State of Readiness: Are Winter Car Tyres Worth Having?

Great Britain has a temperate climate. That no one seems to have told the climate about this is by the by: the sort of conditions we experience every year are officially classified as being ‘temperate’. Yet facts are facts and like all of us, our car tyres have to cope with markedly different climatic conditions. In high summer, the mercury can hit the 30-degree mark, in midwinter, it can fall well below zero. Can a single set of tyres handle this? Let’s find out.

In winter, accidents increase by a less-than-modest 267 per cent. This begs the question of what is a winter tyre? More appropriately, what is it about winter tyres that make a difference? Car tyres conform to a given set of physical characteristics – they must, to be safe, legal and functional. However certain elements among these characteristics can be ‘tweaked’ and it is these differences that make a winter tyre.

The first tweak is to the tyre’s compound, the mix of rubber used in its construction. Water freezes when the ambient temperature is low. Car tyres don’t freeze but they harden, especially when the temperature falls to under seven degrees Centigrade. Winter tyres have a softer compound through containing more natural rubber than conventional tyres and this improves their grip in cold conditions. This specifically softer tread element gives a significant reduction in stopping distance. It also has a knock-on effect in performance terms. Because winter tyres offer superior grip, your car’s cornering, acceleration and braking benefit, as does your confidence.

The next point contains a paradox. After all, isn’t it true that car tyres with a softer compound will wear faster? In a word, no. In fact, conventional tyres have a particularly hard time in winter, pun intended. In practice, they wear out up to 20 per cent faster in cold conditions, so winter tyres can save you money. Some suggest that winter tyres’ enhanced grip means that your car’s engine has less work to do than with conventional tyres, so that fuel economy is also enhanced. This may be a moot point but a Finnish tyre maker says of its winter product, ‘Lower fuel consumption by lower rolling resistance, shorter braking distance on wet road, stronger aquaplaning protection and better snow grip are its benefits.’

The final point concerns noise. Winter tyres have a more open tread pattern, the better to clear away mud, snow and ice. This might suggest they give increased road noise when in use. However, most manufacturers claim that their winter tyres are as quiet and comfortable as normal tyres. This makes sense, as the tread compound is significantly softer.

So, are winter tyres a worthwhile investment? The above suggests that they are. Ideally, it would be best to have two sets of tyres, one set for summer use and one set for when the climate forgets to be ‘temperate’. The bottom line is still more telling. Given the use of grit and salt on the roads during a UK winter, it would make a lot of sense to acquire not only a set of winter tyres but also a set of ‘winter wheels’!

Merityre are a leading UK independent supplier of car tyres. Why not visit their website at www.merityre.co.uk and see where you can buy your next set of tyres.

Elements, My Dear Watson: How To Drive Safely Whatever The Weather

Here are a few sobering figures. When you’re driving, the grip of your car tyres ultimately determines how quickly it can stop. At 30mph, the tonne or more of moving metal you’re piloting is travelling at 45 feet per second; every second equals 2.8 car lengths. At 70mph, every second’s travel is 105 feet. In ideal conditions, a car travelling at 30 mph takes 75 feet to stop; at 70mph, it’s 105 feet. In wet conditions, the 30mph stopping distance jumps to 120 feet and at 70mph, it’s a whopping 560 feet – that’s 35 car lengths. The strategies for coping when driving in poor conditions aren’t all obvious but the need for them will become so. Read on and learn.

It’s clear that when driving in rain, we need to leave more stopping space, to give your car tyres room to work with their reduced grip. Reducing your speed is a good idea too.

Car tyres have more to deal with than just surface water. If it rains after a long dry spell, the road surfaces’ build up of dirt and diesel, plus water, makes for near skid-pan conditions. Moreover, it isn’t just car tyres that are affected by rain. It’s a fact that vision is compromised on many levels by rain. First, a rain-sodden windscreen isn’t the same as a dry one, regardless of how efficient windscreen wipers have become. Furthermore, any car has areas of unwiped glass. Second, clammier conditions lead to misting up. This can be cleared by demisters and heated windows, but this is rarely instant and it obviously affects vision. Third, heavy rain and the resultant spray compromises vision yet more. Fourth and last, pedestrians tend to shy away from the rain and are unlikely to keep as sharp a lookout as they might.

