Reading Your Sidewall
There is a lot to learn from the sidewall of your tire. Although at first glance you may think you stumbled across tire hieroglyphics, you've actually found molded into the tires side its own user manual.
Example Tire Size: P205/55R16 91W
P identifies your tire as a Passenger Tire. The P stands for PMetric. If your tire size starts with LT rather than a P than it identifies the tire as a light truck tire.
205 identifies the tire section width, which is the measurement of the tire from sidewall to sidewall in millimeters. This measurement varies depending on the rim to which it is fitted.
(There are 25.4 millimeters per 1 inch.)
55 is the two-figure aspect ratio. This percentage compares the tire's section height with the tire's section width. For example, this aspect ratio of 55 means that the tire's section height is 55% of the tire's section width.
R indicates the construction used within the tire's casing. R stands for radial construction. B means belted bias and D stands for diagonal bias construction.
16 The last dimension listed in the size is the diameter of the wheel rim, which is most often measured in inches.
Load Index and Speed Rating
91 The load index and speed rating, or service description, are the numbers that follow the tire size.
The load index tells you how much weight the tire can support when properly inflated. Load indices range from 75 - 105 for passenger tires, with each numeric value corresponding to a certain carrying capacity. The carrying capacity for each value can be found on a load index chart. On each U.S. passenger car tire, the load limit is listed in pounds. European tires have the load limit listed in kilograms and sometimes pounds.
W Speed ratings are represented by letters ranging from A to Z. Each letter coincides to the maximum speed a tire can sustain under its recommended load capacity. For instance, S is equivalent to a maximum speed of 112 mph. Even though a tire can perform at this speed, continental tire does not advocate exceeding legal speed limits.
DOT Serial Number
The "DOT" symbol certifies the tire manufacturer's compliance with the U.S. Department of Transportation tire safety standards. Tires made in the United States have the DOT serial number located on the inside sidewall near the rim.
Below is a description of the serial number. Starting with the year 2000, four numbers are used for the Date of Manufacture, the first two numbers identify the week and the last two numbers identify the year of manufacture.
Prior to year 2000, three numbers are used for the Date of manufacture, first two numbers identify the week and the last number identifies the year of manufacture. To identify tires manufactured in the 90s, a decade symbol (a triangle on its side) is located at the end of the DOT serial number.
How to Build a Radial Tire
Tires are not just round and black -- they are sophisticated products that can take years of research and development to produce. If you have ever wondered how tires are made, the following is a roadmap for the construction of a radial tire:
Start with Rubber and Additives
Tire construction starts when raw chemical additives such as sulfur, carbon black and solvents are combined with natural and synthetic rubber. The process takes place in a large machine called a banbury.
In addition to mixing and grinding, the banbury heats the rubber to make it workable in preparation for further applications. The raw product emerges in the form of long, flat bands of rubber, which are then worked in rolling mills.
Six Main Components
The Green Tire
The six components (tread, ply, belts, sidewalls, liner and beads) come together on the tire-building machine. These six components are assembled into what is known as an uncured, or green, tire in two stages.
The carcass of the tire, including beads, plies, sidewalls and liner, is constructed on one side of the machine. The tread and the underlying belts are assembled next to the carcass on the other side of the machine. The two sub-assemblies are then joined together and the result is a green tire.
The next phase is vulcanization, the molecular transformation of the soft, gummy green tire into the tough, and long-wearing, modern passenger tire. The green tire is placed in a curing mold and is subjected to intense pressure and high heat internally and externally for a specified period of time. Simultaneously, the tread pattern is imprinted onto the rubber. When it comes from the mold, the tire is ready for final finish and inspection.
Final Finish and Inspection
For showroom quality, any excess rubber is trimmed off the cured tire. Every tire is thoroughly inspected. The tire then undergoes various uniformity checks to assess ride and comfort quality. Once the tires have passed all the checks and inspections, they are sent to the distribution warehouse for shipment.
History of the Passenger Tire
Dateline 3500 B.C.--Today, man invented the greatest invention ever seen, THE WHEEL!
Thousands of years later, the wheel has come a long way. For one thing, it is no longer made of wood and it is guaranteed that the ride is much smoother. What hasn't changed is the fact that it is still one of man's greatest inventions. Could you imagine where we would be today without it?
The early wheel was very simple: a solid curved piece of wood. Later, leather was added to soften the ride. As time progressed it became solid rubber, which led to today's tire--the pneumatic, or air inflated, radial tire.
The first wheels made of metal or wood were very durable but did not provide a very comfortable ride. The nearest thing to the first tire was a metal hoop. There were many individuals that made contributions in creating the tire as we think of it today.
Vulcanization and Charles Goodyear
Rubber was not always as useful as it is today. Early rubber did not hold shape; it would be sticky in hot weather and become inflexible in the cold.
In 1839 Charles Goodyear was credited with the discovery of the vulcanization process. Vulcanization is the process of heating rubber with sulfur. This transforms sticky raw rubber to firm pliable material, which makes rubber a perfect material for tires.
