 |
Understanding Tires
All about Tires Any driver worth his salt knows his tires. It's not enough to know that your tires let you roll over the road surface and thereby let you get to your desired destination. Tires don’t work as simply as that. If they did, there'd be no need for complicated tire designs and precisely-engineered tires; you can get any set of tires and drive on.
Tires for City Driving versus Off-Road Driving You require a different set of tires depending mainly on the road conditions. You could say that city driving requires the least complicated tires. Most roads in the city are paved and you're unlikely to be climbing over rocks and crossing ditches. If you are going to keep your driving within the city or suburbs, therefore, you don’t have to put too much to the tires affixed to your car. Just buy your car and trust the car manufacturers to know what they were doing when they chose to furnish your car with its current set of tires. For off-road driving, however, your tires play a crucial role in how successful you'd be. The exact configuration of treads, lugs, voids, or sipes on your tires have bearing on how easy or hard you’d find off-road driving to be. The size and pressure of your tires, the tire’s tread design, sidewall strength, and wheel alignment, among other things, also have bearing on your truck's off-road capabilities. Therefore, if you are planning on buying a car or a truck – especially if you are planning an off-road adventure – you'd better read on and learn what makes up a tire, what factors need to be considered when evaluating or assessing tires, what are the basic tread configurations, basic tire constructions, and some standard terminologies associated with tires.
The Basics: What makes up a Tire? A car or truck tire is not a product of random thought and design. Tires have essential components, without which they would not be able to function well and probably cause accidents besides. Under this section, you would learn all there is to know about tire components. The tire casing is the tire's skeleton – that which gives the To reinforce the body ply, a tire usually has multiple layers of rubber-coated plies. These are called the belts. They are similarly coated with rubber (and they have heat and impact resistance, as well) and their composition may be the same or different from that of the main body ply; main body plies are usually made of rubber-coated fabric whereas reinforcing plies can be made of fabric or metal (e.g. steel). The belts can be found immediately underneath the tire tread and they mainly serve to help press the tread flat on the road's surface. Aside from keeping pressure on the tread, however, they also serve to keep the tread in place (they minimize squirm) so that undue friction (and thus undue wear and tear) on the tread could be minimized. The belts, aside from providing protection against undue wear damage, also protect the tire from damage caused by tread penetration and forceful impacts. Finally, a tire has the tread. This is the outermost layer of any tire. It's actually the part of the tire that is in contact with the pavement or the road’s surface. This is where you will see various patterns and designs. Basically, the tread can be composed of tread blocks interrupted by sipes or a series of lugs separated by voids. The rows or blocks of tread found along the edges of the tire are usually called the shoulders. Between an inner tread block and a shoulder, you'll find tread grooves. Between two inner tread blocks, you'll find the tread rib. Some related terms: The tread blocks are the part of the tread that mainly provides the tire traction. The sipes, on the other hand, are small cuts that interrupt the tread blocks; without sipes, the tread blocks would be smooth. These sipes actually help provide traction so that trucks and cars can avoid skids on wet and slippery roads, for example. Generally, moreover, the more sipes a tire has, the better its traction would be. The term “sipes” was coined in honor of the man who thought of creating small cuts on tread blocks. On the other hand, some tires are said to have lugs and voids instead of the more usual tread blocks and sipes. Basically, the lugs are that part of the tread that maintains contact with the road surface. The lugs serve to provide the tire bite and grip. The voids, on the other hand, are simply the spaces that separate lugs from each other. The voids do not usually touch the road surface when driving on highways since the lugs are usually large and the voids deep; however, in muddy and uneven terrain, the voids serve to clean the tires of mud and other clinging dirt so that the lugs could provide maximum traction.
