Truing a bicycle wheel without a jig
This is a sequel to lacing a bicycle wheel. Truing the wheel turned out to be no more difficult than lacing it. Easy, in other words. The only tool required is a spoke key (illustrated). I'm truing a front wheel. The rear wheel is trickier because of the freewheel and unequal spoke lengths.
I don't have a truing jig so I put the wheel in the fork with the bicycle upside down. Standing at the front of the bike with the wheel spinning quickly, you see how it wobbles from side to side and up and down. Reconnecting the brake cable and seeing how the gap changes between the pads and the rim as the wheel spins round gives a good guide on where to begin. Because the brake pads won't be positioned exactly symetrical, the wheel has to be looked at one way, then the other, by switching it round in the fork.
Truing the wheel laterally
Lateral truing is first – correcting the sideways wobble. Tips on cycle wheel truing abound on the web. What it boils down to is that you just pull the wobble in the opposite direction, by loosening spokes on the wobble side and tightening spokes on the other. It's a simple mechanical process. The wheelbuilder's skill, I assume, is being able to see which part of the rim is bent out of true, knowing how many spokes to adjust, and by how much, then doing it all very quickly.
Looking at the wheel end-on, if part of the rim wobbles left from most of the rest, that's the part that needs to be pulled to the right. You begin with the worst bits, where the wobble is most pronounced. The assumption I made is that you don't just adjust two spokes – one on the left and one on the right. You assume that the sideways distortion in the rim is spread over several, especially if they have a roughly similar musical pitch when they're plucked.
The tape trick
I found it helpful to mark the rim with pieces of sticky tape: a piece where the bend was most pronounced and two further pieces each side of it, to mark the limits of the section to be adjusted. Then I spun the wheel in the fork to make sure they were in the right place. When the rim is spinning it's easy to see where it wobbles but not so easy to pinpoint that same spot as you stop it. Using tape removes some of the guesswork.
So there are three pieces of tape on the rim. The one in the middle marks the centre of the wobble and the other two mark its end. The middle tape is where I tightened two spokes on the right and loosened one on the left, each by about a quarter turn of the spoke key. Then in a similar fashion I adjusted the remaining spokes between the bits of tape, but progressively less of a turn on the key as I worked away from the middle.
Spin the wheel again and check the gap between the rim and the brake pad. Adjust a bit more, then spin again. Switch the wheel over in the fork. Adjust a bit more, always loosening on the wobble side and tightening on the other. Move to the next section of wobble and repeat the whole process. Keep doing this in small adjustments and the wheel gradually becomes straighter and straighter. Mine did. I got it straight in about thirty minutes.
(At this stage, when I plucked the spokes, their musical pitch was between B and C. I've read somewhere that on a bicycle front wheel it should be A for butted spokes like mine.)
Truing the wheel vertically
Even though it's straight, the wheel probably isn't yet a perfect circle with the axle dead in the centre. It will have high spots, or 'bumps' as it spins. They are pulled back into line by tightening spokes equally on both sides of the centreline of the rim, around where the bump is. I used the same system of markers with tape as I did when truing the wheel laterally, but made bigger turns with the key, as more force is needed to counter the pull of the spokes on the opposite side of the wheel.
Bumps are harder to pinpoint than lateral wobbles. You can't really use the brake pads as a guide. I did it by spinning the wheel and looking at the ups and downs of the rim from the side, keeping my head perfectly still as I sighted across to a fixed point on the wall (next time, I'll use a cable tie across the fork, just skimming the outside of the rim). I looked for high spots rather than low spots. Correcting a low spot means slackening spokes, and I worked on the basis that tightening is generally required, not loosening.
Stress relief all round
At this point, wheelbuilders recommend some stress-relief: the guitar stringing equivalent of stretching the strings with your fingers whilst you tune them. This can be done in various ways. I put my wheel on the floor and pressed down on the spokes with my foot, then I grabbed them in bunches and squeezed them together as hard as I could.
Finally, I sighted the spinning wheel end-on, and could see it was very different to the one it was an hour or so ago. A proper bicycle wheel, in fact. So I put on the rim tape as a small celebration.
Rim: DRC ST-19 touring; spokes: DT Swiss double-butted stainless; hub: Shimano Deore; tyre: Continental Contact 700 x 37c; bike: Ridgeback Panorama.
One swallow does not make a summer. I haven't become a bicycle wheelbuilder overnight. I haven't built a rear wheel – that is next. Someone called Jobst Brandt has written a whole book about the bicycle wheel. But the wheel I built is now on my bike.