the ABC of
All the information you need about tyres
How long may an unused product be sold as new? This is an interesting question which cannot be clarified clearly in many branches of industry. When buying a yogurt, an informed consumer immediately knows Hands off when the best before date printed on the packaging has already exceeded the personal limit of tolerance. But what about the aging of car tyres?
The Wirtschaftsverband der Deutschen Kautschukindustrie WdK (Trade Association of German Rubber Industry) has published a guideline for passenger tyres which says "Physical and chemical processes cause tyre ageing. This also applies to infrequently or not used tyres. Certain chemicals are added to tyre compounds to counteract this process to prevent the chemical reaction of oxygen and ozone that has an impact on tyre performance. This guarantees that a tyre, which has been stored properly for several, still meets the specification of a new tyre so that it is not affected in its performance.
At the initiative and under the leadership of the Bundesverband Reifenhandel und Vulkaniseur-Handwerk e.V. (BRV German Association of tyre dealers), the main representatives of German tyre industry have developed a clear joint statement concerning the in the past frequently and differently discussed question about how long is the maximum period of several years, as stated in the guideline. Tyre companies like Bridgestone, Continental, Dunlop, Goodyear, Michelin and Pirelli all advise both consumers and dealers to make sure not to buy/sell tyres, which have a production date that lies more than 5 years in the past. Subject to proper storage that means in reverse, that an unused tyre has to be considered as a new tyre and can be sold as a new tyre for 5 years from the date of production.
It is true that, in case of sufficient knowledge of the operating conditions, this statement does not exclude the mounting of tyres which are older than five years at first use. Nevertheless, both tyre dealers and consumers have a considerably clearer legal certainty who else but the manufacturers could have made clear conclusions in compliance with the warranty and product liability laws?
The four digits DOT code vulcanized into the sidewall of the tyre indicates the tyre´s production date. The first two digits represent the week of production and the last two digits represent the last two digits of the year of production. So if you find for example the code 2200 on the sidewall, the first two numbers indicate that the tyre was produced in the 22nd week and the second two digits show that the year of production is 2000.
Regardless of the production date, the legal warranty period starts only to run with the purchase of the tyre!
Not only on the purchase of new tyres it is recommendable to have a closer look on tyre age. Responsible drivers should also inspect their fitted tyres regularly. The tyre industry recommends replacing all tyres that were manufactured more than 10 years ago! Older passenger car tyres should only be used when they have been operating under normal conditions. And they should not be rotated on the car but should remain on current position and operation until the tread is worn.
The ten years rule applies only to passenger car tyres. Tyres mounted on caravans, trailers or other vehicles that are parked for long periods, which are driven infrequently underweight or permanent load, are particularly subject to ageing. Generally tyres and spare tyre have to be checked after longer parking periods and before longer trips. For trailers/combinations of car (or other motor vehicles with a maximum permissible gross laden weight of 3.5 t) with trailer, which provide a 100 km/h-license according to § 18 StVO (Road Traffic Code), the maximum age of the trailer tyres may not exceed 6 years. The BRV recommendation says that tyres mounted on other vehicles of the category standing vehicles as well as spare tyres should be replaced after six years, in any case after eight years at the latest.
For those car drivers who do not rely on their own visual inspection concerning tyre age and condition, but who really want to be on the safe side, it is recommendable that they get their car regularly inspected by a tyre specialist. Additionally, winter storage of the summer tyres as well as summer storage of the winter tyres should be handled by a professional. Using the professionally organized tyre storage, offered by many tyre dealers for a relatively low fee, does not only ensure the optimal service life of tyres. The included tyre inspection, executed by the tyre expert, guarantees that only tyres which are in technically perfect condition will have the chance to be mounted on the car at the beginning of the next tyre change season.
