THE FOLLOWING GLOSSARY WAS BASED ON SCIENTIFIC RESOURCES, OTHER REFRENCES, AND THE KNOWLEDGE AND EXPERIENCE OF RIYADH RETREADING FACTORY:
A variety of factors can influence the ageing process of a tire: Humidity, UV radiation, heat, cold etc.
In order to avoid a reduction in performance, other substances are mixed with the rubber compound to significantly slow down the ageing process. However, you should replace your old tires once you notice ageing appearance on the sidewall. It is a natural process for rubber to age, during which its elasticity and grip can change.
The words ”Air Loss” immediately make you think of a sudden, obvious or gradual loss of air, such as that caused by a puncture.
However, air pressure goes down continually even without any outside influence, as the inner liner of a tire can never be sealed 100%. The following rule of thumb applies: Check your tire pressure every other time you refuel. This is also possible when the tires are filled with a special gas (e.g. nitrogen). However, the special effect of the gas gradually disappears as you top up with normal air.
The correct air pressure is critically important for the mileage and life span of the tires, as well as driving safety. If tire pressure in the tires is too low, it can lead to poor weight distribution and overheating, or even to the risk that the tire may blow out. In addition, rolling resistance is increased, leading to an increase in fuel consumption. Regular studies have shown that approximately only one in four cars on the road has the correct air pressure. You will find the air pressure recommended by the manufacturer in the vehicle’s instruction manual, and also on the fuel fill flap or on the side of the door. Air pressure should be checked at every other stop at a service station, or at least every four weeks. Tires must be checked when cold, as warm tires have a higher pressure. Therefore, never release air from a warm tire! Under certain circumstances, wide tires require different air pressure to standard tires, in this case please make sure to consider the information in the user manual or from the tire manufacturer.
Aluminium rims are rims that are made from aluminium alloy - not from pure aluminium. Pure aluminium is too soft to guarantee the strength required and meet the challenges of driving on the road.
In contrast to steel rims, alloy wheels are available in almost any size or width. Therefore, you can only get 22, 23 or 24-inch rims as alloy wheels.
Alloy wheels add value to any car due to their design. Many are more sensitive to road than steel wheels due to their finish.
Aquaplaning occurs when the grooves in the tire can no longer lead the water under the tire contact area to the outside. The tires then float on the film of water, so braking power and steering power are no longer applied to the driving surface.
Aquaplaning can be recognised by light steering, spinning drive wheels with high engine revolutions, and the sound of water under the car. Anyone who finds themselves unexpectedly aquaplaning should not try to brake under any circumstances but should instead depress the clutch and keep the steering wheel in the direction of travel. The wheels must not lock or be pointing in the wrong direction when they meet the road again. Drivers of automatics should concentrate on their steering and not attempt to change the driving mode. The following applies in the rain: Drive carefully!
Asymmetrical tires have an inner and an outer side. This is indicated by the words “Inside”/”SFI” and “Outside”/”SFO” on the sidewalls.
After fitting, the wheels can be used in any position on the vehicle, in contrast to directional tires. However, the side initially chosen to be the axle side should be kept with subsequent changes of wheel, as tires always wear slightly unevenly due to direction and vehicle set up, and so adapt perfectly to the road.
The profile of asymmetric tires is designed differently on the inner and outer shoulders: Whereas the profile on the inner shoulder provides traction and straight running, the profile on the outer shoulder is designed for optimal steering and stability when cornering.
When changing a wheel, you should bear in mind the axle position, as this indicates what position a wheel was fitted in, or should be fitted in. Regardless of the type of drive, forces affect each wheel differently. As a rule of thumb you can say that tires with deeper tread belong on the rear axle.
So the position of the wheels may be changed to use them evenly, e.g from FL to RL or FR to RR. The axle side initially chosen should stay the same, as the tires adapt to the axle geometry. This guarantees the optimum contact area. Directional tires must always be kept on the original axle side.
With balloon tires, the ratio of height to width is 0.98 :1. They offer good suspension, but poor cornering properties.
Balloon tires are no longer common on modern cars. They are only used with vintage cars and as specialist tires.
The bead or inner ring on the side of the tire contains strong wire cores and has the task of ensuring the tire sits securely on the rim.
In a tire where the pressure it too low, the increase in flexing can give rise to temperatures up to 120° C. Particularly in the shoulder area, this can lead to overheating of materials, causing parts of the running surface to displace.
11.Belted tires, steel belt tires
In belted tires, the fabric is reinforced with metal wires and textile bands that go round the tire like a belt. In belted tires, the fabric is perpendicular to the direction of travel. The belt, which goes over the fabric in line with the direction of travel gives the belted tire similar side wall strength to a diagonal tire, but they are generally more flexible and thus less liable to slip on wet roads.
The big advantage of belted tires in their more stable running surface, giving them better road-holding. A car with belted tires will corner better, has better braking distances, drives more safely on wet roads - and the tires also last longer, but all at the cost of comfort.
Caution: Steel belts can rust. This means any tire with deep damage to the surface such that moisture (even air humidity) could get to the steel wire must be taken out of use immediately.
The distance between pressing the brake and the vehicle coming to a complete stop is known as the braking distance. Several factors influence the braking distance: Driver reaction time and length of braking, brake system reaction time, road conditions (type, wet), weight of the vehicle, condition of the tires (manufacture, depth of profile, pressure) and speed.
