How to read codes on truck tyre sidewalls
Greg Whitaker explains how to decipher the runes on truck tyres
Here at PMV, we often mention how to gauge what sort of life a machine has had by the condition of its tyres, but just what do all of those markings mean? Well, on a tyre for a road-going truck, you are likely to see something as follows: 295/80 R 22.5 152/148 M.
In this case, 295/80 means that the tyre is 295mm wide, while the other number refers to the ‘aspect ratio’ which is the ratio between nominal section height and nominal section width. ‘R’ refers to the construction type, which will generally be radial for road tyres in the UAE, though you may come across cross-ply tyres in other countries. 22.5 is the rim diameter in inches while 152/148 is the load rating. The letter is the speed rating – in this case 130km/h.
More likely than not, you’ll also see the word ‘REGROOVEABLE’ carved in the tyre wall. If you are reading this, then the chances are that you already knew that the life of the tyre can be prolonged by cutting an extra few millimetres of tread when it starts to wear out. However, did you know that you can also re-groove remoulds?
Elsewhere on the tyre, you’ll find the DOT markings. Most know how to read the year of manufacture, but what do the remaining numbers mean? Supposing you have a DOT code that reads as follows: CU BA LMK03 1512.
‘CU’ refers to the factory that produced the tyre – in this case Continental’s plant in Hannover, Germany. At the time of writing, there are some 944 factories worldwide with a tyre code – although some of them may not be currently producing anything. ‘BA LMK03’ refers to the tyre model and size (a Continental Long Distance unit in this case), while 1512 is the week and year of production – in this case the third week of April in 2012.
You might also come across the term ‘ply rating’ or PR on a tyre wall. This was an international standard for the structural strength of the tyre sub-structure.
The term dates from the time when cotton was still used for the fabric sub-structure and referred to the number of ‘plies’ of cotton cord that reinforced the tyre wall. For a long time, the PR reference continued to be used, even on radial belted tyres, but recently manufacturers have felt it to be a misleading term and have instead opted to include ‘service index’, which gives further info on load and rating.
Another word you might find on the tyre is REMOULD. Remould tyres are extremely popular in Europe, although they have yet to command such a market share in the Middle East. However, remoulds from an established brand such as Bandvulc will not only be clearly marked as such, but they also feature a barcode that can track the tyre back to where, when, and by whom it was produced.
Finally, the future of tyre marking could be no physical marking at all, as firms such as Goodyear switch to embedding RFID chips somewhere inside the tyre casings. This will allow anyone with a reader – potentially even at a weighbridge – to wirelessly read all of the information on the sidewall in plain language.