時差N小時:輪胎上為什么有胎紋?

If you've ever driven on a highway during a heavyrain, you know about the danger of skidding. This"waterskiing" on the road is technically calledhydroplaning, and it happens when water comesbetween the road and your tires, causing you to losetraction and go out of control. Your car is less likelyto slide around when the road is dry because thereis enough friction between your tires and the roadto keep you steady, even at high speeds.

如果你曾大雨天開車在高速公路上行駛，你就會知道打滑的危險。在技術(shù)上，這種“路上滑水”稱作“濕路打滑”，當路面和輪胎之間有水時，就會發(fā)生這種現(xiàn)象，致使車子失去牽引力從而失去控制。當?shù)孛娓稍飼r，就不可能打滑，因為輪胎和道路之間有足夠的摩擦力來使車子在高速行駛時保持穩(wěn)定。

But when it rains, a layer of water builds up between your tires and the road. This waterinterferes with the friction that helps your tires grip the road surface. This is where the treadson your tires come in. If the road you are driving along is covered with water, the pressure ofthe tire against the road surface causes the water to be squeezed up into the tire treads. Thesetreads help your tires pump water out from underneath the tire so that the rubber can be incontact with the road, thus creating the friction that will stabilize your car.

但是當遇到雨天時，路面和你的輪胎之間會積起一層雨水。水會減小摩擦，而摩擦力的作用正是幫助加強輪胎抓地力防止其失控。這時輪胎上的條紋就起作用了。如果你一路上駕駛的道路被水覆蓋，輪胎對地表施加的壓力把積水擠壓到輪胎面上。這些紋路會幫忙把輪胎下的水抽出，這樣橡膠就又能與地面接觸，從而產(chǎn)生阻力使你的穩(wěn)步前進。

The faster you go, the more water your tires have to remove. That's why your car may nothydroplane at thirty miles per hour, but might at sixty miles per hour. In fact, at highwayspeeds, during hard rains, each tire must pump away about a gallon of water every second.This is hard for tires to do if they are old and have treads that are worn down. When there isn'tenough space in the tire's grooves, water can't find a place to go and so it creates a layer oflubrication, causing you to do the equivalent to waterskiing on the highway.

你開得越快，輪胎需要排出的積水就更多。這就是為什么你的車時速30英里時不打滑，而時速60英里時卻打滑。實際上，按照高速公路上的行駛速度算的話，在雨天每個輪胎每秒要排出一加侖的水。如果輪胎太舊或者已經(jīng)嚴重磨損的話，排水就會很困難。當輪胎凹槽上的空間不夠時，水無處可去，就充當了潤滑層，造成車子打滑，就相當于在高速公路上做滑水運動。