some good tips!!!

[R-34]

Many people stick to the vehicle manufacturer's recommendation and, in general, that is the best option. However, there are often a number of good reasons for deviating from this recommendation:

1. You may want to upgrade your tyres to a higher speed rating. In this case, you should add 10 per cent to the maximum speed of your car, and then choose a tyre suitable for this speed.


2. Most cars are sold with tyres with good all-round ability. Tyre life is balanced against grip, good wet road ability is balanced against noise, etc, and you may want to change in favour of a bias that suits your preferences

. It may be that the tyres approved 10 years ago for your car are no longer in production, so exact replacements are not possible.

4. You may want to change your wheels and therefore find new tyres to suit. No tyre can have all the qualities a good tyre should have, because some of the qualities oppose each other. The hard tyre that lasts a long time cannot grip like a soft tyre; the prominent tread that prevents aquaplaning is noisy on a dry road and has increased rolling resistance. None of these features is utilised to its fullest extent in a tyre selling at a low price, but some of the more expensive tyres are excellent compromises.

The three main types of passenger car tyres available are:

1. A tyre for popular family cars. This would be a compromise tyre, with good ratings for tread life, directional stability, steering effort, rolling resistance, noise levels and wet road performance.

2. A tyre for top luxury cars. The qualities would be slanted towards comfort and low noise levels, at the expense of tread life and initial cost.

3. An out-and-out sports tyre, with the emphasis on grip and the ability to stay cool at high speed. A further choice is between cross-ply and radial-ply tyres. The cross-plies are cheaper, flex more, have a higher rolling resistance, and a shorter life, and are gradually disappearing from the marketplace. Radials suffer less tread distortion, grip the road better, last longer, and deliver better fuel consumption.

[R-34]

Tires should be inspected often, and the following list highlights some of the faults to look out for. If any of these conditions are present, consult a tyre expert.

1. One-sided wear. This takes various forms. A regular smooth band of wear all around the tyre on the inside or the outside of the tread is a sign of incorrect camber. Too much toe-in causes irregular one-sided wear.

2. Tread-centre wear. Regular wear of this kind is normally a sign of high tyre pressure. Driving fast for long distances may cause this on low-profile tyres, because traveling at 120 km/h wears a tyre out twice as fast as travelling at 70 km/h.

3. Inner- and outer-edge wear. If both inner and outer edges are worn, it usually implies that the tyres have been run at too low a pressure at normal speeds.

4. Irregular bald spotting. Known as cupping, this is usually caused by worn shock absorbers, worn suspension bushes, or even loose wheel bearings.
The importance of the correct pressure can not be over-emphasised. If the pressure is too low it affects the tyre in a number of ways.

As speed rises, excessive contact patch deformation leads to a wave being formed in the tread, which generates excessive heat, causing structural damage or even tyre failure. The extra flexibility will affect steering behaviour, directional stability, durability and rolling resistance. Even occasional low pressure driving, or periodic vehicle overloading, may cause damage that only shows up much later as a blowout.

Tyre pressures, including the spare, should be checked at least once a week, before the tyres have heated up, ie before 10 km have been driven, using a good pressure gauge.

Missing valve caps should be replaced, since they are there to prevent dirt from clogging the valves, which could cause a loss of air pressure.

Tyre rotation is a very contentious area, with some companies recommending it, other companies saying nothing, and BMW for one advising against it. Rotating the tyres regularly evens out the wear, but eventually all the tyres will have to be replaced at the same time, which is expensive.

[R-34]

Dampers, usually incorrectly called shock absorbers, wear out slowly, which is why changes in handling often pass unnoticed, until there is a sudden failure. It follows that, while you use your car in the normal manner, the roadholding, braking and comfort are gradually deteriorating.

The only sure way to test these items is to remove them from the car and plot the movement on a damper dynamometer, but this is not practicable, so a good alternative is to get an experienced technician to drive the car and examine the tyres. He will drive the car uphill on a bumpy road under power to feel for signs of wheel hop, and will also examine the tyres for uneven tread wear. He will take a close look at the units for signs of fluid leaks, rust, and damage to the piston rod, or mounting body.