Source: BRV Bundesverband Reifenhandel und Vulkaniseur-Handwerk e.V http://www.bundesverband-reifenhandel.de/
Proper tyre mounting includes balancing. Due to centrifugal force, a tyre imbalance of 10 g results in an effect of 2.5 kg at a speed of 100 km/h. Firstly, an imbalance in the wheels, especially front, will be felt as a vibration through the steering at higher speeds.There are two types of balancing:
Source: BRV Bundesverband Reifenhandel und Vulkaniseur-Handwerk e.V http://www.bundesverband-reifenhandel.de/
Tyre Brand Restriction
In many vehicle registration documents, there were, until February 2000, in addition to the approved wheel/tyre combinations, clear regulations concerning the tyre brands to be used, i.e. motorists and tyre dealers were legally forced to mount specific brands even if there might have been better or cheaper tyre models of the same size and quality.
This so-called brand-restriction was liberalised by the German minister of Transport. Due to this liberalization the possible indicated entries can be considered as recommendation only, without legal value.
In accordance with the Road Traffic Permit Act (StVZO) this also implies more responsibility for the vehicle owner/driver who is obliged to ensure the roadworthy and safe condition of the vehicle. This includes that there do not occur any safety problems due to the application of tyres subject to the tyre size designations indicated in the vehicle registration papers.
In the high speed segment the brand recommendations should still be followed. This segment starts with the speed index V and particularly relates to W-, Y- and ZR tyres.
For sports cars, approved for road use, e.g. Porsche, Ferrari or Corvette it is recommended to continue to follow the brand restrictions indicated in the registration documents or the recommendations of the car manufacturers.
Source: BRV Bundesverband Reifenhandel und Vulkaniseur-Handwerk e.V http://www.bundesverband-reifenhandel.de/
Tyres do loose pressure each day, through the process of permeation. It is normal that tyres loose air so that the air pressure has to be checked and adjusted regularly. An alternative medium for normal air fillings is nitrogen - a non-toxic and non-flammable gas with larger molecules than oxygen. The low additional costs generated by a nitrogen filling pay off quickly. Nitrogen maintains a more consistent tyre pressure and extends the intervals of tyre pressure checks. Lower tyre wear, better tyre mileage, high stability in curves and optimal braking distance are additional benefits.
If a Nitrogen-filled tyre requires pressure to be added either Nitrogen or normal air may be used.
All Season Tyres
In the passenger car tyre segment there are also offered so-called all-weather or all-season tyres in addition to summer- and winter tyres. Tire names like "All-weather" or "All Season" imply what a special sidewall marking demonstrates: snowflake, leaf, sun and rain drop represent the different weather conditions that the tyre is suitable for.
These tyres are a compromise. They do not achieve the high level of driving characteristics of their corresponding experts under warm and dry or cold and snowy conditions. For motorists who do not live in a mountainous area and who sometimes may leave their car under heavy weather conditions, all-season tyres are a possible alternative.
The sidewall markings of any tyre includes a letter that implies the maximum speed for which the tyre is intended.
Example: 195/65 R 15 H H = up to 210 km/h.
In the following you see the most frequently used speed index letters of the passenger car segment
In the car registration papers you will find the tyres approved for your car.
Markings /Tire markings
The legal regulations are determined in § 36 StVZO (Road Traffic Code) and the Guideline for uniform tyre marking which states:
Tyres, namely pneumatic tyres for vehicles designed for a maximum speed of more than 40 km/h have to wear following markings in addition to the brand:
Example: 225/60 R 15 96 W
The sidewall marking that starts with DOT identifies the age of a tyre by indicating the week and the year of manufacture. DOT stands for Department of Transport and indicates that the tyre meets the safety standard for tyres (USA FMVSS119).
For tyres produced prior to 2000 the week and year the tyre was produced was contained in the last three digits of the DOT number. The first pair of digits identifies the week the tyre was manufactured, the last digit the year of manufacture. 434 e.g. means that the tyre has been produced in the 43rd week of the year 1994. In order to easier differentiate the production 1990-1999, most tyre manufacturers have added a triangle after the DOT number.
Since 2000 the DOT number has four digits with the first 2 digits identifying the production week and the following 2 digits the production year. 0100 e.g. means that the tyre has been manufactured in the 1st week of the year 2000.
Winter and all-season tyres additionally provide the M+S marking.
Retreaded tyres have to provide a retreaded marking. Retreads have to provide the date of retreading (analogous to the tyre production date).
