Anwan International : Tyres General Information

Sipes are the small, slit-like grooves in the tread blocks that allow the blocks to flex. This added flexibility increases traction by creating an additional biting edge. Sipes are especially helpful on ice, light snow and loose dirt.
Grooves create voids for better water channeling on wet road surfaces. Grooves are the most efficient way of channeling water from in front of the tyres to behind it. By designing grooves circumferentially, water has less distance to be channeled.
Blocks are the segments that make up the majority of a tyre's tread. Their primary function is to provide traction.
Ribs are the straight-lined row of blocks that create a circumferential contact "band."
Dimples are the indentations in the tread, normally towards the outer edge of the tyre. They improve cooling.
Shoulders provide continuous contact with the road while maneuvering. The shoulders wrap slightly over the inner and outer sidewall of a tyre.
The Void Ratio is the amount of open space in the tread. A low void ratio means a tyre has more rubber is in contact with the road. A high void ratio increases the ability to drain water. Sports, dry-weather and high performance tyres have a low void ratio for grip and traction. Wet-weather and snow tyres have high void ratios.

Tread Patterns

Tyre tread pattern is a mix of functionality & aesthetics. There are 3 basic types of tread pattern that manufacturers can choose to go with:

Symmetrical: consistent across the tyre's face. Both halves of the treadface are the same design.
Asymmetrical: the tread pattern changes across the face of the tyre. These designs normally incorporates larger tread blocks on the outer portion for increased stability during cornering. The smaller inner blocks and greater use of grooves help to disperse water and heat. Asymmetrical tyres tend to also be unidirectional tyres.
Unidirectional: designed to rotate in only one direction, these tyres enhance straight-line acceleration by reducing rolling resistance. They also provide shorter stopping distance. Unidirectional tyres must be dedicated to a specific side of the vehicle, so the information on the sidewall will always include a rotational direction arrow.

Tread depth & tread wear indicators

For the most part, motoring law in most countries determines that your tyres need a minimum tread depth to be legal. This varies from country to country but is normally around 1.6mm. To assist you in figuring out when you're getting close to that value, most tyres have tread wear indicators built into them. If you look around the tread carefully, at some point you'll see a bar of rubber which goes across the tread and isn't part of the regular pattern (see picture). This is the wear indicator. It's really basic, but it's also pretty foolproof. The tread wear indicator is moulded into the rubber at a depth of about 2mm normally. As the rubber in your tyres wears away due to everyday use, the tread wears down. At some point, the tyre tread will become flush with the wear indicator (which is normally recessed into the tread). At this point you have about 2mm of tread left - in other words it is time to change tyres.

Diagnosing Tyre Wear

Your tyre wear pattern can tell you a lot about any problems you might be having with the wheel/tyre/suspension geometry setup. The first two signs to look for are over- and under-inflation. These are relatively easy to spot:

The following table is some of the more general factors in tyre wear:

Problem	Cause
Shoulder Wear Both Shoulders wearing faster than the centre of the tread	Under-inflation
	Repeated high-speed cornering
	Improper matching of rims and tyres
	Tyres haven't been rotated recently
Centre Wear The centre of the tread is wearing faster than the shoulders	Over-inflation
	Improper matching of rims and tyres
	Tyres haven't been rotated recently
One-sided wear One side of the tyre wearing unusually fast	Improper wheel alignment (especially camber)
	Tyres haven't been rotated recently
Spot wear A part (or a few parts) of the circumference of the tread are wearing faster than other parts	Faulty suspension, rotating parts or brake parts
	Dynamic imbalance of tyre/rim assembly
	Excessive runout of tyre and rim assembly
	Sudden braking and rapid starting
	Under inflation
Diagonal wear A part (or a few parts) of the tread are wearing diagonally faster than other parts	Faulty suspension, rotating parts or brake parts
	Improper wheel alignment
	Dynamic imbalance of tyre/rim assembly
	Tyres haven't been rotated recently
	Under inflation
Feather-edged wear The blocks or ribs of the tread are wearing in a feather-edge pattern	Improper wheel alignment (faulty toe-in)
	Bent axle beam