The inclination (angling) of wheels towards each other, when viewed in the direction of travel, is known as camber. It is shown as the angle of the plane of the wheel to the vertical plane with respect to the ground. If the inclination towards the top points outwards, the camber is positive. This suppresses the tendency to flutter. If the wheels point inwards at the top, the camber is negative, leading to increased lateral control.
This essential element of the load bearing sub-structure of the tire gives the tire its strength and ensures it stays together. Nowadays, carcasses consist of a plastic and cotton fibre fabric or steel cord, embedded in the rubber.
Centrifugal force is the force which pushes the vehicle outwards when cornering. The greater the weight of the car and the speed, the greater the centrifugal force.
The chassis includes the following elements:
- a. Wheel suspension (axles).
- b. Suspension.
- c. Shock absorbers
- d. Steering.
- e. Brakes.
- f. Wheels (rims and tires)
The chassis creates a connection between the bodywork and the road, and its character is responsible for both the comfort of the vehicle and its road holding performance. Car manufacturers are constantly trying to find the balance between safe road-holding and corresponding comfort of the vehicle.
The problem is that one does not actually exclude the other, but they do significantly influence each other. On the one hand, a stiff chassis gives a high level of driving safety, (good traction, directional stability, road holding, speed of reaction), albeit always at the expense of comfort.
17.Commercial vehicle tires
Commercial vehicle tires are tires which have been specially developed for vans, lorries and buses. The main priorities are economy and a long-life span.
The area of the tire that actually touches the surface is known as the contact area. With a car, this is roughly the size of a postcard.
In diagonal ply tires, the cords run at an angle to the direction of travel. This means the side wall of the tire is more stable than in radial tires. However, this leads to a smaller contact area, as well as a reduction in stability when cornering. Whereas diagonal tires are still used today with motorbikes, agricultural and industrial equipment, they have been almost completely replaced by radial tires for cars and commercial vehicles.
Depending on the design they can be used with an inner tube (TT) or without an inner tube (TL).
20.Dimension indications on tires
The dimensions shown on the sidewall of a tire indicate type of construction, size, maximum speed and load capacity. In general, a vehicle must only be fitted with tires as indicated in the vehicle manual.
Directional tires should only be fitted to the car in the direction of travel intended. This direction of travel is identified by an arrow and the word “rotation” on the side wall.
After fitting on the rims this gives two “left” and two “right tires. Directional tires often have a tread which looks like a “V”. This type of tread pattern has the following advantages:
- a. lower level of road noise
- b. better traction in the wet
- c greater aquaplaning safety
The abbreviation DOT stands for the US Department of Transportation and in many countries, it is valid and the legally required approval in the tire industry. DOT means that the tire meets or even exceeds the safety requirements of the Department of transportation.
- The tire meets or exceeds the safety requirements of the Department of Transportation.
- Place of manufacture and plant code (assigned by the DOT)
- Size code.
- Optional manufacturer’s code to identify the brand and tire properties
- Date of manufacture.
There are a number of indicators relating to tire construction that are located on the sidewall in the form of numeric codes. Generally, however, this refers to the tire’s date of manufacture. As of 2000, the week and month of manufacture of a tire have been show as four digits. So the last four digits show the week and year in which the tire was made, for example “1602” means week 16 of the year 2002.
On light trucks or van tires, also known as C tires, there are often two figures for the load index shown on the side of the tire, for example 205/55 R16 C 98/96H.
These two numbers indicate the load capacity for single tires (98) and twin tires (96). In this case the maximum load capacity of a tire would be 750 kg for a single tire, or 710 kg for twin tires (with tire pressure of 2.5 bar). The lower load index in the two numbers always stands for the maximum load capacity for twin tires.
In fine balancing, the wheels are balanced directly on the vehicle. Any remaining imbalances arising from changes to wheel centring, hubs and brake discs are dealt with.
Flexing is the periodic compression of the tire. It distorts the sidewall and the shoulder, releasing heat and creating additional rolling resistance. If tire pressure is too low, the tire flexes more and the tire overheats.
Essentially, car buyers judge the efficiency of a vehicle according to the fuel consumption data, this figure is determined by a variety of factors. These include the weight of the vehicle, efficiency of the engine, the front surface of the vehicle, driving speed, engine speed and accelerator settings. The technical competence and the development efforts of a manufacturer are reflected in the level of fuel consumption of their vehicles.
The expression “Grip” describes the friction between the contact surface of the tire and the surface under the tire.
So the grip is the ability of the tread rubber compound to stick to the road as firmly as possible, whereby experts differentiate between the macro and micro roughness of the road surface.
28.High speed capability
In order to determine high-speed capability, a tire must maintain its maximum speed (speed index) for an hour on a roller dynamometer. In the next test, the speed is increased by 10 km/h every ten minutes, to test when the tire fails.
29.High speed strength
At high speeds, there is an enormous centrifugal force affecting the tire. In order to withstand this, the carcass is firmly bound together by nylon fabric.
Even very minor irregularities in the thickness of material or other issues such as uneven wear can cause tiny imbalances in the tire. When the wheels revolve, these create an imbalance, and the tire no longer spins evenly. In most cases, this can be equalised by a counter weight on the rim.
The inner liner is the name given to the rubber layer which ensure air tightness on the inside of the tire. In tubeless tires, it fulfils the role of an inner tube.
kPa (Kilopascal) is a unit of measure for air pressure. 1 kPa = 0,01 bar 1 bar = 100 kPa
A rim can be affected by lateral run out due to external factors, for example, driving quickly over a kerb stone, or an accident. The rim is then warped in the direction of travel.
