Tyre pressure is the cheapest, simplest, and most overlooked factor in how a tyre performs. It costs nothing to get right, takes a couple of minutes to check, and yet incorrect pressure is behind a huge share of premature wear, poor performance, wasted fuel, and outright failures. Whether you are running a fleet of mowers, a working quad, a loaded trailer, or a compact tractor, tyre pressure has more influence on the outcome than almost anything else you can control.
Here is what pressure actually does, what happens when it is wrong, and how to get it right across the different machines you run.
What Tyre Pressure Actually Does
A pneumatic tyre does not really run on rubber - it runs on air. The air inside carries the load, and the rubber and carcass simply contain it and provide the contact with the ground. The pressure determines the shape and size of the contact patch, which is the small area of tyre actually touching the surface at any moment.
Get the pressure right and the contact patch is the size and shape the tyre was designed for. The load is spread evenly, the tread wears evenly, and the tyre behaves predictably. Get it wrong and the contact patch distorts, and everything else follows from there.
The Problems With Underinflation
Underinflation is the more dangerous of the two errors, and the more common. When a tyre is soft:
- It overheats: A soft tyre flexes excessively as it rolls, and that flexing generates heat. Heat is the enemy of rubber - it accelerates wear and, in the worst case, leads to a blowout. This is the leading cause of tyre failure at speed.
- It wears at the edges: Underinflation lifts the centre of the tread and puts the weight onto the shoulders, so the tyre wears fastest at its outer edges.
- It costs fuel: A soft tyre has more rolling resistance, so the engine works harder to move the machine. On a fleet, that adds up.
- It handles poorly: Soft tyres feel vague, roll in corners, and can creep on the rim under load.
- It damages the surface: On turf, an underinflated tyre with a larger contact patch is not always gentler - the extra flexing and scrubbing can mark and stress the grass.
The Problems With Overinflation
Overinflation is less immediately dangerous but still costly:
- It wears in the centre: Too much pressure bulges the centre of the tread outward, so the tyre rides on its middle and wears fastest there.
- It reduces grip: A smaller contact patch means less rubber on the ground and less traction, especially in the wet or on loose surfaces.
- It rides harshly: An over-hard tyre transmits every bump, which is uncomfortable and hard on the machine.
- It is vulnerable to impact: With less give, an overinflated tyre is more likely to be cut or split by a sharp impact.
- It compacts turf: A small, hard contact patch concentrates the machine's weight onto a smaller area, increasing ground pressure and compaction on fine surfaces.
How to Check Tyre Pressure Properly
Checking pressure is simple, but a few points make the difference between an accurate reading and a misleading one:
- Check when cold: Pressure rises as a tyre warms up through use. Always check before the machine has worked, or after it has stood long enough to cool, so you are measuring against the specified cold pressure.
- Use a gauge you trust: Cheap gauges can be wildly inaccurate. A good gauge is a worthwhile investment, particularly across a fleet.
- Check all of them, including the spare: Do not assume. Check every tyre, and do not forget the spare - it is no use flat when you need it.
- Replace valve caps: They keep dirt out of the valve and provide a secondary seal against slow leaks.
- Keep a log: Noting pressures for each machine helps you spot a slow leak early - a tyre that always reads low has a problem.
Pressure Changes With Load
One of the most important and least understood points is that the correct pressure depends on the load the tyre is carrying. A tyre's rated capacity is quoted at a specific pressure - carry more weight and you need more pressure to support it safely.
This matters most for equipment whose load varies. An empty trailer and a fully laden one have very different pressure requirements, and running the empty pressure under a heavy load overloads the tyre. The same applies to compact tractors fitted with loaders, and to any machine that sometimes carries and sometimes does not. Always check the manufacturer's guidance for the pressure appropriate to the load - do not just set it once and forget it.
Pressure and the Weather
Air pressure changes with temperature - roughly one PSI for every 5 to 6 degrees Celsius. That means:
- Cold snaps drop pressures: A tyre set correctly in mild weather can read low after a cold night. Winter is a common time to find fleet pressures have fallen.
- Heat raises them: In summer, pressures rise as tyres heat up in use, which is exactly why you set them cold rather than chasing a moving figure.
The practical answer is to check pressures more often when the weather changes sharply, and always against the cold specification.
Getting It Right for Different Machines
There is no single correct pressure - it depends entirely on the tyre, the machine, and the job. As a guide to the priorities:
- Turf and mower tyres: Correct pressure preserves the wide, even contact patch that protects the surface. Getting it right is as much about the turf as the tyre.
- ATV and UTV tyres: Often run at relatively low pressures for grip and ride, but not so low that the tyre creeps on the rim or overheats on hard ground.
- Trailer tyres: Set for the laden weight, and check before loading. Underinflation here is a genuine safety issue at road speed.
- Agricultural and implement tyres: Pressure balances flotation and ground protection in the field against load-carrying and stability on the road.
In every case, the tyre or machine manufacturer's figures are the starting point. When in doubt, ask your supplier.
A Small Habit, a Big Difference
Correct tyre pressure is the single most cost-effective thing you can do to get more life, better performance, and greater safety from your tyres. It costs nothing but a couple of minutes, and it pays back in slower wear, lower fuel use, fewer failures, and better protection for the surfaces you work on.
If you are not sure what pressure your tyres should run at, or you need replacements, the Redstone team can help. Call us on 01243 558959 or browse our range online. Next-day delivery is available on stocked items.