Mixing of Tyres It is illegal and could be dangerous to mix tyres of different construction on motorcycles in certain ways; for permitted fitments refer to the table. If in doubt a tyre specialist should be consulted, but to avoid any misunderstanding it is recommended that both tyres on a motorcycle, and all tyres on a combination, should be of the same construction and from the same tyre manufacturer.
Where sidecars are fitted and the sidecar axle aligns with either of the motorcycle axles, the sidecar tyre must be of the same construction as the tyre with which it aligns.
Keep the Pressure Correct
The correct tyre inflation pressure is vitally important for safe handling of the motorcycle. The recommended tyre pressures for original equipment tyres will be stated in the motorcycle owner’s manual. For fitment of aftermarket alternative tyres, advice should be sought from the tyre specialist or tyre manufacturer. Specific advice from the tyre manufacturer is recommended for tyres fitted to classic and vintage motorcycles pre 1960 where pressures quoted in original handbook may be inappropriate.
An indication of maximum load at a given pressure is marked on all tyre sidewalls, this should not be used as a recommended pressure. Pressures must be adjusted appropriately for solo and for pillion and pannier loads.
It is dangerous to re-inflate a tyre which has been run flat or seriously under inflated. Such tyres should be removed for inspection by a tyre specialist. Prolonged under-inflation causes excessive flexing, deterioration of the casing and rapid wear of the tread shoulders/edges. Your motorcycle may also consume more fuel. Over-inflation may result in an uncomfortable ride, a reduced area of contact with the road, accelerated wear on the tread centre and makes the tyre more susceptible to impact damage.
Inflation pressures should be checked once a week when the tyre is cold, since there is an increase in pressure when the tyre has warmed up after being run. A reliable and accurate pressure gauge should be used.
The running-in period allows the tyre to settle itself onto the wheel rim, serves to “scuff-in” the tread surface and allows the rider to adjust to the ‘feel’ and handling of the new tyres.
After fitting andbefore moving off, ensure the tread surface is not contaminated in any way: clean off fitting lubricant, buff around the tread circumference with a dry cloth, ensure the label is removed and confirm correct tyre pressures. Each time new tyres are fitted, the motorcycle should be driven very cautiously and the tyres not subjected to maximum power or speed for the first 100 miles, i.e. avoid sudden acceleration, maximum braking or hard cornering. Particular care should be taken on wet or greasy road surfaces. After 100 miles, the tyres should then be checked to ensure the correct seating and inflation. After this initial period, lean angles, acceleration and braking forces can be gradually increased.
Inspection and Maintenance
Regular inspection becomes increasingly important the longer the tyre is kept in service. Consumers are strongly encouraged to be aware of their tyres’ visual condition such as tread depth, cracking or crazing of the tread or sidewall rubber, cuts or bulges, foreign objects, as well as being alert to any change in dynamic performance or behaviour such as air loss, noise or vibration. Driving over pot holes, kerbs and speed bumps, even at low speeds can result in the weakening or fracture of the tyre structure. The consumer should be the first to recognise an in-service impact and then ensure immediate inspection by a tyre professional, who can also offer advice and guidance. Lumps or bulges could indicate internal damage and should be examined by a tyre specialist without delay. Oil and grease should be removed with a suitable diluted detergent.
Watch your Tread
Tyre treads are designed to give good wet grip but the road surface condition also plays a significant role in tyre to road adhesion. In general, wet grip decreases as tyre tread patterns wear down and as the depth of surface water increases. Motorcyclists should take this into consideration and reduce speed when it is wet.
Motorcycle tyres normally have tread wear indicators in the tread grooves and as these are approached during the service life of your tyre you should consider replacement. Once the indicators are level with the tread surface the tyre should be renewed – but this should not be the only deciding factor on tyre replacement. The legal limit of tyre tread depth in the UK for motorcycles over 50cc is 1mm across 3/4 of the width of the tread pattern and with visible tread on the remaining 1/4. For motorcycles up to 50cc the law requires that all the grooves of the original tread pattern must be clearly visible. The legal requirements may differ in other countries. It is recommended to consider replacing motorcycle tyres in advance of the legal requirement i.e. at 2mm.
Tyre Service Life and Ageing
Tyres can deteriorate with age which may show as cracking of the tread and sidewall rubber, sometimes accompanied by carcass deformation. Cracking is usually an indication that tyres have been in service for an extremely long time, but rubber deterioration may be brought about by poor storage conditions. If cracking is evident seek professional advice or replace the tyre.
Tyres should be removed from service for several reasons including tread wear (down to legal limit), damage (cuts, cracks or bulges etc.) or abuse (overloading or underinflation etc.). Deterioration of the tyre may not always be visible and may become apparent through loss of performance, noise or vibration etc. Motorcyclists should consult their tyre specialist, the vehicle manufacturer or relevant tyre manufacturer regarding advice on the service life of their tyres. The manufactured date of a tyre can be determined by the numbers at the end of the “DOT CODE” located on one lower sidewall of each tyre (E.g. “ DOT XX XX XXX 2703” was manufactured in the 27th week of 2003).
Tyre Load and Speed Markings
Motorcycle tyres have markings to indicate their load and speed capabilities. These are moulded on the sidewall adjacent to, or part of, the size designation as a service description comprising a load index (e.g. ‘73′) for load carrying capacity and a speed symbol (e.g. ‘W’) for speed capability.