Selecting the Right Tyres *

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Road Tyres

Decoding a tyre
All Tyres are made to similar technical, performance, and dimensional standards through a series of interlinked Tyre and Rim Association Standards world-wide. These Standards cover the basics

So let’s stick to the basics of a tyre size code. Let’s take 195/75R15 92H as an example. Now I have to get a little bit technical, because measurements of a tyre are made under strictly controlled conditions, otherwise they too, would be meaningless.

195- dimensions in millimetres of the section width of the tyre (with raised lettering excluded), when mounted on a specified rim ( the measuring rim),

75- the ratio of section width to section height. Section height is measured vertically from bead ledge to the crown of the inflated tyre.

R- The tyre is of radial construction. Nowadays, they nearly all are. If there is no “R”, then they are not Radials.

15- the nominal rim diameter. “Nominal” because it’s not exactly 15 inches,

92. A code for the load in kilograms that the tyre can carry at a specified maximum pressure, in this case 630 kg. If for example, it was 96, this signifies that the tyre can carry a higher load, at a higher inflation pressure, so it has a stronger casing. The smallest code is 0 (zero), which carries 45 kg. That’s probably a wheel barrow tyre. The largest (so far) is 279, which carries 136 tonnes (136,000 kg), the size of which you have probably guessed as those giant machines that work in the mines.

H- A code for the speed capability of the tyre at specified load, temperature and pressure. In this case, it’s 210 km/h. The range of speed categories go from A1 (5 km/h) to A8 (40 km/h) for slow moving equipment. Then B to Z covers 50 to 300 km/h in 10 km/h steps, with 0 (Zero) omitted because it might get confused with O, and H out of sequence (because it was there first!) H comes after U, then follows V, Z,

Z is different. ZR with no other speed category means the tyre has been designed to fit the performance of a particular high performance vehicle.
They’re on your Ferrari or Lamborghini. ZR plus a speed category following, carries that speed category as defined e.g. 275/40ZR17 93W has a maximum speed of W (270 km/h)

Selecting Your Tyres

Road and Everyday Tyres

Selecting the right tires for your vehicle is an important decision. Your safety, as well as driving enjoyment over the next thousands of miles will be determined by this decision. Remember the tyres are the only things keeping you on the road and out of the ditch,

"How many tires do I need?"

Since tires affect the personality and performance of your vehicle, all four tires should be as identical as possible or handling problems may arise. If your tires don't match, it is possible that one end of your vehicle won't respond as quickly or completely as the other, making it more difficult to control.

Consider the following:

JUST ONE TIRE?
If your tires have a lot of remaining tread depth, but you need to replace just one that has been damaged by an accident, road hazard or a vandal, you should replace it with a tire that exactly matches the others. Select a replacement tire of the same brand, line, size and speed rating. While there may be a less expensive tire available, it wouldn't be a bargain this time because it would be different than the other three tires on your vehicle.

A PAIR OF TIRES?
If two of your tires have a lot of remaining tread depth, but you need to replace the other two because they were damaged or have worn out, you should replace them with a pair of tires that come as close as possible to matching your existing tires. While identical new tires are desirable, others of the same size and type can also provide good results. Only consider selecting new tires that are from the same tire category as your existing tires.
New tires should be installed on the rear axle the reason for this is understear is alot more predictable and easier to composite for in a FWD vehicle then overstear.

While your Tyres are being Changed ask your mechanic why one pair of tires have worn faster than the others. Was it caused by a lack of tire rotation, out-of-spec wheel alignment or loose mechanical parts? Once the problem has been found, it can be corrected before it damages your new tires. Keep in mind that your ultimate goal is that all of your tires always wear out at the same time so they can be replaced as a set.

A SET OF TIRES?
If all of your tires are wearing out together, you have the greatest flexibility in tire selection. If you were happy with the original tires, simply replace them. If you want longer tread-wear, a smoother ride or more handling, there are probably tires that will help you accomplish that. Review the tire category types until you find a category description that describes a tire that fits your needs.

Once you know how many tires you will be replacing, determine size and type by answering the questions below:

What is the right size for my vehicle?

Buying the correct tire size can get complicated, especially if you decide to upgrade from your vehicle's Original Equipment size.

A tire's first requirement is that it must be able to carry the weight of your vehicle. No matter how good a tire you select, if its capabilities are "overworked" just carrying the load, it will have little reserve capacity to help your vehicle respond to quick emergency. So when you are in the selection process, make certain that your new tire's size is designed to carry the weight of your vehicle! Don't under-size.

The other size consideration is overall tire diameter. Since many of the functions of today's vehicles are highly computerized, maintaining accurate speed data going into the computer assures accurate instructions coming out. And an important part of the speed equation is your tire's overall tire diameter.


"Do I need summer tires, winter tires, all-season tires?"

