Tyres are among the most important parts of the vehicle but unfortunately the least understood. Without the tyres, your vehicle is useless. You need the tyres to start, move and stop the vehicle. So buying tyres is a task you need to undertake very carefully otherwise your safety and that of others could be put in great danger.
Before you buy any tyre, give serious consideration to (1) the size of the tyre (2) age of the tyre (3) physical conditions of the tyre.
1. TYRE SIZE.
On the side wall of your tyres, you will see figures like 215/75/15R, 195/65/14R and so on. These are designations for your tyre sizes. Check your own tyre to know what is written on it. The first figure from the left is the width (from side wall to side wall) of the tyre in millimeters; the middle number is what is known as the ASPECT RATIO used to calculate the height of the side wall of the tyre. The last number is the ream diameter. When you go to buy tyres you will mention all of those figure to the tyre seller so that he will give you exactly what you want. There are various sizes of tyres in the market that can fit your type of vehicle but that does not mean that those sizes are good/safe for your vehicle.
Every vehicle has tyre sizes specified by the vehicle manufacturer. If you check the tyre placard by the end of your driver’s door, hood or the vehicle’s manual, you will see the specification for your vehicle’s tyre sizes. Please stick to these specification while buying replacement tyre. Don’t let the tyre seller give you something else. The manufacturer of your vehicle has taken a lot of factors into consideration before specifying your vehicle tyre sizes. If you change that, your vehicle may not handle well, may be risking a blowout and a crash. Changing to fatter tyres like some people do may look better but not safer.
In most cases, the manufacturer provides alternative sizes should you not find the original sizes the vehicle came with. The tyre placard will specify these alternatives. However, there are some calculations you can make to get sizes apart from what the manufacturer specified that will give you the same result as the original specification, but you need to know how to do the calculations, otherwise stick to the original specification.
2. DETERMINIG THE AGE OF THE TYRE.
Even more important than the size of the tyre is its age. Unfortunately most motorists as well as tyre sellers themselves don’t know how to check for the tyre’s age. They depend only on visual inspection of the physical conditions. Some will invite a vulcanizer who will do a press up (or is it press down) on the tyre to certify if it is okay – what a wrong and dangerous thing to do.
Why the emphasis on the age of a tyre? Just as age could disqualify and otherwise promising marriage mate, age will disqualify a tyre even if every other thing seems alright from a visual inspection. Do not be deceived by a tyre’s looks. Every tyre has an effective life span beyond which you will be entering the danger zone. As a general rule, any tyre more than 6 years old should be discarded. This rule, however, applies to quality tyres with branded known names. Less quality tyres of course, may not last that long.
So, how do you determine the age of a tyre? Unlike humans, who can hide their ages, every tyre provides information about its age but in a coded form.
Look at the side walls of your tyre and check for the letters DOT. Look around the DOT (to the left or to the right) until you get to either a three digit or four digit number boldly imprinted on the tyre without any alphabet attached to it. Some tyres though, may not have the letters DOT printed on them. Just look around the side wall and you definitely will see a 3 or 4 digit number clearly imprinted on the tyre. The 3 or 4 digit number is the code designating the date of manufacture of the tyre. Since it is a code, you need to decode it to get the age of the tyre. So lets decode it. If it is a 3 digit number, check to see if it has a triangle sign attached to it. A 3 digit number without a triangle means the tyre was manufactured in the 80’s , the first two number from the left tells you the week in the year while the last number tells you the year in the 80’s. for example if you have the number 341 (without a triangle) it means 34 week of 1981 (34 is the first two numbers from the left indicating the week while 1 is the last number indicating the year in the 80’s) if the 3 digit number has a triangle it means the tyre was made in the 90’s. So 341 with a triangle means the tyre was made in the 34th week in 1991. If it is a 4 digit number, it means the tyre was made any year from year 2000. For example, a tyre with 2302 means the 23rd week of year 2002. The first two numbers from the left indicating the week, while the last two numbers indicate the year. Four digit numbers do not have triangle signs with them.
From the date of manufacture you can now determine how old the tyre is do a simple calculation on tyres made in the 80’s or the 90’s and see how old a such tyres could be. Even if a tyre looks brand new don’t be deceived. Check the age repeat, check the age. If possible find out for how long it has been left unused because the more unused a tyre is the more unsafe the tyre becomes. Reasons? See item 4 below. Please note that you start calculating the age of tyre from the date it was manufacture and not from the date you bought it.
3. CHECK FOR PHYSICAL CONDITIONS.
After you are satisfied with the signs and age, check for cuts, wears(either at the edges or the center) bulges, swells, cracks, warp. These may be the time to do your press up (or is it press down) with the tyres. Any of these deformities could be a warning signal to stay off the tyre.
4. SPARE TYRES COULD BE A DEATH TRAP IF……
Given 2 tyres of the same age, the one not in use (for a long time) is more dangerous than the one constantly in use. Surprised? Well that is the way it goes with tyres.
For instance, if you bought two brand new tyres and kept one as spare and didn’t use it for say 12months, the one in constant use is far safer than the one not in use. Why? When not in use, atmospheric gases have more damaging effect on tyres (whether brand new or not)such gases harden unused tyres and make them like brittle. When such tyres are eventually engaged, they could simply disintergrate and cause a crash.
A tyre that is in use counteract with effect of the atmospheric gases as it rolls and flexes. So if you have to engage spare tyres that you have not used for a long time drastically reduce your speed and change to a better tyre as soon as you can. From this you can see that those who park their vehicles for a long time may need to change the tyre when they eventually engage the vehicle again. It doesn’t matter if you remove the tyres and store them somewhere else as long as they are affected by the air, you can be sure the damaging atmospheric damages will impact on them.