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HOW TO TELL WHEN A TYRE WAS MANUFACTURED
All tyres imported into this country must comply with the internationally agreed standard of showing when the tyre was manufactured.
This was done in the nineties by having three numbers in an oval on one side of the sidewall of the tyre. The first two numbers represent the week of manufacture and the last number represents the year of manufacture; Therefore, a tyre marked 339 was made in the 33rd week of 199. Usually there is a triangle after the 9 indicating the tyre was made in the 90’s. Not all Dunlop Tyres manufactured in the 90’s were marked with a triangle, this was due to Dunlop using an alphabetical code until the end of 1992.
Since the year 2000, four numbers have been used for the date, e.g. 1101 will be the eleventh week of the year 2001.
Remember to check the date of manufacture when buying second-hand cars (especially the spare tyre) as tyres are normally guaranteed for a period of 5 years from the date of manufactured
TYRE SIDEWALL MARKING
The sidewall marking would look similar to the illustration below.
With few exceptions tyre size markings are standardized throughout the world. Although millimeters and inches are used (even combined in the case of radials) they no longer relate exactly to the dimensions of the tyre, but serve rather to identify the type of tyre involved and to give an approximation of its dimensions. The tyre markings enable one to know the type of tyre involved. This is important because it is detrimental to mix types i.e. SR steel radial with HR steel radial.
Taking the 175 SR 14, the “R” indicates a radial ply tyre, “S‘ the speed rating, the 175
its cross section in millimeters, and the 14 is the rim diameter in inches. As no reference is made to aspect ratio it will be an 80 series tyre.
The more complicated 195/65R15 91 H shows all of the above, except in the more
modern markings the aspect ratio is specifically indicated, as can be seen here with the
65 defining it as a 65% aspect ratio, or low-profile tyre.
91 – is the LOAD INDEX which is an internationally recognized numerical code associated with the maximum load a tyre can carry at the speed indicated by its SPEED SYMBOL under service conditions specified by the tyre manufacturer (see tyre sidewall for this symbol and its equivalent load).
H – is the SPEED SYMBOL i.e. tyre is capable of speeds up to and including 210 km/h.
Car tyres are produced to various speed ratings/symbols. These are designated ‘S’ ‘T’ ‘H’ ‘V’ ‘W’ ‘Y’ and ‘Z’
Only very high performance cars are fitted with ‘V’ ‘W’ ‘Y’ or ‘Z’ rated tyres, Car manufacturers usually specify the speed rating capability for their vehicles. If a car is designed for high speed performance, tyres must match these capabilities should the owner wish to do so, despite open road speed restrictions.
Due to vehicle manufacturer requirements, the emphasis on HR and VR particularly VR and WR rated tyres is high speed safety and performance. The tread life obtained from these high performance tyres, while being satisfactory,
will be less than a TR rated steel radial tyre.
From a safety point of view and to comply with some regulation requirements, high speed steel radial tyres (HR, VR and ZR fitted as original equipment should NOT be replaced with lower speed rated radial tyres and definitely not With texile radial tyres.
TREAD WEARStandards require tyres to have tread-wear indicators in the centre groove of the tread pattern to show when the tread depth is less than 1.6 mm. In most cases, if the tread on the tyre is level with these indicators, the tyre should be replaced.Good tyre tread is necessary to maintain road grip, especially in wet weather. As most tyres age, the rubber hardens, further reducing wet-weather performance.
DRIVING IN THE WET
Always remember that even with new or slightly worn tyres ,you should reduce speed
in the wet and increase the following distance behind the car in front . This is particularly important after a long dry spell when rubber crumb, diesel fuel and oil, together with pollutants absorbed by the tar, will rise to the surface forming a slippery film.
TYRE INFLATION PRESSURE
If you are inflating a tyre more often than usual , then it might well have a slow puncture, this could have been caused by a nail or a sharp stone lodged in the tyre or a leaking valve. Have it checked by a tyre expert.
Having your tyres inflated properly could save your life and certainly save you money. Correct tyres pressure is vital for balanced braking, maximum grip and long tyre life.
Under inflated tyres will increase fuel consumption and affect the safe handling of the vehicle, while over inflation can mean an uncomfortable ride and reduced grip.
Both under-inflation and over-inflation will cause your tyres to wear out prematurely. Under-inflation causes premature wear on edges, while over-inflation can cause the centre to wear out.
The inflation of all tyres-including the spare-should be checked every two weeks, while the tyres are cold. Even a short trip to the garage will warm up tyres and raise the pressure.
Tyres are legally required to be maintained at the appropriate inflation pressure recommended for the tyre by the vehicle manufacturer. All modern vehicles have a tyre information placard in a conspicuous place, showing the correct inflation levels for normal driving, as well as for higher speeds and maximum loads.
