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Search for a tyre by entering information on the sidewall. For help with your tyre size please see Reading Your Tyre Size, or just Contact Us and we'll be happy to help.

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The pages below have information specific to your application, as well as common tyres for vehicles in each category. Some categories do overlap and there are other aspects to consider, such as Pattern, Load Rating and Construction.

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Big Tyres has a huge range of brands available. If the brand you're looking for isn't listed then don't worry, you can Contact Us and we'll try to help.

Reading Your Tyre Size

A tyre size contains the most important information about your tyre. This will almost always include the tyres Width (Section Width) and the tyres Rim Diameter. The tyres Height (Outer Diameter) is sometimes included, otherwise the tyres Profile (Series) might be given so that the tyre height can then be calculated. The size marking on the tyre also indicates the tyres Construction, whether it be Radial or Crossply. Reading these values will help you search for your tyres.

Below are visual examples of how the size will be written on the sidewall of your tyre, as well as more in-depth explanations for a range of tyre sizes.

Visual Examples

  • 16.9R24 Mitas RD-30
    16.9R24 Tyre Size Labelled
  • 280/85R20 Petlas TA110
    280/85R20 Tyre Size Labelled
  • 21X8.00-9 Dunlop KT856
    21X8.00-9 Tyre Size Labelled
  • 14.9-26 8 Ply SuperKing
    14.9-26 Tyre Size Labelled
  • 480/80-26 Firestone STL
    480/80-26 Tyre Size Labelled
  • 26X11R14 Carlisle R-14
    26X11R14 Tyre Size Labelled
 

Tyre Sizes Explained

There are several methods for giving the size of tyres, with measurements sometimes given in inches, sometimes in millimetres, or sometimes in both! The examples and explanations given below should hopefully make it possible for you to recognise your own size markings.

Example 1: 3.00-4, 3.50-6, 4.00-8, 5.20-10, 6.00-12

The first number i.e. 3.00, tells you the width of the tyre (Section Width). It also tells you the height of the sidewall of the tyre in inches. The '-' means the tyre is Crossply (Radial construction would be represented by an 'R'). The final number, 4, is the Rim Diameter in inches. So a 3.00-4 tyre would fit on a 4 inch rim/wheel, have a 3 inch Section Width and be of Crossply construction.

Example 2: 6-12, 7-14, 8-16, 9.5-18

Same as the above but it does away with the '.00' for the first part of the size. Again, all dimensions are in inches. It is important to note that tyres with very similar markings may not be compatible - a 6-12 tyre will be significantly different in size to a 6.00-12. If in doubt, stick to the exact size that is fitted to the vehicle or recommended by the manufacturer or ask the Big Tyres Team for help.

Example 3: 4.10/3.50-4, 4.10/3.50-6, 5.30/4.50-6

Here we have four parts to the tyre marking. The first, 4.10, is the width (Section Width) of the tyre. The second, 3.50, is the height of the sidewall, the third number is the rim/wheel size (Rim Diameter), and again the '-' tells us its of Crossply construction (Radial construction would be represented by an 'R'). So a 4.10/3.50-4 tyre is 4.1 inches wide (section width of 4.1"), has 3.5 inch tall sidewalls, fits a 4 inch wheel/rim and is of crossply construction.

Example 4: 11X4.00-4, 13X5.00-6, 18X8.50-8, 25X12.00-9

The first part is the Outer Diameter of the tyre (the overall height from the ground to the top of the tyre) in inches. The second part is the width of the tyre (Section Width) in inches, and the third part is the rim size (Rim Diameter) in inches. The '-' tells us its of Crossply construction. So a 25X12.00-9 ATV tyre would be 25 inches tall (25" outer diameter), 12 inches wide (12" section width) and fit a 9" wheel/rim.