34.LI: Load Index
Load Index is generally a two digit number on the end of the size classification, e.g. 175/70 R 13 82 T. The number 82 indicates the load index of the tire. For example, Load Index 82 means 475 kg load per tire.
35.Low profile tires
The profile of a tire describes the ratio of the side height to the width of the contact area. The balloon tires commonly used in the 20’s with a height to width ratio of almost 1:1 gave way to low profile tires (up to 0.15 to 1) a long time ago.
The term low profile tire applies when the side height is less than 80% of the tire width. This definition was created in the 70’s, and much has changed in the car industry since then. So nowadays, the most common tire on mid-range cars is size 205/55R16, which can no longer really be regarded as “low- profile”
There is no official definition for low profile tires. It is fair to say that tires in the range 50 to 55 could be classed as low profile, depending on the tire width. These tires frequently have a flange shield.
36.Low resistance tires
Tires with low rolling resistance thanks to new compound technologies are called low resistance tires. The lower the rolling resistance, the lower the fuel consumption.
37.LT: Light Truck
Reinforced tires for commercial vehicles such as vans.
38.M+S, M&S, M.S.: Mud and snow
The letters M+S identify winter tires and winter-ready all weather tires. On some products there is also a snowflake symbol. M+S tires with a snowflake meet a high quality standard. Their particular qualities come into their own at temperatures of 7° C. Summer tires lose grip and hold at low temperatures because of their rubber compound, leading to increased braking distances, on dry or wet road surfaces. Braking distances on snow are up to 20% shorter than with summer tires. With wide base tires this effect comes into play at 10° C. Moreover ABS, ESP or TCS do not help here, as they are purely electronic aids. They cannot replace winter tires. However, it is important that winter tires have adequate tread depth. If this is under 4 mm, then the risk of aquaplaning increases significantly, traction and braking performance fall noticeably, and driving properties only reach the same level as summer tires.
The abbreviation M/C indicates that the tire in question is for a motorbike. This designation is compulsory in America, and applies to scooters.
The main grooves are usually located in the middle of a tire, and the wear indicator is also located here.
Mileage means the active life span of a tire before it has to be replaced. This depends on the construction and quality of the tire, as well as the type of vehicle, type of driving, UV radiation, storage and many other factors. The tires on the drive axle lock up more quickly, as they are driven more strongly by the increased slip.
42.Minimum tread depth
For cars, vans, lorries and motorbikes, a minimum tread depth of 1.6 mm applies right across Europe. This minimum depth must be present over the whole tire contact area. When a tire approaches this legally required minimum tread depth, braking distance in the wet increases, and there is a higher risk of aquaplaning. The braking distance when aquaplaning with a tire with the minimum tread depth of 1.6 mm is double that of a brand-new tire. For safety reasons, summer tires should be replaced when tread depth is 2 mm, wide base tires when it is 3 mm and winter tires when it is 4 mm.
Mixed tires is an informal term with several meanings.
Legally, mixed tires means the simultaneous use of radial and diagonal tires on the same vehicle. This use of mixed tires is not permitted.
In addition, mixed tires can refer to the use of different sizes of tires at the same time on a vehicle. This is fundamentally not acceptable with regard to cars. One exception to this is where different sizes of tires are fitted per axle on some sports cars. It is only acceptable to use a spare wheel of a different size for a short period. In this case, please note the instructions on the spare wheel.
A third interpretation of “mixed tires” is the simultaneous use of tires of the same size, but with different tire profiles. This is permitted.
In general, tires with the same profile should be fitted to the same axle. The tread depth on opposing tires should not be too different.
This applies particularly to four-wheel drive vehicles. In this case, all the tires should have the same profile and similar tread depth, to avoid any damage to the centre differential.
44.Multi part rims
The three-part rim consists of a wheel star, an outer flange and an inner flange. The three parts are screwed, riveted or welded together. The two-part rim consists of a) Wheel star, base or b) wheel star with outer flange and base with inner flange (moulded in one piece). Both pieces are screwed to the rim base.
45.OE: Original Equipment
Original equipment: refers to tires which have been developed according to the requirements of a vehicle manufacturer, for a certain model. The vehicle in question is delivered with these tires.
We recommend fitting four of the same tires, so that the tires can deliver optimal performance.
46.Off road tires
Off-road tires are special tires for use off-asphalt-road.
Too much air pressure is just as damaging as too little. Shock absorbers and comfort suffer, grip declines and the tires also generally wear faster and unevenly (centre wear).
Over-steer is the term used to describe when the rear wheels lose grip before the front wheels. The vehicle swerves at the back and skids out of the corner.
Driver assist systems such as ESP try to minimise this behaviour.
49.OWL: Outline White Lettering
Special design of sidewall lettering, with white contoured letters.
The letter “P” on tires from the USA stands for private car. This differentiates them explicitly from LT tires for commercial vehicles. This is particularly useful where sizes overlap.
51.PR-code, Ply-Rating, Ply Rating
PR stands for "Ply-Rating".
This originally referred to the number of layers of cotton cord in the carcass. The more layers of cord, the greater the strength. As stronger materials were introduced for the layers, the term no longer related to the actual number of cord layers. Therefore, a tire with a PR of 8 might only have 4 layers of nylon cord, corresponding to the strength of eight cotton layers.
Nowadays, the strength of road tires is indicated by the load and speed indices, instead of ply rating.
The profile ratio of a tire is shown as a percentage. It shows the height of the tire as a proportion of the width and is shown in the dimensions of the tire. For example: A tire size 205/55 R16 is 205 mm wide and the side height is 55% of the width.