Apart from attending to the elements of speed, distance and grip, you need to take further care in wet weather. A flood, for example, can cause major problems. Drive into one too fast and your engine could inhale a measure of water. This could do anything from causing it to stop to doing irreparable damage. What’s more, even if you negotiate a flood successfully, you’ll have wet brakes. Apply your brakes lightly until you feel them start to work properly or they won’t be there when you need them. Also, remember that anti-lock brakes let you steer when skidding but won’t necessarily reduce stopping distance as much as you might think. In fact, a June 1999 National Highway Traffic Safety Administration (NHTSA) study found that ABS increased stopping distances on loose gravel by an average of 22 percent.

What about the still worse conditions of ice and snow, and fog. The former requires gentle, intelligent control inputs - you’ll soon find out how gentle you must be. Fog driving is all about vision. Some clearly feel they have magic tyres but the bottom line is if you can’t see or are following too close, you can’t stop in time, period. Remember to use your wipers when the fog droplets build up on your windscreen.

Lastly, it may seem odd to include ideal conditions, i.e. sunny, dry and bright, under defensive driving. If it does, try this. Picture yourself driving west, late in the day. The level sun is in your eyes, your windscreen’s grimy and your view of the road isn’t at all clear. This would be a good time to stop and clean your screen.

Merityre are a leading UK independent supplier of car tyres. Why not visit their website at www.merityre.co.uk and see where you can buy your next set of tyres.

Just The Ticket: How To Make Sure Your Car Will Pass The MOT Test

In the colourful parlance of the motor trade, an MOT test certificate is called a ‘ticket’. A tax disc is referred to as ‘money on the glass’ and since you can’t buy the latter without owning the former, making sure your car passes its MOT test is essential to keeping it – and you – on the road. Car tyres, unsurprisingly, are candidates for inspection.

Once your car’s passed its third birthday, an MOT test becomes a yearly occurrence. What is the test for? Easy: it is to ensure that your car meets road safety and environmental standards. Should it not meet them, it’ll fail the test, which can be an expensive shortcoming. However, knowing what is tested helps in making sure a pass is within reach.

Let’s begin with the obvious, the car’s wheels and tyres. The tyres must be the right kind, have no excessive wear or damage and have a minimum of 1.6mm of tread. All the wheel nuts must be present and correctly tightened. Oddly, the spare tyre isn’t subject to inspection.

The car’s wheels and tyres naturally can’t do their job unless the mechanisms that secure and control them are sound. So, the fitness of the suspension and steering components is checked, as are the brakes. For these, testing on rollers is de rigeur. The brakes – handbrake included – must perform efficiently and evenly, within set parameters. The state of the hydraulic components is also tested, so ragged brake hoses and leaking fluid mean a fail.

Dependent on the car’s age and the type of fuel it uses, the car must meet precise emission requirements, and so computerised exhaust sniffing is carried out. Moreover, the exhaust system should be without leaks or holes caused by rust or damage.

While looking at the metalwork, the MOT tester will check the car’s structure. Excessive corrosion, damage or sharp edges are fail points. It’s important that all the strong points in the body, those holding the hardware, must be free of rust and damage.

While considering structural elements, the tester must make sure that the car’s seats are secure in their upright position. Seatbelts must be present and correct in the front and rear, as well as working and in good condition. Next out, as it were, the doors must work properly, and have functional locks. The mirrors must also be present and fully usable – a cracked glass may cause a fail.

The matter of visibility comes next. The car’s windscreen must be free of all but the smallest amount of damage, the windscreen wiper blades must be in good order and the screen washer must work and have an adequate supply of fluid.

Now for the lights. All the lights – indicators and hazard lights included – must be secure, properly aimed and working. This just leaves two legalities, the number plates and the Vehicle Identification Number, or VIN. The ‘plates must be in good shape, legible and have the correct format and, so fancy typefaces and ‘plates modified to read in special way can earn you a fail. The VIN, which you’ll find on any car registered after the 1st August 1980, must be present and readable.

