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.
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
70
80
90
100
110
120
130
250
335
450
600
800
1060
1400
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.
Search this Site
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.
Tread
Wear
