Merityre Article Archive

Car tyres can be punctured and go flat. When it’ll happen is unpredictable, although it’s never at a convenient time, but you can change a wheel quickly and safely. Details follow, assuming you have the necessary equipment; you may wish to acquire some of the items mentioned.

There is a cardinal rule about wheel changing – never attempt it on the hard shoulder of a motorway or busy road. If reasonably close to an exit or turnoff, you can ‘nurse’ your car to a safe spot but if you can’t, call your breakdown service. Trying to change a wheel inches from a busy traffic lane is far too dangerous to contemplate.

Your safe spot needs to have a firm, smooth surface. Park your car, turn on its hazard lights and set up your warning triangle. Then find the equipment you need. Your car will have a jack and wheel nut wrench in its toolkit and the spare wheel will be either in or under the car. The handbook will tell you where the spare lives and how to extract it. Before starting, have any passengers get out of the car and stand well away from the car and passing traffic.

And so to work. Ensure your car’s handbrake is firmly applied and that the car is in gear or, if automatic, is in ‘park’. Then, chock the wheel diagonally opposite to the one you must change. Now to position the jack. Place it exactly where the handbook says – nowhere else will do – and raise the car just enough to check the jack is firmly seated. Remove the wheel trim if one is fitted, cutting through any cable ties retaining it. Alternatively, if there are any, remove the wheel nuts’ caps.

Loosening the wheel fastenings can involve applying considerable force. Ensure the wrench engages completely before starting to turn each fastening – they’re usually loosened anticlockwise. The car’s weight stops the wheel turning and all you do now is slacken the nuts or bolts. Always apply force downwards. You may stand up and press on the wrench with your foot but support yourself against the car. If one fastening is an anti-theft locking nut/bolt; there’ll be a fitting you can use with the wheel wrench to loosen it.

Next, jack the car up until the wheel with the flat tyre is off the ground – and never place any part of you between any part of the car and the ground. Now, remove all but the topmost wheel nut/bolt. Then, you can support the wheel, remove the last nut or bolt and take the wheel off. Note that a wheel and tyre combination can be heavy so make sure you lift it with a straight back and a firm footing.

Now to fit the spare wheel. Lift it into place on the hub, align the nut/bolt holes and fit the topmost one. Turn it finger tight then replace the remaining fastenings, also finger tight. Lower the jack and remove it, then fully tighten the fastenings in a diagonal pattern. You can now put the equipment you’ve used – and the offending wheel and tyre – back where it belongs.

All finished now? Not quite. Nowadays, wheel fastenings must be torque tightened to a specific degree. You also need to check the pressure in the spare tyre, adjusting it if necessary; and of course, have the punctured tyre repaired or replaced. The first two tasks should be carried out as soon as possible, for safety’s sake.

Two further points remain. The first concerns making wheel changing as easy and safe as possible. Refinements exist and you may want to take advantage of them, buying a pair of heavy gloves and a reflective waistcoat, and acquiring anything else you might need. You may also want to practise a wheel change at home, when it’s warm and dry.

The second and final point concerns ‘space saver’ spare wheels. Your car may have one and restrictions of speed (usually 50mph) and distance apply to them. In some cars, after a space saver spare is fitted, some dashboard warning lights may illuminate. Some ABS, traction control and automatic gearbox sensors can be confused by the presence of a space saver spare. Once again, your car’s handbook will tell you about this.

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Car tyres might seem to be pretty mundane things but a little research reveals some fascinating facts and figures about them…

The first inflatable tyre was made of leather

In 1887 John Boyd Dunlop developed the first practical pneumatic tyres; not a car tyres but ones for use on his son’s bicycle. However, his December 1888 patent only lasted two yours – Scottish inventor Robert William Thomson had patented the idea in France 41 years earlier.

Dunlop Tyres is the sole supplier of tyres to British Touring Car Championship for 2003 to 2006 and the V8 Supercars Championship from 2002 onward. The company also supplies tyres to the Deutsche Tourenwagen Masters and the American Le Mans Series.

