Tyre Size Guide
Reading the size of your tyre is important to ensure that you have the correct tyres fitted to your vehicle. In addition to your safety and mechanical integrity of your vehicle, other considerations are your vehicle manufacturer and insurance company may take a negative view of your fitting tyres that are not within their specifications, potentially resulting in your warranty or claim being rejected.
In this image the size of the tyre is 195/55R16 87V. What the values above indicate are;
A little more detail on what each item means, below.
The section width of the tyre as measured from sidewall to sidewall
The profile (aspect ratio) as a percentage of the tyre width
R = Radial
The type of construction method used for the tyre
The diameter of the rim in inches
The relative index number of the load the tyre can safely carry
The relative index symbol of the speed rating
NOTE: The width of the tyre as indicated by the size, on the sidewall and in general, is not the width of the tread of your tyre. This measurement is the section width of the tyre, as measured from sidewall to sidewall when inflated to a predetermined pressure on a specific rim. The width of your tyres tread will be less than this measurement and will vary by manufacturer, brand and pattern.
The calculation of the load carrying capacity of a tyre has a direct correlation with the pressure at which it will be operated and is further affected by the speed and duration of operation. A good rule to adopt is to never fit tyres that have a lower load or speed index than the original equipment specified for your vehicle, and to ensure that you always maintain the correct pressures.
The importance of maintaining the correct tyre pressure cannot be stressed enough, it is the most critical part of your tyres performance and handling characteristics.
Most vehicles will have a sticker inside the door frame or fuel cap, indicating the original specifications. Alternatively the owners handbook will detail what should be fitted.
Tyre descriptions also contain other letters which indicate it's design. The table below shows some of the typical abbreviations and their purpose.
|ZR||Applied to tyres of W or Y speed rating - capable of 270KM/H or 300+KM/H|
|M+S||Mud and Snow capable|
|C (LRC)||6 Pr|
|D (LRD)||8 Pr|
|E (LRE)||10 Pr|
|Conti-Seal / Seal||Self-sealing standard production tyres|
|DSST||Dunlop Self-supporting technology (Runflat)|
|DT||Different tread design|
|DT1||New version of the tyre profile|
|EMT||Goodyear Extended Mobility (Runflat technology)|
|HRS||Hankook Runflat System|
|MFS||Max falnge shield - rim protection|
|M/T||Mud / Terrain efficiency|
|NCS||Noise Control System|
|RPB||Rim Protection Bar|
|ROF||Run On Flat|
|OBL||Outlined Black Letters|
|OWL / WL||White Letters|
|OWT||Outlined White Letters|
|RBL||Raised or recessed black letters|
|RWL||Raised White Letters|
|SBL||Serrated Black Letters|
|NW / WW / WWW||White Sidewall|
There are two sets of standards that tyre manufacturers comply with that provide meaningful information to the consumer. These are ECE Label standards and UTQG.
An E-mark confirms that a tyre meets minimum EU or International (UNECE) standards in relation to its dimensions, load and speed rating. E-mark tyres have been tested to ensure adequate tread depth and performance ability. Your tyre should be marked as follows;
- · The E-mark consists of an 'E' or 'e' and a number within a circle or a rectangle
- · A capital ‘E’ denotes UNECE approval, a small ‘e’ EU approval. Either is acceptable.
- · The number following the ‘E’ or ‘e’ denotes the Member State that granted approval.
- · Following the circle or rectangle is a type approval certificate number, issued for tyre size and type.
EC regulations require some tyres to have performance labels, similar to the below example.
This regulation requires that tyres for cars, light commercial vehicles and heavy trucks carry a label showing the tyre's wet grip, fuel efficiency and noise performance, and can also be found in manufacturers product catalogues. Each tyre is given a performance rating from A-G excluding D to avoid an average performing tyre.
The use a ranking system that ranges from A to G (best performance/worst performance)
The use a ranking system that ranges from A to G (Most fuel efficient / Least fuel efficient)
The dB rating indicates the amount of road noise generated by the tyre
Uniform Tire Quality Grading ( UTQG) is the term encompassing a set of standards for passenger car tyre that measures a tyre's treadwear, temperature resistance and traction.
The UTQG rating is made up of three components;
The treadwear grade is a comparative rating based on the wear rate of the tyre. Theoretically this means that a tyre with a 200 grade will wear twice as long as a tyre with a 100 grade.
Traction grades, from highest to lowest, are AA, A, B and C, represents the tyre's ability to stop on a wet paved surface.
The temperature grades, from highest to lowest, are A, B and C. These represent the tyre's resistance to the generation of heat at speed and the tyres ability to dissipate the heat.
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