2006-12-03 04:51:31 · 7 answers · asked by NICOLA L 1 in Science & Mathematics ➔ Engineering
the treads help to disperse the water on the road and thus keep the car stable, different tread types have different advantages - see link:
http://www.tyres-online.co.uk/techinfo/patterns.asp
2006-12-03 05:03:43 · answer #1 · answered by dave a 5 · 0⤊ 0⤋
When a tire rolls slowly over standing water on pavement, the weight of the car pushes the water away so that the rubber tire can make contact with the pavement. Some of the water is pushed out ahead and behind the tire, and some is pushed to the side.
As the car goes faster, the water has to squeeze out faster. The problem is that water has mass, so pressure is required to accelerate the water. The wider the tire, the farther the water has to go to get out from under the tire, so the greater is the acceleration required at any given speed of the car. Not only that, but the water that is pushed out ahead of the tire does not have time to flow off to the side, so a "bow wave" occurs, causing effectively deeper water just in front of the tire.
At some point, the combination of the density of the water, the speed of the car and the width of the tire means that the pressure required to squeeze out the water is greater than can be provided by the weight of the car. At this point the car is "hydroplaning" or "aquaplaning." Rather than the tires being in contact with the roadway, they are riding on a sheet of water. The water is extremely slippery, so the driver needs to stop or steer, the car will not obey. The usual result is an auto accident.
The grooves in the tire effectively reduce the width of the tire so that the water does not have as far to accelerate, and therefore can go faster before hydroplaning occurs. The grooves have to be wide enough and deep enough to allow the water to flow freely.
Many tires today have directional grooves, which encourage the water to flow to the sides and behind the tire and decrease the bow-wave effect.
If you want to explore more about this topic, look for "squeeze-film effect." It's a good thing if you are trying to lubricate a shaft running in a bearing.
2006-12-03 15:11:19 · answer #2 · answered by AnswerMan 4 · 0⤊ 0⤋
The legal minimum tread depth for cars and light vehicles in the UK and EU is 1.6mm across the central three-quarters of the tyre tread width and around the entire outer circumference of the tyre.
It's not just in the rain that you need them. If you have bald tyres it severely increases your risk of skidding in any weather and also getting caught by the police with bald tyres can be costly!!
2006-12-03 13:07:33 · answer #3 · answered by Anonymous · 0⤊ 0⤋
the gaps in the tread enable the water to have a place to goso that the rubber touches the ground.
if the tyres are nearly bald then there is no where for the water to go and the tyre skids on the water.
2006-12-03 16:11:13 · answer #4 · answered by Mark G 2 · 0⤊ 0⤋
go out in the middle of a rain storm without treads an dlet me know what difference it makes if you get home
2006-12-03 12:55:55 · answer #5 · answered by Anonymous · 0⤊ 0⤋
the water covering the road surface needs to have some place to go because it can't get out of the tires way fast enough, if you had perfectly flat, smooth tires the water would get stuck between the tire and the road surface and the tire would suddenly lose traction (hydroplaning)
2006-12-03 15:00:51 · answer #6 · answered by Nick F 6 · 0⤊ 0⤋
So they don't aquaplane.
2006-12-03 12:54:13 · answer #7 · answered by Jon B 6 · 0⤊ 0⤋