Yamaha bolt girder front end
For its first marketing foray into the forkless unknown, Yamaha chose to give the GTS1000 a rather conventional sport-touring ergonomic layout, though the RADD front-end design leaves the future wide open for more radical seating positions. The steering component of this design also requires little space and can be located anywhere within a pretty large area, giving Yamaha more freedom in the placement of critical parts such as the steering head, seat and gas tank. Braking torque from the spinning rotor thus tends to push down on the axle and extend the shock, canceling the forward weight transfer trying to compress it. The design is inherently anti-dive as well, since the disc brake caliper is rigidly bolted to the upright. The trail figure for best handling may be set virtually at will, and changes to it and the bike’s wheelbase will be minimized during braking and acceleration. Bump steer–the tendency of the front wheel to steer the motorcycle as it moves through the suspension travel–is absent since the front suspension is independent of the structure which steers the front wheel. The widely spaced front swingarm pivots spread side and torsional loads over a wider area than traditional steering heads, greatly enhancing rigidity. In theory the single-sided swingarm front-end design of the Yamaha GTS1000 (which, together with the bike’s twin-beam frame and rear swingarm, Yamaha calls the Omega Chassis Concept, after the last letter in the Greek alphabet) eliminates all of the handling quirks associated with a telescopic fork, and presents several opportunities. With a shock absorber mounted between the lower arm and the chassis, the wheel can move more or less vertically while the chassis remains stationary. The wheel pivots on a kingpin at the end of the hooked-shaped swingarm, and steering input is accomplished by a telescoping cylindrical unit mounted between the handlebar and the top of the upright. For the purposes of this road test, if you consult the illustrations you can see that the GTS1000’s front end is essentially a parallelogram formed by the bike’s frame on one side, a case upright on the opposite side, a single-sided swingarm on the bottom and an A-arm on top. Wouldn’t it make more sense to invest that money into an alternative, even a fledgling one, that doesn’t– can’t–possess any of those problems? With a swingarm in from, fuel injection, catalytic converter and ABS, the Yamaha GTS1000 brings state-of-the-art technology to solo or two-up sport-touring.įor a complete description of the GTS1000’s front end and an interview with inventor James Parker, see the technical analysis in Rider, December 1992.
Fork designs that minimize these handicaps are expensive. Yet, even at their best, street motorcycle forks suffer from flex in torsion and seal stiction, to say nothing of bump steer and changing the motorcycle’s chassis geometry during acceleration and braking. True, the telescopic fork has reached a very competent level of development, even with some of the cost-effective designs on street motorcycles. Now that I’ve ridden the GTS1000, I would rather not go back to forks. If Yamaha has made any mistakes with the GTS1000, they have nothing to do with the execution of James Parker’s simple but ingenious RADD front-end concept, or the solidarity with which the company has promoted and stood behind the first mass-produced motorcycle to incorporate it. Who will be responsible? The media, if in a rush to sell magazines and impress readers with snooty, unwarranted criticism it fails to accurately test and explain the machine you, if your mind is closed to change for the better and the rest of the motorcycle manufacturers, if they don’t immediately improve upon Yamaha’s commendable effort and introduce forkless designs of their own, thereby validating the trend for consumers.
If the forkless Yamaha GTS1000 doesn’t prove to be the forerunner of a new era in motorcycle design, it represents a missed cue of colossal proportions.
Public sentiment will surely be on the other side. Photos by Rich Cox/Slide Action Let a man proclaim a new principle. Note: This article was originally published in the April 1993 issue of Rider.