If your wheel has a wobble, it’s either been hit by something which has dented it, or the spokes have loosened, causing the rim to lose its shape. The procedure below won’t help fix a dented rim, but it can be used to get rid of a wobble or compensate for a broken spoke.
The spokes on a bicycle wheel run from the rim to alternate sides of the hub. In order to pull the rim back into true, you have to tighten the spokes that lead to the side of the rim opposite the bump.
To tighten spokes, you don’t actually turn the spoke. Instead, you turn the nipple that holds the spoke into the rim. Turning the nipple means you really have to concentrate on what you’re doing, because it’s easy to mix up “tight” and “loose.”
Nipples still turn clockwise on the spoke to tighten, but clockwise is referenced from the tire side of the rim, not the spoke side. Imagine using a screwdriver to tighten the nipple from the tire side of the rim, then turn the nipple the same way using a spoke wrench on the spoke side of the rim, and you’ll be fine.
Talking of spoke wrenches, make sure you have the correct sized wrench for your spoke nipples. Wrenches come in several different sizes, and using the wrong one (or a crescent wrench) will easily round off the soft metal of the nipples. The wrench should be a tight fit on the nipple.
Wheels can normally be trued while still in the frame. Support the bike off the ground and spin the wheel. Use the rim brake pads or a stick attached to the chain stay next to the rim as a reference point to find where the rim wobbles.
When you find the point where the wheel is closest to your reference point (brake pad or stick), you need to tighten the spoke that goes to the other side of the hub at that point, by about one half turn. Because the spoke will try to move with the nipple, it’s often best to turn the nipple three quarters of a turn tighter, and then back it off one quarter of a turn. Clamp bladed spokes with a crescent wrench
If there’s a big bump, or the wobble extends along the rim for several spokes’ distance, you may need to tighten more of the spokes that go to the other side of the rim. Always start with the most raised part of the bump, and adjust the spokes on either side less (one quarter turn, then one eighth turn) as you move away from the wobble area.
Really pronounced wobbles may also require you to loosen spokes close to the bump which lead to the same side of the rim. Try not to loosen spokes unless you really have to – it’s unlikely that the spoke worked itself tighter over time.
Now spin the wheel again, find the next highest bump, and do the same thing to it. Unless a spoke is noticeably looser than the ones either side of it, try not to turn any one spoke more than a whole turn because otherwise you may start to make the wheel egg shaped.
Continue with this process until there are no noticeable kinks in the wheel, or at least until it is good enough to ride home.
Tip: When you first get back on the bike after truing the wheel, you may notice some cracking noises coming from the wheel – this is the spokes relieving tension along their full lengths and rubbing against each other as they find their new positions.