Radial Daze
Radial Daze
ROUNDUP
STEVE ANDERSON
IF YOU’RE NOT A FOLLOWER OF PRODUCTION-CLASS ROAD-
racing, you may not realize that there’s a revolution going on. Lap times are dropping like they've never dropped before: At our local track. Willow Springs, a good 750 production bike two-and-a-half years ago might have turned a 1:35 time; in the last month, production 750 lap times have dipped into the 1:29s, six seconds faster. In fact, some box-stock 750s are running only a second or two slower than a full-blown AMA Superbike.
Some of this speed increase can be explained by improved motorcycles, and some by the harder riding inspired by the contingency money some manufacturers are offering. But the central speed secret is neither better motorcycles nor better riders. Instead, it’s the high cornering speeds allowed by the phenomenally sticky street-legal tires that are available. The battle between the tire companies has become so intense that D.O.T.approved racing rubber seems to get redesigned or up-
dated about every six months.
Now. if you're not a roadracer, you may be wondering what this has to do with you. Some of the current super-stick tires are as short-lived as they are igrabby, and some provide a fairly choppy ride. In truth, most of the D.O.T-approved racing tires simply don't offer much more utility for the average street rider than would a full racing slick; for the street, such tires are both too much and too little.
But in the last few months, we’ve gotten very excited about some new technology that promises eventually to reward all street riders: the new generation of low-profile radiais as exemplified by Michelin's Lligh-Sport/Motorcycle Radiais and Pirelli’s latest MP7 Sport. Both brands currently are trying to stake out the highest-performance turf in the street-tire business—and at this point, they fit only the few ultra-sportbikes that were designed around the wide rims required for radiais—but we think they point the way to a near future when even touring bikes will be equipped with radiais.
Just a few months ago we sampled the new Michelin radiais (March, 1988), and more recently spent a day at Willow' Springs with Pirelli tire engineer Pierangelo Misani, who both allowed us to try some of the very first MP7 Sports, and helped explain why and how they work.
While there are differences in detail between the Michelins and the Pirellis, the philosophy behind them both is very similar: take advantage of radial construction to create the lightest tire possible, with a very flexible tread area. The result is a noticeably more compliant ride than with most bias-ply or bias-belted tires; light, direct and precise steering; outstanding traction; and excellent high-speed durability. Both companies claim some increase in life with the radial construction (perhaps 25 percent, says Misani). but say that for now. this potentiallv longer life is sacrificed to allow softer compounds.
When we say that these radiais give a more compliant ride, we really mean it: They noticeably improve com-
fort. as well as handling over small ripples and bumps. The amazing thing is that they do this while matching or bettering the pure cornering performance of much stiffer-riding biasbelted D.O.T.-racing tires. These differences aren't particularly subtle, and we think they would be as welcome on cruisers and touring bikes as on racers.
Currently, there's a catch to this: The radial advantages are most profound only for relatively pure radial designs. Ideally, that means a tire profile of 60 percent or so, perhaps as tall as 70 percent for a front. Also, rims have to be at least 70-percent the width of the tire; that means rear rims about 4.0 inches wide for a middleweight, perhaps as wide as 5.5 inches for a literbike. The radial revolution is not one that can easily be retro-fitted.
But it’s one we think will appear on new motorcycles surprisingly quickly, and may be one of the purest examples of technological trickle-dowm from the world of racing. If so, Grand Prix wins on racing radiais may make possible the tires for the 1990 Gold Wing.
Oops!
In the test of the Kawasaki Ninja 1000 that appeared in last month’s issue, we printed two erroneous performance numbers. One was in the specification chart's Speedometer Error category, which stated that at an indicated 60 mph the Ninja was really traveling 58 mph. That is incorrect, for at an indicated 60 the Ninja's true speed was 54 mph.