Evaluating and Assessing Tires
To begin assessing a tire, look to its side and find the series of numbers and letters that begin with either a P or LT. Read on to find out what these characters indicate. Purpose: At the head of the series should be P or LT. This portion of the series indicates the purpose for which the tire is best suited. If it says P on the tire’s side, then that tire is ideal for cars or trucks that are used mainly for hauling passengers. If it says LT, then the tire could be used for light trucks (thus the term LT) that are made for hauling not just passengers but cargo as well since they are designed to carry more weight. Width: After the letter/letters, there should be a three-digit number. This is the width of the tire as measured from the edge of that sidewall to the other sidewall. The unit of measurement is millimeters so a measurement of 220 means that the width of the tire is 220 mm. Height: This is another characteristic of a tire, but this information is not readily available on the tire itself; this has to be computed using the aspect ratio. Basically, the height is the distance from the rim to the tire tread. Aspect Ratio: Following the width and a forward slash, you should find a two-digit number. This is the tire's aspect ratio measurement. The aspect ratio is simply the ratio of the tire’s height to the tire’s width. This is measured in percent so an aspect ratio of 60 indicates that the tire's height is 60% of the tire’s width. Therefore, if you want to know how high your tire is, you should divide the tire's width by the aspect ratio (expressed in decimal). The quotient would be the tire's height, expressed in millimeters. Ply Material: After the aspect ratio, you would find a letter which can be R or B. This merely indicates the type of material used in the tire's ply or plies. When it's R, this simply means that the tire is a Radial tire. When it says B, this means that the tire is of the Bias-ply type. You would learn more about the difference between the two in the following section. By the way, you'll find the exact material composition of the tire on the same tire sidewall, near the inner edge (rim edge) of the tire (in line with the DOT rating and PSI rating). Diameter: A two-digit number should follow the letter R or B. This is the measurement of the wheel's diameter, expressed in inches, for which the tire has been constructed. To find out the diameter of the rim or wheel on which the tire should be used. Thus, a value of 15 merely indicates that the tire is made for use with 15-inch rims. Load Capacity: This is the number that follows the space after the diameter measurement. This number indicates the tire's maximum load capacity. This is expressed in pounds. Thus, a 90 load capacity means that the tire can take a maximum load of 90 pounds. Speed Indicator: The tire also has a maximum speed capacity and it is indicated by the letter following load capacity measure. However, you should only look for the speed rating if it is a P tire (a tire designed for passenger vehicles) since LT tires have no speed indicators. The letter is some sort of code that has a maximum speed rating equivalent. The lowest rating is Q (a tire with this letter has a maximum speed of 99 miles per hour) and the highest rating is Z (a tire with this letter has a maximum speed capacity of over 149 miles per hour. Other speed codes are the letters between Q and Z except X; there's also an H rating. Letter S has a rating of 112 miles per hour and the next two letters – T and U – indicate a maximum speed of 112 plus 6 and plus 12 mph, respectively. Following U is H with a speed rating of 130 miles per hour. V has a rating of 149 mph while W has 19 mph greater speed capacity (or 168 miles per hour). Then, there's Y which indicates a maximum speed of 186 miles per hour. Uniform Tire Quality Grading: On the other end of the tire's sidewall (across the tire’s opening), you should find the tire's UTQG which should indicate the tire's performance. This rating, however, is not found on tires made for use on snow. The following are the three variables measured for quality grading: Tread Wear: This is indicated by the term “tread wear” and a corresponding numerical value. The greater the numerical value is, the more enduring the tire is. A value of 100 is average so anything less than this number means that the tire tread will wear out fast. Likewise, a value greater than the average means that the tire tread can be expected to last long. Of course, tread wear measurement was done under controlled conditions and on a standard track. The actual length of time that your tire would endure would depend mainly on actual road conditions and your driving skills. Moreover, tread wear ratings do not mean much when you are making a comparison between two different brands of tires; they are significant only when two tires were made by the same manufacturer. By the way, tires come with a tread wear indicator. These are rubber markings on the tread and are used to determine whether a tire should be replaced with a new one. Traction: There are only three codes for traction and they are A, B and C with A as the rating for tires with the best possible traction whereas C is the rating for tires with acceptable traction. B is a rating reserved for traction between Best and Acceptable levels. The tire's tread is measured under controlled testing conditions and they just indicate the tire's ability to ‘get a grip’ and suddenly stop on wet and slippery roads when driving straight. Temperature: This factor is graded using the same codes as that of traction: A, B and C. These codes, furthermore, mean the same thing (best for A, etc.). Tires are graded for heat resistance through laboratory testing. Mark of DOT Compliance: At the inner edge of the tire's sidewall, you should find a code that indicates the tire complies with the Department of Transportation’s requirements. This line of characters should also have the unique identification of the tire (the tire's serial number). Tire Pressure: This is a number found along the inner edge of the sidewall and is expressed in PSI. This is the maximum pressure allowable for a particular tire and you should not exceed this benchmark. Moreover, tire pressure should also be checked periodically, especially if the temperatures are changing.