In 1910, the BF Goodrich Company was the first to extend the life of car tyres by adding carbon black to tyres’ rubber compound.

In 1946, Michelin introduced the first radial car tyre.

Car tyres leave their mark. In the US, nearly 50 million pounds of rubber is worn off tyres every week. That’s enough rubber to make 3.25 million new car tyres.

Americans throw away between 240 and 260 million worn car tyres every year. Car tyres make approximately half a million cubic yards of landfill every year in New York State alone.

Not car tyres but truck tyres this time – it takes half a barrel of crude oil to make just one.

In Australia in July 1964, Donald Campbell set a new land speed record and took the car tyre to a new level. His car, the Bluebird CN7, had tyres 8.2 inches (21cm) wide and 52 inches (1.32 metres) high. Each tyre weighed 50 lbs (23 kg) and was filled with nitrogen at a pressure of 100psi. The car reached 403.10 mph.

A top Formula One pit crew can change all four car tyres and refuel in just 3 seconds.

Knowing how to maximize the life of your car tyres isn’t only a simple way of saving money in the long run. Looking after your car tyres also keeps you safe and legal; being neither can be very costly in more than a financial sense.

Run the tyres at the right pressure

This is a good starting point. Too little pressure wears the edges of the tread prematurely, lets the tyres flex too much and can cause overheating. Too much pressure increases the wear on the centre of the tread. Remember that, comfort and safety aren’t the only issues – running tyres at the wrong pressure is illegal.

Make sure your wheels are properly aligned

Misaligned wheels are another sure-fire tyre killer. Misalignment can make your tyres wear unevenly, wear the inside or outside edges and cause problems with both braking and steering. Moreover, a significant amount of such wear means you’ll have to throw your tyres away far too soon.

Drive sympathetically

 Your car may have traction control and ABS but you can still trash the tyres effectively despite them. How? By driving aggressively. Make sure you accelerate as gently as possible whenever you can and use the brakes carefully, not as though every stop is an emergency stop. Don’t forget that unnecessarily hard cornering shortens the life of your tyres. On a front wheel drive car, the front tyres wear more quickly because they have to transmit power to the road, and take steering and braking forces.

Drive slower

Consistently driving fast will wear out your car tyres sooner.

Choose the right tyres

You could get ‘long life’ tyres for your, which wear more slowly though they tend to be a little noisy. Tyres having a softer rubber compound will be nice and quiet and will wear more quickly. Always follow the tyre fitter’s recommendation of the best compromise for your needs.

Always keep your car under cover

All car tyres degrade over time. If you can keep your car in a garage, out of the sun, you can be sure your tyres will last longer. If you see a fine lattice of cracks has appeared in your tyres’ sidewalls after, say, five years, the tyres are unsafe and must be replaced.

Give your tyres a break

Remember that ‘traffic-calming’ measures shorten the life of your tyres but you can help your tyres out by driving intelligently. Always cross speed bumps slowly. Never straddle speed bumps. Instead, make sure that the only wheels on one side of your car pass over them. Keep an eye out for potholes, avoiding them where you can. When parking, make sure you never mount a kerb. Apart from making life easier for your tyres (and your wheels), these actions will prevent your wheels being knocked out of alignment, leading to wear – and possibly worse.

Using these proven top tips means your car tyres will last longer. This means you’ll save money by not having to replace your tyres before their useful life ends.

Have you ever noticed that tyres have moulded markings on their sidewalls? You’ll probably have spotted the maker’s name but does the rest mean anything to you? Can you tell what 205/70R14 88 T is all about? Perhaps not yet but understanding these codes could save your life. Why? If they show your tyres aren’t the right ones for your car you can arrange replacements.

We can start by breaking down the example above; the markings denote the tyre size, construction, and load and speed rating. How? Like this…

205 – This is the width of the tyre’s section in millimetres. The section 205 is a little over eight inches wide.

70 – This is the tyre’s aspect ratio, the sidewall’s height expressed as a percentage of its width. Here, the height is 70 per cent of the width. ‘Low profile’ tyres are fashionable so aspect ratio figures go as low as 30. Ultra-low tyres like this give tremendous grip but you pay for it, in a poorer ride quality and very little protection for your wheels against kerbs, potholes and speed bumps.

