- The rear wheel steering prevents and / or controls the swinging of the trailer
- Helps to reverse and brake the trailer on slippery surfaces
- Provides stability during abrupt maneuvers
- Help with tightening tropics
- Probably a $ 1,500 to $ 2,000 option
Anyone who has pulled a trailer, large or small, has likely experienced the harrowing onset of the trailer. You will feel the back of your towing vehicle pulling it in one direction and then the other as you watch it swing from side to side in your mirrors. Taking off the gas or braking can make it worse, while (contrary to intuition) a slight acceleration can help stabilize. However, if it continues and builds up to the limit, it can damage or discard anything in or on your trailer, causing a loss of control with serious consequences. And even when you steer properly to counter that, a swaying trailer is always annoying and at times scary.
Most modern truck-based trucks and SUVs that are tow-equipped have a standard or available sway control function (via automatic selective rear wheel braking and / or interaction via the trailer hitch). Some premium couplings claim to prevent swaying and modern, high quality trailers are less prone to it. But what if your tow vehicle could feel a sway at the beginning and its rear wheels could counter-steer almost imperceptibly to steer it?
All-wheel steering to the rescue
This is an important advantage of the Active Kinematics Control (AKC) from the German supplier ZF, which steers the rear wheels of a vehicle slightly in the same direction as the front axle so that it runs straight and true at highway speeds (with or without a trailer) and stabilizes when changing lanes and reduce the need for driver corrections during the trailer. It also assists braking, makes it easier to reverse a trailer (and prevents creaking) and, by turning the rear wheels relative to the front wheels, reduces a vehicle’s turning circle for better maneuvering in tight spaces.
Think about it. Every time you dodge a pothole or quickly change lanes, the back of your vehicle will follow the front, but with a slight lag that can result in imbalance, a small fishtail, or – especially on smooth surfaces – a rear wheel slide. However, if your rear wheels are spinning in the same direction as the front wheels at the same time, the vehicle can roll in one direction or the other with much more stability. And at low (parking) speeds, the rear of the car can turn more sharply during U-turns and maneuvers in tight spaces if it turns in the opposite direction to the fronts.
History of rear wheel steering
Rear-wheel steering (also known as all-wheel steering) has been around for years and is widely used in agricultural and construction machinery, “monster” trucks, and some large European buses. Honda offered it as an option for its 1987 Prelude, Mazda tried 626 sedans for 1988, and General Motors offered “Quadrasteers” for Chevrolet and GMC pickups and SUVs from 2002 to 2005. However, all of these options were discontinued for lack of customer interest, largely because their prices far outweighed the perceived benefits.
In recent years, however, newer generations of all-wheel steering have become available either in packages or as standalone options for a growing number of (mostly luxury) cars, CUVs, and SUVs. The majority are ZF AKC systems, which are now offered on European and some US Audi A6, A7, A8 and Q7, BMW 5, 6, 7, X5, X6 and X7, Porsche 911 and Panamera. The supplier reports that it has built half a million AKC systems in less than six years since production began. And ZF is now targeting U.S. pickups and SUVs, where they make a lot of sense for many reasons, including highway stability, braking, towing, and low-speed maneuverability.
How it works
ZF supplies two variants of AKC. A center-drive version is ideal for front-wheel drive vehicles and larger pick-ups and SUVs, while a two-drive system uses one on each rear wheel to save space for a fuel tank, driveshaft, and rear axle of a rear-wheel drive car, even the Engine and gearbox of a rear-engined Porsche.
To test AKC, we tried a number of maneuvers in a lightweight, full-size pickup truck fitted with the center-drive version, both with and without 7,000 pounds. Trailer at ZF’s Michigan test facility, and its benefits quickly became apparent. When the system was switched off, the trailer swayed noticeably during lane change tests … but not when the system was switched on. It also improved trailer-less stability and helped stabilize hard braking with one side of the truck on a wetted, smooth surface. At low speeds, driving down a narrow, cone-lined slalom was much easier and allowed for a (19 percent) tighter turning circle than the truck could handle with the system turned off.
What does all-wheel steering cost?
We are therefore convinced that AKC will be a worthy driver assistance and safety improvement for most trucks or SUVs, regardless of whether they are used for trailers or not. No US truck manufacturer has yet to offer such a system, but we can speculate that its retail price would be between $ 1,500 and $ 2,000. For example, Audi offers “Dynamic All-Wheel Steering” for USD 1,950 as a standalone option for the US A8, BMW offers “Integral Active Steering” for USD 1,150 for a variety of models, and Porsche charges USD 1,620 for “rear-wheel steering” on the Cayenne SUV and Panamera sedan and $ 2,090 on some 911 sports cars.
It probably won’t be long before it becomes available in more and more U.S. truck and SUV option lists, as well as in other vehicles, especially since it supports automated driving. It has the potential to partially steer a vehicle – for example to keep it lane-centered – without turning the front wheels. And it is suitable for hybrids and pure electrical systems as well as for conventional vehicles with internal combustion engines.