AGV Backmarker: Is 2WD Still Crazy?

Standing water, wet leaves, manhole covers, diesel spills. Ask yourself one question: Are you more afraid of losing the back on that crap, or the front? If you answered, front, you’d like a motorcycle that could, in a split-second, transmit power to the front wheel. So, why don’t you have one?

Over the last ten years, Yamaha and Öhlins have devoted thousands of man-hours and millions of bucks developing a hydraulic motor capable of driving a motorcycle’s front wheel. KTM has patented a system that uses an electric motor in the front hub, but there’s no reason to think it will show up any time soon at your local dealer. The most viable two-wheel-drive system is the one produced by Steve Christini here in the U.S. In many ways, it’s the most old-fashioned; it relies on a system of chains and driveshafts that any gearhead can easily understand.

So far, the two-wheel-drive research and development that manufacturers have conducted in the open has mostly focused on off-road applications. The results have prompted most major sanctioning bodies to ban two-wheel drive from the sport of motocross.

What about road bikes? A review of patent applications suggests that several manufacturers have unpublicized two-wheel-drive research-and-development projects. They’re looking to improve handling and safety under conditions of low grip, to gain traction and increase outright performance, or to capture energy that’s now lost in braking and increase efficiency. Occasionally, they drop their veils to test at a public race or tease us with a concept bike, but they’re not eager to talk about their findings.

Now, Rodney Aguiar—who works with noted custom-builder Roland Sands—has fit a Christini two-wheel-drive system to one of Sands’ 450cc Super Single road racers. This is probably the least-closely guarded two-wheel drive road prototype, and it may help determine whether two-wheel drive is Next Big Thing in road bikes, or another dead end.

But the question isn’t, “Would 2WD be the biggest safety advance for real riders on real roads since ABS?” Frankly, I’m already sure that’s true. The question is only, “Will you see it in your lifetime?”

Before World War II, several manufacturers converted conventional bikes to 2WD for use in trials competition. The use of same-size front and rear wheels, and simple girder forks, made it relatively easy to use a couple of additional chain drives to drive the front hub off the countershaft.

The challenge of getting power to the front wheel became more complex when telescoping forks became the de facto industry standard. Still, dozens of inventors have cobbled together systems using various combinations and permutations of shafts, chains, and cables, or hydraulic drive.

The most (commercially) successful was a Californian named Charles Fehn, who created the Rokon. It’s hardly changed at all in fifty years. The large disc wheels are hollow, and Rokon points out that they can be used to carry extra gasoline or water. If left empty, they apparently make the bike float. Off-road? Heck, you can use this thing off land.

The success of the Audi Quattro automobile in the early ’80s was probably the impetus for Suzuki’s two-wheel-drive Falcorustyco concept bike, shown at the ’85 Tokyo Motor Show. It had hub-center steering and hydraulic drive. The Falcorustyco was purely a concept, although the following year, Suzuki showed the Nuda. It had mechanical drive to both wheels and looked tantalizingly close to something they could build and sell.

In the early ’90s, Yamaha took the slightly less-farfetched GTS1000 into production. It’s been reported they planned to produce a two-wheel-drive version. They licensed James Parker’s RADD suspension technology for the GTS, and that system was well-suited to 2WD. In fact, Parker had patented a 2WD version of his own.

“It was something we talked about, but that was all,” Parker told me. “There were always two factions at Yamaha: one group that wanted to experiment with new technology, and their ideas came thick and fast, but they were in the minority. Another, more conservative group, made it clear that if the GTS wasn’t an immediate commercial success, development would be stopped.”

I reached Hiroshi Takimoto, who was one of the key designers of the GTS at Yamaha, via email. He was utterly dismissive of the 2WD GTS project. Tantalizingly, though, he mentioned that Yamaha researchers had studied 2WD long before the 2-Trac/Öhlins project. He told me that while the advantages in the wet were always obvious, any conclusive advantage in the dry remained elusive.

The 2-Trac system, developed by Yamaha’s Öhlins subsidiary, has probably generated more publicity than any other 2WD system. Yamaha sold about 400 2-Trac enduro bikes, and there were plans to incorporate it into several KTM models. But in the end, it was another commercial disappointment.

From what Lars Jansson, Öhlins’ research-and-development manager on the project, has to say about it, 2-Trac might have been better suited to road bikes. The Swedes fit a hydrostatic drive to a Yamaha R1, and when they tested it in wet conditions at Karlskroga, it was (unsurprisingly) five seconds a lap faster than a stock one.

Even in dry conditions, the 2WD bikes were slightly faster at mid-corner, but slower overall. The added weight of the 2-Trac components (about 20 pounds in total, of which seven are unsprung) hampered the bike, especially in high-speed transitions. It also takes a few horsepower to maintain the system’s high hydraulic pressure.

But, maybe it just wasn’t given enough of a chance. Jansson also told me, “If you have a rear-wheel-drive bike and you give it too much power, the rear will start to slide, but the front end will automatically keep pointing in the right direction. If you have power going to the front wheel, as you approach the limit, you have a drift angle at the front, too. That went against our riders’ natural instincts. But all of them were convinced that with more practice, they could have gone faster in the dry, too.”

Only a little power needs to be delivered to the front wheel. Just overcoming the front tire’s rolling resistance makes a big difference, especially in the wet. At that point, all the available traction can be used for turning forces. In addition, wet tarmac is analogous to a flat turn on gravel. Kurt Nicoll, the former Grand Prix motocross racer and KTM North America’s director of racing, rode both mechanical and hydraulic-drive KTM prototypes, and he told me those were the precise conditions under which the bikes excelled. The front drive doesn’t just kick in when the rear wheel spins up; it also kicks in whenever the front loses traction, pulling you through your turn after a split-second hesitation.

Although the R1 was the only bike Jansson would discuss, over the course of our conversation, it emerged that Öhlins had made five different 2WD sport bikes, including two at the request of other manufacturers.

Right about the time that Yamaha was shutting down its expensive 2-Trac R&D program, Steve Christini was filing his patents for a mechanical 2WD system. If his system ends up becoming the industry standard, it will prove that patience is, indeed, a virtue for inventors.

Right now, Christini’s kits are available for Honda and KTM enduro and dual-sport models, and versions for Gas Gas and Kawasaki are in final testing. From his perspective, selling the kits isn’t a business in itself, it’s more a way to prove his concept works, and that there’s a demand for it. His long-term plan is to license his system to major manufacturers.

Christini’s product works best in terrible weather, but he admits it’s not particularly easy to sell in a stormy economic climate. “If the [industry] hadn’t taken a dive, we might already be talking about some kind of cooperation with one of the big manufacturers,” he says. “Instead of talking about 200 units, we might be talking about 2,000 units.”

Right now, the world of 2WD motorcycling can basically be divided into two enemy camps: the hydraulic (AKA “hydrostatic”) drive camp, of which Öhlins has the most developed technology, and the mechanical-drive camp, of which Christini is, by far, the most sophisticated. The third force is electric drive, which is in its nascent stages but which offers the prospect of regenerative braking (AKA “KERS,” for kinetic energy recovery system) While this is the least commercially developed concept, there will be a surge in interest if crude-oil prices get back up to the levels they were at last summer.

Christini was circumspect about projects for road bikes, but he admitted to confidential discussions with several Japanese and European manufacturers that have current 2WD research projects in the works, and that have talked to him about testing his system. “Although it will need to be refined for the street, we know there will be real benefits there,” he told me. “That’s where Rodney’s bike comes in. He’s helping us out by putting it on that bike and playing with it.” Since the Super Singles class mandates stock frames, it was easy for Aguiar to “plug and play” with a two-wheel drive version.

The end result is that this is almost the first time anyone’s made an open, extensive, apples-to-apples comparison between a two-wheel-drive sport bike and its conventional sibling. Aguiar’s still in the relatively early stages of “learning” his bike. For example, he’s had to retune the Sprague clutch to begin transferring power to the front at much slower rates of rear-wheel spin; in the dirt, the Christini system allows the rear to spin 20% faster than the front before it kicks in, and spin ratios rarely get that high on tarmac. Now, he’s got it engaging when rear-wheel spin hits around 5%. He’s already experienced that “gyroscopic steering damper” effect, noting that the front-wheel-drive bike is much more stable, even though the Christini kit reduces trail.

I may get a ride on Aguiar’s bike soon and tell you what it’s like. But until then, my guess is that he and Christini will eventually prove what Lars Jansson and Öhlins came to suspect after their tests: That 2WD gives an immediate, massive advantage in wet conditions, and—once riders have time to adapt to it—a slight overall performance gain in dry conditions, too.

But we won’t see 2WD in any high-profile racing series in the foreseeable future. They’re all desperately trying to cut costs, not introduce new technology, and several organizations have already preemptively banned it. So this is one new bit of bike tech that won’t take the homologation route into the marketplace. That means the first 2WD road bikes probably won’t be race replicas.

The best we can hope for is to see a few dual sport and adventure bikes with this option in the next few years. They’ll prove to be way more surefooted in real-world/real-rider situations, and may create enough demand to get manufacturers thinking.

In concert with best of breed ABS (i.e., Honda) and traction control (Ducati), a real-time 2WD system would give motorcyclists unprecedented control and confidence in bad weather. It’s all tantalizingly close, but in the words of Paul Simon (whose first hit song was, appropriately, “Motorcycle”), “ You know the nearer your destination. The more you’re slip slidin’ away.” Next week, I’ll try to shed some more light on why this promising technology faces an uphill climb to the market.