You get better at wheel-truing with practice. These instructions start you off and they can rescue you if your wheel is too buckled to ride on.
Rest the bicycle upside down, then remove the buckled wheel. Strip off the tyre and tube. This makes it easier to see what you are doing, and also releases pressure on the rim, making it easier to true accurately. Replace the wheel in the frame. Spin the wheel and look carefully at the part of the rim that passes between the brake blocks. If the wheel is too badly buckled to pass between the brake blocks, slacken off the brakes as much as possible with the barrel-adjuster on the brake lever or unit. In extreme cases, remove one or both brake blocks.
Before getting out the spoke key, have a look at the rim to confirm what you’re aiming to do. Look at the part of the rim nearest you, as well as the parts of the hub you can see behind it. You will also see spokes leaving the rim and heading for the hub. There are an equal number of these, connecting alternately to the left and right sides of the hub.
Tightening a spoke that connects to the right side of the hub pulls the small portion of rim that it’s connected to across to the right. Tightening a spoke that attaches to the left side of the hub pulls that part of the rim to the left. The rim is held in tension between the right spokes pulling to the right and the left spokes pulling to the left.
Slackening a left spoke allows the right spokes to pull the rim over – just as with a tug-of-war team one team, can move the central flag by pulling harder, but the same effect can result when the other team is tired and isn’t pulling as hard. The aim of truing wheels is to balance the tension in all the spokes so that the lefts are
pulling the same as the rights, holding the rim exactly central.
With this in mind, spin the wheel gently while watching the gap between the brake blocks and the rim. As the wheel spins, you will see that the rim moves from side to side. Imagine the centreline the rim ideally runs on, an equal distance between the brake blocks. Identify the area of the rim that has the biggest buckle.
“If you get it wrong and turn the nipples the wrong way, you make each buckle worse rather than better”
Centre of the buckle
Look closely at the buckled area and identify the spoke at the centre of the buckle. You have to adjust the tension in this spoke to encourage the rim to sit more centrally. If the buckle pulls the rim to the right of the imaginary centreline, then spokes that go to the right-hand side of the hub must be loosened, and spokes that go to the left must be tightened.
Adjust the nipple at the centre of the rim by a half-turn. The spokes are laced alternately to the left and right sides of the hub; if one spoke goes to the left, both its neighbours go to the right. So, once you’ve adjusted the spoke at the centre of the buckle by half a turn, adjust both its neighbours by a quarter-turn in the opposite direction. Spin the wheel again and look for the next biggest buckle. It may be in the same place or somewhere else. It’s better to work slowly, adjusting three spokes then checking by spinning the wheel.
Working out which way the nipple turns to tighten or loosen the spoke catches many people. If you get it wrong and turn the nipples the wrong way, you make each buckle worse rather than better. Eventually, if you persist, the wheel collapses. If you see things are getting worse and not better as you true, stop and think carefully about what you’re doing.
Looser or tighter
When I was learning, I had to think about which way to go all the time. Eventually, I drew two circles on a piece of paper, one with a clockwise arrow that said ’looser’ in the middle and one with an anticlockwise arrow saying ’tighter.’
It lived in my toolkit for ages, and every time I had to true wheels, I put it on the ground underneath the wheel. I would spin the wheel to identify the buckle, then turn it so that the area I had to work on was at the bottom, over the paper. That way, I always knew which way to turn the nipples.
After a while, your hands remember, and you don’t have to think about it any more. It’s a good idea to get into the habit of using the spoke key in this position, since if a spoke breaks as you turn the nipple (which happens), it hits the ground harmlessly. Don’t turn the wheel so you can see the head of the nipple you’re turning, as this puts your eyes and face in the firing line.
It’s possible you may not get the wheel completely straight. If the wheel stops improving, stop. As long as it passes through the brake blocks, you can ride the bike somewhere to get it dealt with.
Source : BIKE MAINTENANCE TIPS, TRICKS & TECHNIQUES
See also bike maintenance tips, tricks and techniques “Rims and rim tape”