On Physics and Driving

As a cyclist I don't much like rain, it's cold, it makes my sweet ride dirty, (and being that I am both vain and anal a dirty bike is simply a bike that needs to be brought into the house for a good proper cleaning that ought to take at least 8 or 10 hours). But one good thing about a bike in the rain, the narrow (23mm wide) tyre slices through water and has plenty of grip.

Cars are a different matter. Tuesday I was driving to work in what I would call white knuckle driving. The rain was coming down in buckets and the expressways had some pretty hefty flooding. The roads felt slick and I was sure the car was going to spin out somewhere, yet all around me the motorists on the parkway were roaring along at a million and six miles an hour (well more like 10 to 20% over the posted limit).

I think this is a good place to review what happens when a car tyre is on a wet road. Water builds up in front of the tyre. A narrow bike tyre does not have this problem, and since bikes go slower than cars, the water has time to migrate around the tyre, which is more than I can say for the car. As the car roars along a lip of water in front of the tyre forms, if the car then accelerates just the tiniest bit the car can literally jump onto that lip and now the car is said to be hydroplaning. That is to say, the car is now floating on the surface of the water, there is zero contact between the rubber and the road.

I guess I should not be so surprised, after all these are Toronto drivers we are talking about. Sigh.