In practice, the four most common MOT failure points are suspension, brakes, lights and, of course, tyres. The checklist above will guide you towards winning an MOT pass, which will save you both hassle and money. However, if in any doubt about any aspect of your upcoming MOT test, it’s advisable to call in the experts. Consult a garage or tyre bay as necessary.

Merityre are a leading UK independent supplier of car tyres. Why not visit their website at www.merityre.co.uk and see where you can buy your next set of tyres.

Car Tyre Technical Questions and Answers

The world of car tyres is awash with technical terms. You don’t need to know them but they sometimes come in useful. So try answering the following questions, each of which has only one correct answer. The answers are at the foot of the list and for those planning to scroll down and cheat - we’ll know what you did!

1: What is BS AU159f?

A: The British Standard for puncture repairs to car tyres.
B: The British Standard for puncture repairs to Australian car tyres.
C: A code to access holiday discount vouchers on the Internet.

2: What do the initials RWL stand for?

A: Reprogrammable Warning Lights.
B: Right Wheel Latitude.
C: Raised White Letters

3: What is an aspect ratio?

A: The number of attacks per bird experienced if you bend over in a chicken run.
B: The ratio of a car tyre’s height to its width expressed as a percentage.
C: The ratio of tyre pressure (in lbs per sq. in.) to tyre life (in miles).

4: What is a car tyre’s bead for?

A: Holding it on the wheel rim.
B: Keeping it in balance.
C: Threading on a string.

5: What is a butyl liner?

A: A rubber cruise ship.
B: A fine layer in a tyre that prevents sudden deflation if a puncture occurs.
C: A fine layer in a tyre that makes fitting it easier.

6: What is calendaring?

A: The method of assessing tyre wear per month.
B: Adding markings that denote when a tyre was made.
C: Part of the tyre-making process.

7: What is carbon black?

A: The measurable polluting content of a carbon footprint.
B: The marks left on a snooker table by the last ball to be potted.
C: A filler material used to make grey rubber into black tyres.

8: What is de-vulcanisation?
A: A process of mechanical and chemical decomposition that affects tyres.
B: The post court-martial execution of the first officer of the Starship Enterprise.
C: The final process in tyre manufacture.

9: What is a contact patch?

A: A damp chamois leather pad used with the electric chair.
B: The area of a tyre’s tread in contact with the road at any given time.
C: A place where you go to meet with business associates.

10: What is deformation?

A: An offence you can be sued for?
B: The flexing of a tyre in response to the forces acting on it.
C: The distortion a tyre undergoes during fitment.

11: What is an E Marking?

A: A marking all post-June 1997 tyres carry to show they comply with European requirements.
B: A marking carried by all post-May 1986 tyres to show they may be sold in Yorkshire.
C: A marking all post-July 1990 tyres carry to show their sell-by date.

12: What is a sipe?

A: A medium sized, skulking wading bird with short legs, a long straight bill and poor spelling skills.
B: A tyre-fitter’s contraction of the words ‘stand pipe’.
C: A narrow slit between two blocks in a tyre’s tread, designed to dispel water and enhance grip.

Answers
1A
2C
3B
4A
5B
6C
7C
8A
9B
10B
11A
12C

Merityre are a leading UK independent supplier of car tyres. Why not visit their website at www.merityre.co.uk and see where you can buy your next set of tyres.

The Specials: Tyres for Unique Tasks

All car tyres may seem to be the same but they aren’t. Road tyres have different characteristics designed to maximise their performance for specific types of use. However, these differences pale into insignificance when you consider the different tyres offered for competition use.

Take rally car tyres. These must cope with a huge array of surfaces in innumerable different climatic conditions. In addition, rally car tyres usually have to be road legal and must last longer than racing car tyres.

