Leaning in – Can Three Wheels Deliver Safe Motorcycling Thrills?

Motorcycles are fun, but dangerous. Aside from the fact that they possess absolutely no occupant safety features whatsoever, the have the rather unfortunate quality of being unable to stand up by themselves. Ask any 3-year-old learning to ride a bicycle what their biggest fear is, and you immediately understand the one inherent flaw of the motorcycle.

To stay upright, single-track vehicles, like motorcycles and bicycles, depend on the gyroscopic effects of wheels in motion and constant corrective steering inputs, which together result in an elegant balancing of forces. But once the wheels stop turning, if you don’t put a leg out, you will fall.

There is however, another solution.

One of the most unusual threads to emerge over the past decade of motorcycle design has been the return of the three-wheeler. A strange and unnatural looking vehicle at first glance, the three-wheeled motorized cycle has been with us almost from the beginning. The first car, Karl Benz’ Patent Motorwagen, was a three-wheeler. Bicycles in 1880’s Paris were fitted with two rear wheels to make them practical delivery vehicles for postal and grocery delivery. Motorcycles evolved from bicycles, starting about the same time, so people experimented with tricycle layouts right away.

Over the past century, the motorized tricycle has seen some modest success, largely as a low-speed, light commercial transport. Notable in the genus’ family history is the 1966 Ariel 3, a scooter fitted with two rear wheels that hinged with the rest of the chassis, allowing the scooter to lean in corners like a regular bike while the rear wheels remained horizontal. The Ariel 3 was a dismal failure as a product. But it did inspire Honda to buy a licence for the patented layout, beginning a leaning three wheel dynasty that continues to this day with the Honda Gyro, Japan’s takeout delivery vehicle of choice.

Throughout most of the 20^th century, three-wheeled motorcycles remained a curio, typically nothing more than home-brewed or limited-production aftermarket conversion kits for conventional motorcycles by small companies, often using car parts on the rear end. In the late 1970’s, the All Terrain Cycle (ATC) hit the dirt with the promise of making the exploding motocross market safe for kids and grandpa, only to end with nearly 1,000 deaths, and the voluntary ban on ATC production by the major manufacturers.

The scandal of the ATC hinged on one inconvenient fact: three-wheeled vehicles are inherently unstable in parabolic (turning) motion. While the unassisted single-track motorcycle flops on its ear at a standstill, the laws of physics turn decidedly in their favour once they roll along, transforming the motorcycle into a paragon of predictable handling at virtually any speed. By contrast, vehicles with three points of contact are balanced at rest and low-speed, but become prone to tipping when loads change suddenly, such as high-speed cornering, especially downhill.

A three-wheeler in parabolic motion produces an undesirable combination of high torque forces on both the roll and yaw axis that are only too happy to overcome gravity and toss you into a ditch.  Sidecar riders know this, which is why they have to adopt counterbalancing body postures when cornering to prevent a roll over, particularly on inclines.  Even still, it takes little force for the inside wheel to “unstick”, or lose contact with the ground, which causes the center of the vehicles’ roll axis to move further to the outside of the turn, overloading the remaining two wheels.

Reverse trikes such as the Can-Am Spyder and Polaris Slingshot have some significant handling advantages over their ATC predecessors. Because they have two wheels up front, they generate substantially more grip when it is needed most, such as during changes in direction and under braking.

However, the sole rear wheel travels along the centre of the roll axis, and so can act as a pivot point during high energy turns, levering the inside wheel off the ground and flipping the vehicle. This is all mathematically predictable, so it can be engineered out of the vehicle’s performance envelope by using sophisticated electronic counter-measures.  But without them, a high-powered, high center of gravity three-wheeler is incapable of executing predictable, safe, high-speed turns without flipping. It is a reality of the laws of physics. The ATC was not unsafe, it just brought too many casual users too close to the edge of the performance envelope.

