Reader submission to 4x4offroad eZine:
As part of the DOT code on any motorcar tyre, there is a tyre manufacture date stamped on the sidewall. Oddly this code is sometimes only on one sidewall so you might need to get under your car and look at the inward-facing side of the tyre. Take a look at yours - there will be a three- or four-digit code. This code denotes when the tyre was manufactured, and as a rule-of-thumb, you should never use tyres more than 6 years old.
The rubber in tyres degrades over time, irrespective of whether the tyre is being used or not.
When you get a tyre change, if you can, see if the tyre place will allow you to inspect the new tyres first. It's not uncommon for these shops to have stuff in stock which is more than 6 years old. The tyre might look brand new, but it will delaminate or have some other failure within weeks of being put on a vehicle.
Reading the code. The code is pretty simple.
The three-digit code was used for tyres manufactured before 2000. So for example 1 7 6 means it was manufactured in the 17th week of 6th year of the decade. In this case it means 1986. For tyres manufactured in the 90's, the same code holds true but there is a little triangle after the DOT code. So for this example, a tyre manufactured in the 17th week of 1996 would have the code 176 Tyres with a 3 digit code is too old and past their “use by” date, and therefore dangerous. If you have such tyres fitted, replace them ASAP!
After 2000, the code was switched to a 4-digit code. See pictures above and paragraph 1. Same rules apply, so for example 5 1 0 7 means the tyre was manufactured in the 51st week of 2007 on the first tyre, and on the second tyre, 1 0 0 3 means the tyre was manufactured in the 10th week of 2003.
The "fresher" the better and keep those receipts of when you purchased the tyres. This is a factor that every tyre buyer should pay attention too, even more so on imported tyres. Tyres offered on specials are often older tyres, close to their 4th or 5th anniversary, so check those dates!!
AND MORE SIDEWALL INFO:
Temperature grades are an indication of a tyre's resistance to heat. Sustained high temperature (for example, driving long distances in hot weather), can cause a tyre to deteriorate, leading to blowouts and tread separation.From highest to grade lowest, a tyre's resistance to heat is graded as “A”, “B”, or “C”.
Traction grades are an indication of a tyre's ability to stop on wet pavement. A higher graded tyre should allow a car to stop on wet roads in a shorter distance than a tyre with a lower grade.
Traction is graded from highest traction to lowest as "AA", "A", "B", and "C".
Tread wear grades are an indication of a tyre's relative wear rate. The higher the tread wear number is, the longer it should take for the tread to wear down.
A control tyre is assigned a grade of 100. Other tyres are compared to the control tyre. For example, a tyre grade of 200 should wear twice as long as the control tyre. This may however reduce traction.