Examining two types of rally car tyre in more detail gives an idea of how the various factors in the tyres interact. Gravel tyres have to clear away the top coating of soft dirt or loose gravel, just as car tyres must clear away rainwater. To do this, they have big, chunky blocks that are made of relatively soft rubber. This lets the tread’s blocks grip while protecting the reinforcing plies that lie beneath them. The tyre tread and carcass’s being rigid enough to resist tearing while being sufficiently elastic to return to their initial shape guarantee toughness and a long life.

Snow/ice tyres can boast an effective grip-enhancing addition. Some can have up to 380 carbide-tipped studs in their tread. This is tough on the surface beneath the tyre but the surface can be tough on the studs themselves. At 75mph, each stud hits the snow or ice 17 times…per second! The impressive part – other than that (most of) the studs are still present when the car stops – is that the car is running on a total of about 50 studs at any one time. The total area the studs offer is about the size of a postage stamp.

In some instances, the tyres have no tread at all. Such tyres are called slicks and are used in drag racing. ‘Top Fuel’ dragsters are the fastest and can reach 330mph in less than 4.45 seconds – the time it takes them to cover the quarter mile. Accelerating faster than the space shuttle launch vehicle or a catapult-launched jet fighter requires as much grip as can be found.

It’s common for all kinds of dragsters to do something memorable. The driver places the car so its rear tyres are sitting in two puddles of water laid down near the start of the drag strip. The driver then applies power, spinning the rear wheels in the water. The immediate result is huge clouds of rubber smoke and steam around the tail end of a car that’s standing virtually still at practically full throttle. Yet this isn’t for show. After a ‘burn out’ like this, the tyres’ tread surfaces are extremely hot and sticky – and therefore grippy.

Often, drag racing car tyres look distinctly soft as the car approaches the start line. This is unsurprising, as the tyre pressure used is around the 12 to 15 psi mark. Why so soft? For two reasons. Soft tyres give better grip but they have another benefit. As the wheels rotate faster, the tyres enlarge. This is like putting bigger wheels on the same car; drivers get a higher top speed from the tyres’ radial expansion.

As you can see, even from just these two forms of motor sport, specialist car tyres are essential. They do what’s asked of them and in doing so, they increase the performance of the car involved in whatever sport is concerned. Think about this the next time you find yourself believing car tyres are all the same!

Merityre are a leading UK independent supplier of car tyres. Why not visit their website at www.merityre.co.uk and see where you can buy your next set of tyres.

Tread Carefully - Your Car Tyres’ Grip Depends on their Treads

Here’s something about car tyres that’s both interesting and thought provoking. Take a look at the sole of your shoe. Why? Well, you may not know it like the back of your hand but here, you’re looking at your shoe’s sole for a reason. The area of the sole of your shoe is approximately the same as that of a car tyre’s contact patch, the amount of tread it has on the road at any one time. Multiply this area by four and it represents all that’s stopping your car, and anyone on board, from sliding off into the scenery when travelling.

Now, say your car weighs one tonne. The car tyres’ four contact patches therefore have to keep one tonne on the straight and narrow. Or do they? In fact, they must often cope with greater loads. When you drive round a corner, you feel centripetal force (not centrifugal force) pushing you towards the outside of the car. Your car tyres create this force and while it’s unlikely that your car can create a cornering force of 1g, it might well do so under very heavy braking. So, during accelerationg, cornering and braking, that four shoe soles’ area is coping with keeping you on the road, rain or shine, summer or winter.

The law says that the minimum depth of the tread on your car tyres must be 1.6 millimetres, across the central ¾ of the tread around the complete circumference of the tyre. If you haven’t this amount of tread on your tyres, you might get 3 penalty points on your driving licence and a £2,500 fine. This is per tyre, so multiply it by four for the worst-case scenario.

There is, however, an even worse case scenario that affect car tyres. RoSpa, the Royal Society for the Prevention of Accidents carried out some tests. On a hot rolled asphalt surface, a car with barely legal tyres travelled 36.8 per cent further before stopping. On a smooth concrete surface, the same car went 44.6 per cent further. Unsurprisingly, RoSpa recommends tyres be changed when the tread depth falls to 3 millimetres.