R – The next letter indicates the tyre’s construction. Here, R means radial.

14 – This next number is also simple. The figure 14 refers to the diameter of wheel the tyre will fit, in inches.

88 – Not so simple but extremely important. This tyre load index is a code for the maximum load capacity of the tyre when driven at its maximum rated speed. The figure 88 denotes a rating of 560 kilograms. Car tyres need to be correctly rated for load.

T - The last letter indicates the tyre’s speed rating. The letter T means the tyre can cope with extended use at a maximum speed of 118 miles per hour. The top speed rating is Z, which appear on tyres for cars capable of maintaining 149mph and above.

There are other tyre sidewall markings but most are for the attention of the tyre fitter. Markings show the tyre complies with EEC, ECE and US regulations. There might be an arrow symbol showing the tyres’ direction of rotation and there’ll be a ‘TWI’ mark indicating where the running surface’s tread wear indicator lies. There will also be a safety warning, perhaps the country of manufacture, whether the tyre is tubed or tubeless, and coloured markers showing the fitter where to fit the tyre in relation to the wheel’s valve.

All these are largely for the fitter’s information but there’s one marking you’re advised to note. The last four digits in the ‘DOT’ code reveal the tyres’ date of manufacture. Four-digit codes began after 2003 so if you see, for example, the code 3 0 0 8, the tyre was made in the 30^th week of 2008. You should never use tyres over 6 years old but a good tyre fitter won’t fit ‘new’ tyres that are beyond their sell-by date.

It’s true that checking your tyre markings could save your life, simply because underrated tyres could fail, especially under high speed/load conditions. The right tyres could save you something else –under-specified car tyres can invalidate your insurance.

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Your car tyres are all that keep you on the road and in dealing with heat, cold, wet and dry conditions and various surfaces, they have a hard life. Knowing what tyres are made of and how they’re built will help you understand how they cope.

Car tyres are built round an inner liner of halobutyl rubber sheet with additives that help keep air inside the tyre. The next part out is the body ply, which consists of three layers, one of rubber, one of reinforcing fabric and a second layer of rubber. Rayon, nylon, polyester or Kevlar have replaced cotton as the reinforcing fabric and it is the tyre’s one or two body plies that give it structural strength while making it flexible.

Externally, the car tyre’s sidewalls make it resistant to abrasion and chemical attack. Sidewall material includes antioxidants and antiozonants to help maintain strength and flexibility. This goes on in and behind the sidewalls on which you can see the tyre maker’s name and the various code digits that the confirm tyre’s size and rating.

The tyre beads lie at the edges of the sidewalls. They are bands of high tensile steel wire, coated with an alloy of copper or brass to prevent corrosion. The beads, inside their rubber casings, are strong points in tyres. They are what holds it firmly to the wheel and help seal in the air. The apex is the section that joins the bead and sidewall. Triangular in section, it is the cushion between the two.

Now for the belt package, the part that lies beneath the tread. This consists of a two rubber layers sandwiching a layer of steel cords. Here’s where ‘radial’ tyres gets their name; the cords run radially in the package. This steelwork gives the tyre the strength to resist dents from road impacts.

Like the sidewalls, the tread is a visible part of a car tyre. The tread compound is as important as the tread pattern. Tyres made of hard compounds wear well, while softer ones grip the road better. ‘Compromise’ is the watchword.

How are car tyres built? This process starts by wrapping the inner liner, body plies, sidewalls and beads around a special drum. The belt package and tread are then added. During this process, the components are ‘spliced’ together, before the ‘green’ (uncured) tyre is blown up and shaped. These tasks are generally automated.

Now comes the curing process. Though spliced, the various parts of the tyre have yet to be bonded together. This involves applying heat in a mould, to speed the chemical reactions between the different materials. During this stage, a rubber bladder, the equivalent of an inner tube, is used to force the tyre into the mould. Unlike an inner tube, the bladder is filled with steam, hot water or an inert gas. Tyre curing is done at very high pressure – about 350 psi – and at around 350 degrees farenheit. A passenger car tyre can be cured in around 15 minutes. Finally, the tyre is run on a mock road surface, to test for imbalance and local inflexibility. All tyres are visually inspected, some are even X-rayed.

