1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172 
Tyred and oversized
Page 35
If you've noticed an error in this article please click here to report it so we can fix it.
ALAN BUNTING is quite correct in his (CM,October 4) letter with regard to the conversion of Imperial tons to kilograms. The Dunlop Truck Tyre data book shows 6 tons equivalent to 6100kg and 6.5 tons equivalent to 6610kg.
With regard to axle weights, the maximum permitted imposed weight on a single axle is ten tons where the axle is fitted tiwh twin wheels having 300mm minimum tyre centres, or single wide tyres with overall widty of 300mm or above. Otherwise a two-wheeled axle may not exceed nine tons. Construction and Use Regulations permit steering axles to be seven tons (7120kg) or nine tons (9150kg). The seven-ton axle needs no load-compensating device.
In all cases the actual legal permitted axle load is the DTP plated figure on the individual vehicle.
As your correspondent suggests, the probable maximum "practical" weight for singletyred steered axles is seven tons and the minimum tyre size which could be fitted is 11.00-24 16 ply, or alternatively 12,00-20, 13-22.5, or the low-profile E22.5 (315/75-22.5). Dunlop Stabila, the latter three sizes having the capability of carrying 7.51 tons (7630kg) plated axle load. Fitting the tyres on the front, while providing commonality of size down the train would however mean fitting unnecessarily large and more expensive tyres — four of them — on the rear.
The fitment of these tyres to steer axles could obviously cause clearance problems and this would need checking on individual vehicles, but I am sure that your correspondent appreciates that the subject of oversizing is not only a subject to be dealt with by tyre manufacturers but also the vehicle manufac. turer. Oversizing on certain oc. casions makes sound economir sense.
P. W. ROSS