Do you drive your car only in sunshine, or also through rain and snow? To successfully meet each of these driving conditions requires a different type of tire.

Ask yourself these questions to determine which performance category you should choose from:

WHAT IS THE WORST DRIVING CONDITION I WILL ENCOUNTER?

If you use one set of tires for every season, you may get good performance under many conditions, but you will compromise your vehicle's performance when the conditions are at their worst.

So the important thing to do is to select your tires so that they match the worst driving condition you expect to encounter. When you're stuck in the snow or in the mud because your tires don't have the appropriate capabilities, you'll curse their limited performance in your worst driving condition...and you'll quickly forget how smooth and quiet they were at other times!

WHAT ARE THE TYPICAL DRIVING CONDITIONS I WILL ENCOUNTER?

If you only drive around The local Neighbourhood and a "long trip" is Popping down to the shops, almost any tire will do. But if you drive your vehicle on congested city streets and Motorways during peak times you will be better served by more responsive tires. If you drive long trips on motorways you will want quiet, smooth riding, long wearing tires. Or if you like to drive quickly on twisting roads or through the mountains you will want good handling tires. And if you drive on the track or in Drag events, you will want the best competition tires available.

BALANCING THE REQUIREMENTS OF YOUR DRIVING CONDITIONS.

If your worst driving conditions and your typical conditions are similar, one set of tires will be all you need.

If your worst driving condition occurs for a long period of time (you drive through snow all winter) and is dissimilar to your typical driving condition, you may want to consider selecting two sets of tires for your vehicle. Each set will be designed to master the specific conditions without compromising your driving satisfaction at the extremes. While purchasing two sets of tires may appear expensive, the set you're not using won't wear while you are using the other set, and combined they'll provide longer total wear than either set could individually!

The Importance of thread patterns

Ideally you should have two sets of tyres one for the wet and one for the dry like Rally cars and formula 1 cars do, but this is impractical in day to day use

So a Compromise has to be made either compromise dry performance or wet performance, thread patterns play a big part in the efficiency of your car to evacuate water from between the tyre surface and the road surface the wider the thread pattern the more effectively the water is evacuated, but here comes the trad off, the wider thread pattern means you will loose some traction during dry conditions as you have a little less tyre in contact with the road, I hear you saying so I'll slow down a bit during the wet problem solved, it's not as easy as that there is a little thing called Aquaplaning,
Aquaplaning can occur when the car drives through puddles of standing water. If the water cannot squirt out from under the tire quickly enough, the tire will lift off the ground and be supported by only the water. Because the affected tire will have almost no traction, cars can easily go out of control when Aquaplaning.

Some tires are designed to help reduce the possibility of Aquaplaning. These tires have deep grooves running in the same direction as the tread, giving the water an extra channel to escape from under the tire

the way the thread is orientation plays a big part in the way the tyre behaves in the way of grip, groves running the length of the tyre means you can corner quicker where as groves running across thee tyre mean you can get off the line and accelerate without spinning wheels, his is why most tyre manufactures choose to put both in their tyres as well as threads going diagonal ways through the tyres as this offers 50/50 boath forwards and sidewards grip,

Problems With Tires
Underinflation can cause tires to wear more on the outside than the inside. It also causes reduced fuel efficiency and increased heat buildup in the tires. It is important to check the tire pressure with a gauge at least once a month.

Overinflation causes tires to wear more in the center of the tread. The tire pressure should never exceed the maximum that is listed on the side of the tire. Car manufacturers often suggest a lower pressure than the maximum because the tires will give a softer ride. But running the tires at a higher pressure will improve mileage.

Misalignment of the wheels causes either the inside or the outside to wear unevenly, or to have a rough, slightly torn appearance.

 

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Track Day and Drag tyres

Slick tyre

slick tyre (also known as a "racing slick") is a type of tyre that has no or very minimal tread pattern, used mostly in auto racing. By eliminating any grooves cut into the tread, such tyres provide the largest possible contact patch to the road, and maximize traction for any given tyre dimension. Such tyres are used on all four wheels for road or oval track racing, where steering and braking require maximum traction from each wheel, but are typically used on only the driven (powered) wheels in drag racing, where the only concern is maximum traction to put power to the ground.

Slick tyres are not suitable for use on common road vehicles, which must be able to operate in all weather conditions. They are used in auto racing where competitors can choose different tyres based on the weather conditions and can often change tyres during a race. Slick tyres provide far more traction than treaded tyres on dry roads, but typically have less traction than treaded tyres under wet conditions. Wet roads severely diminish the traction because of aquaplaning due to water trapped between the tyre contact area and the road surface. Treaded tyres are designed to remove water from the contact area, thereby maintaining traction even in wet conditions.

