Tyre pressures and rims: how they affect fuel use and handling

The wrong tyre pressure increases fuel consumption, shortens the life of your tyres and makes the car handle worse. That is why Traficom, the Finnish transport agency, recommends checking the pressures at least once a month. You will find the correct values in the owner's manual and usually also on a sticker on the driver's door frame.

What the wrong pressure does

Pressure that is too low is the more common fault, because tyres lose air gradually and cold weather lowers the pressure. The tyre flexes more, rolling resistance increases and fuel consumption goes up. The tyre wears at the edges, and the steering feels vague.

Pressure that is too high reduces the area of the tyre in contact with the road. Grip suffers, especially in the wet, the tyre wears in the middle and the car feels harsh over bumps. According to Traficom, wet grip and fuel economy are at their best when the pressure matches the manufacturer's recommendation.

How to measure the pressures correctly

• Measure when the tyres are cold, before driving or after the car has been standing. In a tyre warmed up by driving, the pressure reads higher than it really is.
• Use the value that matches the load. The owner's manual often gives different pressures for an empty car and a fully loaded one.
• Remember the spare tyre, if the car has one.
• A tyre pressure warning system tells you if the pressure drops, but it is no substitute for measuring. If the car has an indirect system, reset it after adjusting the pressures, as described in the owner's manual.

Checklist for city driving

In the city, tyres and rims take a beating from kerbs, potholes and tram rails. These are worth checking regularly:

• The same tyre keeps going flat. The cause may be a nail, damage or a leaking valve. A small hole in the tread can often be repaired: Tubeless / tyre repair costs €50–70.
• Hitting a kerb or a pothole. Check the sidewall of the tyre and the edge of the rim. A bulge in the sidewall means the tyre must be replaced.
• Vibration at a certain speed. The most common cause is a wheel out of balance, for example because a balancing weight has come off. A bent rim can cause vibration that balancing won't cure.
• Uneven wear. A tyre worn on both edges points to pressure that is too low, and one worn in the middle to pressure that is too high. If only one edge is wearing, the cause may be the wheel alignment.
• Brake dust on the rims. Wash the rims regularly, because baked-on brake dust is hard to remove and can damage the surface of the rim. With us, the tyres are washed in every wash.

Tyre size and choosing tyres

You will find the correct tyre size for your car in its registration details. When choosing new tyres, check the EU tyre label: it shows how the tyre affects fuel consumption, wet grip and noise. The label does not apply to studded tyres. There is more information on Traficom's page Summer and winter tyres for cars.

How we can help

If the steering wheel or the car vibrates, book Wheel balancing (€79). When tyres need to be mounted on rims, for example new tyres on old rims, choose Rim work 15–17" (from €139). It includes balancing too. The price applies to 15–17 inch rims, and larger rims cost extra for each size up.

If the car pulls to one side or a tyre wears on only one edge, read our article on why a car pulls to one side.

Read more

• When to change your tyres and what to check at the same time
• Car pulling to one side? When to have the alignment checked
• Small checks you can do yourself on a city car