These tyres are designed to replace pneumatics, utilizing the original wheel, providing the wheel is a flat-base and splits in some way, i.e. bolts together (2-piece wheel) or has a loose flange and lock ring (3-, 4- or 5-piece wheel).

1. Sections about 300 mm long by about 10 mm thick are built up over a ring in overlapping layers rather like brickwork. This is finished off with tread rubber and the semi-finished tyre is then removed from the ring and placed in a mould where it is cured at high temperature and pressure.
2. Material is continuously extruded on to the ring which is rotating and is built up until the pre-determined size is reached. The tyre is then cured in the same manner as above. The basic difference during extruding is that the change of materials from the base compound to tread rubber is gradual and automatic.
3. The easiest way to describe the third method without going into complications of actual manufacturing is filling a casing with resilient rubber, although this is not strictly true.
4. This method utilizes the existing rim which is used in place of the mould. Rubber is bonded directly to the rim, cured and then buffed to size. If a tread is required, this is hand cut into the rubber after curing. The advantage here is that any heavy duty wheel can be used, it does not have to split.

1. It is slow - several days are necessary for bonding and curing
2. If the bonding or wheel fails there is no quick remedy
3. If this process has been done to a split wheel and a change back to pneumatics or the conventional puncture proof tyre is required, the rubber has to be burnt off and loose flanges and lock rings obtained as these are discarded when originally molded.

One of the biggest problems with a solid rubber tyre is internal heat. This heat is caused by one of three factors or a combination of any one of them

• speed
• overload
• duration

What in fact happens is that the centre of the tyre becomes so hot that the vulcanizing process is restarted. With normal pneumatic tyres the heat is quickly dissipated through the relatively thin sidewalls. However, with a solid tyre the sidewall virtually extends from one side of the tyre to the other. Rubber being a good insulator of heat does not allow for rapid dissipation and the tyre can get so hot it may burst.

A point to remember is that once the point has been reached when revulcanisation starts to take place, it is too late to rectify the matter and the tyre will fail in due course. Due to these factors, larger industrial tyre companies manufacture solid tyres of the same size but in different compounds. The cooler a tyre runs, the longer it will last. The tread rubber generally remains the same, it is the inner core between the base and tread which is varied. By substituting rubber which will dissipate heat more quickly, a cooler running tyre is obtained.

Needless to say, when selecting a puncture-proof tyre to replace a pneumatic the more information that can be supplied the better.

1. Distance of run
2. Speed and frequency of cycle
3. Commodity to be handled
4. Tyre to be fitted to drive or steer axle
5. Mass of truck loaded and unloaded
6. Condition of working area
7. Description of terrain

These factors determine the choice of tyre, compound and tread pattern. Due to the superior load carrying capacities of puncture-proof solid tyres, it is not always necessary to replace size for size when the vehicle is being changed from pneumatics. For instance, lO.OOx2O or, in some cases, a 9.OOx2O solid puncture-proof can successfully replace an 11.00 x 20 pneumatic. When this is done the criteria is the loaded rolling radius. Providing this measurement remains the same, which in the above case it would, as a solid tyre does not deflect as much as a pneumatic, the ground clearance would not be affected.

On puncture-proof tyres there are two types of tread pattern; lug and smooth. Generally there is no difference in cost but the benefit to the user is undoubtedly there. Lug tyres are primarily used as a drive tyre but they can be used on a steer wheel. With a nondirectional tread the pattern offers both traction and braking ability. The smooth or slick tyre is primarily for steer wheels. On forklift trucks, the steer wheels can be locked from side to side to approximately 95-98 degrees. When a treaded or lug tyre is used on this axle the tractive ability offered can be detrimental as it imposes extra stress and strain to the steering geometry. Also, by the action of turning the wheels from lock to lock, the twisting imposed to the rubber can, and does tear the lugs from the tyre. Needless to say this is usable rubber being thrown away.

From a wear point of view only, there is no advantage in fitting a puncture-proof tyre in place of a pneumatic. The wear rate of both types of tyre is roughly the same. The only advantage is that the puncture-proof can be worn down much further. However, it must be remembered that the smaller the tyre gets, the more shock is transmitted to the machine and this, naturally, could increase the maintenance costs.

What should be done, is to treat the puncture-proof tyre as a pneumatic and when the tread is worn away consider replacement. Where the true economics come in is the complete absence of punctures, blow-outs and general tyre maintenance, hence greater productivity. Also as puncture proof tyres have a considerably superior load carrying capacity, they offer greater stability and safety.

A point not often considered is that if pneumatic tyres are under inflated they will absorb considerably more power in order to move. This applies to both electric and internal combustion powered machines. Puncture proof tyred machines, over a period, show a saving on 'fuel' costs due to the fact that power absorption is constant.

There are two basic types of holding tyres on the rims. Air pressure expands normal pneumatics and the bead area is forced against the rim. With solids once again there are two basic methods the oldest being the tyre is made too small for the rim coupled with too wide. It is then stretched and pressed on, held under pressure when either the bolts holding the two halves together are tightened or the loose flange and lock ring is fitted. A modern technique utilizes a method commonly called "clip". The tyre has a hard section molded to the base which fits into the lock ring groove. The lock ring and flange is then disposed of thus saving the manufacturer of the machine the cost of a full wheel. The main disadvantages of this method is tyre suppliers have to double up on their inventories and secondly, which is far more important, is in many cases machines are working in countries and areas which do not cater for this type of sophistication, resulting in lock rings and flanges having to be obtained in order that normal pneumatics or standard solids can be fitted.

Tyre types

• Back to Technical Information.
• Pneumatic tyres
• Pneumatic tyre filled with polyurethane.
• Press on solid and cushion tyres.
• Urethane press-ons / Bonded tyres.

Other technical information.

• Why Industrial Tyres Fail.
• Rules for longer tyre life.

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