So as this shows, there is more to a car tyre than meets the eye. It’s no wonder car tyres are tough enough for the tough job they have.

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Most garages selling car tyres offer a wheel alignment service but not all customers know what this is or what it’s for when they come to buy new tyres. As its name suggests, wheel alignment is to ensure that your car’s wheels are parallel to each other and perpendicular to the ground. Aren’t the wheels like this anyway? They should be but wear and tear, especially that aggravated by speed bumps, can put the wheels out of alignment, as can damage caused by touching a kerb or hitting carriageway debris. Misalignment can cause a braking car to pull to one side or the other, give inaccurate steering and drastically shorten tyre life.

What is involved?

There are usually three factors to be checked and if necessary, adjusted.

The first test is to ensure the wheels are vertical as viewed from the front of the car – this is checking the camber angle.

The second check is slightly more complicated. A car’s front wheels are turned from side to side when you steer. Imagine looking at a front wheel from the side of the car. If you had X-ray vision, you’d see that the steering pivot isn’t vertical but leans back at the top, towards the rear of the car. This is the castor angle, which, if out of adjustment, can cause all manner of strange steering behaviour when you drive.

The third and last check is the tracking. Again looking from the front, the car tyres are usually ‘cross-eyed’, they ‘toe-in’. This is so slight you can’t see it but the setting is important. The tyres are generally set to toe-in so that the when the car is driven, the forces acting on the front wheels and suspension make the front wheels run parallel to one another. If the tyres ‘toe-out’ (think Marty Feldman) through misalignment, or toe-in too much, steering accuracy will suffer and tyre wear will increase. On many cars it’s also possible for the rear wheels to be misaligned.

Should car tyres be worn through misalignment and/or have worn or damaged steering or suspension parts, or even the wrong tyre pressures, correct alignment could be difficult or impossible. The technician will ensure you know about what, if anything, needs adjusting, repairing or replacing.

Man at Work

Wheel alignment used to be achieved with mirrors, weights and string. But such paraphernalia is old hat now; technicians usually use computerised, laser-equipped measuring installations. With these, they can measure and adjust wheel alignment quickly and extremely accurately. So while you enjoy a refreshing cup of tea or visit the shops, your car’s wheels will be aligned with precision, which will extend the life of your car tyres.

What is involved?

How can you keep them this way? Simple – all that’s needed is a little care when you drive. Avoid any debris on the road and watch out for potholes. Take your time over speed pads and straddling speed bumps damages tyres and suspension; drive so that only the wheels on one side of the car go over the bump. Most importantly, when manoeuvring, do not hit kerbs.

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Driving carefully by not over accelerating, braking hard and sharp corning is the best way to extend the life of your car tyres. This article has five other tips to keep your car tyres in good condition:

1. Correct Tyre Pressure

Regularly check your car tyres are not under or over inflated.

Under inflation causes greater flexing of the rubber, increasing the operating temperature and reducing the tyre’s lifespan.  The wear on the edge or shoulder of the tyre is increased and damage can be caused to the vehicle’s suspension when driving over a pothole.

Under inflation also results in poor fuel economy. Increased rolling resistance makes a car engine work harder and uses more fuel.

Over inflation is equally bad by increasing the wear in the centre of a car tyre’s tread; an area important for protecting the tyre against impact damage.

To find the recommended tyre pressure check the owner’s manual or look for a plaque on the inside of the fuel flap.

2. Balance and Alignment

Whenever your car tyres are repaired or replaced make sure they are correctly balanced when remounted on your car. If not this will cause vibrations, increasing tyre wear, damaging suspension and leading to driver fatigue.

Correct alignment is necessary to have the steering, suspension, wheel components and car tyres all working in harmony to achieve the optimum performance from your vehicle.

