Caring for the Tyres

[Saaber]

Friday, January 04, 2002 By Chips

 

Tyres, to most motorists, are parts of the car which they assume require no maintenance. The only times they might look at the tyres are when there's a need to add air, when they have a puncture, or when it's time to change the tyres.

 

 

 

While it's true that today's tyres are so well designed that they can take a lot of abuse, they still need some caring and attention if you want to obtain your money's worth in mileage and performance.

 

 

 

The first important consideration in tyre care is that they are the right ones for your car. Fitting fat tyres may get you 'macho' looks but there's the possibility that the tyres will rub against the wheel arches and get damaged. There are also owners who want to get a sportier look with extra low-profile tyres but bear in mind that such tyres have a short sidewall. This means that the chances of the rim getting dented in bumps and potholes are higher. Always consult the Owner's manual for the recommended sizes or ask your tyre dealer.

 

 

 

Pressures

 

Without air, a tyre is useless so the pressure must be checked periodically. If your car is new, tyre pressure information can usually be found in the Owner's Manual or a sticker in the are of the driver's door.

 

 

 

The recommended pressures are generally on the low side for comfort and a few psi more won't affect performance negatively or reduce ride comfort. For most family saloons, 190 kPa about (27 psi) is reasonable.

 

 

 

Bear in mind that front-wheel drive cars should have slight higher pressures in front than at the rear while for rear-wheel drive cars, the reverse applies. This is to compensate for the inherent handling characteristics of both configurations.

 

 

 

Tyre pressures should be checked only when the tyres are COLD as various factors can cause individual tyres to heat up - and therefore increasing pressures - differently. Thus the best time to check is in the morning before moving off.

 

 

 

Check pressures often (once a week is a good idea) and see that the valve caps are screwed on properly. Do not rely on looks to determine if a tyre is properly inflated as today's radial tyres always tend to look under-inflated because the softer sidewalls bulge out more. Ideally, you should use a reliable pressure gauge to check the pressure - the old 'kicking the tyres' method is definitely out! And while you are down by the tyres, take the opportunity to look for cuts or nails that could eventually allow air to leak.

 

 

 

Rotation

 

Because the front tyres also steer the car, they scrub the road a lot more than those at the rear. This causes their wear rate to be faster and in order to even out the wearing between front and rear, regular tyre rotation is recommended.

 

 

 

Most manufacturers suggest certain intervals but generally, tyres should be rotated every 10,000 to 13,000 kms. There are various patterns of rotation but the simplest to remember would be to exchange the front left wheel with the rear left and the front right with the rear right. Don't forget that your car has five tyres so include the spare in your rotation pattern as well.

 

 

 

Balancing

 

Imbalance of the tyre and wheel will cause vibration as the unevenly distributed weight spins around. This could affect the overall performance of the tyres even if you can live with the shaking steering wheel (in really bad cases, the whole car also shakes).

 

 

 

The imbalance comes mainly from the tyre wearing out and usually not in an even manner. It is therefore important to have the tyre/wheel balanced from time to time. Most tyre shops and some service stations offer the service and remember that if the vibration persists, you can ask them to do the job again.

 

 

 

There are two types of balancing methods, the more common one having the wheel mounted on a spindle. This is linked to a computer that analyses the centrifugal forces created as the wheel and tyre are spun around at speed. Areas which generate erratic out-of-balance forces are identified and a weight is clipped to the wheel (stuck on if it's an alloy sports rim) to offset the imbalance.

 

 

 

The computerised machines are pretty accurate these days and, in about 90% of the cases, there is no need for the other type of balancing, ie on-car balancing. In this method, the wheel is mounted on the car and its balance is checked by a stroboscopic light. This method is often used for difficult cases where the suspension assembly also has some influence.

 

 

 

Alignment

 

Keeping the wheel geometry in the correct, factory-recommended orientation is very important if you want even wear and proper handling. Bumps and normal wear and tear in various components usually cause a wheel to go out of alignment after a while and when that happens, the tyres do not roll straight ahead but might drag along the road sideways. This naturally causes the tread to wear out faster. Misalignment can also cause different areas of the tyre to wear out faster and if left unchecked, will render the tyre useless before long.

 

 

 

Many of the larger tyre shops have sophisticated alignment machines which can do the job with extreme accuracy. The machines are computerised and some have alignment data on most of the popular models of cars. It is recommended that alignment be carried out every 6 months or so, more frequently if you travel on bad roads.

 

 

 

Changing tyres

 

Unless severely damaged, a tyre is usually changed when its tread is worn down to the point where the drainage grooves are too shallow and water cannot be channeled out efficiently. Contrary to what some people may tell you, using a tyre until you the rubber is entirely worn out is positively not in your best interests - and don't compare to the 'slicks' of F1 cars which are used only in dry conditions.