Basic Tread Configurations or Design There are two standard patterns for tires designed for off-road driving. They are all-terrain tire patterns and mud-terrain tire patterns. These two types of tire patterns or treads mainly vary in the type of terrain for which they are suited. The mud-terrain pattern of tire treads is best suited for The tire's traction and grip is mainly due to the tire's lugs. The lugs are big, raised portions on the tread. They bite on to mud and also grip the edges of obstacles that the off-road vehicle is required to climb over or cross. Between the tire lugs are the voids, which are deep indentations on the tire tread. The voids give the mud-terrain tires their self-cleaning ability. After the lugs have been able to hook onto the terrain, the void will throw or scoop out the material (mud, for instance) upon the tire's revolution. This way, the lug would remain clean or free from dirt and would have the same effective grip all throughout the trip. The mud-terrain type of tread is not ideal for driving on the highway and especially not on wet and slippery roads. This type of tread design performs poorly on pavement since only the widely-spaced lugs are in contact with the pavement. They are also very noisy, which adds to its undesirability for street/city driving. The all-terrain pattern, on the other hand, are found on treads that have enough bite or grip and minimal self-cleaning ability but work adequately for off-road and on-road driving. On this type of tires, the lugs are spaced more closely so the tire performs better on highways than the previous type (they have better traction on smooth pavements and are less noisy, too). They also perform adequately well on less demanding off-road terrains (sand, snow, etc.). However, this type of tread design is not as efficient when it comes to self-cleaning. Due to the closer-spaces between lugs, tires with this type of treads usually acquire a lot of dirt which could reduce the grip of the lugs. Basic Tire Construction It has been mentioned above that one of the tire characteristics found on the sidewall of the tires is the material construction of the tire's ply. It has also been mentioned that this characteristic is expressed as either R (Radial type) or B (Bias-Type). In this section, these two types of tire construction would be discussed and differentiated in greater detail. If you will recall the discussion on the various parts of a tire, a tire has one or more belts underneath to support the tread and maintain the tread’s contact with the road, among other purposes. These belts can be made of fabric or metal (e.g. steel). Radial tires are tires whose belts are mainly composed of steel. Definitely, these tires' steel belts are coated with rubber to improve their resistance to heat and extreme temperatures. After the steel belts have been coated with rubber, they are arranged across from one bead end to another bead end. These steel belts, when they have been properly placed on the casing, would be at right angles to the tire's centerline. As a result of this specific arrangement, there’s less squirm and therefore aids to protect the tread from undue wear as well as helps to increase a car's fuel efficiency. Radial tires also have more flexibility than bias-type tires. The steel belts actually serve to separate the tread from the tire’s sidewall. This means that when rolling, the tires' sidewall can flex more with the load and the car's weight without varying the tire’s tread. Due to the increased flexibility of radial tires, the tire is more resistant to puncturing. Radial tires’ performance can also be further improved when larger belts are used. These will improve the tire's resistance to both heat and puncturing. Finally, the arrangement of the steel belts provides even pressure all over the tread so that the tread lies evenly on the ground. This reduces skids and increases traction. On the other hand, Bias tires, are tires with belts made of fabric (typically nylon). The fabric is also rubber-coated for improved heat resistance. Aside from the main ply material, though, bias tires also differ from radial tires in the way the belts are arranged. Specifically, the plies on bias tires run diagonally from one bead to the other; the angle of bias is usually 30 degrees. Furthermore, the layers or plies in a bias tire are arranged in alternating directions. Bias tires are not as widely used as radial tires, however. The main reason for this is the tire's relative inflexibility as compared to radial tires. Instead of keeping the tread separate from the sidewall, bias belts actually integrate the tread and sidewalls of the tire. Therefore a distortion on the sidewalls results in distortion on the tread. The tread, therefore, cannot maintain an even footprint on the terrain so traction is decreased and the tread also becomes easily worn out. Moreover, bias tires are not as efficient at heat distribution. Since bias tires have to have more layers for more tire strength, they are also more heat retentive. This further reduces the tires' effective life.
Some Standard Terminologies Associated with Wheels and Tires The following are some of the terms that are commonly used with tires and off-roading activities. Read on and wise up so you're not left wondering when someone says “plus-sizing, hydroplaning, wheel balancing etc. Plus sizing is a term hat simply refers to increasing the ratio of your tire's height to your tire's width. This process id accomplished by adding more plies or layers to the tire. Then, you can also change the wheel's diameter. When you do plus-sizing, your tires will look much more impressive (they’d look taller, for one), they'd be stronger and better road performers. Hydroplaning, on the other hand, refers to the action of water (especially on wet pavement) on the tires. This happens when the tires have poor treading or when tires have become so worn out. Wheel balancing is done by adding metal clamps on the rim to equalize the weight of the rim and tire and thereby increase a tire’s stability. Wheel alignment, on the other hand, refers to the configuration of the four tires on an automobile. There are two basic standards for wheel alignment: two-wheel (each of the front wheel is set at a standard distance and angle to one another) and four-wheel (each of the wheels conform to the standard distance and angle relative to the centerline of the automobile).
|
