Naked Science Forum
General Science => General Science => Topic started by: paul.fr on 14/06/2007 10:22:51
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we must have all been out on our bikes in the rain, the spray from your tyres hitting you in the face and soacking your saddle at the other end. Is there a type of tread pattern that will reduce the spray, or send the spray to one side?
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I think that the problems of the cyclist and the problem the tyre is overcoming are in conflict. The tyre is trying to grip a wet road, and so needs to get rid of the water in order to increase surface area with the road. This means deep treads with arcs that face forwards, so that as the tyre spins, water is vented out along these channels. If you look at a wet weather tyre, especially from F1, the arcs generally begin in the centre of the tyre, and go outwards to each side. This would be the most efficient way of expelling water, so that no arc has to cover more than half of the width of the tyre. Unfortunately for the cyclist, this means that the increased efficiency of the tyre for traction means an increase in spray. A reduction in spray means less water moved, which means less tread on the tyre, and some sort of nasty accident. I think that if you had the tread going from the outside of the tyre inwards, such that all the water was vented under the car, the tyre would not be able to expel as much water as was necessary, and would aquaplane.
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Just another thought about spray - again I'm thinking about F1, and they send an enourmous amount of spray up. The main reason for this is the low pressure that they create underneath and behind the car that then drags the water from the road and into the air. This will be replicated to some degree in ordinary traffic, and increases with speed. So, I guess at least some of the spray is not necessarily linked to the tyres.
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The problem is that not all the water gets moved to the sides by the thread. Some water will adhere to the rubber and, as the wheel spins, flies off again. Unfortunately not to one side but in the plane of the wheel. And so you'll catch a bit of dirty, muddy and cold water. :-)
Be glad somebody invented the mudguard...
Edward