On some tyres you can find further markings such as rotation these are directional tyres. An E followed by a number, for example E4, certifies that the tyres comply with the European requirements. The number associated with the letter 'E' is the code number of the government which granted the type approval, in this case 4=Netherlands. Tyres produced after October 1st, 1998 have to provide this e-mark. If non-e-marked tyres are mounted the general certification for the vehicle will expire!
The tyres approved for your car are specified in the registration papers.
Generally winter tyres have to be stored in summer and summer tyres in winter before they are mounted again. The simplest solution for the motorist is to leave the storage of the tyres/wheels to the tyre dealer. Subject to a modest fee the tyres are not only properly stored but also cleaned and checked for damages.
If you store your tyres you should follow the following tips:
Before removing your tyres note their direction and position:
Remove any gravel that has been trapped in the tyre grooves.
Store your tyres in a cool, dry location which is free of fuel, oil, grease or chemicals.
If your tyres are mounted on rims stack them flat preferably on a wooden pallet. If your tyres are not mounted on rims store them standing up and rotate them regularly.
Tire Inflation/Tire Pressure
Many tyre damages and accidents are caused by improper tyre pressure. But tyre pressure has a decisive influence on tread wear and fuel consumption, too.
Especially low air pressure of one or more tyres has a considerable economic and ecologic impact:
According to statements of American tyre manufacturers, there are daily wasted $ 6.1mio on American roads due to underinflation of tyres. 28% of the US-citizens are supposed to drive with underinflated tyres.
Additionally low pressure is very dangerous. Lower tyre pressure causes added flexing work of the tyre sidewalls. This can lead to overheating and may cause a temperature of more than 130° in the carcass (tyre casing), at worst leading to a tyre blowout.
The vehicle manufacturer's pressure recommendation can be found in the vehicle owner's manual or as placard label on the fuel filler door or on the doorjamb. Tire pressure should be checked every time when you are refueling or at least once a month. Always check the air pressure when the tyres are cold since warm tyres may show a higher pressure. Never deflate a hot tyre!
Don`t forget the spare tyre. In an emergency case you urgently need it, thus it should be ready to run!
There are so-called runout tolerances for wheels and tyres. If it occurs that two peaks meet then matching may help. First the tyre has to be deflated and is moved on the rim by a quarter rotation until lateral and radial runout have been minimized (lateral runout = horizontal variance, radial runout = vertical variance).
In case of extreme radial runout, harmonization is required. In this case the radial runout is diminished or even eliminated by reducing the rubber tread. However, these kinds of production defects cease to be an issue today.
According to the legal regulation of the Road Traffic Act (StVZO, §36) it is, strictly speaking, only prohibited to mount tyres of different construction, i.e. radial and diagonal tyres may not be used on one vehicle.
In the current language you talk about mixed tyres if you mean to mount summer and winter tyres on the same car or different treads, tyre sizes, brands etc. In this respect it is illegal to mount different tyre sizes exception: mounting of spare tyre in case of a breakdown in order to drive to the next garage. There are additional exceptions for some sports car models; but it has to be indicated explicitly in the vehicle registration certificate that different tyre sizes have to be used on front and rear axle.
Even if it is not explicitly prohibited tyre experts and car manufacturers recommend to use tyres of the same brand and tread design only.
The driving performance may be particularly affected if summer and winter tyres are mounted on the same vehicle. The benefits of these tyres are designed for the special operating conditions. Depending on road and operating conditions it may occur that one tyre type still provides full grip while the other tyre type has reached or exceeded its adhesion limit. On icy or snowy roads in winter, the axle equipped with summer tyres starts inevitably earlier to skid and the brake will immediately lock.
The early change from summer to winter tyres should be a matter of course for every car driver. Early means before the first snow falls!
Modern winter tyres are designed to provide safe driving not only on icy and snowy roads but already at temperatures of 7°. Due to their compound summer tyres loose grip, causing longer braking distances at lower temperatures, on dry as well as on wet road surface. Equipped with winter tyres stopping distances are by 20% shorter than with summer tyres. When the car is equipped with wide tyres the effect begins at 10° already. In this respect ABS, ESP or TCS cannot help since these are electronic aids only. They cannot replace winter tyres.
