Car tyres

Winter tyres

Winter tyres should be used according to weather or driving conditions during November, December, January, February and March. During this period, the tread main grooves must have a minimum depth of 3 mm.

Winter tyres can be studded or non-studded. Non-studded winter tyres are often called friction tyres. There are different friction tyres designed for northern and central European conditions. If you have purchased a vehicle from abroad and it comes with friction tyres, check that they are designed for Nordic conditions. 

In snow and slush, traction is primarily determined by the tyre’s pattern and friction properties. The traction is poorest on wet, smooth ice. In this case, it can be improved by studs or other anti-slip accessories (e.g. chains).

If studded tyres are used in a passenger car or van, they must be used on all wheels and the number of studs per tyre must not vary by more than 25 percent. However, the difference can be greater if the number of studs on each tyre corresponds to at least 75 % of an equivalent new tyre.

In addition to passenger cars and vans, the winter tyre requirement also applies to trailers with a maximum authorised mass of over 750 kg (O₂ class), i.e. typically towed caravans and heavy trailers. If the vehicle has studded tyres, such trailers must have at least winter tyres, but they do not need to be studded. Conversely, if the trailer has studded tyres, the vehicle can have non-studded winter tyres. There is no winter tyre requirement for light trailers, but it is still advisable to use winter tyres in slippery conditions.

The winter tyre requirement also applies to quadricycles and other light motor vehicles with four wheels, as well as mopeds and motorcycles. For mopeds and motorcycles, coarse-pattern tyres suitable for winter use are accepted as winter tyres.

The winter tyre period

Winter tyres should be used according to weather or driving conditions from 1 November until 31 March. Studded tyres are permitted during this period, and they may also be used outside the season if weather or road conditions so require.

During the period from November to March, summer tyres may be used if the local road conditions are not slippery or at risk of becoming slippery, also taking into account side roads. In individual cases, road traffic authorities determine whether the conditions require winter tyres. It is the driver’s responsibility to ensure that the vehicle has winter tyres in winter conditions.

Winter tyre markings 

The winter tyre is marked M + S, M.S or M & S (the letters M and S stand for mud and snow). Winter tyres with the 3PMSF (3PeakMountainSnowFlake) marking (the “mountain marking”) are type-approved for demanding winter conditions and meet the standard’s requirement for snow traction.

From 1 December 2024, the M + S marking alone will no longer be sufficient for winter tyres. All winter tyres will have to be type-approved for demanding winter conditions, i.e. they must have the mountain marking or be studded. A POR-marked tyre for off-road use is also accepted as a winter tyre. In Class O₂ trailers, M+S-marked winter tyres will be accepted until 30 November 2029.

Summer tyres

The main grooves of summer tyres must be at least 1.6 mm deep.

The TWI marking on the side of the tyre shows where there is a wear indicator in the groove of the tread pattern. When the tread has worn down to the wear indicator, the tyre is worn out and no longer meets the legal requirement of 1.6 mm. Even before that, the tyre’s traction is considerably reduced and presents a higher risk of aquaplaning, especially during rain.

Summer tyres typically have about 8 mm of tread when new. When more than half of it has worn out, the traction is reduced in rainy weather and can create a hazard.

Non-studded winter tyres can also be used outside the permitted period for studded winter tyres. Worn friction tyres often have relatively poor driving properties especially in wet weather, and they are not designed for summer conditions.

Worn tyres increase the risk of aquaplaning

The performance of tyres on wet, snowy or icy surfaces decreases significantly even before they approach the minimum legal requirement of 1.6 mm for summer tyres or 3.0 mm for winter tyres. The tyre’s ability to retain the necessary traction is particularly impacted by the accumulation of rainwater in the tread grooves and slush from melting or gritted snow.

Aquaplaning means that the tyre is not able to displace the water or slush layer on the road surface quickly enough. The tyre lifts off and rides on a cushion of water, which acts as a kind of lubricant between the tyre and the road surface. Traction between the tyre and the road surface disappears completely, and the tyre no longer transmits steering or braking forces to change the direction or speed. During aquaplaning, even a small amount of lateral force may also cause the vehicle to slide sideways.

If you feel the front wheels starting to aquaplane, keep the steering wheel straight and release the accelerator. If you turn the steering wheel too much during aquaplaning, the vehicle may change direction abruptly when traction is regained. Stay calm and avoid rash steering manoeuvres. Keep your speed down to avoid aquaplaning again.  

Aquaplaning is influenced by the vehicle speed, but also by the tyres, their model, width and wear. Reducing speed is the best way to avoid aquaplaning. If the tyres are in poor condition, a speed reduction of 20–30 km/h compared to driving on good tyres is required to avoid aquaplaning. You should also avoid driving in ruts, because water accumulates in them. In wet, snowy or icy conditions, the poor traction of worn tyres also significantly increases braking distances and makes it difficult to control the vehicle when cornering.

The vehicle is most responsive when all tyres provide roughly the same traction. To ensure that the tyres wear evenly and maintain the same level of traction, they can be swapped from front to back during service. If, during service, the tyres show clearly different levels of wear but are still in usable condition, the recommendation is to put the best tyres on the rear axle. Better rear traction reduces the risk of the vehicle skidding sideways, and a head-on impact tends to be safer than a side impact in the event of a collision. However, the direction of rotation must not be changed, as tyres are usually designed to roll in one direction. This is indicated by an arrow on the side of the tyre. For example, if the back and front tyres are swapped, each tyre should remain on the same (right or left) side of the car. If there is more wear on the inside or outside edge, or if there is saw-tooth wear, the toe alignment probably needs to be adjusted. This requires a four-wheel alignment carried out by a service professional. 

