Fitting the right tyre to your caravan, trailer or motorhome
The original tyres for a caravan are determined by joint consultation between the caravan and tyre manufacturers and take into account all aspects of operation. Any changes in tyre size or type should not be undertaken without seeking advice from the caravan or tyre manufacturer. In some European countries it is illegal to use replacement tyres which differ in certain respects such as size, load or speed rating, from the tyre originally fitted by the manufacturer.
It is essential that tyres of the correct specification are fitted to caravans, trailers and motorhomes. The same tyre construction type, i.e. radial or cross-ply, should be fitted to all tyres on the same axle.
Across an axle, tyres should also have an equal size, load index and speed rating with identical wheels. The same combination should apply to the spare. Tyre pressures across an axle should also be equal.
Older caravans may be fitted with cross-ply tyres that are no longer available, meaning that radial ply tyres must be fitted. If a caravan is converted from cross-ply to tubeless radial tyres, the latter must only be fitted to safety type rims, i.e. those with a hump or flat ledge on the outer bead seat. Many older caravans do not have safety type rims and the previous recommendation has been to fit tubes with radial ply tyres. Before doing so, the tyre manufacturer must be consulted, as not all radial ply tyres are suitable for use with tubes.
It is essential that the combined tyre load capacity is sufficient for the maximum weight (MTPLM) of the caravan, but as an extra safeguard it is strongly recommended that the MTPLM does not exceed 90% of the tyre’s load capacity.
Overloading tyres is extremely dangerous and should be avoided at all times. A poorly distributed load can also lead to overloaded tyres even when the maximum total permissible load is not exceeded. Loads should be spread evenly around the caravan and as low down as possible to maximise the stability and safety of the car and caravan combination.
The police may take action against drivers whose caravans are found to be overloaded or have a poorly distributed load.
To ensure tyres are not overloaded, it is advisable to keep the caravan operating weight below the specified maximum limit. A 10% margin will partly help to compensate for some unequal load distribution. For maximum safety and reassurance regarding vehicle weight, use a Public Weighbridge to check the load.
Spare Tyre / Wheel
It is strongly recommended that a compatible spare wheel and tyre assembly is carried for the caravan. As caravan tyres and wheels are rarely the same as those on the towing vehicle, the spare tyre and wheel assembly from the towing vehicle must not be used on the caravan, even in an emergency situation. The caravan spare tyre should be the same size, load index and speed rating to those already fitted to the axle.
When checking the pressures and condition of the tyres on the towing vehicle, remember to check the spare tyre as well.
The National Caravan Council’s Caravan Towing Guide recommends that the noseweight should be varied to find the optimum for towing depending upon the actual laden weight of the caravan. Experience and research has found that the noseweight should be around 5% - 7% of the actual laden weight for optimum stability. However, this may be restricted by the towing vehicle manufacturer’s limit and the caravan’s hitch limit.
If there is insufficient weight on the hitch the caravan may snake leading to instability and control issues.
For vehicles are kept in storage
All tyres should be examined for signs of wear and damage regularly but this is particularly important for caravans when they have not been used for an extended period. Caravans, motorhomes and trailer tents which are not used over the winter period should have their tyres thoroughly inspected prior to re-use during the spring and summer.
When examining the tyres, particular attention should to be paid to looking for signs of age deterioration such sidewall cracking or carcass deformation.
Tyres left on a stationary vehicle, particularly if parked in coastal areas, will suffer from ageing issues much more quickly than those in regular and frequent use. If possible, caravans left standing for any length of time should have their tyres covered to shield them from damaging UV rays and be jacked up to remove any load on the tyres.
If you are in any doubt about the condition of your tyres, get them checked immediately at your local ATS Euromaster Centre
Wear and Damage
Tyres can suffer from damage and premature wear for a variety of reasons. Below are some of the most common types found on caravan tyres.
In this condition, the tyre will be showing more signs of wear on the shoulders compared with the centre of the tread. This is likely to have been caused by either under-inflation or overloading and can significantly increase the chances of suffering a blowout. When under-inflated, excessive heat builds up within the tyre, especially on long or high-speed journeys, causing the tyre to fail. You should try to find the cause of under-inflation and resolve it. Start by checking the pressure, then look for any punctures, faulty valve caps or faulty valve stems.
Tyres suffering from this condition will show wear that is more pronounced in the centre of the tread compared with the shoulders and is likely to be caused by over-inflation. The tyre pressures should be checked when the tyres are cold and adjusted to the correct levels using an accurate gauge.
Brake flatting can be caused by either excessive braking or defects to the braking system. The signs are very localised wear, in which the size and shape resemble that of the contact patch with the road surface. There may also be scratches and cuts to the rubber which run in a circumferential direction. Often the other tyre on the same axle will show the same signs of damage. If the wear is severe, the tyre may need to be replaced. Owners should check the braking system if the damage has not been caused by excessive braking.
Impact / Pinching
In this condition, the tyre may not show any signs of impact damage on the sidewall such as cuts or grazes, but will have a localised bulge or blister on the sidewall. This is usually a serious deformity which occurs because of an accidental rupture to one or more cords in the casing ply. This may have been caused by a severe impact with an obstacle such as a kerb, pot hole or stone, or through the sidewall being pinched between the rim and an obstacle. This type of damage is most likely to occur when the tyre is under-inflated or the caravan is overloaded.
The cords of the tyre may become exposed through cuts or other damage. If the cords can be seen then the tyre is both unsafe and illegal and must be changed immediately. When checking the sidewalls to inspect for damage, owners should remember to make all efforts to inspect the inner sidewall of the tyre as well as this may also be suffering damage.
When checking or changing wheels, wheel nuts or bolts should be tightened with a torque wrench. If under tightened, a wheel fixing may shake loose. If it is over tightened it can deform the seating on the wheel itself and, again, it can shake loose. A torque wrench ensures the correct load is applied. Torque settings for wheel nuts can be found in your owner’s manual.
When replacing a wheel, torque the wheel nuts up in the correct sequence and then re-torque again after the recommended bedding in distance, typically 30 miles.