I have, in the not so distant past on this page, emphasised the importance of a set of good tyres to the optimal performance of a vehicle, and the comfort and safety of the vehicle’s driver and occupants.
Tyres, as vital components of an automobile, are very important but often ignorantly presumed by motorists to just be mere appendages of the vehicles. Presumptions, especially based on ignorance, may be bliss, but it is usually very costly. And to save readers from the life-devastating consequences of tyre-borne financial and environmental waste: like burning fuel and other physical mishaps easily caused by bad tyres, I will enumerate the important information a motorist needs to know about tyres before homing in on our specific topic for today: tyre speed ratings.
A typical tyre carries lots of helpful information in the forms of markings (numerical and alpha-numeric specifications) on its side walls: the number stated beside the “psi” indicates the maximum number of air pressure to be pumped into the tyre as recommended by its manufacturer. It’s however important to stress that a motorist must give priority to the psi specified by the manufacturer of the vehicle (which can be found on the plate sticker usually attached to the driver’s side door-post) on which the tyre is to be used.
Tyres also bear a four-digit numerical mark which states the week and the year of its manufacture (for example, “4106” means the forty-first week, “41”, of the year two thousand and six, “06”). This information is utterly important because the lifespan of an average tyre, whether used or not used at all, is five years internationally but the Standards Organisation of Nigeria and the Federal Road Safety Corps have recommended four years for Nigeria because of the extenuating circumstances tyres are subjected to on our roads. So, if a tyre is looking pristine and has never been used at all, but bears 0105, it is already a bad tyre!
The climate in which the tyre can be used is also usually specified on the tyre by its manufacturer. A tyre with the mark stating that it should only be used in a snowy environment/weather must not be used in our tropical clime. Indeed, in countries where such a tyre is illegally imported as used tyres to Nigeria, such a tyre is only used during the winter months and is changed in the summer.
Other vital indicators like the alphanumeric sign that states the nominal section width of the tyre, “165,” stroke the “aspect ratio,” i.e. the height of the tyre’s sidewall as a percentage of the nominal section width, “65,” with “R” radial construction, and, “14,” the diameter of the tyre’s inner rim in inches. All these come out as “165/65R14”
The information that is seldom understood and adhered to is the load capacity of a tyre, say “79” on the attached picture, and the tyre speed rating–i.e. the maximum speed for the tyre at full load–usually depicted as an alphabetical letter, “T” in our pictorial sample – M: 81mph or 130 km/h, – N: 87 mph or 140 km/h, – P: 93 mph or 150 km/h, – Q: 99 mph or 160 km/h, – R: 106 mph or 170 km/h, – S: 112 mph or 180 km/h, – T: 118 mph or 190 km/h, – U: 124 mph or 200 km/h, – H: 130 mph or 210 km/h, – V: 149 mph or 240 km/h, – Z: in excess of 149 mph or 240 km/h plus, – W: 168 mph or 270 km/h, – Y: 186 mph or 300 km/h), should strictly be respected by drivers.