Tyre Sizes Explained- what do all those numbers and letters mean?

Here are a few examples of Tyre wall markings you will find on the side of your tyres and explanation of what they mean.

Example 1
235/65R17 106T

235= Section or Width of tyre in mm
65= Aspect Ratio, or height of sidewall as a % of Section (width)
R= Tyre contstruction, in this case Radial.
17= Rim diameter in Inches
106= Load Rating (see below)
T= Speed Rating (see below)

Example 2
9.50R16LT

9.50= Width in Inches
R= Tyre Construction, in this case Radial
16=Rim Diameter in Inches
LT= Light Truck construction

Example 3
32x11.50R15 LT

32= Diameter of the tyre mounted on the rim in Inches
11.50= Section Width in inches
R= Tyre Construction, in this case Radial
15= Rim diameter in Inches
LT= Light Truck Construction

Speed Rating:
Symbol- Km/h
L 120
M 130
N 140
P 150
Q 160
R 170
S 180
T 190
U 200
H 210
V 240

Load Rating:
Index #- Max Load in Kg

60- 250
70- 335
80- 450
90- 600
100- 800
110- 1060
120- 1400
130- 1900

How do I tell the age of a tyre?

All tyres are produced with a serial Tyre Identification Number (or serial TIN) that shows the date of manufacture of a tyre (See Figure 1&2 below). The last three digits (for tyres made pre 2000) or four digits (for post 2000 tyres) of the serial TIN indicate the week and year that the tyre was made. For example, Figure 1 below shows a tyre made in the 37th week of 1995 and Figure 2 shows a tyre made in the 12th week of 2004.

Figure 1: Serial code for 37th week of 1995


Figure 2: Serial code for 12th week of 2004

Also a tyre made in the 1990's can be distinguished from a tyre made in the 1980's due to a triangular indentation after the last number which is not present on 1980's tyres.

Now that's a great bit of information, thanks. I've only just started to come to terms with tyre sizing, after looking at a move from 31" tyres to 33's. I originally got confused when people talked about 33"s as there were two different size tyres which seemed to fit the catagory (285/75R16 and 305/70R16). However then I reallised the 70 and 75 was a percentage of the width, and all fell into place.

I have been told that if you look at the last four digits on the stamped serial number on the side of the tyre, the first two of the four are the week the tyre was manufactured and the last two is the year. Eg. Serial number 012340410 would indicate the tyre was made in the 4th week of 2010. Hope this last bit of info is correct, if not let me know and I'll remove it.

Thanks Bloke

You are absolutely correct. I have updated the above info with a description of the TIN (Tyre Identification Number).

Thank you for your contribution

Admin

Hi all,
one last piece of info is, most manufactures recomend a tyre life of only 4 years
Alan