Many service centres have so-called "shock absorber test machines", but they often give results that, taken on their own and interpreted by an unskilled operator, are far off the mark.

The familiar bounce test ­ depressing the suspension at each wheel in turn, and taking note of how the car bounces ­ needs interpretation. If the car dips and then recovers immediately without any further bounce, the damper may be fine, but could still be below par when it has to damp small movements.

http://www.cartoday.com/images/car_magazine/booklets/diy/Shockhi.gif

[R-34]

Statistics show that cooling problems are high on the list of roadside complaints motoring organisations have to attend to. Many of these problems can be prevented by proper maintenance, and there is a lot more to it than just making sure there is enough water in the radiator.

Modern engines need a good anti-freeze. The resulting mixture is a cooling fluid that acts as a corrosion-inhibitor, in addition to its ability to lower the freezing point and raise the boiling point. The concentration should be as specified on the container, and nothing will be gained by adding more fluid to the radiator, but it may be harmful if the mixture contains more water than specified. It should be changed every 18 months because the chemicals gradually lose effectiveness.

The water level should be inspected every week; investigate any unusual drop in the level. It may be an external leak that you can fix by replacing a hose, or taking the radiator to a specialist radiator repair shop, or it may be a weak radiator cap spring or gasket. It could also be a leaking cylinder-head gasket, but in this case there would be some symptoms that you should look out for. Bubbles arising from an open radiator is one of the signs, and water in the oil is another.

Fan belt tension should be checked and adjusted, as discussed elsewhere, while the fan blades are visually examined for cracks, and the hoses examined for signs of cracking and the soft feeling that comes with old age. On an older vehicle, the Welch plugs, round steel discs that cover inspection holes in the head or cylinder block castings, should be checked for signs of external rust. They tend to spring a sudden leak, often with disastrous consequences. Grass seeds, and other objects sticking to the radiator, must be carefully removed from time to time.

Many people, even mechanics who should know better, tend to remove the thermostat at the first sign of overheating. The purpose of the thermostat is to
ensure rapid warm-up as well as to keep the engine at a near- constant temperature, so it follows that if it is removed engine wear will increase and the fuel consumption will suffer, because both of these aspects depend on the
engine being at its proper operating temperature.

Water hoses should be examined (when cold!) from time to time. A hose in good condition feels firm, but a hose on its way out is soft and squelchy.

[R-34]

We know, from reader complaints and motor industry feedback, that many alignment centres are NOT doing the job properly. Not only do some shops rush through the work, but they often use the wrong specifications, because they have out-of-date information, or use their own pet values.

A limited amount of alignment can be done at home, especially on older cars, where it is usually possible to adjust castor, camber and toe. However, many modern workshop manuals state that only the toe is adjustable, and if any of the other settings is out, then some suspension parts are bent and should be replaced. In theory, the toe is the value by which the front wheel centrelines converge (toe-in) or diverge (toe-out), expressed in millimetres, as measured across the track.

Most measuring devices use the outside edge of the tyres as their reference, but you can also measure this at home by using the inside edge as a reference. Simple and inexpensive toe adjustment gauges can be bought, or simply use the extension facility of an old umbrella to make up a gauge. Keep in mind that the tyres have to be at the correct pressure, the vehicle has to be on level ground, and any link-rod adjustment must be done in such a way that the steering wheel position remains central. This is not always easy, even if somebody holds the steering wheel rigid while you make the adjustments.

Camber can also be checked with a plumb-bob draped over the top of the wheel in the straight-ahead position, but you would need either a large protractor or a knowledge of high-school geometry to convert the distance into an angle, because camber is usually given in degrees.

