is that traction and control are decreased, but not necessarily compromised, when the vehicle is at high speed.
A bias-belted tire is an improved version of the bias tire in that it is further reinforced by steel belts in between the plies. The belts and the plies are at opposite direction with each other. This type combines the flexibility and the drivability of the bias tire coupled with superior tire traction and control.
The semi-pneumatic type of car is not pressurized despite its having a hollow. They are not yet used for automobiles at the moment but are installed in special types of machine or equipment that require mobility such as wheel barrow and wheel chairs. However, there is much research towards the direction of employing them for automobiles. This type of tire does not go flat, so this is going to be a breakthrough development in automotive to be able to perfect one that will suit the requirement of the usual land transportation vehicles.
Maintenance for Safety and Longevity
They play an important role in vehicle riding comfort and safety. This means that the proper maintenance and care due to vehicles in general is also due to the them in particular. The Rubber Manufacturers Association has four very simple tips for tire care, and will not even take so much of your time . At least once a month, they need to be checked for pressure, alignment, rotation and tread. The right amount of tire pressure is specified in the vehicle door edge and in the owner’s manual, and this has to be followed.
An incorrectly inflated tire is the number one tire killer and passenger hazard. An under inflated tire tremendously decreases the tire’s life span, makes for unstable driving and risks the safety of the passengers. On the extreme, a flat tire is a tire that deflates and may be caused by a damage, a leak or by just the normal wear and tear of usage. A vehicle with a flat tire should not be anymore driven, as doing so will further damage both the tire and the rim. The damage may be beyond repair and at the same time endanger the safety and lives of the driver and the passengers. An overinflated tire also brings about the same effects.
Furthermore, when there is already that pulling or shaking effect, as when the vehicle is moving itself to one side when the steering wheel is left on its own for a moment, there is already the need for the tire alignment to be addressed. The next move is to refer this concern to the tire dealer.
Rotation is a must for cars preferably every 5,000 or for the specified period indicated by the tire manufacturer. The purpose of rotation is to even out the wear and tear of each tire. This provides for a smooth ride.
Checking for tire tread is a very important safety concern. The tread is what hugs the ground, and it determines the level of control of the vehicle in terms of steering actions and directions. In checking the tread, what must be spotted are the high, low, smooth and damaged portions as they affect the overall performance of the traction of the tire.
Moreover, one more safety concern on the subject, aside from the unsafe condition brought about by wear and tear, is the tire age itself. Notwithstanding that the tire is not used, its age from the date it came out of the manufacturing plant is also a factor in terms assessing tire condition. They too degrade as they age, and they degrade faster in tropical weather conditions. Manufacturers recommend that they be in fact used only within six years.
Recycling and Disposal
When not anymore used, they are called scrap tires. This does not mean however that all scrap tires are not fit for use. Others are still in a reusable condition, and may be retreaded for further utility. A more rational and environment friendly process for finding some breakthrough use for discarded ones are still to be established. These tire wastes yet to be addressed as when left or abandoned in open ground serve as ideal breeding places for mosquitoes. Also, they react to heat and produce certain chemicals that may seep underground and pollute the water supply. This is why use in landscaping of those already discarded are not readily acceptable due to the release of certain hazardous chemicals that these tires may produce under certain conditions and over time.
They come in all sizes, designs, construction, and application. They also serve multiple functions in making transportation easier, safer and more comfortable. Civilization has come a long way from iron tires in early times, to natural rubber and to synthetic rubber at this time.