A de Dion tube is an automobile suspension technology. It is a sophisticated form of non-independent suspension and is a considerable improvement over the swing axle, Hotchkiss drive, or live axle. Because it plays no part in transmitting power to the drive wheels, it is sometimes called a "dead axle".
De Dion suspension uses universal joint at both the wheel hubs and differential, and uses a solid tubular beam to hold the opposite wheels in parallel. Unlike an anti-roll bar, a de Dion tube is not directly connected to the chassis nor is it intended to flex. In suspension geometry it is a beam axle suspension.
The de Dion tube was named after Comte Jules-Albert de Dion, founder of French automobile manufacturer De Dion-Bouton. The tube, however, was invented around 1894 by co-founder Charles Trépardoux for use on the company's steam tricycles.
Alfa Romeo is probably the most famous adopter of this technology, using it on the Alfa Romeo Alfetta, GT, GTV, GTV6, Giulietta, Alfa 6, 90, 75/Milano, SZ/RZ. Other production vehicles using this suspension include the Lancia Aurelia (fourth series onwards) and Flaminia, first and second generation Prince Gloria, the original Mazda Cosmo, Volvo 300-series, Rover P6, Chrysler minivans (all wheel drive versions from 1991 to 2004), DAF 46, DAF 66, all Iso cars (Iso Rivolta IR 300, Iso Grifo, Iso Fidia, Iso Lele) and early Bizzarrini 5300 GT Stradas, some of the largest Opels, such as the Opel Diplomat "B" of 1969, all Aston Martins from 1967 to 1989, Ferrari 375 and 250TR, first generation Maserati Quattroporte, Bugatti Type 251, Mercedes-Benz W125 and W154 as well as Auto Union Type D.
The Smart Fortwo and Smart Roadster micro-compact cars produced by Daimler AG, Mitsubishi i kei car produced by Mitsubishi Motors and the Caterham 7 (a development of the Lotus Seven after Lotus sold the design rights to Caterham Cars), are the only cars currently in production that utilize this arrangement, as well as the products of some kit car companies. A recent vehicle to use this suspension coupled with leaf springs was the Ford Ranger EV. The American built MV-1 van by VPG, produced from 2010 to 2016, also used this suspension in the rear with leaf springs. 4WD variants of the Honda Fit and Honda HR-V subcompact SUV have been reported as using a De Dion style suspension; however, these vehicles actually have a twist-beam rear suspension, with the cross beam element located even further forward (and thus even more like a trailing arm and less like the beam axle of a de Dion) than the 2WD variants.
Most models of the Kawasaki MULE line of utility vehicles feature a leaf-sprung DeDion rear suspension with a distinctively curved tube axle that clears the rear subframe to provide 50mm of wheel travel. Benefits include simplicity, durability, compactness and a relatively low liftover height for the cargo bed.
Walter Snow Fighter plow trucks produced by the Walter Truck Company of Long Island, New York throughout the mid 20th century used DeDion axles with portal gear hubs for both the front and the rear suspension, allowing the use of large differentials for durability without increasing unsprung weight or reducing ground clearance. Forged steel axles were used instead of tubes.