POINTS TO CONSIDER
MIXING VARIOUS SPEED RATED TYRESWith the proliferation of car tyre sizes and makes of tyre in the Nigeria market, the same size tyre with various speed ratings is readily available.Many people are of the opinion that with our open road speed restrictions, they do not require a tyre capable of 210 km/h (H rated) or higher fitted as origin equipment to the vehicle. Purely from a speed point of view, this may be so, and a ‘T’ rated tyre (190 km/h) may be more than adequate, but other aspects such as the tyre’s construction and rubber compounding must be taken into consideration.The higher the speed rating, the more emphasis is placed on road holding, steering response, stability and high speed safety. It is for these reasons that when tyres with a lower speed rating or a budget equivalent are fitted, the driver sometimes feels that the car no longer handles as it did previously.Note: if for some reason 2 tyres of a lower speed rating are fitted, they must be fitted to the steering axle. The same reasons apply, i.e. TR tyres have a higher slip angle than HR tyres.
DO NOT BUY ‘DOWN’
From a safety point of view and to comply with insurance requirements, high speed steel radial tyres (HR, VR, ZR) fitted as original equipment must not be replaced with lower speed rated steel tyres (TR, SR) and definitely not with textile radial tyres.
DON’T FORGET THE SPARE TYRE
Particular attention must be paid to spare tyre tyres. Old or aged spare tyres should be used with caution, and replaced as soon as possible.
When replacing tyres, remember to fit the spare tyre onto the car. This ensures that the tyre will be used within a few years of manufacture.
It must be borne in mind that a tyre that has not been on the road and has spent 5 years or more in the boot of the car may have the appearance of new tyre. In actual fact, from a manufacturing point of view, the tyre is 5 years old. Anti-oxidants and anti-ozonants which tyre manufactures build into tyres to slow down ageing, gradually migrate to the tyre’s surface. This finally results in the rubber compound oxidizing, thereby losing its protective capabilities. The same applies to the various compounds used in the process of bonding the rubber to the steelcord. In both cases degradation takes place, irrespective of whether the tyre is being used or not.
Obviously, using the spare tyre when replacing tyres does not apply to vehicles which have space-saver tyre spares,
but it must be borne in mind that space-saver tyres have a restrictive speed which must be adhered to (see the sidewall of the tyre for details).usually a maximum speed of 80km/h is allowed.
NEW TYRES TO THE REAR
Many motorists and tyre outlets are of the opinion that, when only 2 tyres are replaced
on a car, they should be fitted to the front axle. This is not correct.
However, the current recommendation on the part of the Tyre Industry is, as a general rule:
NEW TYRES TO THE REAR. This applies to both front and rear wheel drive cars.
Primarily, the justification is increased safety, particularly in the wet, where it has been demonstrated that, with the partly worn tyres fitted to the rear, their diminished water dispersal capability leads to a greater tendency towards oversteer and thus loss of control. Similarly, straight line braking in the wet can be adversely affected. It is also arguable that used tyres are more prone to punctures and since it has now been established that rear deflations are more likely to cause loss of control, this is another reason for fitting new tyres to the rear.
As a secondary benefit for the owners of low annual mileage front wheel drive cars, the switching of the partly worn rear tyres to the front, enabling the new tyres to be fitted to the rear, creates a cycle which helps prevent their deterioration due to ageing/prolonged exposure. The rear tyres wear relatively slowly and leaving them in their original positions for a prolonged period, can result in the need to replace them before they are significantly worn.
Note: There are certain circumstances where the principle of NEW TYRES TO THE REAR does not or may not apply. For example:
- Where the front and rear tyre sizes are different.
- Where the two new tyres are of a lower speed rating.
- Where the characteristic rear concave wear pattern has developed to an extent
- that moving rear tyres to the front would affect the stability of the car.
- Where the “system” concept of directional front and asymmetric rear tyres is applicable.
- With certain combinations of winter and summer tyres.
- On certain four wheel drive vehicles where it would result in significant
- differences in tread depth. If in doubt please contact the tyre manufacturer.
FIT NEW TUBELESS VALVES WITH NEW TYRES
One of the main components of the tubeless valve is rubber, which will, as in the case
of tyres, deteriorate (perish) over a period of time. This is due to exposure to the sun, ozone, solvents etc. for added safety; replace the tubeless valve when fitting new tyres. Remember, the main cause of sudden tyre failure is dangerously low inflation pressure.
These very important items keep dirt and moisture out of the valve and prevent air leaking from the valve if the valve core is faulty.
The tyre/rim assembly is usually balanced when tyres are being replaced.
This procedure is vital to avoid unnecessary vibration and irregular wear on tyres fitted to cars, bakkies, caravans and trailers.
1. EXTEND TYRE LIFE
It has happened to almost everyone:
You buy a set of tyres, and before long one or two tyres are wearing out before the others. On today’s cars, this
applies to both rear and front types. The most common cause of unusual tyre wear is incorrect alignment.