Example 5: 10X3, 18X4, 260X85

This marking is becoming obsolete, but you may still have tyres marked in this way. Measurements can be in inches or millimetres (it's fairly obvious which is which). The first part is the overall tyre height (Outer Diameter), the second is the tyre width (Section Width). The Rim Diameter is not mentioned in this size marking, but it can be easily worked out, because the tyre sidewall height will be the same as the tyres width. So, an 18x4 tyre is 18" tall (outer diameter), 4" wide (section width), and fits a 10" diameter rim (18" overall height minus two lots of 4" high sidewalls). The modern equivalent size for an 18x4 would therefore be 4.00-10. A 260x85 tyre would be 260mm high and 85mm wide. Converting these dimensions to inches gives us a tyre 10" high, 3" wide on a 4" rim. The modern equivalent size would be a 3.00-4.

Example 6: 255/60-10, 195/50R13, 420/85R28

The first part is the width (Section Width) of the tyre in mm, the second part, is the Profile of the tyre (height of the sidewall expressed as a percentage of the width), and the third number is the rim size (Rim Diameter) in inches. The 'R' when present within the size, means the tyre is of RADIAL construction, whereas the '-' shows its of CROSSPLY construction. So a 420/85R28 is 420mm wide (SECTION WIDTH), has a PROFILE of 85% (side walls are 85% of 420mm = 357mm tall), is of RADIAL construction and fits a 28 inch rim (RIM SIZE is 28"). A 195/50R13 tyre would be 195mm wide, have a sidewall height of 98mm, fit a 13" rim/wheel and be radial construction.

It is becoming more common for ATV/Quad tyres to be marked up in this manner. They are usually dual marked with their traditional inch dimensions also, but with a calculator, it's possible to convert from one to the other. For example, a 255/60-10 ATV tyre would be 255mm wide, have a 153mm sidewall height and fit a 10" rim. Converting these dimensions to inches would give us 10" width, 6" sidewall height and 22" overall height (10" rim plus two lots of 6" high sidewalls). In traditional ATV tyre size marking, this would become a 22x10.00-10.

Example 7: 145R10, 155R12

The first part is the width (Section Width) of the tyre in mm, and the second number is the wheel/rim diameter (Rim Diameter) in inches. The 'R' means its of Radial construction, whereas a '-' instead would mean its Crossply. There is no profile number percentage indication included in the tyre size, but with this type of marking the tyre sidewall height is normally taken to be 80% of the tyre width. So its assumed the profile is 80. You may sometimes see a tyre with the 80% in the size too eg. 155/80-13.

So, a 145R10 is a radial tyre, 145mm wide, sidewall height of 116mm (80% of 145mm) and fits a 10" rim/wheel. The approximate overall height of the tyre can be worked out by converting both dimensions to either mm or inches, and adding the rim diameter to twice the sidewall height.

 

Understanding Your Tyre Specs

As well as the tyre size there are other things to consider when choosing a tyre, such as how much weight it can safely carry, the maximum speed it can travel at, if the tyre requires an inner tube and whether the tyre tread pattern is suitable for the ground it is being used on.

Pattern

The most obvious aspect is the Pattern: which determines how and where the tyre can be used. The Big Tyres Blog has an article on common pattern types for Agricultural, Construction and Earthmover/OTR machinery but many other patterns exist.

When replacing tyres it is normally best to choose new tyres with a similar pattern, unless the current pattern is not suitable for the machine or its environment. For example, the 12.5/80-18 tyre size is used on a range of machinery and has different patterns for each application:

  • AW Rib Pattern
    12.5/80-18 BKT AW 702

    This pattern would be used on farm trailers and implements where the wheel is free-rolling (not on a driven axle). These tyres offer great longevity on the road but very little traction or protection from punctures.

  • Industrial Block Pattern
    12.5/80-18 SOLIDEAL BHZ

    This pattern is normally used on industrial machines, such as loaders and skid-steers, which operate on hard surfaces such as concrete or tarmac. The thick block tread makes for a long-lasting tyre which is difficult to puncture, but there is not much traction/grip on soft ground.

  • Industrial Lug Pattern (R4)
    12.5/80-18 SOLIDEAL SL R4

    This pattern is again used on industrial machines, sometimes known as a "Dog Leg" or "Hockey Stick" pattern. It is designed to give a balance between traction on soft ground and good wear on hard ground, and will often come as standard on construction machines.

  • Agricultural Lug Pattern (R1)
    12.5/80-18 BKT AS 504

    This pattern would be used on agricultural loaders and tractors, where traction is important for use in the field or on muddy ground. This is also known as an "Open Centre" pattern.