Race tires are tires which are only suitable for the race track. They are not approved for use on public roads.
With radial tires the cord piles run radially inside the carcass, at a right angle to the running surface. The radial position of the cord piles give a greater contact area compared to diagonal tires. This has major advantages for almost all driving properties:
- grip in the wet
- driving precision
- grip when cornering
Radial tires were introduced by Michelin in 1948 under the name “X-Technology” and are now the standard for cars and lorries.
The height of the wheel measured from the centre to the ground is known as the static radius. It is always measured with the same load on the tires and pressure conditions.
Regrooving refers to a one-off deepening of the tread grooves, in order to increase profile depth. This is considered as part of the manufacturing process of the tire. Regrooving is only allowed on commercial vehicle tires which have "REGROOVABLE" on the side. Regrooved tires may only be fitted to the steering axle. This also applies to the spare wheel. Regrooving should only be carried out by an expert in accordance with the manufacturers guidelines.
57.Repairing damage to a tire
Nowadays, tires are very durable. However, they can be damaged by external factors. The most common causes are:
- a. tire pressure is too low
- b. damage caused by going over a kerb
- c. damage by a foreign body
- d. damage from oil, fuel, and tar
Many forms of damage are visible to the naked eye, even to a non-expert. So you should make the effort to inspect your tires every so often.
Cuts, splits, lumps or broken tread are all cause for concern, as well as any penetrating foreign bodies such as nails.
Uneven wear of the running surface is frequently caused by wear and tear of parts in the chassis or steering. But the brakes or an imbalance in the wheels can cause tire damage of this kind.
If you find any kind of damage or irregularity in your tires, you should try to repair by tire specialist as soon as possible. Some kinds of tire damage can be repaired, saving money and resources. it is not possible to make a global statement about what damage can be repaired without endangering driving safety. Often it is inevitable that the damaged tire must be replaced. Ultimately, only an expert can judge this.
58.Replacement Tire Monitor (RTM)
Unique marking that visually shows the need to replace the tire by changing from “Replacement Tire Monitor” to “Replace Tire” based on tread wear.
Fundamentally, tires must be replaced when the tread depth reaches the 1.6mm minimum. In general, tires (for example spare tires) should not be more than five years old. Any replacements due to wear and tear should be done axle by axle.
Please bear in mind equal profile depth, type of profile and manufacturer. Never buy or fit used tires where you don’t know where they came from.
When the running surface of a tire reaches the limit of wear, but the other components of the tire are unaffected, the tire can be retreaded. A legal condition of this is that the side wall must be marked “retreadable”.
When retreading, the carcass, steel belt and side wall are initially checked for faults. Then the worn running surface is removed and replaced with a new one. This can be done by cold or hot vulcanisation. The side wall is then marked “retread”.
High quality retread are a low-cost alternative particularly in the commercial vehicle area.
The rim base is the area between the rim flanges. This is where the width of the rim is measured. As with rim diameter, width is measured in inches.
The common international size specifications for rims (e.g. 7Jx15) indicate the width from flange to flange (in this case 7 inches) as well as the height (in this case 15 inches). The “J” stands for the shape of the hump.
Rim contour or rim profile means the rim’s construction type. For example, “J” describes an asymmetric base.
The rim diameter is the area the tire sits around. It binds (seals) the inner radius of the tire and thus connects the rim to the tire.
The rim flange is the outward bending edge of the rim. Weights may be attached to this to help balance the wheels.
The rim protection on a tire consists of a rubber strip that runs along the ridge on the outer sidewall. It protrudes somewhat over the edge of the rim and thus protects the rim e.g. when the tire meets the kerb. Depending on the design and the tire-rim combination being used, the rubber strip can also protect the sensitive sidewall from being damaged. The protective function is effective at low speeds, for example when parking. If the rubber strip is badly damaged or if parts of it are torn or broken off, the tire should be checked for additional damage.
The area on the rim between the rim flange and hump which the tire sits on is known as the rim shoulder.
The interior size of the rim is measured between the rim flanges.
The rim holds the tire. Generally, steel is used in the manufacturing process. In addition, there are light alloy wheels made from aluminium or magnesium alloys. These have better run-out accuracy, reduce the weight of the unsprang mass and improve the appearance of the vehicle. For example, for rim size: 6Jx15 H2 = 6 inch rim width, flange design "J", 15 inch diameter, hump design "H2"
Rolling circumference indicates the distanced covered by any point on the tread during one revolution of a wheel. Therefore, the rolling circumference depends on the diameter of the tire. It has an influence on the transmission and the tachometer drive. Based on standard production tires, a tire with a smaller rolling circumference will tend towards shorter transmission. This has a positive influence on acceleration, but the rev counter could well be in the red at top speed. In addition, the smaller tires lead to increased speedometer signal swift. Tolerances of plus 1.5% and minus 2.5% are acceptable. Where there are larger deviations, the speedometer must be corrected, at the very least.
Rolling resistance indicates the force needed to move the tire. Winter tires have a higher rolling resistance than summer tires due to their deeper, more heavily treaded profile and their higher pressure per square centimetre. Load and tire pressure also come into consideration.
A tire can consist of up to 16 different rubber compounds. However, the tire manufacturers keep the exact composition to themselves. In order to make a good tire, a lot is demanded of the rubber compound: low abrasion, tear-resistance, anti-slip properties, low rolling resistance, dynamic stability, air tightness and resistance to ageing.