It doesn’t cost much for your local garage or car tyre specialist to check the vehicle’s balance or alignment.  Without it the resulting cost of repair will be far greater.

3. Inspection

A visual inspection once a month does not take long and is important to maintain your car tyres in a safe condition.

Check the tread depth. Most tyres have a tread wear indicator built into them. Look for a horizontal bar of rubber located between the tread patterns, at a depth of 2mm.  When the height of the tread wears down to the height of this bar it is time to replace your car tyres.

Check the car tyres for any unusual bulges or lumps as these are often a sign of internal damage. Inspect the tread and sidewall rubber for any signs of cracking. If found change the tyre as soon as possible as cracking can cause a blow-out.

Remove any stones and other objects stuck in a car tyre’s tread. If a nail is found embedded in the rubber, do not remove as the tyre will rapidly deflate. Instead take the tyre to a specialist who may be able to repair the puncture.

4. Repairs

Don’t risk driving on a car tyre that is losing pressure. Take it to a specialist who will give the tyre a complete inspection and make the decision whether it can be repaired or replaced.

Driving on a flat tyre for even a short distance will damage it beyond repair.

Never try repairing a car tyre yourself. This should be handled by a trained professional.

5. Tyre Rotation

The weight of a vehicle is not evenly distributed on all of the car tyres. By regularly rotating the tyres their lifespan is extended and uneven car tyre wear is avoided.

Visit a car tyre specialist for further advice and to check the condition of your current car tyres.

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You don’t have to be an automotive expert to spot potential problems when buying a new car. Here are five visual checks that will help you make the decision whether to buy a second hand car.

1) Car Tyres

Ask when owner last fitted new car tyres. Check the tread depth. If it’s below 3mm the car tyres will soon need to be replaced. The legal limit for tread depth is 1.6mm.

Look for uneven wear. This may indicate a problem with the car’s steering, suspension or brakes.

Check the car tyres for any unusual bulges or lumps as these are often a sign of internal damage.

Inspect the car tyres’ sidewall rubber for signs of cracking. Crazing and cracking due to weather exposure usually becomes evident on car tyres that are more than five years old.

Don’t forget to check the spare tyre.

2) Vehicle Identity Number

The vehicle’s identity number (also known as the VIN number) is a 17-digit figure that can be found on the car’s engine, at the base of the windscreen or on the driver’s door. Check that it matches the number printed on the car’s registration document and logbook.

Don’t risk purchasing a car if the VIN numbers do not match or cannot be found in any of the specified locations.

3) Bodywork

Check the car’s paint finish and look for any signs of repair. It is easier to spot dents and imperfections by looking along the side of a car.

Compare the seams where the body panels join. Any differences may indicate the car has been repaired after an accident.

It is worth lifting the carpet in the boot to look for any evidence of hidden repairs and check the engine for any signs of welding.

4) Oil

Use the dipstick to check the vehicle’s oil. If the level is low this may indicate a leak or the engine may be burning oil. Have a look underneath the car for further signs of leakage.

The oil on the dipstick should look relatively clean and golden. Black and tar-like oil indicates it has been a while since it was last changed.

5) Mileage

‘Clocking’ is term applied to the illegal practice of winding back a car’s mileage counter.

Look for any evidence that the dashboard has been tampered with. Check the steering wheel and driving pedals for signs of wear and see if this tallies with the car’s mileage. A shiny, worn steering wheel is often a giveaway for a vehicle with low mileage.

If in doubt ask to see the MOT certificates as these will have the car’s mileage printed on them. If not available then there are companies who can provide this information, usually for a fee.

For further advice about car tyres, bodywork or checking the vehicle’s documentation consult a specialist or visit your local garage.

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Car tyres are the only point of contact between a vehicle and the road. Keeping them in good condition is essential for safe driving and achieving the optimum performance of your car.

Here a ten car tyre tips:

1. Regularly check car tyre pressures. By spending an extra 5 minutes at the petrol station checking your car tyres are inflated to the manufacturer’s recommended pressure, fuel economy can be improved by 10%.