Since there is no tread pattern, slick tyre tread does not deform too much under load. The reduced deformation allows the tyre to be constructed of softer compounds without excessive overheating and blistering. The softer rubber gives greater adhesion to the road surface, but it wears out much more quickly than the harder rubber tyres used for driving on the streets. It is not uncommon for drivers in some autosports to wear out multiple sets of tyres during a single day's driving.

In Formula One slick tyres are no longer allowed, yet dry weather tyres are still often referred to as 'slicks' as they have no appreciable tread pattern (having only circumferential grooves intended to reduce total traction) and similar behaviour in wet weather. They will be re-introduced into the sport in 2008.

They are also usually of a lower profile then their street equivalent thus giving more feedback and response But less ride comfort

Drag racing slicks

True Drag racing slicks are typically very large, to deal with the enormous power delivery. often the car must be modified merely to account for the size of the slick, raising the body on the rear springs for the height of narrower slicks, and/or replacing the rear wheel housings with very wide "tubs" and narrowing the rear axle to allow room for the wider varieties of tyres. Open wheel dragsters are freed from any such constraint, and can go to enormous tyre sizes. Some utilize very low pressures to maximize the tread contact area, producing the typical sidewall appearance which leads to their being termed "wrinklewall" slicks. Inner tubes are typically used, to ensure that the air does not suddenly leak catastrophically as the tyre deforms under the stress of launching.

"Wrinklewall" slicks are now specifically designed for the special requirements of drag racing, being constructed in such a way as to allow the sidewall to be twisted by the torque applied at launch, softening the initial start and thus reducing the chances of breaking traction. As speed builds, the centrifugal force generated by the tyre's rotation "unwraps" the sidewall, returning the stored energy to the car's acceleration. Additionally, it causes the tyres to expand radially, increasing their diameter and effectively creating a taller gear ratio, allowing a higher top speed with the same transmission gearing.


Soft Compound Street tyres

The development in This technology has affected the development of tyres for racing series other than drag racing as well. When other forms of auto racing similarly instituted classes which require DOT approved street tyres, some manufacturers similarly began to market tyres which superficially resembled their high performance street tyres, but with the least tread permissible and with very soft, sticky rubber, intended specifically for competition because the soft tread would wear too quickly for street use. These became known, loosely, as R compound tyres. With additional years of progress, this class of tyre has in its turn followed its own line of development, to the point where they have little in common with true street tyres of the same brand. this has led to new classes of racing which require not only DOT approval, but also a minimum tread-wear rating, in an effort to eliminate the R compound tyres from competition and require "true" street tyres. Theese are the mos commonly used tyres used on the Run What You Brung and Track days

For the true motor-sport fanatic Rain tyre's

Rain tyres or Wet tyres are special tyres used in motor sport in wet weather as opposed to a slick tyre used in dry conditions. They are very similar in many ways to the tyres found on normal road cars.


Structure

Rain tyres have a specially designed structure making them better adapted for their application than any other tyres. However not all rain tyres obey the same design principles. Certain factors need to be taken into account when designing a good rain tyre, such as the:

speed of the car
weight of the car
power of the car
lifespan of the tyre

Grooves
Rain tyres are cut or moulded with patterned grooves or tread in them. This allows the tyre to quickly displace the water between the ground and the rubber on the tyre. If this water is not displaced, the car will experience an effect known as Aquaplaning as the rubber will not be in contact with the ground. These grooves do not help the car grip contrary to popular belief, however if these grooves are too shallow, the grip will be impaired in wet conditions as the rubber will not be able to make good contact with the ground. The patterns are designed to displace water as quickly as possible to the edges of the tyre or into specially cut channels in the centre of the tyre. Not all groove patterns are the same. Optimal patterns depend on the car and the conditions. The grooves are also designed to generate heat when lateral forces are applied to the tyre.


Rubber
Rain tyres are also made from softer rubber compounds to help the car grip in the slippery conditions and to build up heat in the tyre. These tyres are so soft that running them on a dry track would cause them to deteriorate within minutes. Softer rubber means that the rubber contains more oils and other chemicals which cause a racing tyre to get sticky when its hot. The softer a tyre, the stickier its gets, and vice verse with hard tyres.


Shape
Sometimes rain tyres are designed to have a smaller diameter than their dry counterparts. This means that the wheel spins faster and more water is thrown off the tyre by centrifugal force. Some rain tyres are also narrower than the dry counterparts. This smaller "footprint" reduces the chances of aquaplaning.


Intermediate Tyres
Some racing series such as Formula 1 allow an intermediate tyre. This tyre is designed to be used in conditions too wet for slick tyres and too dry for wet tyres. They are some sort of “in-between” tyre or intermediate tyre as the name suggests. They are made with rubber compounds slightly softer than slick tyres and are cut with grooves like the rain tyre but shallower to prevent excessive heat build up.