2009
20
This is not a technical explanation.
This is a nightmare for for people with longer cars which have very little Ground Clearance. What is exactly “Ground Clearance”?
No, its not the available ground in front of your car to cruise on. It’s much more complicated, and I must say important than that.An average road car has the wheels, which touch the ground, and then the rest of the stuff that do not touch the ground. Its the minimum difference between this ‘rest of the stuff’ and the ground is what is called “Ground Clearance”.
As illustrated in the diagram.
The actual ground clearance that is available to a vehicle.
The perceived ground clearance. Although it's not the actual GC, it is the part that is important in crossing over a Bump. The higher the height, the better are your chances
The first figure shows the actual distance between the things hanging from under the car and the road that it is on. The lowest point of any car is always between the wheels. This is the part where a numerous protruding components jut out (called suspension arms) to give you a comfortable ride.
The second figure is an illustration of the perceived idea of ground clearance that we get when we see a car. This is not very important while going over large objects but it is very important while going over speed breakers. If the height available to your car is less than the height of the speed breaker, chances are you will scrape the bottom of your car, and that’s not good.
So what do you do?
Simple. You avoid this by minimizing the chances of this happening.
Approaching the speed bump head on increases the distance that your car's suspended body travels over the bump
The angular approach to a speed bump reduces the distance that your car's body actually travels over the bump.
The two figures above do the explaining themselves. In the first, you approach the speed breaker head on and hence increase the distance your car travels suspended over the Bump increasing the chances of a scrape happening.
In the second figure, given traffic situation, you can approach the bump at an angle so that the distance your car travels suspended over the Bump is reduced to a bare minimum. In fact, if you have a shorter car, you can manage to have one wheel on the bump at all times negating any chances of a scrape.
Speed breakers on Indian highways are mostly unmarked and appear suddenly. Caution is needed while driving at night and even in daytime. It is tough to spot a moderately high speed breaker if the road is partially shaded with trees. These speed breakers (or Humps as the locals would call it) are made for truck traffic and sometimes can be as high as 30 cm.
Going over them at high speeds can be catastrophic.