The story of Charles Goodyear is a sad one. Although he dedicated his entire life to making rubber a better form, he would never profit from all his work. Charles Goodyear died bankrupt.
Forty years later, a rubber company would honor his hard work by using his name for their new tire company.
Solid Rubber Tires
Soon after the discovery of vulcanization, tires were made out of solid rubber. These tires were strong, absorbed shocks and resisted cuts and abrasions. Although they were a vast improvement, these tires were very heavy and did not provide a smooth ride.
Today there are still types of tires made of solid rubber.
The pneumatic tire uses rubber and enclosed air to reduce vibration and improve traction. Robert W. Thomson, a Scottish engineer, first patented the air-filled tire. Unfortunately the idea was too early for its time and was not a commercial success.
In 1888 John Boyd Dunlop of Belfast, Ireland, became the second inventor of the pneumatic tire. Dunlop claimed to have no knowledge of Thomson's earlier invention.
The second time around, the pneumatic tire caught the public's attention. The timing was perfect because bicycles were becoming extremely popular and the lighter tire provided a much better ride.
Bias Ply Tires
For the next fifty years, vehicle tires were made up of an inner tube that contained compressed air and an outer casing. This casing protected the inner tube and provided the tire with traction.
Layers called plies reinforced the casing. The plies were made of rubberized fabric cords that were embedded in the rubber. These tires were known as bias ply tires. They were named bias ply because the cords in a single ply run diagonally from the beads on one inner rim to the beads on the other. However, the orientation of the cords is reversed from ply to ply so that the cords crisscross each other.
Today you can still find bias-ply tires as authentic equipment for antique and collector cars, as well as for certain type of off-the-road tractor tires.
The first introduced steel-belted radial tires appeared in Europe in 1948. Radial tires are so named because the ply cords radiate at a 90 degree angle from the wheel rim, and the casing is strengthened by a belt of steel fabric that runs around the circumference of the tire.
Radial tire ply cords are made of nylon, rayon or polyester. The advantages of radial tires include longer tread life, better steering and less rolling resistance, which increases gas mileage. On the other hand, radials have a harder riding quality and are about twice as expensive to make.
Driving Tips for Wet Roads
Driving in the rain can be dangerous; in fact thousands of car accidents each year are caused by wet driving conditions.
Routinely Check Your Tires
It is a good idea to always check your tires before you hit the road. To ensure your tires are working at their best, make sure you do the following routine maintenance:
Recover From a Skid
Skids can even happen to the most cautious drivers. If your car does skid, remember not to slam on the brakes, and do not pump the brakes if you have an anti-lock braking system (ABS). Instead apply pressure to the brakes in a firm manner and steer the car in the direction of the skid.
Keep a Safe Distance
It takes about three times longer to break on wet roads than on dry roads. Since more distance is required to brake, it is important not to tailgate. Keep more than two car lengths between you and the vehicle in front of you.
Recover from Hydroplaning
When it rains, water creates a barrier between the road and your tires. The liquid film that forms can cause you to lose traction and glide or hydroplane across the water's surface. If this happens, do not brake. It is better to take your foot off the gas, hold the steering wheel in place, and lightly apply the brakes. If you have a manual transmission, push in the clutch and let the car slow down on its own.
Your tires are the only part of your vehicle that actually touches the road when you drive. It only takes a couple of minutes of maintenance each month to keep your tires working at their best.
Check Your Air Pressure Once a Month
Incorrect air pressure is the leading cause of tire damage. To avoid tire damage you need to check your tire's air pressure once a month.
The correct tire pressure can be found in the following places:
Don't get stranded and avoid costly towing expenses. Check your air pressure on your spare regularly. Note: If you have different rims than came on your vehicle originally, make sure that the bolts on your spare tire are the correct fitting.
Failure to keep your tires properly inflated can increase wear and will have a negative effect on your vehicles handling.
When checking and adjusting tire pressure, the following should be kept in mind:
To prevent hydroplaning and skidding, your tires must have proper tread depth. The minimum tread depth is 1/16th of an inch.
Ask anyone: the easiest way to check your tread depth is the penny test. Take a penny and place it in the tread of your tire. If part of Lincoln's head is covered by the tread, your tires have enough tread. If you can see Lincoln's entire head, you should buy a new tire.
You should also check your tire tread for uneven wear. Irregular wear shortens the life of your tires. If you think you have uneven wear, you should take you vehicle to Tireman.
The best way to prevent uneven wear is to have your tires rotated every 5,000 - 7,000 miles or as specified in your vehicle's owner manual.
Potential Tire Troubles
You should replace your tires with the same type of tires that came on your vehicle original equipment. This includes tire size, type and speed rating.
Safe Winter Driving
Thanks to their special compound, winter tires offer the elasticity required to ensure maximum grip throughout the cold season, regardless of the road conditions. Summer tires can become hard when the temperature falls below 45 degrees, thereby losing the flexibility needed to build up sufficient grip for braking, starting off and cornering. Because of their greater suppleness in the cold, winter tires are able to interlock with asphalt, snow and ice, even at lower temperatures.
Here a few tips to keep you from slipping and sliding on the way to work in the morning: