The base model is a 16-inch old model with 18-inch front and rear wheels. By installing block pattern tires on it, I can create a "custom machine for street riding" in the style of VMX (Vintage Motocross), which is very popular right now! This project started from a fantasy. While there are more and more high-performance, off-road models, on the market, the design of vintage off-roaders makes you feel at home. Now is the time to enjoy creating your own unique custom machine!
- Just changing a tire makes a difference in your presence.
- If you don't need to take data, you can use wire cutters.
- Paint that can be found on old stock steel rims.
- Bending of outer spokes added for improved fit
- If it's a normal tension, both left and right side start from the inside.
- Aiming for high assembly accuracy at the temporary tightening stage
- 18 inch + block pattern is brilliant!
Just changing a tire makes a difference in your presence.
Dunlop's trials universal is highly popular among users of old motorcycle trail models. They used to be available in a variety of sizes, but are now sold in only a limited number of sizes. It is also known as the standard tire on the Kawasaki 250TR. Many fans will be happy to see the re-release of the 2.75-18 size, which is a one-size narrower rim width of 1.40 to 1.65 x 18 inches, and the 14-inch front and rear miniature sizes.
If you don't need to take data, you can use wire cutters.
Removed the front and rear wheels from a parts motorcycle and cut the rusted spokes with wire cutters. I don't plan to reuse it and I found out that it is tensioning to align the rim center to the hub center, so I proceeded to work on it. There is a case that the front and rear tire center does not appear unless it is offset tensioned, so it is better to take data before disassembling. If the nipple is loose and can be removed, it is enough to have one each of the inside and outside left and right as a spoke sample.
Paint that can be found on old stock steel rims.
When you remove the tire from the iron rim motorcycle of the period, you may find the inside of the rim is painted. If you have a new rim or good quality parts, you can paint the inside of the rim to prevent rust. When removing rust, try to use a brass brush or bon-star.
Bending of outer spokes added for improved fit
Various sizes of holes and counterbored holes were made in the 10mm thick aluminum plate, and the angle of the bend under the neck of the spoke and the length of the part that hooks onto the hub were adjusted. This is a superbly used tool. The spokes are hooked into the holes and lightly tapped with a plastic hammer to make fine adjustments to the desired angle.
If the angle under the neck is too shallow, the spokes may spread outward from the hub hole to the nipple hole on the rim, resulting in a bowed shape. In order to ensure smooth assembly, the spokes are slightly bent back under the neck. Bending back is not recommended as it may cause a lack of strength.
If it's a normal tension, both left and right side start from the inside.
In this case, Honda stock spokes were used as the material, and the angle of the outer spokes was fine-tuned by bending. The spokes with 161mm inside and 163mm outside neck are used. The thickness of the spokes is Φ3mm for both front and rear. However, since the rear rim was for a model with a slightly larger nipple hole (I used an old steel rim), I used a nipple with a slightly larger outer diameter to match the dimensions. The angle of the barnacle hole on the rim side is determined by the hub diameter and hub width.
Aiming for high assembly accuracy at the temporary tightening stage
By using an electric screwdriver to temporarily tighten the nipples, work can proceed quickly and securely. First assemble the inner spokes on both the left and right, and then the outer spokes in that order. The key point when assembling is to use the threads of the spokes as a reference and temporarily tighten the nipples in the same amount. Strictly speaking, it is better to temporarily tighten all the inner spokes first, and then temporarily tighten the outer spokes. In this case, we left two spokes on both the inner and outer spokes. To avoid mistakes, you can put torn masking tape on the inner spokes.
If all the nipples are tightened to the same amount when the temporary assembly is completed, the assembly accuracy should be quite high. At this stage, reconfirm if the rim center is aligned (not offset). Use a metal tape measure to reconfirm that the hub center and rim center match. Roundness to the wheel hub is measured by the inner circumference circle around the tip of the tire bead on the inside of the rim. The lateral run-out was measured at the outer circumference of the steel rim, but in the case of the aluminum rim, it is measured at the standing wall inside the rim because it is easy to be scratched. The measuring element of the dial gauge is an aluminum blind riveter as a consumable.
18 inch + block pattern is brilliant!
After choosing the spoke dimensions and making minor adjustments, the actual temporary assembly time was about 5 minutes per wheel. I'm sure some DIY Sunday mechanics have experience with spoke tensioning, but just by asking how long it took, you can get an idea of how skillful they were. The words "good work setup" and "good workmanship" are perfect for this work scene.
- Point 1: A practical motorcycle with 16-inch tires was changed to VMX custom with 18-inch + Prock tires.
- Point 2: When disassembling the old rim, make a note of how many millimeters the rim edge is stretched against the reference surface of the hub.
- Point 3: When using spokes, pay attention not only to the length under the neck, but also to the bending angle of the neck and the dimensions above the neck.
- Point 4: In order to achieve the accuracy of centering and run-out quickly, it is important to temporarily assemble the nipple to tighten it evenly.
- Point 5: As the name suggests, "centering and run-out" is done after 80% centering and run-out of both sides at the same time. If you tighten the nipple too tightly, the spoke will be broken, so adjust while loosening the other side.
With good quality hubs, new rims, and spoke sets of matching length, it only takes a few minutes to temporarily assemble the front and rear wheels, and a few minutes to "center and remove run-out" from each wheel. That was the scene of this work. If we, the Sunday mechanics, were to try this work, it would be so intensive that we would completely forget the passage of time, but Mr. Suzuki says that this is a regular occurrence at the spoke specialty shop, Face. However, he says that all this work progresses on the premise that high-precision rims are used. Even if new spokes are put into a good quality hub, if the rim is distorted or partially dented due to a fall, naturally it cannot be assembled with high precision. On the contrary, there are cases where they refuse the assembly request saying, "This is not possible". The rim of a spoked wheel can be distorted even by a slip-down fall.
In the motocross scene, where falls are common, spoked wheel adjustment work is of great importance. A fall on a road motorcycle, whether on the track or on the street, can cause a fair amount of external damage, but in motocross, it's commonplace for riders to get up and get back on the motorcycle after a fall. This is why many riders check the wheel rims for run-out during post-race maintenance. After riding, they check the nipples for looseness and practice retightening. After a fall, even when the tire is installed, we check the run-out and adjust the nipple tightness to compensate for the run-out in many cases.
The most important part of the spoke tensioning process is to temporarily assemble the wheel with as little run-out as possible in both directions. When the spoke wheel is measured with a dial gauge after the centering work, the deviation of the pointer is less than 1/100mm both in the center and in the sides! In general, a new rim is assembled with new spokes. In general, when a new rim is assembled with new spokes, a run-out of 5/100mm or less is considered to be excellent, but values below that are very rare.
For manufacturing purposes, the rim is roll-formed and then welded together to form a ring. As a result, there are inevitably bumps in the weld area. However, if the nipple is over-tightened, the spokes will be stretched so tightly that the slightest impact may cause them to snap. When assembling a rim with such inaccuracies, it is better to "aim for the best finish possible" rather than forcibly pulling on the weld area, says Faith Suzuki.
Photo cooperation: Faith
