More angle is now possible, and the future system will take up less space too.
Rear-axle (or rear-wheel) steering is not something new. It was first introduced in 1985 on the R31-generation Nissan Skyline, and since then, we've seen it on numerous other cars. The original BMW 8 Series featured this technology, as did the Mitsubishi 3000 GT. In more recent times, we've seen a rear-steer system on the likes of the Porsche 918 Spyder, the Ferrari F12tdf, and Lamborghini's Aventador Ultimae. The technology has also been employed on more everyday cars like the Renault Laguna GT and, in models equipped with Integral Active Steering, BMW's big-body 5 and 7 Series sedans. However, these systems are not all they can be, and BMW wants more.
In filings uncovered by CarBuzz, the German automaker has applied for a new invention with the United States Patent and Trademark Office. Herein, the Bavarian brand claims that existing systems are too unwieldy. This is because most systems use a track rod to adjust the toe of each rear wheel, but in this space, the vehicle must also house a subframe, an axle, and additional components like a differential and side shafts. This limits angles to, "at most 5 degrees," says BMW. The solution? An additional wheel carrier on each hub, with each featuring an actuator on the lower portion that is maintained by a grooved guide. According to the documents, this could allow for as much as 10 degrees of rear-wheel angle without adding to the space constraints of the rear subassembly.
If the invention makes it to production, it could have benefits across the automaker's range. On something like a BMW M4, one could dramatically reduce the virtual wheelbase, thereby vastly enhancing low-speed tight-turn handling. Naturally, high-speed stability is also improved, but we suspect that this technology will likely first do duty in a large vehicle like a new 7 Series. These luxury machines are getting larger every year, and parking them is certainly not easy. With a shortened virtual wheelbase thanks to this enhanced rear-axle steering system, monstrosities like the XM could be a little easier to live with on a daily basis.