Tyres
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Tyre condition:
Vehicle and trailer tyres must have at least 1.6mm of tread
over the central 75% of their width for
their entire
circumference, although a legal tyre with under 3mm offers
little grip in the wet especially at speed.
Tyres must be free from deep
cuts and bulges (which indicate they could be breaking
up)
It is illegal to use
cross-ply and radial tyres on the same axle.
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Tyre sidewall markings :
The illustration above
provides an explanation of the markings currently found on a
tyre sidewall.
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* does not apply in the U.K.
Retreads - must also show either 'RETREAD' or 'REMOULD' on
the sidewall, together with 'BSAU 144' in place of ECE Type
Approval Mark.
Aspect ratio - ratio between the height of the sidewall and
the width of the tread, expressed as a percentage. In the
example above, the figure is 70%.
Nominal section width - on radial tyres this is expressed in
millimetres, on cross ply tyres, inches are used.
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Load Index
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The LOAD INDEX is a
numerical code associated with the maximum load a
tyre can carry at the speed indicated by its Speed
Symbol under service conditions specified by
E.T.R.O 1991, passenger car tyres section 13,
reproduced below. |
|
Load
Index |
Load
kg |
Load
Index |
Load
kg |
Load
Index |
Load
kg |
Load
Index |
Load
kg |
Load
Index |
Load
kg |
Load
Index |
Load
kg |
|
60 |
250 |
71 |
345 |
82 |
475 |
93 |
650 |
104 |
900 |
115 |
1215 |
|
61 |
257 |
72 |
355 |
83 |
487 |
94 |
670 |
105 |
925 |
116 |
1250 |
|
62 |
265 |
73 |
365 |
84 |
500 |
95 |
390 |
106 |
950 |
117 |
1285 |
|
63 |
272 |
74 |
375 |
85 |
515 |
96 |
710 |
107 |
975 |
118 |
1320 |
|
64 |
280 |
75 |
387 |
86 |
530 |
97 |
730 |
108 |
1000 |
119 |
1360 |
|
65 |
290 |
76 |
400 |
87 |
545 |
98 |
750 |
109 |
1030 |
120 |
1400 |
|
66 |
300 |
77 |
412 |
88 |
560 |
99 |
775 |
110 |
1060 |
121 |
1450 |
|
67 |
307 |
78 |
425 |
89 |
580 |
100 |
800 |
111 |
1090 |
122 |
1500 |
|
68 |
315 |
79 |
437 |
90 |
600 |
101 |
825 |
112 |
1120 |
123 |
1550 |
|
69 |
325 |
80 |
450 |
91 |
615 |
102 |
850 |
113 |
1150 |
124 |
1600 |
|
70 |
335 |
81 |
462 |
92 |
630 |
103 |
875 |
114 |
1180 |
125 |
1650 |
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Speed Symbol
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The SPEED SYMBOL indicates the
speed at which the tyre can carry a load corresponding to
its Load Index under service conditions specified by the
tyre manufacturer. For caravans and light trailers see
conditions specified by E.T.R.O 1991, passenger car tyres
section 13, reproduced below. |
|
Speed
Symbol |
Maximum car speed for which tyre is suitable |
|
km/h |
mph |
|
J |
100 |
60 |
|
K |
110 |
69 |
|
L |
120 |
75 |
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M |
130 |
81 |
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N |
140 |
87 |
|
P |
150 |
93 |
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Q |
160 |
100 |
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R |
170 |
106 |
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S |
180 |
113 |
|
T |
190 |
118 |
|
U |
200 |
124 |
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H |
210 |
130 |
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V |
240 |
150 |
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E.T.R.T.O. 1991 - Section 13 - Caravans & Trailers:
An increase of 10% over the load capacity quoted in the
tables is permitted when tyres are fitted to caravans and
light trailers with a maximum operating speed up to 100
km/h. (60 m.p.h.). The basic inflation pressure should be
increased by 3 p.s.i. / 0.2 bar.
This 10% bonus loading is widely used in the U.K. light
trailer industry, but should only be used on trailers that
are to be sold within the U.K. The caravan industry in the
U.K. tends to ignore this bonus loading and use loadings at
130 km/h / 81 m.p.h.
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Load & Tyre Ratings
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A table covering popular trailer sizes is given below.
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Tyre
size |
Max
speed |
|
100 km/h |
60 mph |
130 km/h |
81 mph |
|
Axle
Load kg |
PSI/Bar |
Axle
Load kg |
PSI/Bar |
|
400 x 8
(4ply) |
540 |
60/4.2 |
- |
- |
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400 x 8
(6 ply) |
680 |
75/6.2 |
- |
- |
|
500 x 10
(6 ply) |
860 |
50/3.5 |
- |
- |
|
5.20 x
10 |
616 |
32/2.2 |
- |
- |
|
145 x10 |
693 |
35/2,4 |
630 |
32/2.2 |
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145 x 10
(R/F) |
781 |
42/2.9 |
710 |
39/2.7 |
|
140/70 x
12 |
1060 |
62/4.3 |
- |
- |
|
155/70 x
12 |
1800 |
90/6.2 |
1636 |
87/6.0 |
|
145 x 13 |
825 |
53/3.7 |
750 |
32/2.2 |
|
155 x 13 |
935 |
35/2.4 |
850 |
32/2.2 |
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155 x 13
(R/F) |
1045 |
42/2.9 |
950 |
39/2.7 |
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165 x 13 |
10445 |
36/2.5 |
950 |
33/2.3 |
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165 x 13
(R/F) |
1166 |
45/3.1 |
1060 |
42/2.9 |
|
175 x 13 |
1166 |
36/2.5 |
1060 |
33/2.3 |
|
175 x 13
(R/F) |
1276 |
45/3.1 |
1160 |
42/2.9 |
|
175 x 13
(6ply) |
1407 |
54/3.75 |
1340 |
54/3.75 |
|
183 x 13
(6ply) |
1500 |
54/3.75 |
1460 |
54/3.75 |
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185/70 x
13 (Avon 950) |
1900 |
87/6.0 |
1800 |
87/6.0 |
|
175 x 14
(6ply) |
1491 |
54/3.75 |
1420 |
54/3.75 |
|
175 x 14
(8ply) |
1628 |
65/4.5 |
1550 |
65/4.5 |
|
185 x 14
(6ply) |
1628 |
54/3.75 |
1550 |
54/3.75 |
|
185 x 14
(8ply) |
1785 |
65/4.5 |
1700 |
65/4.5 |
|
195 x 14
(6ply) |
1785 |
54/3.75 |
1700 |
54/3.75 |
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195 x 14
(8ply) |
1995 |
65/4.5 |
900 |
65/4.5 |
|
600 x 16
(6ply) |
1533 |
52/3.6 |
- |
- |
|
650 x 16
(6ply) |
1890 |
62/4.3 |
- |
- |
|
750 x 16
(6ply) |
2100 |
51/3.5 |
- |
- |
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N.B. - It is dangerous to inflate a tyre to more than
its maximum pressure
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