describes a hard or soft cover used to protect unoccupied passenger seats in a convertible
A convertible is a type of automobile in which the roof can retract and fold away having windows which wind-down inside the doors, converting it from an enclosed to an open-air vehicle...
A roadster is a two-seat open car with emphasis on sporty handling and without a fixed roof or side weather protection. Strictly speaking a roadster with wind-up windows is a convertible but as true roadsters are no longer made the distinction is now irrelevant...
, or for a pickup truck
A pickup truck is a light motor vehicle with an open-top rear cargo area .-Definition:...
bed. Hard tonneau covers open by a hinging or folding mechanism while soft covers open by rolling up.
The tonneau cover is used to conceal cargo. When the cover is pulled out, it keeps items out of the sun and provides extra security by keeping personal items out of sight, as well as shielding the driver from view.
was an open rear passenger compartment, rounded like a barrel, on an automobile
An automobile, autocar, motor car or car is a wheeled motor vehicle used for transporting passengers, which also carries its own engine or motor...
and, by extension, a body style
Automobiles' body styles are highly variable. Some body styles remain in production, while others become less common or obsolete. They may or may not correlate to a car's price, size or intended market classification. The same car model might be available in multiple body styles comprising a...
incorporating such a compartment. The word comes originally from French, mostly meaning barrel or sometimes cask or container. Most tonneau covers were fixed in place as an optional element at purchase, but some could be removed as on the Crestmobile
Crest Manufacturing Company was a manufacturer of automobiles in Cambridge, Massachusetts.The 1904 Crestmobile was a touring car model, notable for its removable tonneau. With the tonneau in place, it could seat 4 passengers and sold for US$850. The vertical-mounted single-cylinder engine,...
or the two-part (frame and cover) of the early MGB.
Early tonneaus normally had a rear-facing hinged door, but single and dual-side doors were soon introduced. The first US side-door tonneau was made by Peerless
Peerless was a United States automobile produced by the Peerless Motor Company of Cleveland, Ohio from 1900 to 1931. The company was known for building high-quality, precision luxury automobiles. Peerless' factory was located at 9400 Quincy Avenue in Cleveland...
, but others quickly followed. This led to the development of the modern sedan/saloon, with Cadillac manufacturing the first US production closed-body four-door car in 1910.
Early open-bodied touring-type automobiles used tonneau covers to protect unoccupied rear seats. As early as the 1930s, lakes racers, searching for that extra competitive edge, pulled a page directly from early aircraft construction and skinned the cockpits of their roadsters and streamliners with removable canvas. The skins covered gaping cockpits that would otherwise disturb airflow and create undue drag; as a result, tonneau-equipped cars ultimately went faster with a given amount of power.
Tonneau covers are available for open sports cars such as the Porsche Boxster
The Porsche Boxster is a mid-engined roadster built by Porsche. The Boxster is Porsche's first road vehicle to be originally designed as a roadster since the 550 Spyder....
, MGA, Triumph, and Austin-Healey. These covers, made of leather or vinyl, cover the entire passenger compartment, and are zippered to enable the driver's seating area to be uncovered, while the passenger seat and small rear storage space behind the seats remained covered. Tonneau covers may be used in lieu of hard or soft convertible tops.
Air as it courses over the windshield at speed, creates turbulence as it cascades into and summarily bounces out of the cockpit. This turbulent condition is called buffeting, which grows annoying over time. A tonneau cover reduces that buffeting at all speeds. Heat generated by a heater leaves as that turbulence exchanges the cockpit's warmer air for cooler ambient air. A tonneau cover is capable of both retaining a vast amount of heat, and shielding a driver from UV exposure.
Truck use and styles
Tonneau covers are used by owners of utility vehicle
Utility vehicle is used to describe a vehicle, generally motorized, that is designed for a specific task.-Sport utility vehicle:Vehicles similar to a station wagon but built on a light-truck chassis, usually with off-road capability....
s and trucks to cover and secure their pickup bed and come in a variety of styles.
The most common style is the roll up tonneau made from cloth or vinyl which uses a rib-like structure to support the fabric and keep it taut. A snap-based system is also used, but has become less common due to truck owners not wanting to install the snaps on their vehicle as they typically require drilling or use permanent adhesive. Roll up Tonneaus are opened by rolling the cover up toward the cab of the truck.
Another common style of truck bed tonneau cover is a retractable unit, which is mounted at the front and sides of the bed and rolls up or retracts from the tailgate towards the cab. Usually, there is a small rectangular canister attached at the front of the bed to store the tonneau cover when retracted. The retractable tonneau is typically made of vinyl, plastic or aluminum. Retractable tonneaus have the benefit of being more convenient to use than vinyl roll up styles as they don't involve any difficult or time consuming assembly or disassembly. Retractable tonneau styles are also usually lockable.
Fiberglass or hard plastic tonneau covers are also common. Some may be painted to match the truck, are solid in construction, and can be locked. These covers are usually heavy and require gas struts to assist in opening and closing. They operate much like a vehicle's hood, typically opening from the tailgate end of the bed (back to front). However, some are available with multiple compartments that will open front to back, back to front, side to side, or even rise vertically. Fiberglass or hard plastic tonneau covers are sometimes installed as a factory option with some new vehicles.
The word is sometimes spelled incorrectly as "tonno."
Tonneau covers offer a number of benefits to pick-up truck owners:
- Protection from elements: Truck bed covers protect the bed and its contents from sun, rain, sleet, snow, hail, wind, leaves, and vermin.
- Security: Truck bed covers hide the contents and offer increased security because the time it would take to open or remove a truck bed cover would discourage theft. Some covers can be locked. Truck bed covers also keep the contents from being blown around or blown out of the truck.
- Aesthetics: Tonneau covers add a look many consider to be stylish by giving the truck bed a streamlined look.
Improved aerodynamics and gas mileage on trucks
Many sellers will state that tonneau covers will improve gas mileage because they make the truck more streamlined. However, air currents create a wake inside the pickup bed which helps the aerodynamics. A tonneau cover interferes with this wake and scientific tests have shown little to no improvement in mileage by using a tonneau cover traveling at less than 70mph. A similar effect is seen when the tailgate is down and the mileage goes down. The only device that tests show will significantly improve mileage is using a mesh in place of a tailgate since it both keeps the truckbed wake in place and reduces tailgate drag.
"Tonneau case" is used to describe a type of watch case, with rounded, bulging sides resembling a barrel (or cask).