2.SPOT TYRE PROBLEMS EARLY
Regular once in a fortnight inspection of the tyres will increase the chances of spotting any alignment or mechanical wear early. By doing regular checks, small problems can
be resolved before they become big, costly ones.
3. ENSURE SAFE DRIVING
Should the rear axle be misaligned, it will try to take over the steering function, causing the driver to correct with left hand or right hand down. This causes irregular and rapid tread wear on the front tyres and can also lead to vibration.
A periodic four-wheel alignment check makes sure your car handles properly and, more importantly, provides an opportunity for inspecting the suspension system for defective parts. The safe driving aspects may be the most important benefit of regular wheel alignment checks.
4. STRETCH FUEL MILEAGE
Fuel efficiency increases as rolling resistance decreases. Proper wheel alignment sets all four wheels parallel which, in turn, ensures minimum rolling resistance. This plus
proper inflation provides top efficiency for maximum kilometers.
5. IMPROVE HANDLING
Does your car pull to one side? Do you constantly have to adjust the steering wheel to keep your car traveling straight ahead? These and other handing problems can generally be corrected by a four-wheel alignment check.
6. GET A BETTER RIDE
Correct alignment will result in easier driving, enhanced comfort and stability as well as a greater degree of safety.
Follow the vehicle manufacturer’s recommendation in your owner’s manual. As a general rule your vehicle’s alignment should be checked every 20,000 kilometres or at least once a year.
You should have the alignment checked if you notice any of the following:
- Odd tyre wear, front or rear
- Steering wheel pulls to left or right
- Feeling of looseness or wandering
- Steering wheel vibration or shimmy
- Steering wheel hard to turn
VEHICLE VIBRATIONS AND RIDE DEFECTS
An imbalance in any rotating component of a car can cause vibration. In many cases it can be easily rectified by normal tyre balancing.
If, after accurate balancing, the vibration continues, then the problem will in all probability be centred in any of the following components – tyres, rims, prop shaft,
shock absorbers, engine mountings or half shafts.
Garages and tyre specialists are equipped to deal with this problem.
It is recommended that all the above factors be checked. The procedure for inspecting tyres and rims is as follows:
1. Check that tyres are inflated to recommended pressure.
2. Ensure the tyres are correctly fitted (se tyre fitting).
3. Warm the tyres by driving the car for a minimum of five kilometers.
4. Immediately jack up all four wheels and check tyres for radial and lateral run out.
5. When the run-out exceeds 1,5 millimetres, removes the tyre and check the rim bead seats for radial and lateral run-out. If this exceeds one millimeter, the rim should be rejected. If the rim is within limits, refit the tyre and by progressively moving it around the rim, establish the position of minimum radial run-out. If it is not possible to
achieve less than 1,5 millimetres, refer the problem to the tyre manufacturer.
6. If after completing step 5, the run-out has been brought to less than 1,5 millimetres,
the tyre should be re-balanced and returned to its position on the car.
Choosing tyres for your vehicles
There is no one fit for all purpose tyre, that is no tyre is perfect for all conditions, when choosing tyres, you should select ones appropriate for your vehicle and the kind of driving you will be doing
Tyres are designed to carry a specified amount of maximum load and to operate at a given maximum speed at a specified pressure.
Ensure you know the maximum load carrying capacity of your tyre and the speed rating of your tyre.
Do not just buy tyre by rim diameter alone, the height, section width and the overall circumference of the tyre are other important considerations for optimal benefit from your tyre performance.
Tyres and other compounded rubber components deteriorate with age and if cracking or crazing is present it may indicate that the rubber is perished and structural integrity cannot be assured. Therefore, tyre has expiration date, DN TYRE & RUBBER PLCrecommends that five years after the date of manufacture, you should change your tyre, whether in use or not. If you are in doubt about the condition of your tyres have them inspected by our experts in DN TYRE & RUBBER PLC .
How to check if your tyre has expired, check for a stamp like this: (1210) at the sidewall of the tyre The first two numbers ‘12’ will tell which week of the year the tyre was manufactured, and the last two number ‘10’ represents the year of manufacture, one year has 52 weeks, therefore 1210 means the tyre with this date code was manufactured in the twelve week of year 2010. Precisely in the fourth week of March 2010.
‘2505’ means the tyre was made in 25th week of year 2005.
Check all your tyres for safety purposes. Do not use expired tyres, they are likely to burst (especially when running in hot weather) because the rubber component may have hardened and cracked – Note this four digit number must be part of moulded lettering on the tyre sidewall and not hand written on moulded tyre, reject any tyre with altered date code or hand written date code. See tyre expert for advice if in doubt.
OBA AKRAN AVENUE, IKEJA, LAGOS STATE, NIGERIA
DN TYRE AND RUBBER PLC