1. Basic concept of a tyreWhat is a tyre?
A tyre is one of the most important vehicle parts, because it is the only part that directly contacts the ground and ensures vehicle maneuverability and ultimate safety.... It is important to know how tyres help the vehicle run smoothly, drive agilely and reach a point as fast as a person wishes.
Although a tyre looks like a single round and black object, it is utterly unique, because it consists of various kinds of components, each material of which plays an important role in order to do its job as a vehicle component. It is round and made of rubber, therefore it is like a balloon in terms of a vessel to contain air inside; but it’s not exactly the same because it can carry heavy loads. Tyres are reinforced by steel wires inside to maintain their shape and stability when installed on a wheel. Some tyres can run on super cars faster than 300km/h — It is really amazing! Rubber, which is a natural or synthetic, high performance polymer, plays an vital role to bring out its performance.
2. Four major functions
3. Tyre Construction
The special components are adopted for High Performance tyres in order to increase cornering performance and reduce noise
Bead Filler : Improve cornering performance at high speed operation by high bead rigidity
- Increase high speed performance to avoid belt lifting
- Reduce road noise to absorb belt vibration
4. Tyre Dimensions
- Section Width: Linear distance between the outside of the sidewalls of an inflated tyre excluding elevation due to labeling, decorations, or protective ribs.
- Overall Width: Linear distance between the outside of the sidewalls including elevation due to labeling, decorations, or protective ribs.
- Section Height: The figure which rim diameter is subtracted from overall diameter and divided by 2, i.e. the distance from bead to tread.
- Overall Diameter: Diameter of an inflated tyre at the outermost surface of the tread.
- Aspect Ratio: Percentage ratio of the section height to the section width of the tyre.
- Aspect Ratio = (Tyre Height / Tyre Width) * 100
- Rim Width: Distance between the flanges of the rim.
- Nominal Rim Diameter: Rim diameter code for reference purpose only, as incorporated in the tyre size designation. Actual diameter is specified otherwise in the table.
- Service Description: Tyre may also be identified by a Service Description consisting of a Load Index and a Speed Symbol.
- Load Index: Numerical code associated with the maximum load a tyre is permitted to carry at the speed indicated by its speed symbol under service conditions specified by the tyre manufacturer.
- Speed Symbol: Maximum speed at which tyre can carry a load corresponding to its Load Index under service description specified by the tyre manufacturer.
- Load Capacity: Maximum load a tyre is permitted to carry under specified operating conditions.
- Inflation Pressure: Pressure taken with the tyre at ambient temperature and does not include any pressure build- up due to tyre usage
5. Tread pattern feature
The tread pattern is necessary from a functional point of view. It also practically helps safe driving on wet, rough or snow covered roads and absorbs shocks from the roughness of the road. There are several factors necessary when designing a tread pattern according to its specific purpose.
6. Tread pattern feature
A recent trend has been the development of high performance tyres with circumferential grooves where the “land” area of the tyre never breaks contact with the road and the “sea” area channels water away from contact patch. Both these tyre patterns are claimed to be quieter than block patterns. The noise actually comes from the leading edge of the tyre blocks which contact the road surface and the trailing edge snap back when they break contact. So, the block pattern makes more noise and can cause more irregular wear than its counterpart. Another trend is for the asymmetric and directional patterns. Here are some advantages of the Asymmetric and Directional type tread patterns,
7. Speed Symbol and Load Index
* If tyres are suitable for speeds over 300km/h, the Service Description should be marked within parentheses. 195/50 ZR15 (82Y)
* ZR incorporated size such as 215/50 ZR 15 indicates the speed capability above 240km/h. In the case where the
If Service Description is not shown, consult the tyre manufacturer concerned.
8. Sidewall Markings
The various information for the benefit of the users is engraved on the sidewall of the tyre including tyre size designation. The following marking is a sample representing tyres for the North American market.
Tyre ply composition and materials used
In addition to the markings above, the following information may also be engraved.
- Tubeless for tubeless tyres, •M+S for all season or winter tyres, •Mountain with a snowflake pictograph and 50% wear marking and arrow to indicate its location for Studless tyres, •Light Truck for LT tyres, •Country of Origin,
- Direction of rotation arrow for a Directional Pattern, •Inside or Outside for an Asymmetric Pattern, •Triangle to indicate the location of T.W.I. And so on.
9. Size designation and Tread Pattern Name
Actual markings on the size designation system are as follows
It is very important to know how to take care of tyres to prevent various kinds tyre failure from occurring during daily use as well as vehicle maintenance.
Maintenance of the vehicle and its components
When people think of car maintenance, it is often pointed out that wheel alignment and wheel balancing are the main factors to keep the tyres in good condition and they are very important, because they have significant influence to tyre wear. Wheel alignment widely known as camber, caster and toe in or toe out, is related to the vehicle condition and if it is not properly maintained, tyres are likely to face irregular wear. If a tyre is vertical to the ground and the tyre in the left and right are parallel, abnormal force under contact patch is not generated and the tyres evenly wear down. Wheel balancing on the other hand is to give passengers a good ride. Its technical definition is the equal distribution of mass around an axle rotation. If tyre and wheel assemblies are perfectly balanced, there is no vehicle vibration. Excessive imbalance causes vehicle vibration and even possible irregular wear. Here are detailed explanation.
Camber is the inclination of the wheel from the top of the wheel, measured in degrees. Camber is positive when the top leans away from the vehicle, and negative when leans inward. If the camber is out of tolerance, it will cause tyre wear on one side of the tread.
Excessive negative camber causes onside wear on the tread and vise versa. Approximate camber tolerance varies -40’ to +1°30’.
- Caster is the forward or backward inclination of the kingpin in the pivot which is installed at both end of steering linkage. Caster is positive, if the top of the king pin tilts backward toward the rear of the vehicle. If it is tilting forward toward the front, it is negative. Although caster has little affect on tyre wear, but is important in the steering and drivability of the vehicle. Too little caster causes unstable steering or wandering and weaving problem. Too much caster causes hard steering or shimmy. Approximate camber tolerance varies 2° to 8° positive.
- Toe setting greatly affects tyre wear. The toe is measured by the difference in the distance between the front of the tyres and the back the tyres. If the toe “B-A” shown in the chart is positive, it is in the condition of toe-in and if the toe is negative, it is in the toe-out condition. The toe is usually set in the positive side, which means that toe setting is usually toe-in condition. It is measured in mm and varies between approximately 0 to 5mm. At high toe-in or toe- out condition, the tread of outside or inside area can be completely worn down in a typical feather edge wear pattern.
- Camber is the inclination of the wheel from the top of the wheel, measured in degrees. Camber is positive when the top leans away from the vehicle, and negative when leans inward. If the camber is out of tolerance, it will cause tyre wear on one side of the tread.
11. Irregular Tyre Wear
The mechanism of tyre wear is explained under dynamic characteristics. Here are some typical examples of tyre wear problems:
Main factors of Irregular wear are;
- Less maintenance : Inflation Pressure, Rotation
- Vehicle maintenance : Vehicle alignment, Suspension backlash
- Service condition : Road Condition, Speed, Driving habit