 

Construction

The construction is the structure of the tyre itself, and there are three construction types available: crossply, radial and solid.

Crossply, also known as "Diagonal" or "Bias Ply" is the older construction method but is still commonly used on agricultural, industrial and construction machinery. Crossply tyres are usually cheaper than their radial or solid counterparts, and the stiff sidewalls offer better protection against damage.

Radial is the modern construction method used in a huge number of applications. Almost all road-going vehicles will use radial tyres, as well as an increasing number of agricultural and earthmover machines. Radial tyres are more flexible, reducing soil compaction and giving better protection on the tread area.

Because the construction of the tyre can affect the inflated height and Rolling Circumference of the tyre, it is best to stick with what is on the machine unless all tyres are being changed. Crossply and radial tyres must never be mixed on the same axle. The Big Tyres Blog has an article on crossply and radial tyres.

Solid tyres are tyres which have no internal space for air, and are solid rubber compound all the way through. These tyres cannot be punctured, and are mostly used on forklift trucks and larger materials-handling machines. Solid tyres are not available in most sizes, generally only in forklift and some construction sizes, but our tyreFoam Filling Service is a good alternative to create the same effect for other industrial and construction machinery.

 

Tube-Type (TT) and Tubeless (TL) Tyres

Some tyres require inner tubes: these are normally crossply tyres and are marked on the Big Tyres website with "TT", for Tube-Type. Tubes are used when the tyre, the wheel rim, or the seal between them is not air-tight, for example a forklift truck with two-piece split rim wheels would require an inner tube to stop the air escaping.

Almost all radial tyres are Tubeless, and marked as "TL" on the Big Tyres website. Tubeless tyres have a special lining on the inside that makes the tyre air-tight, but the rims have to be one-piece for the assembly to hold air. Inner tubes cannot be put in tubeless tyres on any machine that is being used at high speed.

For more information on inner tubes, and for help on finding the right tube for your tyre, have a look at the Big Tyres Inner Tube Guide.

 

Load and Speed Rating

Another key component of the tyre spec is the load that it can carry, and what speed it can safely carry this load up to.

Ply Rating

Older crossply tyres will normally have a Ply Rating: the higher the ply rating the more weight the tyre can carry. It is important to always choose replacement tyres which meet or exceed the spec of the original tyres. The exact carrying capacity of a tyre will vary by size and brand, but if the tyre size and ply rating are the same then carrying capacity between brands should be very similar.

Load/Speed Index

Almost all radial tyres will instead have a Speed/Load Index. The first part is the load rating, given as a number, and the second part is the speed index, given as a letter or a letter with a number. Use the examples and the table below to understand your own tyres speed/load ratings.

Load/Speed Index Examples:
  • 137A8

    This index would be found on a radial tractor tyre. The first part, "137", means that the tyre is rated to carry up to 2,300 KG per tyre. The second part, "A8", means that the tyre is suitable for speeds of up to 25 MPH or 40 KPH.

  • 134A8/131D

    An index given twice like this gives the speed/load index for different uses, in this case low speed use ("134A8": 2,120 KG at 25 MPH or 40 KPH) and high speed use ("131D": 1,950 KG at 40 MPH or 65 KPH). This means that if the vehicle needs to travel at 40 MPH then a lower load limit applies.

  • 152/149K

    An index like this where the load rating is split is normally found on tyres for trucks and other commercial vehicles. In this index "152" is the load rating of one tyre, which is 3,550 KG for one tyre and 7,100 KG for the axle. The "149" is the load rating per tyre when two tyres are mounted together, so 3,250 KG per tyre, 6,500 KG for the two combined and 13,000 KG for all four tyres on the axle. The "K" rating is 68 MPH, or 110 KPH.

Load Range

Load Range is an older way of giving the carrying capacity, mainly used in the USA. It is used on radial tyres as a direct equivalent of a ply rating (see table).