However, it is important that winter tyres provide sufficient tread depth. If the tread depth left is below 4mm the aquaplaning risk increases and traction and braking force decrease considerably, driving performance only achieves the level of summer tyres.
Car drivers who watch their money should consider that many insurance companies refuse to pay out where a driver has not fitted winter tyres and had an accident. Then, an accident under winter conditions not only means trouble but may become very expensive!
Following rules must be followed for the mounting of winter tyres:
Run Flat Tire, Wheel/Tire Systems and Tire Pressure Monitoring Systems
The security guards increasingly draw public attention not at least since there is a growing number of car types and models which come equipped with those safety features. While tyre pressure monitoring systems (TPMS) are permanently monitoring the tyre pressure during operation and are alerting if the pressure deviates from the set value, tyres or tyre/wheel systems with run-flat features are supposed to provide a maximum of safety in case of a tyre puncture. Additionally no spare tyre is needed. The runflat tyres provide technology that allows you to drive up to 200 km at a maximum speed of 80 km/h to the next garage with a flat tyre. No tyre change at the road side, additional space in the trunk, lower fuel costs due to lower weight these are arguments for the runflat system. The downside of modern technology: complicated electronics of these new safety guards which require professional care and maintenance.
Members of the BRV are regularly informed about actual market developments of these systems. Additionally the BRV provides written documentations as well as mounting and training offers so that the member companies are always provided with the actual required professional knowledge.
If you want to know whether your car is equipped with run-flat and/or tyre pressure monitoring system or whether there are add-on systems available, you may open the actual overview (Word-Document 1.3 MB).
Safe wet, mud and snow handling depends on the tyre tread, especially on the tread depth. New passenger car tyres provide a tread depth of approx. 9mm. The legal minimum tread depth is 1.6mm (§ 36 Road Traffic Permit Act StVZO).
Wear indicators (bars molded into the tread) may show you whether the tyre is worn to minimum tread depth. TWI is the abbreviation for Tread Wear Indicator and shows you where these bars are located. Michelin tyres for example have a Michelin man marking. If these bars are clearly visible and if they are flush with the remaining tread, the tyre is worn to the minimum depth of 1.6 mm.
Car drivers, who ignore the minimum tread depth, risk a fine of 50.-(owner of the car even 75.-) and 3 penalty points at the German transport central office in Flensburg at a police check.
But car drivers should avoid this risk. Experts recommend:
It is not illegal to drive the tyres until they are worn to the minimum tread but this puts your insurance cover at risk. In such a case, noted the regional court in Itzehoe, an accident is caused by gross negligence.
Wheel Nuts or Bolts/Torque
The principle as tight as possible= as safe as possible does not always apply for the tightening of bolts. If the wheel nuts are over-tightened or unevenly tightened the wheel carrier, the brake disc or the rim may stretch. The proper way to tighten nuts/bolts is to use a tyre iron or a torque wrench. This can be obtained from the car accessory trade.
There are differences for the tightening torques for light-alloy and steel wheels for different vehicles. You should carefully read the individual operation constructions. The easier and safer way is to leave it to an expert.
In addition the expert will retighten the wheel nuts after a certain distance after at least 20 km, maximum after 200 km.
If the marking regroovable" is vulcanised into the tyre sidewall, the tyre may be regrooved, i.e. the tread grooves may be deepened by cutting to the base of tread. You wont find this word on passenger car tyres since it is prohibited by law to use regrooved passenger car or two-wheel vehicle tyres.
For commercial tyres, however, the professional regrooving of tread grooves may extend service life considerably. This fact has been considered by the tyre manufacturers in the construction of the tyres and regrooving of treads may only be executed by experts according to the instructions of the tyre manufacturers.
From the registration papers you can take the tyres that are approved for your car. Purchase and mount only tyres that are approved for your car otherwise this leads to a loss of the general operating permit.
Basically it is the best to replace all four tyres at once, but at least you must replace them in pairs. Tyres of different manufacturers with different treads or different tread depth should not be used on one axle since driving and braking performance can be affected.
Passenger car tyres with this designation are reinforced, i.e. these are products for wagons or vans requiring higher load capacity than normal tyres. The same applies to the description XL Extra Load (also for V-rated winter tyres).
