From The Road Up – Tyres
The vast majority of people would regard the tyre as a subject in its own right and there is absolutely nothing wrong in that, however, very few people would consider tyres to be a component part of the suspension system. Consider running over a small object in the road such as the ubiquitous cats eye, the first thing to react to this impact is the tyre, the treat area will deflect inward towards the wheel and the sidewalls will expand outward on either side. Despite this two plane deformation the remainder of the tread will have the capability to maintain contact and therefore grip with the road surface. All this without the normal suspension componentry, springs, dampers etc having to do much work at all.
So that’s the suspension aspect of the tyres job, what else does it have to do? Unlike most other vehicle components the humble tyre is faced with dealing with a multitude of tasks including maintaining grip on the road surface, coping with extremes of temperature (both road and atmospheric), resisting mild but often repeated impact, virtually instantaneous clearance of water from the tread/road contact point, clearing itself of mud, ice and snow all this and still must retain the ability to provide directional stability when manoeuvring and, depending on vehicle type, transmit engine power to the road surface.
Tyre manufacturers expend vast resources in tyre development but despite this the demand from both vehicle manufacturers and customers in the aftermarket is for a product range to address differing vehicle needs, the rugged and aggressive construction of a type suitable for off road applications will be vastly different to that required for the average family car. It would be virtually impossible to produce a tyre of one construction to suit all needs simply by changing the tread pattern. To achieve these requirements tyre manufacturers will consider the vehicle end use, the off road tyre will be able to self clean larger amounts of tread blocking mud and it will have a far greater resistance to puncture in both the tread and sidewall areas than its purely on road cousin. The flip side to these attributes is a tyre far noisier on normal road surfaces, less precise handling characteristics and its extra weight will reduce fuel efficiency. For Mr/Mrs Average, tyres need to be of a reasonable price, have a good service life, be as quiet as possible in operation and provide grip over a wide range of road surfaces.
The Components Of A Normal Road Tyre
So what is a tyre actually made from? Most people would say rubber, a few less would say rubber with some sort of reinforcement and fewer still would say anything more complex. The average car tyre is made up from variations on the following basic mix; rubber 38%, fillers (carbon black, silica) 30%, reinforcements (steel, rayon, nylon) 16%, various oil and resin based plasticizers 10% and a 6% jot of various chemicals to help resist sunlight and other atmospheric conditions.
Hopefully the above will show that the tyre is not just a ring of black rubber, it is one of the most underrated components of the modern motor vehicle, further, and almost to the point of being incredible, the average family car sits on four contact patches each little bigger than the sole of a size 9 shoe, at 60mph on a good road surface covered in rainwater, the tyre at each corner will be able to clear 1 gallon (5 litres) of water from that contact patch every second!