Load/Speed Index Tables
Load Index
IndexKGIndexKGIndexKGIndexKGIndexKGIndexKGIndexKG
0 45 40 140 80 450 120 1,400 160 4,500 200 14,000 240 45,000
1 46.2 41 145 81 462 121 1,450 161 4,625 201 14,500 241 46,250
2 47.5 42 150 82 475 122 1,500 162 4,750 202 15,000 242 47,500
3 48.7 43 155 83 487 123 1,550 163 4,875 203 15,500 243 48,750
4 50 44 160 84 500 124 1,600 164 5,000 204 16,000 244 50,000
5 51.5 45 165 85 515 125 1,650 165 5,150 205 16,500 245 51,500
6 53 46 170 86 530 126 1,700 166 5,300 206 17,000 246 53,000
7 54.5 47 175 87 545 127 1,750 167 5,450 207 17,500 247 54,500
8 56 48 180 88 560 128 1,800 168 5,600 208 18,000 248 56,000
9 58 49 185 89 580 129 1,850 169 5,800 209 18,500 249 58,000
10 60 50 190 90 600 130 1,900 170 6,000 210 19,000 250 60,000
11 61.5 51 195 91 615 131 1,950 171 6,150 211 19,500 251 61,500
12 63 52 200 92 630 132 2,000 172 6,300 212 20,000 252 63,000
13 65 53 206 93 650 133 2,060 173 6,500 213 20,600 253 65,000
14 67 54 212 94 670 134 2,120 174 6,700 214 21,200 254 67,000
15 69 55 218 95 690 135 2,180 175 6,900 215 21,800 255 69,000
16 71 56 224 96 710 136 2,240 176 7,100 216 22,400 256 71,000
17 73 57 230 97 730 137 2,300 177 7,300 217 23,000 257 73,000
18 75 58 236 98 750 138 2,360 178 7,500 218 23,600 258 75,000
19 77.5 59 243 99 775 139 2,430 179 7,750 219 24,300 259 77,500
20 80 60 250 100 800 140 2,500 180 8,000 220 25,000 260 80,000
21 82.5 61 257 101 825 141 2,575 181 8,250 221 25,750 261 82,500
22 85 62 265 102 850 142 2,650 182 8,500 222 26,500 262 85,000
23 87.5 63 272 103 875 143 2,725 183 8,750 223 27,250 263 87,500
24 90 64 280 104 900 144 2,800 184 9,000 224 28,000 264 90,000
25 92.5 65 290 105 925 145 2,900 185 9,250 225 29,000 265 92,500
26 95 66 300 106 950 146 3,000 186 9,500 226 30,000 266 95,000
27 97 67 307 107 975 147 3,075 187 9,750 227 30,750 267 97,500
28 100 68 315 108 1,000 148 3,150 188 10,000 228 31,500 268 100,000
29 103 69 325 109 1,030 149 3,250 189 10,300 229 32,500 269 103,000
30 106 70 335 110 1,060 150 3,350 190 10,600 230 33,500 270 106,000
31 109 71 345 111 1,090 151 3,450 191 10,900 231 34,500 271 109,000
32 112 72 355 112 1,120 152 3,550 192 11,200 232 35,500 272 112,000
33 115 73 365 113 1,150 153 3,650 193 11,500 233 36,500 273 115,000
34 118 74 375 114 1,180 154 3,750 194 11,800 234 37,500 274 118,000
35 121 75 387 115 1,215 155 3,875 195 12,150 235 38,750 275 121,000
36 125 76 400 116 1,250 156 4,000 196 12,500 236 40,000 276 125,000
37 128 77 412 117 1,285 157 4,125 197 12,850 237 41,250 277 128,500
38 132 78 425 118 1,320 158 4,250 198 13,200 238 42,500 278 132,000
39 136 79 437 119 1,360 159 4,375 199 13,600 239 43,750 279 136,000

 

Speed Index
IndexMPHKPHIndexMPHKPH
A1 3 5 L 75 120
A2 6 10 M 81 130
A3 9 15 N 87 140
A4 12 20 P 94 150
A5 16 25 Q 100 160
A6 19 30 R 106 170
A7 22 35 S 112 180
A8 25 40 T 118 190
B 31 50 U 124 200
C 37 60 H 130 210
D 40 65 V 149 240
E 43 70 Z 149+ 240+
F 50 80 W 168 270
G 56 90 (W) 168+ 270+
J 62 100 Y 186 300
K 68 110 (Y) 186+ 300+
Load Range
Load RangePly Rating
A 2
B 4
C 6
D 8
E 10
F 12
G 14
H 16
J 18
L 20
M 22
N 24
 

