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Why The Wire-Spoke Wheel Remains In Use


Hugh Janus

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Here is a classic: the very light front wheel—brake disc omitted for clarity—of a 1970s Yamaha XS650 twin. The cast-wheel revolution raged in racing, but production bikes still rolled on this conceptual hand-me-down from the bicycle. Rim, one-piece cast hub, two sealed bearings with a spacer tube between them, and you’re done. There’s nothing wrong with wire wheels!
Here is a classic: the very light front wheel—brake disc omitted for clarity—of a 1970s Yamaha XS650 twin. The cast-wheel revolution raged in racing, but production bikes still rolled on this conceptual hand-me-down from the bicycle. Rim, one-piece cast hub, two sealed bearings with a spacer tube between them, and you’re done. There’s nothing wrong with wire wheels! (Jeff Allen /)

The safety bicycle, which exploded into a popular craze around 1895, can be regarded as a confluence of technologies that matured at that time—the ball bearing, pneumatic tire, seamless-drawn steel tubing, roller chain and sprocket drive, and super-strong hard-drawn steel wire. A final ingredient might be the production and shaping of thin metal sheet by rolling.

The last two together made possible one of the most efficient structures known to mechanical engineering: the tension-spoked wire wheel. A roll-formed rim is made by slitting sheet steel into strips, then roll-forming those strips into a wheel-rim section that was finally roll-bent into a circle. The butt ends were joined by ­brazing or welding.

The wheel hub consisted of a pair of spoke flanges joined by a tube, spinning on the new screw-­adjustable cone ball bearings, ­supported on a nonrotating axle.

Rim and flanges were drilled or punched for a suitable number of spokes. The spokes themselves were threaded on their outer ends, and cold-headed and bent on their flange ends. Each spoke is provided with an internally threaded nipple (usually of brass, to prevent rusting to the spoke), which are pushed through dimpled holes in the rim from the OD side, to finally screw onto the spoke ends. The rim material around each spoke hole is dimpled inward to fit the head of the nipple, and each hole is angled to align with the axis of the spoke it will tension.

This Triumph Scrambler wheel shows how the wire wheel can adapt—all its spokes thread through the rim flanges, leaving nothing to be sealed to allow tubeless tire use. Spoke-nipple location is reversed—now they reside in heavy lugs that are part of the hub rather than being in the rim valley. High-angle straight spokes give good torque capacity and lateral stiffness.
This Triumph Scrambler wheel shows how the wire wheel can adapt—all its spokes thread through the rim flanges, leaving nothing to be sealed to allow tubeless tire use. Spoke-nipple location is reversed—now they reside in heavy lugs that are part of the hub rather than being in the rim valley. High-angle straight spokes give good torque capacity and lateral stiffness. (Jeff Allen /)

To assemble a wheel, spokes were threaded through the holes in the two hub flanges, then arranged in the desired pattern (defined by how many other spokes each one crosses). The rim is set in place, and the assembler loosely screws together each spoke and its nipple. Beginners often fall at this first hurdle, but persistence and common sense are rewarded in time.

The process of transforming this loose assembly into a round wheel that is light and strong is an acquired skill that any motivated person can learn, and the result is beautiful in and of itself, much esteemed by custom builders who create endless variations.

Under the tension of the many spokes (36 and 40 were common on motorcycle wheels), the rim is placed in uniform compression that its flanged shape prepares it to support without buckling. Each spoke is a tension spring. A good description of how such a wheel supports loads can be found in Bicycling Science by David Gordon Wilson. He likens this process to that by which a radial tire supports a load. As the tire flattens against the ground, the tension in its thereby slightly less-tensioned nearby carcass fibers (which he likens to spokes) is somewhat reduced, such that the load is supported by a corresponding increase in the fiber tension elsewhere in the tire. It is the great elasticity of the thin wire spokes that makes this work.

Lateral and torsional forces are withstood by angling the spokes. The wheel is braced against lateral forces by spacing the two hub flanges apart to form two “cones of spokes.” Torsional forces are ­handled by angling the spokes rather than running them straight from hub to rim.