Check summer tyres at least in the autumn and winter tyres during winter holidays

A good opportunity to check the condition of the tyres is when changing from summer to winter tyres and vice versa. Especially in spring summer tyres wear faster as road surfaces are rough after being exposed to studded tyres all winter. In summer, heat waves also increase wear. Checking the treads regularly saves you from surprises. For example even though still using summer tyres, you should inspect your tyres when the rainy season starts in the autumn.  

Similarly, in winter, especially if you have driven extensively on snow-free asphalt roads, it is advisable to check the tyres by the start of the winter holiday season. There is a risk of a “second winter” well into the spring, and accidents such as multi-vehicle collisions tend to happen during unexpected snow storms in late winter or early spring.

Tyre pressure

Tyre pressure is important for safe, economical and environmental performance.

When the tyre pressure is too low

• the vehicle is difficult to control in unexpected situations,
• steering starts to pull in one direction, and a tyre might puncture,
• fuel consumption increases by 3–6%, and
• the life of the tyre will be reduced by 25–50%.

Tyre pressures should be checked at least once a month in accordance with the recommendations of the tyre or vehicle manufacturer. The recommended tyre pressures can be found in the vehicle manual and often in other locations that are easier to check, such as the fuel tank cap or the driver-side door or its pillar. The recommended tyre pressure usually also depends on the vehicle load. Tyre pressures should be checked if transporting exceptional loads or numbers of people.

Tyre pressure usually lasts well. Temperature fluctuations have some effect on the pressure. If the pressure starts to gradually drop only in one tyre, there is usually something wrong with it. For example, there could be a nail or screw embedded in the tyre. Initially the leakage may be minimal and the only sign is a slow drop in the pressure. The actual cause of abnormal pressure should be investigated to avoid having a flat tyre in the middle of a journey.

Newer cars have a tyre pressure monitoring system. Some cars automatically “learn” different sets of tyres and their correct pressures, but in some vehicles they must be specified manually after replacing tyres. The warning light indicates a pressure drop in a tyre, and the cause should be investigated immediately.

New tyres and tyre markings

Worn tyres should be replaced with new ones well before the minimum legal limit is reached. There is a vast selection of both summer and winter tyres available, and the great choice can be confusing. One good source of information is car magazines, which publish the results of the latest tyre tests in spring and autumn. Tyre experts in car shops can also give advice to buyers.

In passenger cars and vans, tyres that share the same axle must have the same dimensions, structure and other properties. A spare tyre that is different from the other tyres can be used temporarily in the event of flat tyre. The spare tyre is often a lightweight special tyre with a maximum permissible speed and permitted for temporary use only. On many new vehicles, the spare tyre has been replaced with a tyre repair kit to save space and weight. The kits are perfectly adequate for fixing smaller punctures. The kits are marked with the expiration date, and the refill bottle should be replaced periodically, usually after a few years.

When buying new tyres, the first determining factor is the tyre size. The type-approved tyre sizes are indicated in the vehicle registration details. If the registration certificate is not available, the registration details can be checked based on the registration number from the “Transport matters in My e-Services” section of the Finnish Transport and Communications Agency’s online service. (Opens in a new window)

New tyres must be marked with the EU energy efficiency label. It states the rolling resistance, which affects fuel consumption, the wet grip rating, which affects safety, the rolling noise, and from 1 May 2021 the ice and snow grip rating. The ice and snow grip rating must be indicated on all non-studded winter tyres designed for northern European conditions. The new markings improve the comparability of different tyre models and make it easier to buy them online. The new regulation does not apply to studded tyres.

As of 1 May 2021, the wet grip classification is indicated by letters A to E; Class A provides the best grip and Class E the poorest. Classes D and G are no longer in use. The classification is based on a test to measure the braking distance on wet asphalt at 80 km/h. The difference in the braking distance between adjacent classes is 3 to 6 metres, i.e. approximately the length of the vehicle.

The following markings can be found on the side of the tyre:

• Manufacturer’s name or trademark
• Size and type, e.g. 185/65 R 14 88 Q: (width 185 mm, the aspect ratio: the height is 65% of the width, R means radial design, 14” wheel size, load index 88, speed rating Q)
• tubeless
• TWI, the tyre wear indicator
• winter tyre, M or MS
• The “mountain label” 3PMSF in winter tyres that meet the requirements of the snow grip test
• manufacturing code week/year e.g. 2520 (week 25 year 2020)

In addition, the tyres must be of an e-, E- or DOT-approved model or labelled with the text “Retread” or “Pinnoitettu – Regummerad”.

Winter tyres for trucks and buses

In trucks and buses, if the weather or road conditions so require, between 1 November and 31 March winter tyres with a tread main groove depth of at least 5.0 mm must be used on the drive axles. The requirement does not apply to steering drive axles. During the same winter period, tyres with a minimum tread depth of 3.0 mm must be used on the other axles of trucks and buses and their trailers.