 

Imperial to Metric Size Conversion

Tyre sizes are listed in either imperial form or metric form. Sometimes these sizes are interchangeable, or sometimes the older imperial format will now have been replaced with the newer metric equivalent. You should try using both the metric and imperial version of your tyre size in your search if you're unsure which is correct/current. Radial tyres are now more commonly marked in metric sizes. The chart below shows how to convert your imperial tyre size into its metric equivalent. Please note that although these tyres should be interchangeable in terms of overall height and rolling circumference, the differences in width mean that new rims might sometimes be required.

RimImperial SizeMetric Sizes
95 Profile90 Profile85 Profile80 Profile75 Profile70 Profile65 Profile60 Profile55 Profile50 Profile
20" 9.5-20     250/85R20 260/80R20   300/70R20 340/65R20      
11.2-20     280/85R20     320/70R20        
12.4-20     320/85R20     360/70R20 420/65R20      
13.6-20     340/85R20              
24" 9.5-24     250/85R24              
11.2-24     280/85R24              
12.4-24     320/85R24              
13.6-24     340/85R24     380/70R24 440/65R24 480/60R24    
14.9-24     380/85R24     420/70R24 480/65R24      
16.9-24     420/85R24     480/70R24 540/65R24      
17.5L-24           440/70R24        
17.5L-24           445/70R24        
17.5L-24           460/70R24        
19.5L-24           495/70R24        
19.5L-24           500/70R24        
26" 16.9-26     420/85R26     480/70R26 540/65R26      
18.4-26       480/80-26   520/70R26        
23.1-26         620/75R26   750/65R26      
28.1/28L-26             750/65R26      
28" 9.5-28     250/85R28              
11.2-28     280/85R28     320/70R28        
12.4-28     320/85R28     360/70R28 420/65R28      
13.6-28     340/85R28     380/70R28 440/65R28 480/60R28    
14.9-28     380/85R28     420/70R28 480/65R28 520/60R28    
16.9-28     420/85R28 440/80-28   480/70R28 540/65R28 600/60R28    
19.5L-28           495/70R28        
30" 14.9-30     380/85R30     420/70R30        
16.9-30     420/85R30     480/70R30 540/65R30 600/60R30    
18.4-30     460/85R30     520/70R30 600/65R30   710/55R30  
23.1-30         620/75R30 650/70R30        
32" 8.3-32 210/95R32                  
9.5-32 230/95R32     270/80R32            
11.2-32 270/95R32                  
12.4-32     320/85R32 300/80R32            
24.5-32         650/75R32 680/70R32        
30.5L-32             800/65R32   900/55R32 1000/50R32
34" 14.9-34     380/85R34              
16.9-34     420/85R34     480/70R34 540/65R34      
18.4-34     460/85R34     520/70R34 600/65R34      
36" 8.3-36 210/95R36                  
9.5-36 230/95R36     270/80R36            
11.2-36 270/95R36                  
12.4-36     320/85R36              
13.6-36     340/85R36              
38" 9.5-38 230/95R38                  
11.2-38 270/95R38                  
12.4-38     320/85R38              
13.6-38     340/85R38              
14.9-38     380/85R38              
16.9-38     420/85R38     480/70R38 540/65R38 600/60R38    
18.4-38     460/85R38     520/70R38 600/65R38 650/60R38    
20.8-38     520/85R38     580/70R38 650/65R38 710/60R38    
40" 7.2-40 180/95R40                  
9.5-40 230/95R40                  
42" 9.5-42 230/95R42                  
12.4-42 300/95R42                  
16.9-42     420/85R42              
18.4-42     460/85R42       600/65R42      
20.8-42     520/85R42     580/70R42 650/65R42 710/60R42   900/50R42
44" 8.3-44 210/95R44                  
9.5-44 230/95R44                  
11.2-44 270/95R44                  
46" 12.4-46 300/95R46                  
14.9-46     380/85R46              
18.4-46     460/85R46              
20.8-46     520/85R46     620/70R46        
48" 9.5-48 230/95R48                  
11.2-48 270/95R48                  
13.6-48     340/85R48              
52" 12.4-52 300/95R52                  
54" 11.2-54 270/95R54                  
12.4-54   320/90R54                

