A tonneau is an area in a vehicle that protects any passengers and is often covered by a soft or hard cover. The tonneau can be compared with a truck bed and has many different names. Modern cars don’t really have the structure to correctly use this term.
What is a tonneau
A tonneau is a side cover that is used to surround/protect a passenger seat. This can be made from different materials and is often seen on vehicles that either have no roof, have a foldable roof or have a small roof. It is not a type of roofing, but surrounds the passengers, instead of covering them. It is an open compartment which often has a rounded shape. The earlier models had a hinged door at the rear as a means to enter the compartment. Later models had a side entrance. On modern cars the tonneau can also be referred to as a truck bed. The tonneau cover is a sheet of vinyl-like material or (fake) leather that covers the truck bed and prevents water from getting into the truck bed. Some hardcovers for tonneaus are also available, often made from fiberglass, hard plastic or aluminium.
Different types of tonneau
Tonneaus can be found on many different vehicles. Later style vehicles such as the early cars had a removable type of “barrel” at the rear for passengers that either had a hinged entrance at the rear, or at the side. Smaller and later vehicles had the tonneau incorporated into the body of the car. These areas often where covered up when not used to prevent dirt and moisture getting into the compartment. More modern vehicles where better protected against the elements and would have windows and roof that provided a rain-proof seal against moisture, this made the tonneau cover often obsolete. The tonneau can be directly linked to a hard or soft top that is used on convertibles, although it is debatable if the compartment that is being covered should still be considered to be a tonneau, due to difference in type of construction and manufacturing.
Covers for the tonneau have been added to cars as early as the 1930’s. When the insight into turbulence and air-friction increased, the use of covers got a new use. Covering up an empty space, or covering an open area would improve the airflow, creating less drag and improving mileage and performance at greater speeds. Thus making racecars with a tonneau cover perform better and winning more races. In modern cars the truck bed cover is the best example of a tonneau cover. It is wrongfully thought that these can improve mileage and performance. The modern vehicles are designed in such a way that the truck bed actually creates an air flow that doesn’t need a cover to decrease the air-resistance. Hard covers can still be used to protect the load inside the truck bed, such as tools and equipment.
Cleaning and detailing tonneau covers
The soft cover is most often made from a vinyl-type material or a (fake) leather material. Some manufacturer can cover the vinyl with a layer of fabric for aesthetic purposes, resembling the look of a convertible soft top. Vinyl can be cleaned with regular shampoo, and even Traffic Film Removers. A chemical product should be diluted prior to applying and rinsed thoroughly. It can be difficult to correct surface imperfections and it is not easy to polish. In some cases a finishing polish can correct some smaller marks. Dressing can be applied to the surface and the type of protection should resemble the material i.e. vinyl = a type of plastic. Fabric covers can be cleaned in the same way as a soft top, and leather should be cleaned with mild cleaning agents only.
Hard covers are usually made from aluminium, hard plastic and/or fiber glass and is often painted to match the color of the vehicle. If painted, these can be corrected and protected in a similar way as regular paintwork. If unpainted, it would require a metal polish and protectant. Fiber glass can be polished in a similar way as paintwork although care should be taken to prevent overheating.