This bump is actually the result of the space reserved for the shaft to pass under the vehicle. We call this mound “shaft tunnel”.
First of all, let’s give a brief information about this system. Shaft; A powertrain that carries the power of the engine to the rear wheels in rear-wheel drive cars. Since there is no need for such a transmission in front-wheel drive vehicles, there is no shaft going from the middle to the rear. If front wheel drive vehicles do not have such a drivetrain, have you ever said why my car also has this bump? Yes, most front wheel drive vehicles have this bump as well. Let’s take a closer look at what a shaft tunnel is.
Why do most front-wheel drive cars have a shaft tunnel when the shaft is not needed?
Of course, not all front-wheel drive cars have a shaft tunnel, but most front-wheel drive cars do. Because this tunnel provides great convenience to the manufacturers even though the shaft is not used.
In front-wheel drive cars, this tunnel is used as an installation space in general, although it differs from manufacturer to manufacturer. Along with the exhaust line of the vehicle, the line of systems such as electricity, fuel and brake is also passed through this tunnel. In some brand vehicles, only the exhaust line can be passed, while in others we see that all of them are passed.
The shaft tunnel has an even more important purpose than the plumbing cavity: Robustness.
The bottom of a car should be solid. As if the bottom part pulls all the weight of it, the pits, fast take-offs and many other things that we can’t count add weight to the bottom part. Here, most car manufacturers want to hide the shaft tunnel that runs through the middle of the vehicle as if it were a half pipeline to further strengthen this lower part. This slope provides significant durability as if there is a column in the middle of the vehicle.
Let’s explain the robustness that the shaft tunnel provides to the vehicle with an example.
Imagine you have a wad of paper in your hand. It is very easy to bend when the wad is flat. However, if we bend this wad from the edges and make it into a half cylinder, it will be much more difficult to bend it. The shaft tunnel adds strength to the vehicle precisely with this principle.
Are cars without shaft tunnels not solid?
Of course, that shouldn’t mean anything like that. Some manufacturers are adding different reinforcement methods instead of the shaft tunnel to provide more comfort in the rear seat. Especially on higher vehicles, there may not be a need for a shaft tunnel through the vehicle as the lower parts are easier to hide.