 

Technical Terms Explained

Width (Section Width)

This is how wide the tyre is if you were looking at the tyres tread face on. The number given in your tyre size is not the exact width of your tyre, but more the standard width a tyre should be according to the European Tyre & Rim Technical Organisation (E.T.R.T.O) for that tyre size. In general it can used a good guide to roughly how wide your tyre will be when inflated properly. The actual exact width of your tyre will vary with each Brand, and will be specified by each manufacturer in their tyres technical specification books, and even then individual tyres of the same brand might vary by an additional 2% from a manufacturer's specification.

Rim Diameter

This is the diameter of the rim that the tyre will fit (the diameter of the hole in the centre of the tyre). It is sometimes referred to as the Rim or the Rim Size, and it is given in almost every single tyre size as the last number after the "R" or "-" . The rims diameter is given in inches in 99% of tyre sizes. For some solid tyres/press-on-bands and some other rare occasions it is stated in mm not inches.

Rim Width

This is the width of the actual wheel rim that the tyre will fit. It is different to the tyres width (section width) as normally tyres are slightly wider than the metal wheel rim they fit on. Pneumatic tyres will have a recommended rim size, as well as alternative rims that the tyre will fit. Tyre manufacturers often tell you this information in their tyres technical spec data sheets. Solid tyres will fit only one rim width: this width will normally be given as a separate number after the tyre size. On some older crossply tyres this may be given after the section width in place of the profile.

Height (Outer Diameter)

This is the overall height of the tyre. This information is normally only given on turf, ATV, UTV and flotation tyres as the first number in the size, followed by an "X". It is usually written in Inches. For some small tyres this number is given in millimetres, normally followed by the tyre width in millimetres and then with the tyre rim size omitted.

Profile (Series)

The profile, sometimes known as the series, is the height of the tyres sidewall given as a percentage of the tyres width. This is normally only given on radial tyres, and is preceeded by a "/". To find the height of a tyre with a profile: Height(mm) = ((Profile / 100) * Width(mm) * 2) + (Rim(in) * 25.4).

Construction

Construction refers to whether a tyre is manufactured with either a Radial, Crossply or Solid construction. Each have their own benefits and drawbacks. Refer to these terms below.

Crossply

Crossply is the older pneumatic construction method, which creates a quite rigid tyre with stiff sidewalls. If a tyre is crossply it will be specified in the tyre size marking as a "-" before the rim size (as long as the tyre is not solid). Crossply tyres can be good in construction and forestry applications as the stiff sidewalls help prevent punctures in the tyre sidewalls.

Radial

Radial is the newer construction method used for almost all road-going tyres. This will be specified by an "R" before the rim size. Radial tyres are more expensive than crossply tyres normally, but they are more flexible, giving a more comfortable ride, and handle heat better so are more efficient at high speeds and the tyre tread will not wear down as fast as a crossply tyre might. The tread area is more flexible than a crossply tyre so it can flex over objects better helping it avoid punctures to the tread area.

Solid

Solid tyres have no air and so cannot be punctured. They are normally used on slow machines which operate only on hard, flat ground, such as forklift trucks. A solid tyre will normally say Solid on the tyre sidewall, but other indications are the lack of any air valve on the wheel rim as air is not required. Solid tyres wear well due to the amount of rubber on them, and the puncture resistance is vital in some applications like scrap metal recycling yards. They don't however offer much cushioning compared to pneumatic tyres so the ride can be stiff and machinery is put under more stress.

Rolling Circumference

This is the ground distance covered by the tyre in one full rotation. To avoid damaging four-wheel-drive (4WD) machines the ratio of front rolling circumference to rear rolling circumference must be maintained to within a small tolerance, and is why the front and rear tyre sizes on 4WD machines cannot be changed without considerable thought.