In some cases (a particular Triumph model comes to mind), a wheel might be laced somewhat offset from perfectly centered in relation to its hub. In another case, a bike that turned more easily one way than the other was diagnosed as accidental rim offset.

This DID Dirt Star rim and straight-spoke hub are another take on the classic. The ­angled spoke head necessary to lace to traditional spoke flanges is a source of weakness because it’s loaded in bending. Here, each spoke and its head are perfectly straight, made possible by the fancy angle-­drilling of the hub in this photo. The result is an especially durable spoked wheel.
This DID Dirt Star rim and straight-spoke hub are another take on the classic. The ­angled spoke head necessary to lace to traditional spoke flanges is a source of weakness because it’s loaded in bending. Here, each spoke and its head are perfectly straight, made possible by the fancy angle-­drilling of the hub in this photo. The result is an especially durable spoked wheel. (Jeff Allen /)

Early brake drums and sprocket carriers were bolted to a face of the hub, but as drums grew bigger, it became more sensible to make the spoke flanges as part of the drum itself. Continued growth of brake drums resulted in very short spokes, barely 3 inches long. Because the elastic stretch of which a spoke is capable increases with its length, this loss of “stretchiness” sometimes resulted in wheels whose spokes became loose when the brake drum expanded from the heat of hard use.

The elasticity of wire-spoked wheels can be useful. One Supersport race team tried everything to eliminate chatter from its bike. ­Success finally came with a wire wheel replacing the stock cast wheel. Marketing replied with a firm no when the team urged that a “heritage model” with wire wheels be offered to make them class-legal.

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Yamaha’s Daytona-dominating TZ750 (1974–’82) was always delivered on wire wheels, but most racers replaced them with Morris or Shelby-Dowd cast mags. My experience with several riders was that no one complained of any problem if circumstances obliged us to run a wire wheel.

Cast wheels quickly responded to the rapid evolution of motorcycle tires, and in particular made it possible to run tubeless (saving a significant 3 to 5 pounds of rotating weight). Today, cast or forged one-piece wheels have become normal, and wire wheels are often seen as graphic elements for custom builders and manufacturers. But the wire-spoke wheel remains the primary choice for off-road and ­adventure bikes, which benefit from the strength and resilience of this elegant design.

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  • 7 months later...

My new bike has spokes and is tubeless. The wheel looks similar to the one Honda used on its XL600M thing in the 80s, I think they had a hold on the patent at the time but you see other makes with them now.

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32 minutes ago, Sir Fallsalot said:

Yes normally but there are tubeless spoked wheels available now as Yen said but they did have tubeless spoked wheels on the 1985 Honda XL600 

bikepics-1196568-full.thumb.jpg.4a8e93c76321c7d42c29983711f7f7b5.jpg

I had to push my mate Charlie through the mud on one of those. He came out with road tyres green laning in the middle of winter. My wheels are exactly like that, but have two vertical webs from the rim for the spokes to join onto rather than one as in the picture. Not changed a tyre on it yet, but I'm sure to be doing that before the warm weather hits.

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2 hours ago, skyrider said:

yes im thinking you are on the money with that one 

My Serow had a tubeless rear wheel even though it was spoked.  Personally though I prefer spoked wheels for my type of riding, I don't mind changing a tube on the trail if I have to.

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18 hours ago, XTreme said:

I've got these odd wheels.....which I never noticed till Roger pointed them out.

He reckons they're some sort of spoke type wheel but not in the conventional sense.

gft-min.jpg

the valve idea is brilliant ?

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  • 2 weeks later...
On 13/01/2021 at 20:51, XTreme said:

I've got these odd wheels.....which I never noticed till Roger pointed them out.

He reckons they're some sort of spoke type wheel but not in the conventional sense.

gft-min.jpg

I wonder where they are made, not.

  • Haha 1
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1 hour ago, Bruce said:

If the wheel is too heavy agility is severly compromised as the centrifugal forces and momentum inertia come into play especially on the dirt bike's bigger front wheel.

That's what I thought! :classic_unsure:

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