There are various kinds of rubber used in tire manufacturing.
As well as natural rubber (harvested from the sap of the Hevea tree in equatorial plantations), we are now turning increasingly to artificial or synthetic rubber.
Good, circular running of tires is important for comfort and permanent, complete contact between the contact area and the road surface.
If the wheel does not run in a circle, the driver will feel this in the steering wheel.
75.Runflat, RSC, RFT, SSR, DSST, ZP, RF, HRS, ROF, EMT, TD, MOE, MO Ext.
Runflat tires (manufacturers use a variety of names) are tires with emergency running properties, which allow the motorist to keep driving for a limited distance when tire pressure is lost and / or tire pressure is too low. However, the vehicle must also be fitted with a TPCS. The Runflat system works with a reinforced sidewall that more or less keeps its shape in the event of a loss of pressure. These means the driver can keep control of his vehicle if pressure is suddenly lost. Travelling at max 80 km/h, he can then look for the nearest tire specialist within a radius of 80 km.
Runflat technology offers the driver a clearly recognisable benefit and a real plus in safety and comfort. In addition, you don’t have to change the wheel when you have a flat, removing any need for a spare wheel. All Runflat tires have the common RSC (Runflat System Component) symbol on their sidewall.
The running surface is the only part of the vehicle that is in contact with the road surface, and is responsible for transmission of power, alongside the other tire components. This means the contact area of the tire - the part of the running surface which touches the road surface - is not much bigger than a postcard!
The running surface must handle acceleration and braking power in the direction of travel, and lateral force when steering and cornering. The performance of the running surface is largely determined by the sub-structure (belt, carcass), the bead and side area, but the design of the tread is critical.
Self-Seal Technology refers to tires which can re-seal themselves in the event of damage, e.g. by a nail puncture. The tire contains a special polymer coating which, in the event of a puncture, embeds itself in the damaged area of the running surface, sealing the hole. However, the tire should be replaced as soon as possible.
Better known as Runflat tires. All self-supporting tires have a reinforced sub-structure, an adapted carcass and belt, as well as stiffened sidewalls and bead areas.
The letters SET indicate that the tires come with an inner tube (occasionally also a flap)
Shoulder abrasion refers to the high level of abrasion on the shoulders of the tire compared to the middle of the tread. Increased shoulder abrasion can occur both on one side in isolation and both sides at the same time.
Abrasion on one shoulder occurs mainly when the position of the wheel in relation to the road surface is not ideal. In this case, tracking and camber should be checked with an axle measurement.
Shoulder abrasion on both sides is mainly caused by low tire pressure or over loading.
On wide base tires, more shoulder abrasion is normal.
All information relating to the tire is located on the side wall. In order to avoid any damage, it may be fitted with a flange shield on the outside. External damage can occur when driving hard over a kerb. In addition, this can also break the integrated carcass fibres. Alongside the tire shoulders, the side walls flex the most and are therefore exposed to very high loads.
Silica is the name for the salt of silicic acid. Using silica stabilises the network of connections between the individual materials in the rubber compound. Compared to regular structures, silica increases the strength of the material. This reduces wear and tear, and increases mileage. The tire also grips the road better, as the compound can be designed to be softer due to its increased strength.
Slick tires are racing tires without any tread.
Slip is the difference between the geometric circumference of the wheel and the distance actually covered by one revolution of the wheel. Slip is 100% when the wheels spin or lock. So the higher the drive or braking force, the greater the slip. Even if you don’t notice it: There is always a small degree of slip when driving, and the tire rubs on the road surface with every revolution - hence the wear and tear on tires.
Slip angle refers to the difference between the position of the wheel and actual direction of travel. A high slip angle requires a lot of steering lock in order to bring about a change in direction. A certain degree of slip angle is needed for the wheel to generate cornering force. The stiffer the tire construction, the lower the angle, and the safer the driving behaviour.
86. Snow chains
Snow chains are a driving aid for vehicles on snow covered roods or muddy ground, and they are mounted on the tires. We differentiate between full snow chains and start assistance. Snow chains improve traction on ice and snow, and the direction of the wheels. They consist of chain links made from hardened steel. Depending on the chain pattern, you can choose from ladder chains, zig zag chains, or diamond pattern chain, which is the quietest and safest type. Fitting is made easier by a so-called endless chain. You should always watch your top speed when driving with snow chains!
The designation on the side wall of every tire includes a letter which indicates the permitted speed which this tire is suitable for. Which tire is suitable for your vehicle is shown in the registration document or the vehicle door:
For example: 195/65 R 15 H: H = up to 210 km/h. The following letters are found most frequently in the car tire section for the speed index:
- a. Q = max. 160 km/h
- b. R = max. 170 km/h
- c. S = max. 180 km/h
- d. T = max. 190 km/h
- e. H = max. 210 km/h
- f. V = max. 240 km/h
- g. W = max. 270 km/h
- h. Y = max. 300 km/h
- i. ZR = over 240 km/h
Additional vulcanised steel or hardened metal pins that stick out 1.5 - 2 mm from the running surface in the tread of winter tires are known as spikes. These are designed to give the vehicle more grip, above all on icy roads.
The disadvantage is that tires with spikes have much less grip on dry roads than a pure rubber tire. In addition, there is much greater wear on the road, as spikes cause cracks on the road more quickly.
For these reasons, they are only permitted at certain times of the year, depending on the country in question. In Germany and some other countries, they are generally banned. In addition, speed restrictions are generally enforced. The speed limit is 80 km/h on main roads and 100km/h on motorways. Spikes are permitted on vehicles up to 3.5 t.
