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Tyre Markings/Tyre Sizes
If you take time to look at the side wall of your tyres, whether they be on your 4WD vehicle, caravan, motorhome, camper trailer or RV, you will find a great deal of important information.
Each tyre will have distinct markings. Light truck (L/T) tyres are often used on 4WD vehicles, caravans, motorhomes and fifth wheelers.
Terms:
P = passenger car tyre
There are other types as well ie: ‘ST’ or Special Trailer and ‘LT’ for light truck tyres. There is also a truck or bus tyre which has no prefix like 12Rx22.5 LRH.
205 = (width) is the metric measurement across the widest portion of the sidewall (section width) in millimeters.
/ = The slash is the mathematical term indicating ratio.
65 = (height of side wall) the mathematical result of dividing the section height (depth of the tyre cross-section from the tread to the bead) by the section width (see above). This may also be referred to as the profile or series of the tyre. Eg: low profile or 70 series tyre. Ratios approaching 1 are generally associated with high carrying capacity and lower speed while low ratio .70 to .35 generally are towards a high performance capability with high speed and handling quality. In this case, the tyre height is approx 75% of the tyre width.
R = an alphabetical term for a radial tyre. In a radial tyre the cords run perpendicular to the bead of the tyre directly across the crown to the opposite bead.
16 = (rim diameter) this numerical number is the diameter of the bead of the tyre in inches. Bead seat diameters are manufactured in ½ inch increments. This tyre is designed to fit a wheel with a 16 inch diameter.
95 V = load/speed index (see load range below). A speed designation at which the tyre can carry the load corresponding to the Load Capacity Index.
Car Tyre Speed Ratings
Speed Symbol Maximum Speed
(km/ph)
L 120
M 130
N 140
P 150
Q 160
R 170
S 180
T 190
U 200
H 210
V 240
Z 240
W 270
Y 300
M + S = meets the Rubber Manufacturer’s Association standards for a mud and snow tyre. These can also be recorded as combinations such as M/S or M&S.
Tyre Maximum Load Rating
‘LR’ is the load range and the ‘D’ is the defined carrying capacity. The higher the letter in the alphabet, the higher the carrying capacity. The load range codes relates to the old system of plies. For example, ‘D’ is the 4th letter of the alphabet and multiply it by 2 (4 x 2 = 8) or 8 ply ‘rated’ tyre. (Another example is ‘E’ which is the 5th letter of the alphabet (5 x 2 = 10) or 10 ply). This shows us that the more carrying capacity we need the higher load range we require.
Load Range (LR) D = (8 ply rating) is the load carrying capacity of the tyre. (eg: D = Load Index 110, E = Load Index 116)
Max Load Single 1380 kg (3042 lbs) @ 450 kP3 (65 PSI) COLD
Max Load Dual 1260 kg (2778 lbs) @ 450 kP3 (65 PSI) COLD
‘Max Load’ = the maximum load capacity of the tyre. Operating a tyre over its rated capacity may damage the tyre internally.
‘Single’ = is the stated capacity when the tyre is installed in a single tyre application ie: one tyre on each end of an axle.
3042 lbs = rated carrying capacity of the tyre in pounds when installed in a single configuration.
65PSI = the minimum air pressure required to obtain the carrying capacity of 3042 lbs. If you reduce the inflation pressure the rated carrying capacity decreases. (Tyre pressure is measured in kilopascals (kPa) or pounds per squar inch (psi)).
“COLD” = this is the inflation pressure of the tyre cold, that is the tyre temperature before you commence a journey. See article explaining 4 PSI Rule
Tubeless = has no rubber tube. The tyre seals on the rim via the bead and it has an external valve
Treadplies = rubber coated cords forming the ‘footprint’ of the tyre
Polyester cord = a synthetic fibre that maintains strength properties at high heat levels and eliminates flat spotting.
Tyre Load Rating
Index Number Maximum Permissible Load
(kg)
60 250
70 335
80 450
90 600
100 800
110 1060
120 1400
130 1900
Tyre Age
Even unused tyres perish over time especially those exposed to heat, sunshine (UV radiation) and salt spray. Tyres are marked with the production date of the tyre and understanding these marking can help you determine the age of a tyre.
Spare tyres fitted to caravans, motorhomes, fifth wheelers and trailers are often exposed to the elements and can age prematurely.
It is recommended that you do not use tyres more than 6 years old from the date of manufacture. If a tyre has been in use, it has been reported that the effect of ageing has been lessened to a degree, but depending on the wear they should be replaced before 10 years. If you are in any doubt about the age and wear of a tyre discuss it with a tyre expert or replace it.
How Do I Tell The Age Of A Tyre?
Tyres carry a DOT number on the sidewall that gives a production date. Since the year 2000 the numbers consist of 4 digits instead of 3. The first two digits indicate the calendar week of production and the next two the year of production.
Eg: 3004 – the tyre was manufactured in the 30th week of 2004.
For tyres manufactured in the 1990’s there is a little triangle ∆ after the DOT code. Eg: 4 2 8 ∆ – the tyre was manufactured in the 42nd week of 1998.
If the tyre has a three digit code then it is too old.
Tread Wear
Keeping a check of on the wear of your tyres can increase their life. Follow the 4 psi rule and have the wheels balanced and rotated on a regular basis.
The tread wear indicator is the bump inside the groove. When tread wear indicators touch the ground as the wheel turns, the tyre needs replacing.
Skinny Spare Wheel/Space Saver Spares
Skinny spare wheels or space saver spares are only designed for temporary use. Recent studies have shown traction and stopping distance may be affected when using a skinny spare wheel/space saver spare so you may need to consider modifying your driving.
If you decided to replace the space saver spare wheel with a standard spare wheel and tyre check that it will fit in the spare wheel well.
