Most vehicles come equipped with a temporary spare. These tyres are usually much smaller than the other tyres on your car. It is important to realise that these spares have far more limitations than a typical tyre, including speed and recommended driving distance. Some spare tyres even require the use of a special canister to inflate the tyre. You should familiarise yourself with the spare by reading the owner's manual and the sidewall of the spare. And remember, check the air pressure of the spare frequently.
Three main factors contribute to the loss of traction on wet roads known as hydroplaning:
The Uniform Tyre Quality Grading System, or UTQG, is a system developed by the U.S. government designed to provide consumers with information on tyre treadwear, traction, and operating temperature resistance.
The treadwear grade is a comparative numerical rating based on the wear rate of the tyre when tested under controlled conditions on a specified government test course. For example, a tyre graded 200 would wear two times as well on the course as a tyre graded 100. The relative performance of a tyre depends upon the actual conditions of its use which may depart significantly from the test conditions due to variations in driving habits, service practices, and differences in road characteristics and climates.
The UTQG Traction Rating indicates the tyre's ability to stop a vehicle moving straight forward on wet pavement. The ratings are AA, A, B, and C, with AA being the best.
The UTQG Temperature Rating indicates the tyre's ability to effectively dissipate heat. The ratings range from A to C, with A being the best.
*(UTQG treadwear goes in 20 point increments)
With the right amount of air pressure, your tyres will perform better, wear longer and save fuel. The "right amount" of air pressure for the original equipment or same size tyres is specified by the vehicle manufacturer and may be different for front and rear tyres. Check with your Nitto dealer if the replacement tyres on your vehicle are no longer the same size as the O.E. tyres.
The letters "DOT" certify compliance with all safety standards established by the U.S. Department of Transportation (DOT). This is followed by a combination of up to 12 numbers and letters.
The first two numbers or letters are the plant code where the tyre was manufactured, and the last three to four numbers represent the week and year the tyre was built.
Tyres built in the 1990's will have three numbers and may have a triangle to note the decade. Examples are below.
Note: Recently it became mandatory to apply a partial DOT serial number on the sidewall opposite the complete DOT serial number. The partial DOT serial does not show the week and year that the tyre was manufactured, but may still assist consumers in identifying tyres should a recall be necessary. The purpose in applying the partial DOT serial number was to facilitate tyre identification when the full DOT serial number may have been mounted towards the inboard side of the vehicle, and consequently not visible unless the vehicle was put on a lift for inspection.
With the right amount of air pressure, your tyres will perform better, wear longer and save fuel. The "right amount" of air pressure for the original equipment or same size tyres is specified by the vehicle manufacturer and may be different for front and rear tyres. Check with your Nitto dealer if the replacement tyres on your vehicle are no longer the same size as the O.E. tyres.
The sidewall of a tyre includes a variety of important information. The numbers and letters identify dimensions and performance standards that allow you to compare tyres more accurately and efficiently. This diagram will help you to understand those numbers and letters. For assistance in selecting a replacement tyre, always consult your Nitto Tyre dealer.
The width of a tyre is referred to as its section width. This is the width of an inflated tyre in millimetres at its widest point from sidewall to sidewall.
The section height of the tyre is measured in millimetres also. The section height is approximately the distance from the rim to the tread surface of the tyre when it is not carrying any weight.
The aspect ratio is the dimensional relationship of the section height to the section width. The lower the aspect ratio, the shorter the sidewall and the wider the shoulder-to-shoulder width.
The "R" stands for "radial," indicating the tyre has radial construction.
The "20" indicates the diameter of the wheel in inches. You can learn more about changing the diameter of the wheels of your car in the Plus Sizing section.
The load index number and speed symbol correspond to the maximum load-carrying capacity of the tyre and its maximum speed capability.
The load index is an assigned number that corresponds with the load-carrying capacity of the tyre. For example, "96" indicates a load-carrying capacity of 710kg at maximum inflation pressure. The load index for most passenger car tyres ranges from 75-100. Click here to view the complete load inflation index.