When driving with spikes it should be noted that road noise increases considerably, and that braking distance on a dry road surface also increases.
Note: Tires with spike holes or spikes must not be marked with an “S”, as these cannot meet the required noise regulations because of the spike holes or spikes.
Steering precision in the context or tires and vehicles relates to their ability to steer in and out of corners, and driving behaviour in the corner itself. High performance (Y and ZR) tires designed for sports driving generally have a high level of steering precision.
Stopping distance is the sum of reaction distance and the actual braking distance.
Compared to winter tires, the rubber compound in summer tires is less elastic in order to function more effectively at high temperatures: Rolling resistance and wear are reduced, giving better results with regard to mileage, driving comfort and steering stability. Summer tires are designed for dry roads, high temperatures, high speeds and the corresponding temperature requirements, as well as damp and wet road surfaces.
The parts joining the chassis and the wheels are called the suspension. The main task of the suspension is to keep the wheels in contact with the road always. This means it determines the road-holding, driving comfort and safety of a vehicle. The wheels can be attached to the suspension individually (independent suspension) or together with an axle (rigid axle). The main components of the suspension are: Transverse control suspension, springs, shock absorbers and stabilisers.
93.SUV: Sport Utility Vehicle
A Sport Utility Vehicle is a vehicle which can be driven both in the town and off-road.
Tire temperature has a considerable influence on the coefficient of friction as well as slip and slip angle. In low temperatures the coefficient of friction is on the low side, but it rises as temperature rises. If operating temperature rises further, the coefficient of friction falls as does the force transferred. The coefficient of friction of rubber is temperature dependent.
This abbreviation stands for tubeless tires. In this case the tube is replaced by a inner liner, an air-tight coating. Tubeless tires are standard nowadays with cars and lorries.
Tracking describes the angle between the wheels when viewing the car from above. When the wheels point outwards, this is called “toe-out”.
Toe-out can be used to equalise the driving forces which impel the wheels forwards. This reduces wear and tear on the tires.
Nuts and bolts on a wheel must be tightened to a certain level. The tighter the better does not always apply to these bolts! If nuts and bolts on a wheel are tightened too much or unevenly, it can deform the wheel bearings, the brake discs and the rim. The wheel nuts and bolts may break off.
To tighten nuts or bolts properly, use a torque wrench diagonally. You can get these with adjustable torque at any car accessories specialist.
The torque required is different from vehicle to vehicle and from rim to rim. The correct torque for any original rim will be in the car’s instruction manual, and for after-market rims it will be in the relevant section of the General Operating Licence. It is much safer, and much less effort to leave this to your tire specialist. He will he happy to tighten the nuts for you after a certain mileage (at least 20 km, 200 km at the most).
98.TPMS: Tire Pressure Monitoring System
Tire pressure monitoring systems (TPMS) monitor tire pressure. They are used in wheel tire systems with emergency running features. There are direct systems, built onto the valve, and indirect systems, which take the tire pressure from the wheel revolutions on the ABS sensor.
TPMS is an EU requirement for all new vehicle registrations up to 3.5 t.
Other names for TPMS are: Tire Safety System and RTPMS: Remote Tire Pressure Monitoring System. Moreover, in the USA market, tire pressure monitoring systems have been a legal requirement on all new vehicles with a registered total weight of up to 4.5t since 2007.
Tracking refers to the relative position of the wheel when viewed from above. If they are slightly closer at the front than at the rear, then they are called toe-in. If the wheels are closer together at the rear, then they are toe-out. On front wheel drive vehicles, toe-out reduces the influence of driving force on steering, whereas rear wheel drive cars are set up toe-in. The friction between wheel and road tries to push the wheels out on each side, but the power of the front wheel drive tries to push the wheels together. When steering the car into a corner, the slightly negative tracking created by the arrangement of steering linkage and wheel suspension is more pronounced with toe-out: The wheel on the inside of the corner turns more than the one on the outside. This is necessary because the inner wheel describes a tighter circle. This ties in with support of the steering movements and steering force.
Traction is the ability to convert engine power into forward motion by means of interlocking with the road surface. Traction is no problem on dry roads. It only starts to fall in the wet, or on ice and snow. Then the gripping ability of the rubber compound and the tread profile (v-profile, lamella tires for snow) plays a decisive role.
The positive and negative tread of the tire is made from tread compound. The performance level of a tire when driving essentially depends on this - in the wet, or in hot conditions, and when transferring lateral or linear power. The tread compound also partly determines mileage and noise properties.
102.Tread, tread depth
Safety depends on the tread of the tire, particularly tread depth, especially in the wet or in mud or snow. New car tires have a tread depth of more than 8 mm approx. The European requirement is a minimum tread depth of 1.6 mm. You can check whether this minimum depth has been reached with a tread indicator (a marker in the tread grooves). The location of these markers is indicated by the letters “TWI” on the shoulder of the tire. If this marker is clearly visible, and is at the same level as the rest of the tread, then they tire is down to the minimum of 1.6 mm.
Experts recommend car summer tires are changed when tread is down to 2mm, wide base tires should not go below 3 mm, and winter tires start to lose their effectiveness when tread is down to 4 mm. A driver who allows his tires to go down to the permitted limit of wear and tear is not just breaking the law, they are also putting their insurance cover at risk.
103.TT: Tube Type
This abbreviation stands for a tire which needs an inner tube.