There’s another risk that worn car tyres create in the rain. You may have winter tyres, summer tyres, asymmetric tyres or run flat tyres. All have treads and when the treads are badly worn, their contact patches lose their ability to quickly dispose of surface water. When a tyre aquaplanes, it’s riding on a thin film of rainwater it can’t get rid of. Then, you have no appreciable grip and therefore very little control. There’s a memorable black and white picture, taken when Dunlop Tyre’s technical team identified aquaplaning in 1962. In it, a Mark Two Jaguar is shown at speed on a wet test track. White segments painted on its tyres’ walls show that the front tyres aren’t rotating at all – scary. Car tyres may have improved since then but like its cause, aquaplaning remains.

So, running your car tyres down the hilt tread-wise may be economical but it could cost you far more than you thought possible. Happily, you can keep a check on your tyre treads’ health. All tyres have tread wear indicator bars moulded into the tread pattern. When – or preferably a little before – these are no longer lower than the tread surface, it’s new tyre time. You can also buy a tread depth gauge from most motor parts outlets. Failing all else, you can check the tread depth using an old 10 pence piece. The ring of dots around the rim indicates 1.6 millimetres when the edge of the coin is pushed into the remaining tread. However, Matthew Dent didn’t retain this element when designing the ‘Royal Shield’ coins introduced in summer 2008.

Merityre are a leading UK independent supplier of car tyres. Why not visit their website at www.merityre.co.uk and see where you can buy your next set of tyres.

The Venerable Bead: How the Professionals Change Car Tyres

In the past, people used to change car tyres by hand. Some still might but this arduous procedure has been semi-automated for a long time. Here’s how professional tyre fitters change a car tyre, using a tyre machine.

As the tyre to be replaced will probably have been in service for a long time, it’ll be reluctant to part from its wheel. The beads, where they abut the wheel, will be firmly stuck and this is where the tyre machine’s first weapon comes into play. After unscrewing and removing the valve to let the air out of the tyre, the fitter will position the wheel in the jaws of the bead breaker. One press of a pedal and the bead is ‘broken’ – separated from its location.

Next, the fitter will lay the wheel flat on the tyre machine, clamping it into place. Since wheels – especially alloy ones – are both delicate and expensive, the equipment is designed to not touch the wheel rims directly. Having levered the upper bead upwards over the wheel rim, the fitter will engage the hooked head of the tyre machine under the bead. Another pedal press sets the machine rotating, to skin the tyre off the upper rim. Repeating this process for the lower bead separates the old tyre from the wheel.

A little preparation of the wheel comes next. The old valve body is sawn off inside the wheel and if necessary, the inner faces of the wheel rims are cleaned. The old wheel balancing weights are removed. Having pulled a new valve into place with a special tool, the fitter will coat the wheel rims and the new tyre’s beads with a special compound. This is a lubricant that eases the fitting process though sometimes, a material with sealing properties may be needed.

The penultimate stage of tyre fitting is essentially the reverse of the removal of the old tyre. The fitter uses the tyre machine to force the new tyre on to the wheel, bead by bead. Finally, a compressed air line is used to inflate the tyre, until its beads pop outwards to seal against the inner faces of the wheel rim. Throughout the process, the tyre fitter has done the controlling, while electricity and compressed air have done the heavy work.

This leaves just the wheel balancing. The fitter will have already positioned the tyre correctly in relation to the wheel, using a coloured dot marking on the tyre. However, balance weights are virtually always required and there’s a machine to help with this task. The tyre fitter will clamp the wheel onto the machine. When the guard is closed and the machine starts, it will take the wheel up to a fixed speed, usually about 200 revolutions per minute.

Using its onboard sensors and electronics, the balancing machine points out where the wheel weights should be fitted and how much they should weigh. Having fitted the weights – stick-on or clamp-on as appropriate – the fitter will run the machine once more, fine-tuning the balance with other weights if necessary.

As we can see, what used to be an hour or more’s hard work is done in minutes. What’s more, if you watch the proceedings from the waiting area, you’ll know exactly what’s happening in the tyre bay!

Merityre are a leading UK independent supplier of car tyres. Why not visit their website at www.merityre.co.uk and see where you can buy your next set of tyres.