 

 

 

Virtually all tyres have what is know as the 'Tread Wear Indicator' (TWI). This is molded into the tread and becomes apparent when the tread is worn down to the minimum recommended. At this stage, the channels in the treads appear to be blocked by little 'bridges' between the blocks of rubber. If you look along the sideways just where the tread pattern ends, you'll see either a small triangle or the letters 'TWI' which correspond with the positions of the small 'bridges'. That's a warning to head down to the nearest tyre shop and buy new ones.

 

 

 

Goodyear Malaysia also has a simple test to help motorists determine when a tyre should be replaced. They recommend that a 20 sen coin be slotted into a tread groove, with the '20' upside down and facing towards you. If you can see the word 'MALAYSIA' in full, then the tyre needs to be changed.

 

 

 

Trying new sizes

 

To some extent, you can choose a slightly broader tyre (bearing in mind that this could upset the speedometer reading slightly) but never choose one narrower than the manufacturer-recommended size. It is, however, always best to select the same size, if not brand, of tyre unless you wish to change from the normal 80-series to 70-series or 65-series(a popular switch with no major complications on speedometer readings).

 

 

 

And unless you are absolutely sure of what you are doing, mixing tyre types can be very dangerous because you will be introducing different tyre characteristics either at the front or rear of the car. This could be hazardous under certain conditions. It is possible to have wider tyres at the rear than at the front but do so only if you have proper technical advice or really know what you are doing. The technical personnel in many leading tyre companies will be able to offer good advice.

 

 

 

Running-in tyres

 

Like a new car, new tyres need a bit of running-in. Initially, they may feel slippery because of a protective silicon coating applied at the factory but this wears off after about 60 kms. Generally, you should drive smoothly

 

without hard or sudden braking and maintain proper pressures. Sudden bursts of acceleration are not advisable when the tyres are still new.

 

 

 

Extending tyre life

 

Your driving habits will be important in determining how long your tyres last. Fast wheel-spinning starts and panic stops will definitely accelerate wear; the latter resulting in flat-spotting.

 

 

 

The road conditions in some places are already bad enough so don't abuse your tyres unnecessarily by charging over kerbs and potholes. Hard cornering is also detrimental to tyre life and you should think of the squeal as your tyres ' 'cry for mercy'.

 

 

 

Heat is a big enemy of tyres and a tyre's life can be dramatically shortened through under-inflation. Depending on how comfortable you like your ride to be, inflating your tyres anywhere between 190 kPa (27 psi) and 225 kPa (32 psi) is acceptable. The higher pressures will sharpen handling and improve fuel economy a ee bit, but can increase bumpiness a bit.

 

 

 

Over-inflation is not a good idea, not only because the ride will be intolerable but also because the centre of the tyre will wear out faster. This is because the tyres curvature will be greater due to the higher pressure,

 

raising the edges off the road. Traction can also be reduced for the same reason.

 

 

 

Punctures

 

Today's tyres are more puncture-resistant and even when pierced by small nails, they don't deflate immediately. You could go for a few weeks with a nail in your tyre and would not realise it until you checked with a pressure gauge or woke up one morning to find the tyre flat. So check the pressures often as a persistent drop in pressure is an indication that there's a slow leak somewhere. Driving on an under-inflated tyre, as mentioned earlier, will make it wear out faster and more unevenly too.

 

 

 

The moment a tyre loses all or most of its air, it should be replaced by the spare immediately. Prolonged driving on a deflated tyre, even if it is possible, could damage it beyond repair. It's therefore important to ensure that your spare tyre is always properly inflated and in good condition. Many people often neglect to keep the spare properly inflated and are in a fix when they do need to use it!

 

 

 

Most punctures and cuts up to 6 mm can usually be repaired but you should do so only at reputable tyre shops. Plugs or patches are used, depending on the nature of the puncture. Punctures larger than 6 mm and punctures in the sidewalls cannot be repaired satisfactorily and should be discarded.

 

 

 

Wheel alignment should be done every 6 months.

 

 

 

Hard braking wears out tyres faster and more unevenly

 

 

 

Replace tyres with treads that are too shallow

[Raycsk]

To add some more info...

 

Most tyre tend to turn grey after some time. This may appear as a uniform colour or patches. Rubbing with your fingers, you will find that this grey layer comes off.

 

This grey stuff is wax that is mixed into the rubber compund when manufactured. The wax is an anti-UV protectant. Without it the tyre will dry and crack and some cases crumble.

The wax is emnbedded deep into the rubber and migrates to the surface over time via temperature and centrifugal action.

 

Most aftermarket tyre shine and so called protectant actually remove this wax layer. Avoid tyre conditioners that contain Petroleum based solvents. Rather look for products that contain polymers and emulsifiers.

 

Sadly most products do not show the chemicals used. If they smell like petrol or benzene, avoid.