It is one of the most common questions in tire management: when the truck is heavily loaded, should I put more air in the tires? The short answer is that the load tables say yes, up to the tire’s maximum, and that the exact amount comes from the axle weight. The longer answer is more interesting, because it exposes two traps. The first is guessing, which usually leads to a number that is either wasteful or unsafe. The second is believing that pressure can make up for an overloaded axle, which it cannot. This guide explains the axle-weight method using the Goodyear load capacity ladder, shows how much capacity each increment of pressure buys, and sets out what Prometeon, Hankook and Bridgestone say about overload. For related reading, see our steer, drive and trailer pressure guide and the master pressure chart.
Pressure carries the load
Prometeon’s manual states the principle clearly: it is the compressed gas in the tire that supports the load. More load needs more pressure to hold the tire at the same deflection. If the load rises and the pressure does not, deflection increases, heat builds and the tire ages faster. The load tables from every manufacturer express this as a ladder: for each load index, capacity rises with pressure in small steps. Heavy loads therefore do need higher pressure, but only as much as the ladder says, and only up to the maximum.
The Goodyear ladder for load index 152
Load index 152 covers the 295/80R22.5 152/148. Goodyear’s table lists capacity per axle for single fitment (two tires) at each pressure. The table below also gives the pressure in psi and the capacity in pounds, so you can compare with US charts:
| Pressure (bar) | Pressure (psi) | Capacity per axle, single (kg) | Capacity per axle, single (lb) | Gain per step |
|---|---|---|---|---|
| 5.00 | 72.5 | 4,640 | 10,230 | — |
| 5.50 | 79.8 | 5,010 | 11,045 | +370 kg |
| 6.00 | 87.0 | 5,370 | 11,840 | +360 kg |
| 6.25 | 90.6 | 5,560 | 12,260 | +190 kg |
| 6.50 | 94.3 | 5,730 | 12,632 | +170 kg |
| 6.75 | 97.9 | 5,910 | 13,030 | +180 kg |
| 7.00 | 101.5 | 6,080 | 13,404 | +170 kg |
| 7.25 | 105.1 | 6,250 | 13,779 | +170 kg |
| 7.50 | 108.8 | 6,420 | 14,154 | +170 kg |
| 7.75 | 112.4 | 6,590 | 14,529 | +170 kg |
| 8.00 | 116.0 | 6,760 | 14,904 | +170 kg |
| 8.25 | 119.7 | 6,930 | 15,278 | +170 kg |
| 8.50 | 123.3 | 7,100 | 15,653 | +170 kg |
The ladder reveals a rule of thumb: each 0.25 bar (3.6 psi) adds about 170 kg (375 lb) per axle, or roughly 85 kg per tire. Put another way, one extra psi buys about 104 lb of axle capacity, or 52 lb per tire. If your axle is loaded 1,000 lb heavier than your last setting, you need about 10 psi more, provided the tire has the headroom. That is why a lightly loaded and fully loaded axle should not run the same pressure.
The axle-weight method in five steps
- Weigh the axle. Use a weighbridge or on-board scales, loaded and unloaded, and record the highest realistic weight per axle.
- Convert to the correct unit. Match the table: kg per axle for Goodyear and other European books, lb per tire or per pair for TRA-based books.
- Choose the correct fitment. Single (two tires) or dual (four tires).
- Find the first pressure that carries the load plus a margin. Use 5 percent as a minimum and 10 percent for variable loads.
- Set the cold pressure and label the axle. Record it on the log and the truck.
A worked example
A steer axle on a 295/80R22.5 tractor weighs 5,200 kg loaded. With a 10 percent margin the planning load is 5,720 kg. Reading the ladder, 5,730 kg is the first capacity at or above the planning load, at 6.50 bar (94.3 psi). With a 5 percent margin (5,460 kg), the answer is 6.25 bar (90.6 psi). The difference between the two policies is 3.7 psi, which changes capacity by about 170 kg. A fleet in a hilly region with heavy braking would take the higher figure; a motorway fleet with steady loads might accept the lower.
