PRESS ON SOLID AND CUSHION TYRES
As the name implies, these tyres are pressed on to the wheel and are held in place by the interference fit between the base of the tyre and wheel.
There are two basic methods of manufacture:
- Rubber bonded to a steel band and the complete unit pressed on to the wheel i.e. steel to steel.
- The base area of the tyre is manufactured in hard rubber with either a wire mesh or several wire beads just below the surface.
The second method generally requires costly special tools for mounting and dismounting.
There is, in fact, no such thing as a cushion tyre, it is merely a term to describe the extra thickness of rubber over a solid tyre. For example, two tyres-size 20 x 8 - 16 and 22 x 8 - 16 would both fit the same wheel. The latter (cushion), would have an overall diameter of 22" and the former (solid), an overall diameter of 20".
Measurements of press-on solid tyres are obtained as follows:
e.g. 22 x 8 - 16
- 22 overall diameter in inches
- 8 width at wheel in inches (not tread)
- 16 I.D. of tyre in inches (O.D. of wheel).
If the size is not known, by measuring the wheel (width and O.D.) and determining what clearance is available under the frame or behind the lift carriage, the size of the tyre can be worked out. Larger manufacturers of press-on tyres offer their full range in several different compounds and tread patterns.
The compounds available are:
Standard / general purpose
This type of compound is generally satisfactory for the majority of applications and unless the application specifically calls for a specially compounded tyre. It is false economy to purchase the most expensive believing "you pay for what you get."
Not to be confused with "antistatic". This type is designed for battery electric vehicles. The tyres recover to its original shape almost immediately it comes off the ground, thus helping to propel the truck. By offering minimum rolling resistance, maximum operational times between battery charging periods are obtained.
Electrically conducting / Antistatic
Electrically conducting tyres are used on vehicles where inflammable materials in solid, liquid or gaseous forms are present or where the risk of fire is a constant hazard. These tyres have an upper limit of resistance of 5 X 10e4 ohms or less. Antistatic tyres have a resistance of 5 x 10e4 ohms and less than 10e8 ohms.
Generally manufactured of neoprene' rubber, these tyres are utilized where oil-based products are present. As oil has a detrimental effect on normal rubber, making it soft and spongy, a greater life span is obtained due to the resistance of this tendency.
Hardened, shredded steel wire is compounded with rubber. Utilized in situations where additional resistance is required to tread cutting and chunking under severe conditions. It offers maximum protection where metal swarf, broken glass etc. is a continual hazard.
This tyre is of a two-part construction, a base material of very high resilience covered with a wear compound. It offers improved traction on wet surfaces or where ramps make operations difficult. On forklift trucks with front-wheel drive load wheels, the maximum advantage is when the truck is unloaded, as under these conditions there is the increased tendency to obtain wheel spin. Wear resistance is approximately 20% lower than the standard compound.
Originally a whitish-grey colour. Utilised in bakeries, food factories and bottling plants where inspectors objected to black tyre marks on the floor. The chief disadvantage was the fairly rapid wear due to the reduction of the quantity of carbon black in order to obtain the grey/white appearance. One manufacturer can offer a non-marking tyre which is black and offers nonmarking together with normal wear.
All press-on tyre manufacturers of repute, mark the different grades of tyres with an identification coding using combinations of symbols on the sidewalls.
Press-on tyres are available in five different basic tread designs:
Designed primarily as a drive tyre, it can.be utilised on the steer axle. On the heavier patterned tyre designed for maximum traction, damage to the tyre can be experienced when fitted to steer wheels as lugs can be torn off due to the acute steering angles imposed. Also bond failure sometimes occurs due to too much traction when trying to turn, the rubber is literally torn off the wheel.
DIAMOND AND CHEVRON PATTERNS
Now almost obsolete, they were originally designed for drive wheels. A limited number are still available for older type machines.
Utilised on drive but primarily on steer wheels. The smooth grooved tyre generally is from 8" wide tyre upwards. The purpose of the groove or grooves is simply for heat dissipation and to allow the material to expand into the centre when under load preventing bunching. Smooth tyres on drive wheels are normally used on smooth dry concrete floors with no ramps.
Specifically a steer tyre. It has a pronounced radius and convexed surface, and should not be used as a drive tyre except in cases of extreme emergency and if utilised, should be changed for the correct type as soon as possible.
Wherever possible the recommendation for maximum tyre life is - choose the compound and tread pattern for the application and always consider the fitting of smooth or smooth-crowned tyres to the steer wheels.
Tyre types
Other technical information.
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