104.TWI: Tread Wear Indicator
Tread wear indicators are built into the tread grooves on the running surface. When tread depth is 1.6 mm, they form a continuous bar with the tread itself. The location of these indicators is shown by triangles on the side wall, the letters TWI, or small, brand-specific symbols.
Twin tires means fitting two tires on both sides of the axle. Twin tires are used particularly on the rear axle of commercial vehicles.
On axles with twin tires, you should avoid mixing different tire manufacturers and tread patterns. Only tires with the same air pressure and dimensions should be used together.
Caution: For twin tires, the lower load index applies.
Tire age is determined by two factors:
On the one hand, small amounts of ozone in the atmosphere penetrate the rubber of the tire and affect the sulphur compounds between the rubber molecules. This means the rubber loses its elasticity.
On the other, tires also age when they are stored, unused, and they harden, becoming brittle and porous. This can then lead to hairline ageing cracks. Sun, wind and weather, as well as contact with grease, oils and chemicals attack the tire and speed up the ageing process.
Tires form the only point of contact between the vehicle and the road. This means they should be checked regularly. The most important things here are tire pressure and remaining tread depth, which must not be below 1.6 mm in the EU. The correct tire pressure can be found in the vehicle’s user manual, or from the manufacturer and tire specialists.
If a tire loses an excessive amount of air, then it should be checked out for damage by an expert. He can spot any damage which, if repaired in good time, will improve the safety, comfort and life of the tire.
You should check your tire pressure every other time you refuel at the very least. This is also possible when the tires are filled with a special gas (e.g. nitrogen). However, the special effect of the gas gradually disappears as you top up with normal air.
108.Tire classification, tire size
You can interpret the code on the tire as follows in this example:
195 / 50 R 15 82 V
195 = Tire width in mm
50 = Tire profile, ratio of height to width as a percentage
R = radial construction
15 = Tire interior diameter (rim diameter) in inches
82 = Load-Index (in kg)
V = Speed-Index
To develop and produce a new tire, you must go through several steps.
The focus within tire manufacture is on:
110.Tire purchase, fitting
Which tire is suitable for your car is shown in the registration document or the vehicle door. Basically, the following applies: Tires should be replaced at least per axle. Tires from different manufactures, with different treads or different tread depth should not be used on the same axle, as this can lead to uneven driving and braking properties of the vehicle.
111.UHP: Ultra High Performance
Ultra-High-Performance tires are very wide, and can withstand speeds of at least 240 km/h (speed index V). Compared to regular tires, they perform better when changing lanes, and offer better driving stability.
If you drive with too little air in your tires, you will jeopardise safety and experience several disadvantages e.g. damage to long term strength, spongy driving performance, reduced mileage from the tires, higher fuel consumption. So, the following rule of thumb applies: Check your tire pressure every two weeks, when your tires are cold.
Under-steer is the term used to describe when the front wheels lose grip before the rear wheels. The vehicle skids out of the corner over the front wheels.
Driver assist systems such as ESP try to minimise this behaviour.
Uniformity is what tire technicians call the manufacturing accuracy of a tire. Uniformity is an important condition for a wheel to roll perfectly and quietly, without irritating noises and vibrations. The better the uniformity of the tire, the easier the wheel is to balance.
115.UTQG: Uniform Tire Quality Grading
The UTQG quality grading established by US department of transport rates the tire’s performance level based on three criteria: Tread wear, Traction, and TemperatureResistance.
It only applies to tires (excluding winter tires) with a rim diameter of at least 13 inches. The tread wear figure is a comparative value based on wear and tear of a tire compared to a standard tire which has been tested on a certified test track under controlled conditions. A tire with the rating 150 will wear one and a half times more slowly than the standard tire, which has a tread wear rating of 100. The actual tire performance depends on the relevant conditions of use and can deviate substantially from the norm due to driving behaviour, maintenance, different road surface properties and weather conditions.
The Traction rating is shown by the letters AA, A, B and C in descending order. It indicates the grip properties on wet surfaces, and is measured under controlled conditions on a certified test track.
Temperature: Temperature is shown by the letters A, B and C. These values show how resistant the tire is to heat, and how well it can disperse the heat on a pre-determined test wheel under controlled, laboratory conditions. Excessively elevated temperatures can have a negative effect on the material of a tire, reduce its life, and cause frequent tire damage.
The temperature rating relies on tires having the correct air pressure, and excludes over-inflation. Excessive speed, incorrect tire pressure, and over inflation, in isolation or together, can cause a build-up of heat or tire damage.
We differentiate between two types of valve: Rubber valves, which seal off the whole in the rim themselves, and metal valves, which use a grommet for sealing.
Caution: Valves are very sensitive to dirt, dust and humidity. Therefore, the valve cap must always be screwed on firmly.
Valve caps protect the actual valve from dirt and moisture.
Vulcanisation is the last stage of the tire production process, also commonly known as “tire baking” amongst tire professionals. Not only does the tire blank get its final tread in the vulcanisation process, the individual tire components are also combined by the targeted control of pressure and temperature for precise periods, thus becoming elastic rubber. This takes place at 165-200° C and pressure of 12-24 bar for around 9-17 minutes.
On wet surfaces, the tire’s positive blocks must divert the water through the drainage grooves.
120.Wear and tear
Wear and tear depends on how the tire ages and level of driving. Durability of the tire is determined by the driving style, vehicle loading, UV radiation, road conditions and maintenance (air pressure, storage). With the same type of vehicle and tire, it is possible to find differences in performance of several thousand kilometres.