Now suppose the same tractor is empty and the steer axle weighs 4,000 kg. The ladder shows 4,640 kg at 5.00 bar, so the tire would be safe even at the lowest pressure in the table, but running at 5.00 bar is not recommended in normal operation. Most fleets would keep the pressure at the loaded setting for the sake of consistency, accepting a firmer ride when empty.
Pressure cannot fix overload
The most dangerous misunderstanding is that more air makes it safe to carry more load. It does not. Each tire has a maximum load, defined by its load index at maximum pressure, and a maximum pressure. Prometeon says that overload leads to effects similar to under-inflation. Bridgestone warns that any tire known or suspected to have run overloaded may have permanent structural damage such as steel cord fatigue. And Hankook’s guidance allows only a small compensation: for heavy loads, add pressure but do not exceed the tire’s maximum inflation or the maximum axle load. In one example, Hankook allows slight over-inflation of not more than 10 percent to compensate for a max load condition, perhaps with a speed reduction.
The rule is simple. If the load requires more pressure than the tire’s maximum, the tire is overloaded, and no amount of extra air will change that. The solution is to reduce the load, choose a tire with a higher load index or a higher load range (see 11R22.5 load range G vs H), or add axles.
Reefers, bulk and other special cases
- Bulk liquids and slurries: the load surges during braking and cornering, so use the 10 percent margin.
- Refrigerated trailers: loads often sit near the legal limit and shift towards the front, increasing the weight on the drive axle group.
- Livestock and loose cargo: uneven distribution can overload one side. Weigh side by side if possible.
- Vocational trucks: mixers, tippers and cranes see static and dynamic loads that exceed highway norms. Consult the manufacturer for each setup.
- Liftable axles: when the lift axle is raised, the other axles carry more. Re-check the pressure of the tires that remain on the road.
How often should you re-weigh?
Re-weigh whenever the commodity, trailer type or loading pattern changes, and at least twice a year. A truck that moves from hauling pallets to hauling steel coils can have an axle load 20 percent higher. A fleet that only weighs the gross vehicle may miss an overload at the axle. Many scale systems and telematics providers can now report axle weight, which makes it easier to link pressure to load. For a broader view of how to pair load and pressure, see our truck and bus tire pressure guide.
Costs of getting it wrong
If the pressure is too low for the load, the tire runs hot and loses casing value, as set out in our post on underinflation damage. If the pressure is too high for the load, the tire wears in the center, as described in overinflation and uneven wear. The cost per tire is modest, but fleet-wide it adds up to a significant share of total tire cost; see the total cost of ownership analysis. A pressure policy tied to axle weights is the cheapest fix.
Pressure and loading discipline go together
Pressure is only half of a load policy. The other half is the way the vehicle is loaded. A trailer loaded with the heaviest pallets at the front, or a tanker that is partly full, can put 2,000 lb more on one axle group than the same cargo evenly distributed. Training loaders and dispatchers to balance the load across axles reduces the highest axle weight and therefore the pressure needed. It also reduces wear on the heavily loaded axle. In some fleets, simply moving the sliding tandem or fifth wheel a few holes to rebalance weight has done more for tire life than any change to pressure. Review axle weights regularly, adjust loading and fifth-wheel position, and then set pressure from the final numbers.
FAQ
How much more pressure do I need for 1,000 lb extra?
About 10 psi on the 295/80R22.5, based on the Goodyear ladder. The exact figure varies by size, so read your table.
Can I run maximum pressure all the time to be safe?
No. It gives a smaller contact patch, uneven wear and a harsher ride, and it uses capacity you rarely need.
What if my axle weight is above the table’s maximum?
Then the tire is overloaded. Reduce the load or choose a tire with a higher rating.
Key takeaways
Heavy loads need higher pressure, but only as much as the load ladder specifies, and never beyond the maximum. Weigh axles, add a margin, read the table, and re-check when conditions change. Continue with the pressure management hub for more.