A car tyre that is inflated below its recommended pressure will wear faster because of its higher operating temperature and the extra flexing of the rubber. This causes deterioration of the tyre casing and rapid wear of the tread shoulders.

Over inflation can also increase wear due to the decreased size of the contact area between the car tyre and the road. It accelerates the wear in the centre of the tread, an area important for protecting the tyre against impact damage.

2. Always carry a spare. It is not a legal requirement but you’ll be thankful you have one when a tyre gets a puncture in a remote location. If using a compact spare tyre remember not to exceed 50 mph and replace it at the earliest opportunity.

3. Check the car tyres for any unusual bulges or lumps as these are often a sign of internal damage. Inspect the tread and sidewall rubber for any signs of cracking as this can cause a tyre blow-out.

4. Keep the tyre valves clean and always remember to replace the dust cap.

5. Avoid driving over of potholes in the road. The extra flexing of the rubber will hasten the tyres deterioration.

6. Remove any stones and other objects embedded in a car tyre’s tread. If you find a nail do not remove it as the tyre will rapidly deflate. Instead take the tyre to a specialist who may be able to repair the puncture.

7. Keep the car in a garage if possible.  Weather exposure causes crazing and cracking on the car tyres of vehicles kept outside.

8. Take care when using a pressure washer as it can cause damage to a tyre’s sidewall. Only use at a safe distance.

9. Try to replace all four tyres at the same time. If this is not possible replace either the two front or the two back tyres together. It will prevent uneven wear which can affect the vehicle’s handling.

10. Consult a car tyre specialist before replacing a tyre. They will advise on the right choice of tyre according to your car’s make, your budget and your driving circumstances.

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Car tyres in good condition are not an excuse for driving fast in heavy rain. There is a high potential of aqua planning, significantly reduced visibility and you may encounter a flooded road.

This article provides advice about driving in heavy rain and what to do if you encounter a flood.

During the winter months regularly check your windscreen wipers to ensure they can cope with heavy rain. If the rubber has deteriorated, replace it immediately. It’s very simple to do or local garage will be happy to help.

If caught in a downpour then double the distance between yourself and the car in front. This is because stopping distances are increased on wet roads as your car tyres struggle to find grip. Visibility is also reduced which will lower your reaction time if required to brake suddenly.

Even today’s modern road surfaces struggle to cope with a heavy downpour and standing water is a potential hazard. Try to avoid standing water and slow down. If you don’t there is a high risk of the car aqua planning.

Aqua planning occurs when the car tyre’s tread pattern is unable to disperse enough water to maintain a point of contact between the tyre and the road. This makes the vehicle uncontrollable with the loss of steering, grip and a sensation of driving on ice. It can be a very frightening event as I’m sure anyone who has experienced it will agree. The best advice when it happens is to hold your steering wheel lightly and lift off the accelerator until your car tyres regain their grip.

If you’re unlucky enough to break down in heavy rain, stay with your car but check you are not in a location that is at risk of flash flooding. Your engine may have been affected by the water and in many cases the car will restart when it has had a chance to ‘dry out’. If you have called for assistance do not prop the bonnet open until help arrives. This will cause the electrics to become rain-soaked and the car will be even harder to restart.

The rain may be so heavy that you experience a flooded road. The AA provides some good advice about how to deal with this:

1. Do not drive through flooded water unless you know how deep it is.

2. Stay in the middle of the road. This is known as the crown of the road and should be where the flood water is shallowest.

3. Drive slowly to avoid creating a bow wave, which can cause neighbouring houses to be flooded.

4. Pass one vehicle at a time through flood water. Allow the oncoming traffic to pass first.

5. Do not risk driving through fast moving water as your car can easily be swept away.

6. Driving at speed through a flood can cause expensive damage. Even a small quantity of water sucked into the engine through the air intake will cause serious damage.

7. As you drive through the flood water, keep the engine revving by slipping the clutch. This prevents water in the exhaust which may stall the engine.

8. Test your brakes as soon as you leave the water.

Car tyres in good condition will be able to cope with most wet driving surfaces. But with heavy rain or a sudden downpour extra care must be taken to avoid a possible accident or injury.

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