This error, which was a result of a malfunction in our computerized third-wheel test equipment, wasn't discovered until after the test was published, and it also affected our Braking Distance figures. We claimed that the Ninja made a record. 107-foot stop from 60 mph; but because of the error, it actually stopped from just 56 mph. On retest, the Ninja still stopped hard from an actual 60, but no longer set a record: 60 to 0 mph took 115 feet. But the stop from 30 actually improved the second time around, requiring only 26 feet. So, all in all, we can safely say that Kawasaki’s fastest Ninja has great brakes—and a lousy speedometer.
End of the three-wheel era
A fter almost a year of study and investigation, the U.S. Department of Justice and the CPSC (Consumer Products Safety Commission) have convinced Honda, Kawasaki and Yamaha to stop the sale of three-wheeled ATVs in the U.S. At a press conference held on December 30, 1987, Deputy Attorney General of the Department of Justice Arnold Burns announced that ATV manufacturers, including Suzuki and Polaris, which make fourwheeled ATVs only, have signed a consent decree wherein they voluntarily agreed to several strategic points concerning ATV marketing and safety.
Burns said that the consent decree “represents a giant step toward reducing injury and death associated with these machines.” He and Commissioner Scanlon, head of the CPSC, both said that at this time four-wheelers are not involved, and that so far the four-wheeled ATVs have a safety record that is significantly better than do the three-wheelers. The consent decree was put forth as a way of having an immediate response to the ATV problem without protracted and costly litigation. Burns said, “This is the best possible resolution of the problem achievable under current law.”
The decree states that, among other details, the manufacturers agree to do the following, or be forced into litigation by the Justice Department:
— Manufacturers must immediately halt sales of all three-wheeled ATVs, and buy back all unsold threewheel inventory from the dealers and distributors.
—They must provide, free of charge, hands-on safety training with every new machine they sell. This is retroactive for one year.
—They must notify, in writing, all known past buyers of ATVs, and instruct them about the risk associated with ATVs.
-They must provide dealers with four-foot-by-tour foot signs that contain warnings about the dangers associated with ATVs. These signs must be prominently displayed in the dealerships.
This by no means signals the end of the ATV issue, because the Justice Department has reserved the right for the CPSC to seek a further recall than is provided for in this consent decree; and a future recall could conceivably include four-wheelers. Kawasaki and Yamaha had al ready stopped producing three-wheelers for the U.S.
market, but thousands of machines remain in dealerships and distributor warehouses. The cost to the Japanese companies is hard to assess, but it is certain that they will all suffer economic difficulties because of this development.
New Honda 1000R?
The latest rumor from Europe has Honda launching a racy new CBR1000R for 1989. The bike would use a modified Hurricane 1000 engine (with gear-driven cam shafts and mega-horsepower) with all-new running gear.
Its chassis woi~ld be crafted in aluminum, similarly io that of the CBR400RR shown at the 1988 Tokyo show. Unlike the RC3O V-Four 750, the CBR1000R would use a heavily braced, twin-sided swingarm, much like that of its smaller 400cc cousin. However, even if our European source is correct, there's still a question of whether American Honda, which refused to import the RC3O, would bring such a high-performance motorcycle into the U.S. The answer to that may depend on how far Kawasaki's speedy ZX-1O Ninja 1000 cuts into Hurricane sales.
Thumper notes
The Husky 5 10 four-stroke, currently the lightest and best dirt Thumper, may soon receive major improve ments; it also may soon face stiff Japanese competition. The last Husky to be built in Sweden was completed this past fall, and all production is being moved to the Cagiva factory in Varese, Italy. A revised and updated Husky four-stroke is scheduled for manufacture in Varese this summer, with a general upgrading of materials, and perhaps some significant improvements in chassis. Ex pect all 1989 Huskys to come with White Power upside down forks, for example.
But shortly after the updated Husky arrives in the U.S., Suzuki may announce some tough competition for it. Suzuki has been discussing the possibilty of building a lightweight four-stroke in an RM-quality chassis, and has reportedly gotten far enough with the project to ask Honda XR-expert Al Baker to help develop the machine. We expect it to be a 500-to-550cc oil-cooled Thumper, weighing less than 260 pounds and making about 40 horsepower at the rear wheel. If it doesn't show up in 1989. it's a sure bet for the following year.
