Truing Bicycle Wheels
Any cyclist who hopes to be reasonably self-sufficent mechanically should learn to do at least minor wheel truing.The best way to learn this is to start by building wheels from scratch but not everybody has the courage or inclination to attempt this.
This article, adapted from my Wheelbuilding Article, is an attempt to offer guidance for the cyclist who wishes only to do minor repairs to existing, damaged wheels.
You will need a spoke wrench to fit your bike's nipples, there are a couple of different sizes, so you should bring your bike along when you go to buy one to make sure it fits.In a pinch, you can use a "Crescent-type" adjustable wrench, but it is awkward and slow to do this. Real spoke wrenches are cheap and small and light.
A truing stand is a convenience, but not necessary. If you're not going to get into wheelbuilding it doesn't make sense to invest in a truing stand.
For the purpose of this article, we presume that you are working on a wheel that was once true, but is not true any longer. Before you can fix the problem, you need to determine the cause of the problem. In particular, you need to determine wether the problem is a bent rim, or something to do with the spokes.There are a number of possiblities:
Bent Rim-Sideways
Bent Rim-Vertical
If you have crashed orBroken Spoke
Loose Spokes
Now you are ready to put the wheel into the truing stand. If you are lucky it will already be fairly true, but don't be surprised if it is way off. If the spokes are still very loose, so that you can wiggle the rim back and forth easily, tighten each spoke one full turn. Start at the valve hole and work your way around until you get back to it, so that you won't lose count. Make sure you are turning the nipples the right way.When you work with a screwdriver, it is easy to figure out which way tightens them, clockwise. It gets confusing when you start using the spoke wrench, because now you are working from the back side of the clock!
Continue bringing up the tension one full turn at a time until the wheel begins to firm up.
Once there begins to be a little bit of tension on the wheel, you should start bringing it into shape. There are 4 different things that you need to bring under control to complete the job: lateral truing, vertical truing, dishing, and tensioning. As you proceed, keep checking all 4 of these factors, and keep working on whichever is worse at the moment.
Try to make your truing adjustments independent of each other. For lateral truing, spin the wheel in the stand and find the place on the rim that is farthest away from where most of the rim is. If the rim is off to the left, tighten spokes that go to the right flange and loosen those that go to the left flange. If you do the same amount of tightening and loosening, you can move the rim to the side without affecting the roundness of the wheel. For example, if the rim is off to the left, and the center of the bend is between two spokes, tighten the spoke that goes to the right flange 1/4 turn, and loosen the spoke that goes left 1/4 turn; If the center of the left bend is next to a spoke that goes to the right flange, tighten that spoke 1/4 turn, and loosen each of the two left spokes next to it 1/8 turn; If the center of the left bend is next to a spoke that goes to the left flange, loosen that spoke 1/4 turn, and tighten each of the two right spokes next to it 1/8 turn. After adjusting the worst bend to the left, find the worst bend to the right, and adjust it. Keep alternating sides. Don't try to make each bent area perfect, just make it better, then go on to the next. The wheel will gradually get truer and truer as you go.
For vertical truing, find the highest high spot on the rim. If the center of this high spot is between two spokes, tighten each of them 1/2 turn. If the high spot is centered over one spoke, tighten that spoke one full turn, and each of the two spokes next to it that go to the other flange, 1/2 turn. It takes a larger adjustment to affect the vertical truing than the horizontal truing. Vertical truing should usually be done by tightening spokes, gradually building up the tension in the wheel as you go along.
As soon as the lateral truing gets reasonably good (within a couple of millimeters) start checking the dishing. Put the adjustable feeler of the dish stick over the axle on one side of the wheel and adjust it so that both ends of the dish stick touch the rim while the middle feeler rests against the outer locknut on the axle. Then move the stick to the other side of the wheel without re-adjusting the feeler. If the dish stick rocks back and forth while in contact with the outer locknut, the spokes on that side of the wheel have to be tightened to pull the rim over. If the ends of the dish stick sit on the rim but the feeler won't reach the locknut, the spokes on the other side of the wheel need to be tightened. If the dishing is off by more than 2 or 3 millimeters, you should start at the valve hole and work your way around the rim tightening up all 18 spokes on the appropriate side the same amount, perhaps 1/2 turn.
When the dish is starting to get within 1 or 2 millimeters of being correct, go back to working on the lateral truing, except now you will not be alternating sides. If the rim needs to move to the right to improve the dish, find the worst bend to the left, adjust it, then find the new worst bend to the left, and so on.
All the time you are doing this you need to keep checking the vertical truing, and whenever the vertical error is greater than the lateral error, work on the vertical.
You also need to keep monitoring the tension on the freewheel side spokes. There are three ways to check tension. One is by how hard it is to turn the spoke wrench. If it starts to get hard enough that you have to start worrying about rounding off the nipple with the spoke wrench, you are approaching the maximum. Fifteen years ago, this would be the limiting factor, and you would just try to get the wheel as tight as you could without stripping nipples. Modern, high quality, spokes and nipples have more precisely machined threads, however, and now there is actually a possibility of getting them too tight, causing rim failure.