Castor cannot easily be checked at home, but suitable DIY gauges do exist.
Unfortunately, full electronic front- and rear-wheel alignment, as specified
for many new models, is beyond the scope of the home mechanic. You simply have to bite the bullet and go to a good alignment shop. But ask around first; don't trust lady luck.

Wheel alignment normally refers to the toe, camber and castor angles. Toe is defined in the text, while the camber and castor angles are shown below. V is the vertical centreline, S is the line about which the wheel swivels, W is the wheel centreline, A is the kingpin inclination angle, B is the camber angle and C is the castor angle. All the angles are exaggerated for the sake of
illustration.


http://www.cartoday.com/images/car_magazine/booklets/diy/FRONT%20SUSPENSION.GIF

[R-34]

Poor consumption could be due to one of the following reasons:

1. You've been listening to somebody bragging about your model's consumption and there is, in fact, nothing wrong with your car.

2. The engine needs a good tune-up. If it pulls strongly, idles smoothly at the correct speed and starts easily, then there can't be much wrong with it. On the other hand, if it misbehaves in any way, this will usually show up in a worsening fuel consumption, and a good
service should set matters right.

3. The brakes may be binding. This can be checked by stopping
on a slight incline and seeing if the car will run forward when you release the brakes. If it doesn't run forward the most likely reason is a binding handbrake, or rear drum brakes. Disc brakes often make a slight scraping sound when coasting, which is normal.

4. The wheel alignment may be out, and on modern front-wheel drive cars the rear wheels also have to be set, in many cases. This can be checked by inspecting the tyres for abnormal wear patterns, as discussed elsewhere in this booklet.

5. The tyres may be running soft, ie the pressures are too low. This will show up as an unworn strip in the centre of the tread area.

6. Other drag-inducing elements are roof carriers, even when they're unladen, and aftermarket spoilers.

7. There may be a fuel leak in the line, either underneath the car or under the bonnet. Look at your garage floor after you've pulled out to spot such leaks.

8. Examine your driving style. One of the oil companies has found that in its own fleet the difference between the worst driver and the best in terms of fuel consumption on similar models is something like 15 per cent. The following habits all waste fuel; frequent full-throttle acceleration; keeping the choke operative after the engine no longer needs it; frequent braking in traffic because of bad planning; cruising at high speed.

9. The engine may be running too cold because the thermostat has
the wrong heat value or has been
removed. This will also increase engine wear.

http://www.cartoday.com/images/car_magazine/booklets/diy/Rack.gif

[R-34]

Sooner or later you have to take your car to a garage, and the best way to handle the situation is to give them as little leeway as possible by being precise in what you want them to do to your car.

For example, don't say, "Cure the misfire", which means they could deliberately misunderstand the instruction to give your engine an overhaul, but rather say: " 'Phone me if the misfire is not due to something small". Give them written instructions to ,phone you before tackling anything expensive, try to get a written quote and, if you're a female, always take a man with you, because they'll assume you know nothing. If you have the slightest doubt about their honesty, or if some of their excuses are difficult to believe, then contact the manufacturer of the vehicle. He has a representative in each area to look after your interests, from the manufacturer's point of view, not from the dealer's point of view. This is especially true of warranty repairs, because some dealers will try to avoid such work, by delaying the customer with ridiculous excuses.

Buying parts has also become a hazardous enterprise. Fake parts, ie parts that look and pretend to be genuine, but are inferior, are entering the country at an alarming rate. Generally these are fast-moving items such as filters, spark plugs, tyres, and even windshields. Between the fake and the quality factory-approved part is the non-franchised part, which does not pretend to be genuine, and whose quality varies from shocking to excellent.

How can one decide whether a part is genuine or of good quality? One of the best ways is to only buy parts from a reputable spares outlet. A good mechanic will know from his own experience which dealers can be trusted. Another way is to inspect the part, including its packaging, very carefully, because inferior
workmanship is often easy to spot. Beware of ridiculous claims, and pseudo-scientific explanations that the salesman himself doesn't understand.


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[Tuong-Vi]

thnx R.. good info