To get started a truing stand of sorts needs to be set up. This doesn’t have to be anything special and I used a bench vice, adjuster block, rear axle, spacers, a series of old bearings and washers, and the axle nut. The reason I went to the trouble of clamping the hub in place was to eliminate any possibility of the hub sliding back and forth on the rim, which would make my truing efforts difficult.
Next, some sort of gauge will be needed so the amount of runout can be seen. I used a dial indicator attached to a magnetic base, however more simple solutions could easily be fabricated.
Axial (side to side) runout will be corrected first. Here you can see there is a noticeable difference in gap size between the rim and pointer through a full revolution of the rim.
The process of tightening and loosening the spokes to pull the rim from side to side can be performed at all the high and low points surrounding the rim. Continue to turn and rotate the rim around until the gap between the rim and pointer evens out. Some areas may require tightening the spokes and pulling the rim one way while other areas may need to be loosened to allow the rim to move back the opposite way. Take your time and make small changes as you go. As I mentioned before, it doesn’t take much to see a significant change in rim location as the spokes are tensioned.
As the rim is fine tuned for side to side runout, the pointer can be moved closer to reduce the gap. Reducing the gap as the rim is trued will make it easier to see smaller differences in runout. To really fine tune things I like to use a dial indicator, setting the contact point up on the outer edge of the rim. Again, this isn’t absolutely necessary and similar accuracy could be achieved with a simple pointer.
The rim I was working on is centered on the hub. Some rims will be offset and it will be more important to pay attention to the relationship between the edge of the rim and a feature on the hub (usually the brake disc machined surface or the machined surface for the sprocket). Your service manual will provide specs for measurement points and specify how much offset should be present. Setting the offset correctly is important because if the offset is off, the front or rear wheel will not be inline with the other wheel. This can make the bike's handling very interesting! I don’t think a little misalignment is too noticeable on dirt, but it is definitely a problem on asphalt.
A straightedge can be used to measure from the indicated surface, outer edge of the sprocket, or brake disc to the edge of the rim. If measuring off the sprocket or brake disc, you’ll need to subtract the thickness of the sprocket or disc from your measurement.
Next, the radial runout must be corrected. To do this move the pointer so that it sits past the outer edge of the rim.
This time to induce change in runout, all the surrounding spokes in the area will either be tightened or loosened evenly in unison. To increase the gap, as I’m doing in the following photo, all the spokes are tightened which pulls the rim inward, enlarging the gap between the pointer and edge of the rim.
As long as all spokes in the affected area are tightened or loosened evenly, the side to side runout will not be affected. Slowly rotate the rim and make the necessary tweaks until the gap between the edge of the rim and pointer is close to the same as the rim rotates around. The pointer can be moved closer and closer to refine the roundness of the rim. The surface of my rim was too beat up to take accurate measurements so I simply relied on eyeballing the gap to set its roundness.
Once the rim has been trued both axially and radially, the spokes will still be relatively loose. The spokes will all need to be tightened gradually and evenly so that all the efforts of truing the rim are not wasted. Since the majority of rims are either 32 or 36 spoke rims every 4th spoke around the rim can be tightened. This results in an even 8 or 9 step pattern which is repeated four times to tighten all the spokes. First all the red spokes are tightened, then the greens, yellows, and finally blues. Tighten each spoke ¼ turn at a time.
Alternatively, ThumperTalk member ballisticexchris, suggested a pattern where every third spoke is tightened. This would allow the tensioning of both sides of the rim within the same revolution of the wheel. I've always had good results with the pattern I've outlined but believe his suggested pattern will work equally well and is another option for you to use.
Next, use your hand to squeeze the spokes which are parallel to each other together. Squeeze all the spokes evenly around the rim. Squeezing the spokes will help gauge the tension, ensure the heads are fully seated, and help relieve stress built up in the spokes.
After you’ve finished tightening all the spokes it is never a bad idea to check runout both axially and radially one final time to confirm the rim hasn’t shifted. As long as the spokes were tightened evenly, changes in runout should not be an issue. Once you have checked runout one last time you are all set to install a new rim strip and put on the tire.
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