TIPS FOR MOTORCYCLE RIDERS

IMPORTANT INFORMATION				TYRE FITMENT
TECHNICAL INFORMATION				STORAGE OF TYRES
		TYRE MAINTENANCE

TECHNICAL INFORMATION

Basic terms

M/C - Motorcycle tyres, which are designed for use on M/C motorcycle rims having a bead seat diameter, which differs from that of rims with the same designation for passenger car and commercial vehicles.

MOPED - Motorcycle tyres designed for motorcycles that have a speed capability 50 km/h or less.

MST - Motorcycle tyres designed for special service having a wider tread than equivalent sizes with the same tyre size designation.

NHS - Motorcycle tyres designed for off-road applications. They must not be used on public highways.

PR - identifies different versions (load capacity/inflation pressure) of tyres having the same size designation.

REINF - Motorcycle tyres designed for loads and inflation pressures higher than standard version.

TUBELESS - Tyres specifically designed for fitment without an inner tube on appropriate rims.

TUBETYPE - Tyres specifically designed for fitment with an inner tube.

 

Parts of a tyre

Since existence of motorcycle; this is now for over 100 years; exist also special tyres for motorcycles. These tyres have undergone a lot of changes in all these years, they have developed and now we have more different types of tyres, which are different in basic construction and outside appearance. Both the outside appearance and construction depend on use or type of motorcycle. Regardless we speak about scooter, motocross, enduro or street tyres, they all have following parts:

• Tread surface - is the upper part of the tyre, which is in contact to the road. The tread pattern and the rubber compound provide grip on the road or of-road, wet or dry. The task of tread pattern is also water drainage. Grip depends of a rubber compound. In principle provides softer rubber compound better grip and shorter lifetime and inversely, harder compound provides less grip and longer life time of a tyre.
• Sidewall - wears all the data of speed symbol, load, tyre name, manufacturer, country of origin, ECE homologation number and others. At riding the sidewall carry side forces and play very important rule at chocking the oscillation and prevent tyre deformation.
• Carcass - is the supporting part of the tyre and provides tyre shape at every force, that occur during the riding. It is made of two or more layers of cord. Material for cord can be rayon, nylon, polyester or Kevlar.
• Bead - provides the strong connection to the rim to provide tyre not to roll over the rim. It is made of wire bead and layers of cord that go round the wire bead. This way tyre get the necessary stiffness in bead area to overcome all accelerating and braking forces and transferred them to the chassis. At tubeless tyres beads provides sealing against loss of air pressure.

Type of tyre construction

According to type of carcass, tyres are divided into following categories:

• Diagonal tyres - are known for the most time and are the most expanded on the market. The carcass of diagonal tyres consists of two or more layers of textile cord (rayon, nylon, polyester), which are crossed at specified angle. Diagonal tyres are the right choice for smaller motorcycles with less powerful engines, scooters and for the older motorcycles, which have a chassis adjusted to the diagonal tyres.
• Bias-belted tyres - are basically diagonal tyres with a reinforcement of the diagonal belts under the tread surface. These tyres are marked with letter B (bias-belted) for example 130/90B15. Tyres are the right choice for stronger motorcycles, which do not have a chassis adjusted to the radial tyres, but demand stronger tyres.
•  Radial tyres - have a carcass with a layer of cord laid at angle of 90 degrees according to direction of driving. Over the carcass the reinforcement layers of cord are laid to stabilize the tread surface of the tyre. Radial tyres are the right choice for strong motorcycles, and they have to bring the huge forces of acceleration, braking and cornering to the road. Radial tyres have a lot of advantages (see chapter page), most important advantage is at very high speeds. Centrifugal force cause high heat build-up and greater chance for tyre to damage, less grip and bigger wear. These bad properties of diagonal tyres are almost eliminated by radial design. The behaviour in the limit is more predictable. Cross section of SAVA radial scooter tyre is seen on picture 67.
•  Radial tyres MSB - are an additional kind of radial tyres for very fast and strong motorcycles. MSB – monospiral belt is winded under the tread surface of the tyre in direction of rotation to stabilize the tread surface in all condition of driving.

In SAVA mainly the diagonal construction is used, intense development is going on in the field of radial and bias-belted tyres.


Speed symbol

Speed symbol indicates the maximum speed at which the tyre can carry a load corresponding to its Load Index under service condition specified by SAVA.
Speeds are shown in table 1. These speeds can be applied to tyres, which are in good condition, inflated to the correct pressure, operating within their specific load capacity and fitted to the correct size rim. Speeds in the table are maximum speed of which the tyre is capable to be ridden, not the speed at which it is normally ridden.

Load index

The load index is numerical code associated with the maximum load a tyre can carry (except for loads at speeds above 210 km/h) at the speed indicated by its Speed symbol under service conditions specified by SAVA.
Loads are shown in table 2.
You should fit replacement tyres with precise or higher Speed symbol and Load index referred by motorcycle manufacturer.

