Do you know the maximum
load index for your agricultural tyre?

How do you accurately calculate the maximum weight your tractor tyres can support? How do you work out how much load is transferred from the tool to the front and rear axles? How can you make sure you don't exceed the maximum load your tyres can handle? What weight should you put in the front to offset the weight of the tool behind, without exceeding the load limit for your tyres? What type of tyre is easiest in terms of pressure management? These are all questions you should be asking yourself if you want to avoid ruining your tyres in the space of a few months.

Tractor tire load index

Your tyres' load index is extremely important in deciding which tools you can use with your tractor or how you can load your trailers. If you already know the weight of your tools and you can calculate the load transferred to the tractor axles, you can go ahead and buy the right type of tyres for the work you carry out most often.

We all have a tendency to load our trailers to maximum capacity during our daily work, to quickly calculate the load transfer based on the tool, and to not bother adjusting the tyre pressure between the road and the field because it takes up too much time.

But remember, if the pressure is not adjusted it can lead to rapid tyre wear and will cost you a lot of money, as you'd have to replace your tyres more often and the quality of your work would be affected (vibrations, slip, soil compaction), but not heeding the maximum load per tyre can lead to accidents that cost you even more dearly.

 

How to calculate the load on each axle by weighing

  1. Weigh the front axle with the tool in its working position
  2. Weigh the rear axle with the tool lifted
  3. Ballast the front of the tractor to obtain a weight distribution of 35% at the front and 65% at the rear
  4. Check that the weight obtained complies with the load index of your tyres (see table below)
  5. Adjust the pressure based on the weight and driving speed

 

How to calculate the load on each axle without weighing

Load on each axle
Load on each axle

If you don't have any weighing equipment, you can calculate the load on each axle to make sure you're using the right pressure and that your tyres are protected.

»­To do this calculation, you will need to know:

  1. Your tractor's tare weight: read the manufacturer's information to find the front axle tare weight (FA tw) and the rear axle tare weight (RA tw).
  2. The weight of the rear-mounted tool M2(manufacturer data)
  3. The front ballast weight M1(or front-mounted tool, where applicable)

»­You must then measure:

  1. The distance d1between the centre-point of the front ballast weight (or centre-point of the front-mounted tool) and the centre of the front axle
  2. The distance E between the centre of the front axle and the centre of the rear axle
  3. The distance d2 between the centre of the rear axle and the centre-point of the rear-mounted tool

»­You can then calculate the weight on each axle:

calcul the weight on each axle

 

A TYRE LOAD INDEX OF 171 A8 MEANS A MAXIMUM OF 6150 KG AT 40 KM/H MAX

Indice de charge pneu agraire

 

In the table below you can find the load index that matches the marking on your tractor tyre.

This index tells you the maximum weight your tyre can bear at a given speed.

 

Equivalence table for weight in kg/tractor tyre load index

The tyre load index (LI) given in the table above is only valid if you stay below the speed code stated in the table below. In the photos for example, "171 A8" only applies to this agricultural tyre if you drive no faster than 40 km/h. Anything over this speed and your tyre will be overloaded, and will wear down very quickly and may even be extremely dangerous at higher speeds.

I.C. kg I.C. kg I.C. kg I.C. kg I.C. kg
73 365 74 375 75 387 76 400 77 412
78 425 79 437 80 450 81 462 82 475
83 487 84 500 85 515 86 530 87 545
88 560 89 580 90 600 91 615 92 630
93 650 94 670 95 690 96 710 97 730
98 750 99 775 100 800 101 825 102 850
103 875 104 900 105 925 106 950 107 975
108 1 000 109 1 030 110 1060 111 1 090 112 1 120
113 1 150 114 1 180 115 1215 116 1 250 117 1 285
118 1 320 119 1 360 120 1 400 121 1 450 122 1 500
123 1 550 124 1 600 125 1 650 126 1 700 127 1 750
128 1 800 129 1 850 130 1 900 131 1 950 132 2 000
133 2 060 134 2 120 135 2 180 136 2 240 137 2 300
138 2 360 139 2 430 140 2 500 141 2 575 142 2 650
143 2 725 144 2 800 145 2 900 146 3 000 147 3 075
148 3 150 149 3 250 150 3 350 151 3 450 152 3 550
153  3650 154 3 750 155 3 875 156 4 000 157 4 125
158 4 250 159 4 375 160 4 500 161 4 625 162 4 750
163 4 875 164 5 000 165 5 150 166 5 300 167 5 450
168 5 600 169 5 800 170 6 000 171 6 150 172 6 300
173 6 500 174 6 700 175 6 900 176 7 100 177 7 300
178 7 500 179 7 750 180 8 000 181 8 250 182 8 500
183 8 750 184 9 000 185 9 250 186 9 500 187 9 750
188 10 000 189 10 300            

 

SPEED CODE SPEED (km/h)   SPEED CODE SPEED (km/h)
A1 5   B 50
A2 10   C 60
A3 15   D 65
A4 20   E 70
A5 25   F 80
A6 30   G 90
A7 35
A8 40

 

WHAT TYPE OF TYRE LETS YOU KEEP THE SAME PRESSURE AT ANY SPEED?

Agricultural tyres made using VF technology are the most efficient low-pressure model on the market, enabling you to carry heavier loads with greater resistance per tyre, increase your tractor's traction capacity, and reduce your fuel consumption.

However, the biggest selling point is their reinforced casing design, which allows them work in fields at a very low pressure (0.8 bar), where the compressed tyres distribute the weight across a greater surface area, preserving your crops and your productivity.

They require no pressure adjustments between roads and fields, and are able to withstand higher road speeds at the same pressure as used in the field, while still offering a comfortable drive.

Although they are more expensive, they have so many benefits that most farmers never go back to their previous models, and tyre manufacturers occasionally offer free finance so you can maintain your cash flow while producing more and better.

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The information contained in this publication is for guidance purpose only. Whilst every effort has been taken in its production, no responsibility can be accepted for any loss or damage arising from any kind of undetected technical or commercial error contained in this content. Any data supplied in this publication is subject to possible revision following the date of publication. Due to the constant advance of tyre technology, the contents of this publication are subject to change without notice.