Tyre Guide

Choosing tyres can be difficult as there are lots of factors involved in making the decision on your new tyres. There are certain pieces of information that are critical to getting the correct tyres and you can use the following guide to help get there as quickly and painlessly as possible. We have broken the various information down into sections to make it easier to digest.

Tyre Sizing

Tyre sizes can be displayed in many different ways. You can find your tyre size on the side wall of your existing tyre and it is important to make sure the details match before placing an order. Agricultural tyres come in a variety of different configurations and are listed in both metric and imperial sizing formats. These can be identified as follows:

Metric Sizing

Metric sizing is similar to what you would find on most car tyres. There are usually 3 numbers separated by either "/" or "-" or "R".

Metric Tyre Sizes - e.g. "165 / 70 - 10"

"165" Tyre Width (mm)

In this case width = 165mm.

"70" Tyre Profile

This is the tyre sidewall height dimension measured as a percentage of the width. In this example the sidewall height would be 70% of 165mm (approx. 115mm).

"10" Rim Diameter (Inches)

This is the diameter of the wheel or rim that the tyre requires (10" in this example)

Imperial Sizing

Imperial sizing is still very common on lots of the agricultural and ATV Tyre sizes. There are usually 3 numbers separated by "x" or "-"

Imperial Tyre Sizes - e.g. "25x8-12"

"25" Tyre Diameter (inches)

In this case the height or diameter of the tyre = 25 Inches

"8" Tyre Width (inches)

In this case the width of the tyre = 8 Inches

"12" Rim Diameter (Inches)

This is the diameter of the wheel or rim that the tyre requires (12" in this example)

Tyre Construction Types

The symbol before the rim diameter measurement helps identify what the construction type of the tyre is

"-" Crossply Construction

"B" Belted Bias Construction

"D" Diagonal Bias Construction

The above types of construction are all similar as they all feature woven plies of material into the construction of the tyres, each in a slightly different way.

"R" = Radial Construction

These Differ to the above cross and bias ply tyres as they feature a radial belt that runs around the circumference of the tyre. It is always recommended to run tyres of the same construction type on the same axle or machine. Mixing tyre types can provide unpredictable handling and operating characteristics as well as causing premature wear

What Do The Markings On The Tyre Mean?

If you are wondering what all the numbers and letters on a tyre side-wall mean, then you are certainly not alone! There are a number of pieces of information that are important and essential when choosing the correct tyre for the application. There is more to choosing a tyre than just the size required. Tyres are made and tested to work under certain criteria and limitations and the marking found on the sidewall of the tyre, all help choose the correct tyre for the application.

Maximum Inflation Pressure

Maximum Inflation Pressures show what the maximum pressure that should be used to 'seat the beads' of the tyres onto the rim. Agricultural, Turf & ATV tyres are notoriously difficult to fit and it is tempting to inflate the tyre pressure far beyond the maximum pressure marked on the sidewall. This can cause premature failure of the structure of the tyre and is something that should be avoided at all costs. The use of the correct tyre lubricant and fitting equipment is always recommended to ensure the safe operation and continued reliability of the tyre.

Operating Pressure

Operating Pressure shows what the optimal tyre pressure is to use in the tyre. If the tyre has a load speed index, the operating pressure is where the maximum load and speed are achieved. Inflating the tyre beyond the recommended operating pressure will not increase the carrying capacity or performance of the tyre. This differs from Maximum Inflation Pressure, as this is the pressure that the tyre has been designed and tested to run at to perform at optimal levels.

Load Index

Load Index is the limit of weight that the tyre can safely carry at the recommended operating pressure. Tyre manufacturers design the tyres to operate within certain weight parameters. Once the tyre has passed the tests, it is awarded a load rating. It is essential that the correct load rating is used for all tyres. Most vehicles used around the farm are worked hard and fitting a tyre that doesn't meet the requirements of the conditions can lead to premature wear, tyre damage or failure. Load indices are usually denoted by a number. The number itself is not the actual weight carried but represents the maximum weight that the tyre has been designed and tested for.

Speed Rating

Speed Rating is the maximum speed that the tyre has been designed to operate at. As with the load index, the speed rating is an important part of any tyre purchase. Ensuring you have the correct tyre for the job means better operation, reduced downtime and associated costs and increased overall value. Speed indices are usually shown as a letter ranging from A1 (3mph) to Z (>149mph). Some tyres may not have any load speed index marked on the sidewall, but most e-marked tyres will show the load speed index. The load speed index is usually clearly marked on at least one of the sidewalls of the tyres.

PLY Ratings (PLY or P.R.)

Ply Ratings can be quite confusing in modern times and used to be the standard way to represent the overall strength of the tyre. Ply rating used to show how many plies of rubber that were used to make up the construction of the tyre. For example, if a tyre had a 6PLY rating, it would be made up of 6 plies (layers) of rubber. Modern advances in vehicle tyre technology have led to other materials than rubber being used and construction methods increasing the strength of the tyre. The PLY rating is less commonly used to convey the number of plies and is now more relevant in showing the strength of the tyre AS IF it had that number of plies of rubber. Tyre ply rating is still useful in assessing the overall strength and puncture resistance of the tyre. In some cases, PLY ratings are not shown and instead, there is a star symbol. One star is equivalent to 2 plies so a 3* rating is equivalent to a 6 PLY.

