HOW TO READ A TYRE
On the sidewall of a tyre you will find various codes and markings. The list below aims to simplify those codes and allow you to understand the information imprinted on the sidewall.
Tyre sizes are made up of a number of different numbers and letters. For example the tyre size 255/55R 16 85 V is made up of the following information.
225 This is the tyre width in millimeters.
55 The aspect ratio as a % (the height of the sidewall divided by the tyre's width).
R Denotes the tyre's construction type - in this case it's a radial.
16 This is the rim diameter in inches.
85 This is the load rating of the tyre.
V This is the speed rating of the tyre.
Tyre Age - Tyres carry a three digit age code on the sidewall indicating the month and year of manufacture. For example 129 means the tyre was manufactured in December 1999. Tyres 6 yrs or older need to be changed due to the deterioration of the tyre.
M&S - Identifies Mud and Snow tyres.
DOT Codes - The requirements of the US Department of Transportation contain a mixture of letters and numbers such as DOT DVDE MTA 129.
E-Marks - Tyres sold in the European Community must carry an E -Mark in accordance with ECE Reg 30 - E.g. E4 027550.
The Aspect ratio is the ratio of a tyre's width to it's height. So a 55 series tyre is a tyre whose height is equal to 55% of its width.
The load-index figure imprinted on the sidewall of the tyre, normally just before the speed rating letter, denotes the maximum load capacity of a tyre when driven at maximum speed. A list of load indices and maximum weights is give above.
All tyres carry a speed symbol in the form of a letter indicating the maximum speed for which the tyre is intended. The table below shows which speed goes with each letter.
Stepping to High Performance
wear rates differ depending on the axle on which the tyres are fitted
and whether the vehicle is front, rear or four wheel drive. To extend
the life of your tyres it is advisable to change tyre positions on a regular
basis. Different tyre manufacturers may recommend different rotation periods,
ranging from 4-10,000Km. It is advisable to switch tyres from left to
right periodically as well as from the back to the front of the vehicle.
Current tread depth legislation requires that car tyres must have a minimum of 1.6mm of tread in a continuous band throughout the central ¾ of the tread width and over the whole circumference of the tyre. To help drivers recognise when their tyres are nearing the legal limit, tyres are manufactured with tread wear indicators in the grooves.
However, it is universally recognised in the tyre industry that the legal limit is wholly insufficient to protect drivers in adverse driving conditions. Drivers are therefore recommended to consider replacing their tyres when the tread depth reaches 3mm.
Website Copyright 2007 www.tyres-2-u.com