The second way of judging spoke tension is by plucking the spokes where they cross and judging the musical pitch they make. If your shop doesn't have a piano, and you don't have perfect pitch, you can compare it with a known good wheel that uses the same gauge of spokes. This will get you into the ballpark. Before I started using a spoke tensiometer, I used to keep a cassette in my toolbox on which I had recorded my piano playing an F#, a good average reference tone for stainless spokes of usual length. (For more details on this method, see John Allen's article: Check Spoke Tension by Ear.)
The third, and best way is with a spoke tensiometer. Every well equipped shop should have one. Average freewheel-side tension should be up to shop standards for the type of spokes and rim being used. More important is that it be even. Don't worry about the left side tension on rear wheels. If the freewheel side is correctly tensioned, and the wheel is correctly dished, the left side will be quite a bit looser. You should still check the left side for uniformity of tension.
As the wheel begins to come into tension, you start to have to deal with spoke torsion. When you turn your spoke wrench, the first thing that happens is that the spoke will twist a bit from the friction of the threads. Once the nipple has turned far enough, the twist in the spoke will give enough resistance that the threads will start to move, but the spoke will remain twisted. What a good wheelbuilder can do that a robot machine can't do is feel this twist. If you "finish" you wheel up, and it is perfectly true in your stand, but the spokes are twisted, the wheel will not stay true on the road. The twist in the spokes will eventually work itself out, and the wheel will go out of true.This problem can be prevented by sensitive use of your spoke wrench. What you need to do is overshoot and backlash. In other words, suppose you want to tighten a particular spoke 1/4 turn. You don't just turn the wrench 1/4 turn, you turn it a little farther, then back it up that same little bit. The nipple winds up being 1/4 turn tighter, but the backing up releases the twist in the spoke.
This is much easier to do on straight-gauge spokes, because they are stiffer torsionally, and it is easier to feel the twist than it is with butted spokes. This is one of the reasons I like "aerodynamic" spokes so much; not so much for the aerodynamics, as for the fact that you can tell visually if they are twisted.
Before a wheel is ready for the road it must be stress relieved, because the bend in the spoke has to accommodate itself to the shape of the hub flange and vice versa, and a similar process may go on where the nipple sits in the rim. Some wheelbuilders do this by flexing the whole wheel, others by grabbing the spokes in groups of 4 and squeezing them together. My preferred technique is to use a lever to bend the spokes around each other where they cross. My favorite lever for this is an old left crank:
This particular technique has the added advantage of bending the spokes neatly around each other at the crossing, so they run straight from the crossing in both directions. As you go around the wheel this way you will probably hear creaks and pinging sounds as the parts come into more intimate terms with each other.After you do this, you will probably have to do some touch-up truing, then repeat the stressing process until it stops making noise and the wheel stops going out of true.
Jobst Brandt , author of the excellent book The Bicycle Wheel points out a less obvious benefit of this stressing of the spokes:
"...After cold forming, steel always springs back a certain amount (spokes are entirely cold formed from wire). Spring-back occurs because part of the material exceeded its elastic limit and part did not. The disparate parts fight each other in tension and compression, so that when the spoke is tensioned, it adds to the tensile stress that can be, and often is, at yield.If you have done this, you will wind up with a wheel that is true and round, and will stay that way better than most machine made wheels. In addition, you will have learned a lot about truing wheels, and you will feel more like a real professional mechanic."...When spokes are bent into place, they yield locally and addition of tension guarantees that these places remain at yield. Because metal, at or near the yield stress has a short fatigue life, these stresses must be relieved to make spokes durable.
"...These peak stresses can be relieved by momentarily increasing spoke tension (and stress), so that the high stress points of the spoke yield and plastically deform with a permanent set. When the stress relief force is relaxed these areas cannot spring back having, in effect, lost their memory, and drop to the average stress of the spoke."
For a more thorough analysis of some of the theoretical aspects of spoked wheels, the standard reference book is The Bicycle Wheel, by Jobst Brandt (1981 Avocet, Palo Alto, California ISBN 0-9607236-6-8.) This is available at better bicycle shops everywhere.The use of musical pitch to determine spoke tension is explained in Glenn's New Complete Bicycle Manual revised and updated by John Allen (1987 Crown Publishers, Inc. New York ISBN 0-517-54313-3) p.380. This article is also available on the Web at http://www.bikexprt.com/bicycle/tension.htm
Want to try to build a wheel using mismatched hub/spokes with different drillings? See Benjamin Lewis's "Perverse Wheel Building" article on this site.
A useful set of charts for determining spoke lengths may be found in Sutherland's Handbook for Bicycle Mechanics by Howard Sutherland, Sutherland Publications, Box 9061, Berkeley, California 94709. ISBN 0-914578-06-5
This is not the only wheelbuilding site on the Web. I'd also direct your attention to:
If you have trouble finding tools and materials, in your local area, you can order from Harris Cyclery: For the ne plus ultra of dishing gauges, see the Hoadley-True site.
These illustrations have been around! I created them in the early '80's on a modified Digital PDP-11, using Management Graphics proprietary software, outputting Kodachrome slides. Years later, the slides were scanned onto a Photo CD, then manipulated on my Macintosh, using Adobe Photoshop.
Thanks to John Allen, Daniel Boals, Jobst Brandt , and John Forester for their kind assistance.
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Copyright © 1995, 2008 Sheldon Brown