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Homepage. This page: A booklet looking at the care and maintenance of truck wheels, tyres and suspension, printed by Avon.

Avon tyres.

Aimed mainly at drivers and operators of lorries in the 1930s or 1940s, this booklet, issued by The Avon India Rubber Co. Ltd, has much of interest to owners and drivers of motor-cars. The cover illustration features a lorry driver studiously checking the pressures of his front tyres. Within, the pages are grouped into chapters, with topics such as proper inflation of lorry and coach tyres, overloading and payload distribution, mechanical issues that can affect tyre performance and life, types of lorry wheel rim, and tips on maintenance.
Avon tyres booklet

Tyre wear & incorrect inflation.

Diagrams explain the effects of correct tyre pressure versus over- and under-inflation, and how either of the latter situations will result in a smaller contact patch on the road, equalling less grip, and as a result increased wear on the sections of tyre burdened with the full weight of the vehicle. Under-inflation also leads to excessive movement in the sidewall and eventual over-heating of the cord strands found within the tyres' construction (I'm assuming that they're discussing crossply rather than radial tyres here, but the effects of incorrect inflation are very similar).
High average road speeds are also cited as a reason for increased tyre wear, although after the war I imagine this was kept in check by quite low maximum speed limits for commercial vehicles. Tread wear also increases in summer, thanks to higher road surface temperatures and the drier conditions. Although the advice given in this booklet is 60-70 years old, much of it still has a relevance today. Stop-start motoring, oil and grease left on the tyres, abrasive road surfaces and mechanical problems such as faulty brakes, and worn axle parts also contribute to tyres being scrapped before their time.

What is toe-in and toe-out?

There is then a diagram explaining to new drivers the basics of toe-in, toe-out, camber and castor, with brief descriptions of each. Again this is just as relevant to owners of vintage / classic vans, lorries and cars today.
Describing toe-in and toe-out
Toe-in.
Is the amount by which the distance between the wheel rims in front of the axle is less than that behind the axle, these measurements being taken at hub-height. A degree of toe-in is necessary to offset the tendency of front wheels to run outwards under the effect of wheel camber. Rapid tread wear with fins of rubber on inside of tread pattern will develop if toe-in is excessive.
Toe-out.
This is when the front wheels point outwards, the opposite condition to toe-in. It causes rapid wear with fins of rubber on outside edge of skid design.
Camber.
Wheel camber promotes easy steering and is the extent by which front wheels are inclined outwards at the top. Excessive camber results in uneven and rapid wear on one side of the tyre. A condition where the wheels incline inwards at the top and which is described as "negative camber", must be prevented from developing.
Castor.
Is the angle at which the top of the front axle is tilted towards the rear of the car. Its effect is to hold the front wheels in a straight forward driving position. Irregular castor adjustment will affect steering and cause spotty and uneven wear.
One cause of tyre damage unique to medium and large-scale commercial vehicles, is when an obstruction such as a stone is trapped between twin rear tyres, damaging the casing on both tyres and ultimately leading to either a puncture or a blow-out.
A diagram is also provided, illustrating the types of wheel rim commonly found on commercial vehicles in the late 1930s and early 1940s (shown above). The four main types are described as:
  • 2-piece rim with spring type detachable flange
  • 3-piece rim with one endless loose flange and spring lock ring
  • 4-piece rim with two endless loose flanges and spring lock ring
  • Divided wheel consisting of two pressings bolted together

Tyre switching.

Included within the remainder of the advice given in this publication, are some thoughts on switching tyres around the four corners of a commercial vehicle. Whether this advice still holds true today or not I'm not sure, but 60+ years ago the theory was that new tyres should go on the front wheels, until they are approximately half worn. They'd then be moved to the rear, outside wheels, assuming the lorry had twin wheels at the rear. Their final move would be to a stint acting as the inners for the twin rear setup. Car owners were advised to swap their wheels and tyres to the next position around the car, including the spare within the rotation sequence, every 2,500 miles or so. Whether this advice is still appropriate or not I'm not sure, so mention of it here doesn't constitute a recommendation - it does however shed light on a common procedure found within vehicle maintenance practices, back in the dim and distant past.
More items of paperwork relating to motoring can be found in the Motoring Collectables section, including related items from companies such as Pirelli, a well-known brand to this day.

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