From the registration papers you can take the tyres that are approved for your car.
Tire Damage/Tire Repair
It is true that modern tyres are really resistant to any kind of stress but of course they are not protected against damages which occur during their use. The number of car accidents which are causally related to technical damages or lack of maintenance remains high. In 1999 37 persons died and 2.405 have been injured since tyre damages caused a serious accident with a motor vehicle.
Causes for the most frequent defects:
Many damages are visible to the naked eye, even for non-experts. That is why you should inspect your tyres regularly. Also tyre experts offer professional tyre checks at reasonable prices. Suspect signs are cuts, cracks, bulges or tread chunks and of course penetrations of foreign objects such as nails. In many cases the tyres provide irregular tyre tread wear which is mostly caused by suspension or steering. But also braking or another kind of wheel unbalance may cause irregular tread wear problems. If you do discover any damages see your tyre dealer to have the tyre inspected.
For some tyre damage it might be possible to get it repaired thus saving a lot of money and resources. However, it cannot be generalized which damages can be repaired without risking to reduce the vehicle safety. In many cases the replacement of the damaged tyre is absolutely essential. Finally this question can only be answered by an expert!
On many passenger and truck tyres you can find the word "retreadable". If the tyres are worn, but the tyre casing is intact, tyres showing this designation can be retreaded.
Approx. 50 % of all mounted commercial tyres are retreaded, for passenger car tyres the proportion is significantly smaller. For summer tyres a proportion of 5 % for winter tyres at least 15 to 20 % is estimated.
There are two reasons for the application of retreaded tyres which should be emphasized:
Especially for the application of retreaded truck tyres the cost aspects play a main role since these tyres cost only half as much as new tyres. For passenger car tyres this argument is decreasingly important since many new tyres at very low prices have entered the market, especially new tyres from Far East. Many people buy these tyres, disregarding the actual quality.
However, in this respect, retreaded quality brand tyres like Rigdon, Securo, Condor und Ökon need not to hide behind new tyres. They originate from retreading companies which have established the Arbeitsgemeinschaft industrieller Runderneuerung AIR- (Association of industrial retreading) in the Bundesverband Reifenhandel und Vulkaniseur-Handwerk e.V. (BRV), to set higher standards for quality assurance in the retreading procedure. In most cases their quality and safety standards are higher than that of cheap import tyres. They also compete with brand tyres. Nevertheless, there is an adherent prejudice of lacking mileage and safety.
A closer look behind the scenes shall provide clarification:
Before a casing, i.e. a worn tyre, is approved for retreading, it has to pass an initial inspection in this respect the preselected used tyres are again optically inspected. Tyres with visible damages are sorted out. Only 30 % of all used tyres pass the initial inspection. With millimetre accuracy computer-controlled grinding machines remove the old tyre treads from the casing, which, during removal, must not be damaged. Even minor irregularities in the casing which become visible after the grinding process, cause the final sorting out. Template-controlled cover-extruders add the raw rubber compound which corresponds to the composition of new tyres. The tyre blanks are measured again, and then the tyre press is feeded with these blanks. At a pressure of approx. 15 bar and a temperature of approx. 160° the tyre get its new tread. Before the tyre leaves production, it is checked for the fifth and last time. Only if the tyre passes the inspection without any reservations it will be sold. You can recognize retreaded quality tyres from their TÜV (Technical Standards Organisation in Germany) label on the tyre side. They have to pass the same TÜV tests as new tyres, high-speed tests, long-term operating tests, and maximum stress tests. Additionally their production is subject to EU regulations.
The maximum load rating of a tyre is coded in the tyre marking.
Example: 195/65 R 15 91 H "91"represents 615 kg
Tire pressure, load and speed index always have a direct relationship. Load capacity increases with air pressure and/or reduced speed.
Roof loads of the car and vertical load of the trailer have to be taken into consideration. One or more of the following criteria are extremely dangerous for tyres:
Thus the vehicle must not be overloaded. For this reason the tyre pressure needs checking before holiday journeys and should be set to the maximum pressure (see owners manual). In the car registration papers you can find the tyres approved for your car.