Perhaps that is why three-wheeled vehicles never took off anywhere. Why there are no three-wheeled Roman chariots, tricycle armored vehicles in Afghanistan, and why every three-wheeled car in history failed. Single-track vehicles enjoy an elegant relationship with the laws of physics that allow them to be used safely by anyone in a wide range of conditions, which is how children can pilot an old bicycle around a corner with little training. The ATC fiasco forced motorcycle manufacturers to stick with two and four wheels, the motocrosser and the ATV.

But the story of the three wheeled motorcycle didn’t end there.

An English inventor, Nick Shotter, spent 20 years and most of his money patenting a leaning four-wheeler he called the 4MC. During prototyping he approached Yamaha for technical support, who, according to Shotter, then tried to steal his technology. The European patent office said no, but Yamaha went ahead and presented the leaning four-wheel Tessaract in 2007 anyway.  The Japanese giant knew they were on to something, because when later Italy’s Piaggio launched the MP3 leaning three-wheeled scooter, they accelerated plans for their own leaning three-wheeler based on Tessaract technology, called the Tricity.  Peugeot produced their own, identical product. Patented to wazoo, Piaggio was unafraid to sue both Yamaha and Peugeot for infringement.

The MP3, Yamaha Tricity and Peugeot Metropolis are all configured the same way: two small diameter wheels in the front lean into corners independently, while the rear wheel follows the leaning front, but in the center line – just like on a conventional motorcycle. This layout provides incredible low traction stability (like say, in slippery conditions) and stability at rest (you can put your feet down at a stop, but you don’t have to), while maintaining all of the dynamic virtues of a single-track vehicle in motion. It turns as easily as a bicycle, and requires no special training.

The mission seemed accomplished, but then along came a Spyder.

Presented in 2007, Canada’s own Bombardier Recreational Products (BRP) launched the Can-Am Spyder RS (pictured above), a forward tricycle road vehicle powered by a version of the 1000cc Rotax twin from the spectacular Aprilia RSV Mille. It looked a lot like the snowmobiles that the company was famous for, and like them it did not lean when cornering. The rider sits astride the Spyder and operates handlebars as on a motorcycle, but all of the wheels are always perpendicular to the ground. The suspension is there to soak up the bumps, but does not lean the trike into corners like the MP3.

At this year’s Tokyo Motor Show, Honda threw its hat in the ring with the Neowing, a leaning three wheeler powered by a hybrid system including an inline four cylinder gasoline engine and a battery powered electric motor. Yamaha also upped their game with the conventionally powered MWT-850 (pictured, below), a leaning three wheeler billed as a “corning master”.

Both the NeoWing and MWT-850 are, at present, concept models. But given the amount of innovation presented, production detailing like real world lighting, and the patents filed, it seems highly likely that the world’s largest motorcycle manufacturers will pursue this market. It makes sense, and suggests that the holy grail of motorcycling sensation and added safety have been discovered.

Spyder is not called a motorcycle by either its maker nor its huge user base. According to BRP, the company has sold over 100,000 of them as of May of last year, representing hundreds of millions of dollars in revenue for the company. With the introduction of last year’s F3 model, a sportier, foot-forward power-cruiser variant, sales are likely to continue to grow. “We are pleased with the platform as it is” said Can-Am’s Brian Manning, when asked if new entrants from the majors like the Honda Neowing and Yamaha MWT-850 might inspire BRP to try to lean in. “Those are different products.”

And maybe for good reason.  While the leaning Piaggio MP3, its in-house cousin the Gilera Fuoco, Yamaha Tricity and Peugeot Metropolis are different, their handling virtues do not seem to be resonating with consumers. None have seen a lot of market success in Europe or over here, although the Yamaha Tricity is gaining traction in Asia, according to the manufacturer. The BRP Spyder is, however, going gangbusters. It is not a motorcycle, and perhaps that is its strength. To those looking for open air excitement, it offers more comfort than safety, but enough risk to tempt them away from the convention of a convertible car.

Motorcyclists looking for the leaning sensation, but with a little more assurance, are not being tempted by the scooter derived MP3 and its imitators. Perhaps the bigger, bolder and more performance oriented Neowing and MWT-850 will attract them.

Evidence suggests that, for now at least, leaning is not what the marketplace is asking for.