Understanding the tyrewall

Every tyre shows information pertaining to its manufacturer, size, model etc. So what do the letters and numbers mean on the sidewalls of tyres?

235 / 45 ZR 17 93 W

The following is an explanation of all the terminology used.

235 - means the tyre has a nominal section width of 235 millimetres

45 - sidewall height is 45% of tyre nominal section width

Z - means it's rated for speeds over 150mph (210kmh)

R - means radial S - means Steel

17 - means it fits a 17" diameter wheel

93 W - shows load capacity index (numerical code) and speed category symbol (alphabetic code).

Other common speed ratings are:

S - 113mph (180kmh) T- 118mph (190kmh)
H - 130mph (210kmh) V - 150mph (240kmh)
W & Z - over 150mph

You should always replace a tyre with the same or a higher speed rating. In general, the higher the speed rating, the better the quality of the tyres and the more advanced the technology.

Good Tyres

Good tyres are essential for safe driving They're your only contact with the road and affect steering, braking and acceleration. The part of a tyre that is in contact with the road is known as the "footprint". A standard sized tyre has a footprint approximately the size of an A5 sheet of paper.

So correct tyre pressures are vital for balanced braking, maximum grip and maximum tyre life.

Recommended pressures may vary according to load or speed. Look in the vehicle handbook, or consult your nearest LTC Tyre centre.

WRONG TYRE PRESSURES (high or low) will cause more rapid wear and shorter tyre life.

LOW TYRE PRESSURES also cause increased fuel consumption and consequently increased air pollution. Higher than necessary pressures may give an uncomfortable ride and reduce grip due to the size of the "footprint".