Mud/Snow (M+S Marking)

Some tyres may have been tested and marked suitable for mud and snow conditions or in winter use. The M+S mark or symbol shows that these tyres will perform better in those conditions than a typical summer or non M+S marked tyre.

E-Marking

E-Marks show the specific number allocated to the tyre, that have been allocated for use by the EU. The 'E mark' or 'e number' shows that the tyre has been manufactured to a specific criteria and recorded by the EU for use in the EU. All tyres used on PLG registered vehicles including All terrain vehicles and Utility Vehicles must have e marked tyres to be classed as roadworthy / legal. E marks are also a requirement to pass an MOT test in the UK for PLG registered vehicles.

DOT Codes

Dot Codes are used to identify when a tyre was made. It is usally in the form of a 4 digit code and can be split in to the first two and second two digits e.g. "1620" This indicates that the tyre was made in the 16th week (16) of the year 2020 (20). This can be useful to know in certain applications such as trailers and caravans.

Tyre Load Index Chart

What is a Tyre Load Index?

A tyre load index shows what weight a tyre is capable of carrying, when installed to manufacturer recommendations and pressures. Some tyres may have multiple load capacities at different speeds and pressures. Always refer to the manufacturer guidelines when choosing new tyres and ensure that the load and speed index is suitable for your machinery.

Below is a table of the most common load index marks found on the sidewall of tyres:

Load Index	Load (KG)	Load Index	Load (KG)	Load Index	Load (KG)	Load Index	Load (KG)	Load Index	Load (KG)
0	45	45	165	90	600	135	2180	180	8000
1	46.2	46	170	91	615	136	2180	181	8250
2	47.5	47	175	92	630	137	2240	182	8500
3	48.7	48	180	93	650	138	2360	183	8750
4	50	49	185	94	670	139	2430	184	9000
5	51.5	50	190	95	690	140	2500	185	9250
6	53	51	195	96	710	141	2575	186	9500
7	54.5	52	200	97	730	142	2650	187	9750
8	56	53	205	98	750	143	2725	188	10000
9	58	54	212	99	775	144	2800	189	10300
10	60	55	218	100	800	145	2900	190	10600
11	61.5	56	224	101	825	146	3000	191	10900
12	63	57	230	102	850	147	3075	192	11200
13	65	58	236	103	875	148	3159	193	11500
14	67	59	243	104	900	149	3250	194	11800
15	69	60	250	105	925	150	3350	195	12150
16	71	61	257	106	950	151	3450	196	12500
17	73	62	265	107	975	152	3550	197	12850
18	75	63	272	108	1000	153	3650	198	13200
19	77.5	64	280	109	1030	154	3750	199	13600
20	80	65	290	110	1060	155	3875	200	14000
21	82.5	66	300	111	1090	156	4000	201	14500
22	85	67	307	112	1120	157	4125	202	15000
23	87.5	68	315	113	1150	158	4250	203	15500
24	90	69	325	114	1180	159	4375	204	16000
25	92.5	70	335	115	1215	160	4500	205	16500
26	95	71	345	116	1250	161	4625	206	17000
27	97.5	72	355	117	1285	162	4750	207	17500
28	100	73	365	118	1320	163	4857	208	18000
29	103	74	375	119	1360	164	5000	209	18500
30	106	75	387	120	1400	165	5150	210	19000
31	109	76	400	121	1450	166	5300	211	19500
32	112	77	412	122	1500	167	5450	212	20000
33	115	78	425	123	1550	168	5600	213	20600
34	118	79	437	124	1600	169	5800	214	21200
35	121	80	450	125	1650	170	6000	215	21800
36	125	81	462	126	1700	171	6150	216	22400
37	128	82	475	127	1750	172	6300	217	23000
38	132	83	487	128	1800	173	6500	218	23600
39	136	84	500	129	1850	174	6700	219	24300
40	140	85	515	130	1900	175	6900	220	25000
41	145	86	530	131	1950	176	7100	221	25750
42	150	87	545	132	2000	177	7300	222	26500
43	155	88	560	133	2060	178	7500	223	27250
44	160	89	580	134	2120	179	7750	224	28000

Tyre speed rating chart

What is a Tyre Speed Rating?

A tyre speed rating shows what speed a tyre is capable of achieving, when installed to manufacturer recommendations and pressures. A speed rating is often combined with a load rating to show what weight a tyre will carry up to a certain speed. Always refer to the manufacturer guidelines when choosing new tyres and ensure that the load and speed index is suitable for you machinery.

Below is a table of the most common Speed Rating marks found on the sidewall of tyres

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

Load / Speed Index

A load speed index is usually found on the sidewall of a tyre and is what the manufacturers have tested and rated the maximum loads and speeds that the tyre is capable of. It is very important that you choose the correct load / speed index for your vehicle as per the vehicle manufacturers recommendations. It is usually safe to increase the load / speed index, but again, manufacturer guidelines should be followed.

A load speed index gives the weight and speed a tyre is capable of e.g 116D would indicate that the tyre is capable of carrying 1250kg up to a speed of 40mph. Often in agricultural tyres, the load speed index can alter so that a vehicle travelling at a lower speed may be able to carry more weight. It is always worth checking the tyre manufacturers specifications for further details on this.

ATV & UTV Tyre Size Charts