Issue link: https://read.dmtmag.com/i/703695
101 www.thunderpress.net THUNDER PRESS nAugust 2016n slimmer wheel, and with a vastly wider range of angular loadings, it was harder to make a solid wheel as strong as a laced wire-spoke wheel. So hard, in fact, that as late as 1984, when Honda introduced the fi rst motorcycle fi tted with tube- less tires, the wheels that they were mounted on were not cast alloys! With an R&D budget like no other in the industry, Big Red had come up with a third type of wheel con- struction! Starting in the late 70's, marketed as "Comstar," these wheels were made in a similar manner to the wire-spoke wheel in having a separate rim, and hub, but instead of being laced together with triangulated wire spokes in tension, they were connected by riveted, buttressed alloy plates in compression. Lighter than a wire-spoke wheel, and many cast alloy wheels, they were almost as strong, courtesy of triangulation and cross- sectioning, and were certainly strong enough for race applications. The high-tech computer design indicated (among other things) a big advantage in that the separate components, the hub, rim and spokes, could be man- ufactured by different methods, and in different grades of material. Using a cast hub, extruded rim, connecting plates from rolled sheet, or possi- bly even "spun" (basically the metal "spun" out from maybe a 4" billet, and press-molded to shape) this composite construction was said to offer the compliance of a wire-spoke wheel, minimal cyclic fatigue, massive shock-load- ing resistance, and no cracking or fracturing. Still, not completely superior to wire-spoke wheels overall… and ugly. Honda gave up trying to perfect a wheel no one liked, and switched to more con- ventional (and by now tubeless) cast wheels, as well as continuing to offer wire-spoked wheels. Ultra-exotic carbon-fi ber wheels came on the scene at roughly the same time as Comstars (it should be noted), but for obvious reasons I shouldn't (and won't) explore here, have never become a mainstream alternative to simpler, cheaper wheels. Which brings us to the next innovation in "cast" competition for the (now) century-old wire spokes. Namely, the hollow-spoke cast wheel, which if memory serves was created by the Italian company Marchesini in the late 80's and appeared on Buells in the 90's. Until hollow spokes came along, to make a cast wheel stronger meant thicker spokes or more spokes or both, and both made the wheel heavier. Dymag in the UK was renowned for making some of the strongest and lightest magnesium racing wheels, but they did it by having deep "girder" spokes, very carefully pressure die cast, demanding expensive tooling and very slow manufacturing cycle time, as the wheel had to be con- trol-cooled in the mold before it could be ejected and another one made. The Marchesini hollow-spoke wheel, by contrast, achieved a very high stiffness from minimal metal by using massive spokes—but hollowing them out—and saving expensive manufacturing costs by using a "lost wax" process, via simple gravity sand casting. Great for keeping low-volume costs down, but not so great for making large volumes of wheels cheaply. "Productionizing" the hollow-spoke cast wheel was a task left to Yamaha, which they did with a slick low-pressure die-cast system. Soon enough, they were all like that. Come the millennium, and Buell (among others) fi gured out more ways to minimize mass and improve strength and fl ex characteristics through CAD/CAM tech- nologies resulting in a switch to (mostly six) very thin (almost see-through) spokes, some looking sur- prisingly l ike wire wheels! And that is where we are now. Materials tech- nology and manufacturing technology basically being refi ned to minimize the problems (and costs) of the cast wheel; softer, more malleable alloy compositions helping avoid cyclic fatigue fracture and struc- tural engineering tackling the weight/ strength issue. Where there's a wheel—there's a way For one thing, running over an uneven surface, the bigger in diameter the wheel, the better (the limit is really based more on the human inseam than much else). How easy it is for a wheel to "ramp" a bump is signifi cantly affected by the bump height and angle in relation to the wheel radius. Same goes with dips! Bigger the wheel, the earlier it encounters a bump, and on a shallower portion of the curve from the leading edge to the contact patch, thus offering more leverage to lift the bike over the bump. This is important! When spoke wheels were invented all roads were uneven, full of bumps and dips. Even today, for an off-road machine, bigger wheels are better. So much better that having bigger wheels is more of an advantage than trick suspension. For street applications and so-called ADV machines, tubeless tire technology required new, sealed rim-forms, and that has lead to some novel variations on the wire-spoke wheel. Just to name a couple; there's the "straight" spoke, using a ball-ended spoke with no bent "neck" to loop through a hub fl ange, then hook into a slotted rim. Then there's the upside- down spoke, that puts the hook end through a fl ange on the rim, and the nipple through a fl ange on the hub. Probably one of the more useful and less acknowledged "advances" in wire-spoke technology has been the "forged" spoke, where the hook end is formed from forging the spoke as a single component, rather than taking stock wire, bending to shape the neck/ See "Motorhead Memo," page 105, column 1 The wrong idea for a spoked wheel! Huge diameter, cross-one pattern, too many spokes, weakened rim and hub, narrow, massively heavy and fl ex prone because of it. Proves you can take any good thing and ruin it with wretched excess. But it sure is purty, ain't it? Just one of a number of ways to make a spoked wheel compatible with a tubeless tire, not to mention extremely light, and strong with its "cross-four" lace pattern! BMW offers tubeless spokes using a reversed spokes… why doesn't Harley? Morris "Mag" racing wheel—looks kinda familiar, doesn't it? Harley wheels from the 80's are close copies, but being aluminum are nowhere near as light or strong. Morris wheels were made of magnesium alloy and as such had a fairly short service life… oh, and they could burn very brightly as well! Lester Cast wheels set off the revolution to put cast wheels on every street bike. The battles were won, but the war isn't over—spoke wheels still serve a useful pur- pose and offer advantages after nearly 150 years!