TYRE MAINTENANCE

Inflation pressure

Inflation pressure is vitally important. Driving with tyres that do not have the correct inflation pressure is very dangerous. In under-inflated tyre an excessive heat build up occur and it can result in sudden tyre destruction. Tyre pressure determines tyre lifetime. The correct pressure ensures maximum mileages with satisfactory stability, comfort and road holding properties. The tyre is kept at the contour at which it was designed to run. Insufficient air pressure or the wrong tyre fitment accelerates tread wear and creates additional stress on the tyre carcass. It also increases the risk of accidental damage, adversely affects handling and increases rolling resistance. Excessively high pressure causes rapid wear in the centre of the tread. There is also greater danger of casing fracture and tread cutting. Keep the tyres inflated to the values shown in motorcycle handbook. This correct inflation pressure must be maintained as a minimum. For fast driving on the road, the tyre pressure should be increased by 0.2 bars; for driving with a lot of baggage the inflation pressure in rear tyre should be increased by 0.2 bars.

Inflation pressure has to be checked at least once a week with an accurate tyre pressure gauge when the tyre is cold and always before long journeys. Pressure rises, when the tyre is hot and falls down, when the tyre is cold. Take this fact into consideration.

Loss of pressure may be due to valve core not seating properly or being worn. Check valve core, tighten it for correct seating or replace it if necessary. Always fit valve cap into the valve (finger tight), because they keep dust from the valve as an extra seal. At tubeless tyres the valves should be kept at good condition and replaced when a new tyre is fitted.

 

Tyre and rim

At wire wheels the right rim tapes (flaps) should be used. Rim tapes should be maintained in good condition, while a protruding spoke head can damage a tube and cause a puncture.

Tyre has to be aligned properly on the rim and it has to be checked regularly.
Replace tyre before legal 1mm (1.6 mm in Germany) remaining tread pattern depth is reached. Worn tyres are more susceptible to damage and road holding is reduced especially in the wet.

Damage tyres are very dangerous. Replace damage tyres immediately.
The stones or nails captured in the tread pattern of tyre must be removed. If left, they can penetrate through the carcass and cause a puncture and an accident.

The main advantage of tubeless tyre is its ability to accept penetration by nails without a rapid loss of air. This also means that rider can be unaware of a puncture and if he uses the tyre for a long distance, the damage area will spread and could become serious. When the deflation is noticed, the tyre should be removed from the rim and checked before attempting any repairs. Repairs in shoulder and sidewall area are not recommended. Repairs for tyres with speed symbol P and higher are not recommended.

The behaviour of the tyre is worse, if the tyre was in contact to oil or grease. The tyre has to be cleaned with a cloth damped with petrol.
SAVA tyres are made to fine tolerance, but for higher speeds it is important, that the tyre is balanced. Tubeless tyre-rim assemblies should be balanced with self-adhesive weights, the tube-type tyres on wire wheels should be balanced with spoke weights.

 

Treadwear

A summary of the various factors that can cause abnormal wear:

• Under-inflation/over-loading can cause tread distortion and irregular wear. More seriously they may result in sudden failure of the carcass due to excessive tyre flexing.
• High- speed means rapid tread wear, especially due to harder acceleration and extra braking.
• Temperature of tarmac surface – higher temperature cause faster wear
• Rough tarmac surface cause higher abrasion and shorter lifetime of a tyre.
• Mechanical irregularities such as distorted wheels, incorrect brake adjustment, bad dumpers, excessive tolerance in frame-wheel bearings can cause severe wear.
• Unbalanced rotating weight (heavy spots on rim) can cause irregular tread wear.

TYRE FITMENT

Tubetype tyres

Assembling:

• At tyre replacement it is recommended to replace tube also.
• Rims have to be clean and in good condition.
• Control the condition of rim tape.
• Tube has to be slightly inflated.
• Orient the tyre according to mark ROTATION on the sidewall.
• Put on the tyre with a special tool (finish at the valve). For easier job use special emulsion.
• Inflate tyre up to 3.5 bars and check the position of the tyre beads and tube position. In case of incorrect position deflate the tyre and correct the position of the tube and tyre beads.
• Inflate to recommended pressure by motorcycle manufacturer.

Disassembly:

• Take the valve core out of the valve to deflate the tyre completely.
• Both tyre beads push out of the rim.
• With special tool take down the tyre from the rim.

Tubeless tyres

Assembling:

• Control the condition of the valve, if necessary replace it.
• Rims have to be clean and in good condition.
• The rim and the tyre beads have to be lubricated with special emulsion.
• Orient the tyre according to mark ROTATION on the sidewall.
• Put on the tyre with a special tool (finish at the valve).
• Inflate tyre up to pressure, that tyre beads fits into the proper seat on the rim. (It is recommended to inflate tyre without a core in the valve.)
• Inflate to recommended pressure by motorcycle manufacturer.

Disassembly - same procedure as for tube type tyres.

STORAGE OF TYRES

Tyres should be stored in relaxed condition free from tension, compression or other deformation since these may cause permanent distortion. For short term storage (up to 4 weeks) tyres can be put horizontally, one on top of another up to 1.5 meters only, if tyres have supporting cardboard inside. For longer storage, tyres should be stored upright and rotate them slightly once a month.

Tyres should be stored at temperature bellow 25ºC, preferably below 15°C. At higher temperatures deterioration can be accelerated. Direct contact to heat, radiators or heating pipelines must be avoided. Low temperatures have no bad affect to the tyres. Cold tyres have to be warmed up to 20° and then put to service.

Keep tyres from the ozone, oxygen and chemical agents like fuels, lubricant, chemicals, acids or disinfectants. Keep them in separate rooms.



SAVA wish you good, safe and enjoyable riding with your motorcycle.