121.Wear indicators, abrasion indicators (TWI, DSI, WSI, VAI)
To make the wear on a tire visible, manufacturers equip their product with various optical markings. Small rubber bars in the tread grooves or coloured strips, numbers and symbols on the tread show the level of wear. After wear these markings disappear or become visible. The abrasion indicators give information not only on the actual tread depth, but also on the remaining performance, and thus the safety of a tire regardless of the legal minimum requirements: Thus the disappearance of a water drop marking on a summer tire means an increased danger of aquaplaning. And winter tires lose their winter suitability and should be replaced as soon as the ice crystal marking on the tread is no longer visible. Aside from that, abrasion indicators can indicate wear on one side. Most show symbols, signs and abbreviations on the tire shoulder, where the wear indicators are found in the tread. In addition to the standard abbreviation “TWI” (Tread Wear Indicator), manufacturers also use their own designations for their wear indicators, for example DSI = Driving Safety Indicator, WSI = Winter Safety Indicator, VAI = Visual Alignment Indicator.
The wear pattern of a tire gives an expert valuable information about whether the tires are aligned properly, or if there is any damage to the chassis (axle geometry, shock absorber defects etc.). Therefore, tires should be checked regularly by a specialist workshop (around every 10,000 to 15,000 km).
Unladen weight: Weight of the vehicle when ready for use, weighed without the driver. 75kg for the driver is taken into consideration for commercial vehicles only.
Vehicle load capacity: Difference between unladen weight and permissible total weight. Permissible total weight: Fixed upper weight limit which a vehicle can reach including load.
Roof load: When limit using a roof rack or roof box. Roof load generally lies between 50 and 100 kg. If this is exceeded, there is the risk that the otherwise balanced driving behaviour of a car can become significantly worse, that the rack breaks or comes off after a delay.
Vertical load: maximum weight capacity of a tow bar in a vertical direction. Depending on the type of vehicle, this is normally between 50 and 75 kg.
124.Wet weather performance
When braking in the wet, the tire must be able to divert the water under the contact area as quickly as possible, to prevent aquaplaning. This in mainly influenced by tread pattern, tread depth and grip.
Balancing is the process of adding weights to the wheels, in order to ensure circular motion of the wheel. Poorly balanced wheels are excessively tough on tires, wheel bearings and suspension. Uneven rolling of the wheel makes the whole car vibrate right into the steering wheel, depending on speed. This reduces the contact area, speeding up tire wear. Pressure on the suspension is also increased.
The wheel disc connects the rim and the wheel hub.
Wheel load is the force exerted vertically on a wheel.
Wheel sensors measure the revolutions of the individual wheels. This makes them part of, and the most important element of the anti-lock systems, traction and stability control systems of a vehicle.
n order to widen the tracking of a vehicle, you need wheel spacers which are fitted between the rim and the hub. This allows the rims to stand out further from the wheel arches.
Wheelbase is the distance between the front and rear axle, measured in each case from the centre of the wheel. A relatively long wheelbase allows better seating proportions in the interior of the vehicle, creates short chassis overhangs, improves directional stability and reduces pitching motion of the chassis. As the suspension can be better aligned with a longer wheelbase, driving comfort is improved. However, a shorter wheelbase improves manoeuvrability of a vehicle, leading partly to better control and better cornering.
131.Wide base tires
Wide base tires offer several advantages over standard tires. Wide base tires usually refer to tires with a profile ratio of 55 and lower (e.g. 205/55 R 16). However, there is no common definition.
The advantages include a clear improvement in driving stability, considerably better steering precision and better high-speed performance.
Compared to summer tires, winter tires can be recognised by their coarser tread and characteristic lamellas. Winter tires are more suitable than summer tires for wintery road conditions because of their special cold-resistant rubber compound. This means the vehicle grips the road perfectly, even at the lowest temperatures. The tread profile which is perfectly adapted to poor weather conditions also minimises the risk of aquaplaning and gives perfect grip on ice and snow.
Larger grooves in the tread and extra lamellas guarantee additional stability when moving quickly between snowy, wet, and dry roads. The letters M+S identify winter tires and winter-ready all-weather tires. On some products there is also a snowflake symbol. M+S tires with a snowflake meet a high-quality standard: In many European countries, winter tires are compulsory. This varies from country to country. Since 2010 it has been compulsory in Germany to fit winter tires in wintery road conditions.
133.WL: White Letters
Specially designed side wall lettering with white letters.
134.Yellow and red dots on tires
Some tire manufacturers use coloured markings on their tires, such as yellow or red dots. These do not relate to quality features of the product in question. These markings might relate to various sorting issues from the manufacturer’s different tire factories. So for example, a manufacturer could track a shipment right through the route to market. However, the manufacturers do not publish any further information about these coloured markings.
Z Lamellas are Z shaped, arranged to the midpoint of the wheel. This results in a supporting effect, which gives good traction, excellent grip and steering precision. Z lamellas are mainly used in winter tires and in the high-performance area. Depending on the performance level desired, same direction and opposite direction Z lamellas designs are available.
136.ZR - Tires
Pure ZR tires have no service description. ZR indicates that the tire is suitable for speeds over 240 km/h, but does not state definitively what speed, at what load and tire pressure. These figures are calculated and certified individually by the tire manufacturer, while indicating the vehicle axle load and final speed. However, a service description may also be included on the side of the tire, indicating the maximum limit of a tire e.g. “99W”. A ZR tire is definitely suitable for speeds over 300 km/h. if a letter “Y” in brackets is included, e.g. (109Y)