Speed ratings are determined by indoor laboratory testing methods, which measure high-speed tyre durability under controlled test conditions. These test procedures do not take into account underinflation, tyre damage, vehicle characteristics or road conditions which can lead to sudden tyre failure or loss of vehicle control at much lower speeds than indicated by the tyre's speed rating.
The "LT" designation stands for "Light Truck." These tyres are intended for more severe use often seen on trucks and follow load and inflation standards established by the Tyre and Rim Association (TRA). Load Index values and load capacities for these tyres can be found in TRA manuals.
With the right amount of air pressure, your tyres will perform better, wear longer and save fuel. The "right amount" of air pressure for the original equipment or same size tyres is specified by the vehicle manufacturer and may be different for front and rear tyres. Check with your Nitto dealer if the replacement tyres on your vehicle are no longer the same size as the O.E. tyres.
The "M+S" indicates the tyre is an “all season tyre”. “M+S” is an abbreviation of “Mud & Snow”.. The Mud and Snow designation may also appear as "M&S" or "M/S." This designation is popular in U.S. markets where road conditions vary greatly between seasons and snow covered roads are common.
Plus sizing wheels and tyres has become the hottest trend among enthusiasts. Adding inches to the wheel diameter for wider, low aspect ratio tyres can increase your car’s handling capabilities and improve vehicle aesthetics.
Increase the section width and lower the aspect ratio while retaining the wheel diameter. This replacement tyre increases the contact area and lowers the tread profile for improved traction and quicker response.
This sizing mounts tyres with an increased section width and a lower aspect ratio on wheels of a larger diameter. A Plus One fitment for a car with 14-inch original equipment wheels would use 15-inch wheels.
As a general rule of thumb, Plus One sizing:
Increased wheel widths in plus sizing also contribute to greater tyre stability, and improved cornering and manoeuvrability. A Plus Two fitment for a car with 14-inch original equipment wheels would use 16-inch wheels.
As a general rule of thumb, Plus Two Sizing:
Dealers have additional information for Plus Sizing ABS-equipped vehicles. Always consult your Nitto Tyre dealer when changing the size of tyres on your vehicle.
Loss of vehicle control can occur when tyres with insufficient tread depth are used on wet roads. To avoid this possibility, all tyres must have sufficient tread depth.
The tyre's tread grooves disperse water away from the tyre's contact patch when roads are wet. Where tyres have insufficient tread depth, their ability to disperse water away from the tyre's contact patch when roads are wet is compromised, which can cause the driver to lose control of their vehicle.
When tyres have insufficient tread depth and can’t disperse water from the contact path they can become separated from the road surface. This is known as ‘aquaplaning’ or ‘hydroplaning’ and is very dangerous because the tyre cannot transmit steering, braking and necessary drive forces onto the road surface.
It is also a legal requirement for tyres to have a minimum tread depth of 1.6mm. Standing water on wet roads reduces the size of a tyre's contact patch as shown in the image below. In extreme conditions, the tyre can "aquaplane" as highlighted above.
The tread depth of the tyre will determine how much the tyre's contact patch is reduced in wet conditions and therefore the amount of grip the tyres can provide. The graph below shows an example of how tyre tread depths affect braking distance on wet roads. When new, the tread depth of most passenger car tyres is close to 8.0mm. In Australia, for road worthy purposes, tyres with a tread depth 1.5 to 1.6mm are considered worn out. The graph below indicates the practical reason for this regulation.
All tyres have treadwear indicators moulded into the tread grooves, as shown below. When worn down to these indicators on any part of the tyre, the tyre should be replaced.
When checking the indicators for signs of wear, be sure to examine the whole tread area, including inside the tyre’s tread.
Check your tyres' inflation pressures at the same time as looking for signs of wear to ensure they are completely safe.
Regardless of the tread depth of your tyres, aquaplaning can occur during heavy rain due to the depth and volume of water on the road. Reduce speed and allow for extended braking distances to prevent loss of control and potential accidents.
Regardless of the tread depth of your tyres, grip levels can be very low in the first rain after a long dry period. Drivers in tropical or drought-affected regions of Australia need to exercise caution and allow for extended braking distances to prevent loss of control and potential accidents.