The ability to maintain your wheels is a skill all mountain bikers should possess, especially considering the punishment modern bikes are expected to endure. Vital MTB and Art's Cyclery are here to provide a few wheel truing tips so you can keep your wheels rolling strong for years.
It's good to think of a wheel as a single organism, whose spokes, nipples, hub and rim all interact with each other to create a strong, healthy being. Thus, maintaining overall health, which for a wheel means even spoke tension, is your goal as wheel therapist. Unfortunately, once a rim is bent due to impacts, it has begun an irreversible journey towards retirement. This fate can be put off for a while through good wheel maintenance, but, as we will see, proper spoke tension is hard to achieve with a damaged wheel. Knowing this, the importance of a quality wheel build is easy to understand. When a wheel starts its life perfectly tensioned, it is stronger, more resilient, and easier to fix when something goes wrong.
Keep a few basic tenets in mind. First, when working side to side, tightening spokes will move the rim toward those tightened, so if your rim deviates to the left, tighten the spokes on the right. When fixing out-of-round problems, loosening spokes will let the rim out from the hub, while tightening spokes will pull the rim in to the hub. Avoid trying to completely straighten each deviation the first time you work on that section of the wheel. Instead, work on the problem for a bit and then move around the wheel, rechecking all the spokes to bring them into even tension. Repeat this process incrementally, without turning a spoke nipple more than a quarter-turn at once.
Taper the changes you make out towards the edges of the affected section. For example, if you are working on an out-of-round section of four spokes and turned the two in the center one-quarter turn each, you probably need to turn the two on either end only an eighth of a turn. This is because spoke tension near the edges of the problem area will be closer to the correct tension of the rest of the wheel. Tapering applies when fixing side-to-side deviations as well. Finally, it’s better to have a wheel with correct, even spoke tension that’s a little out of true than to get your wheel perfectly true with fluctuating tension across the spokes—the wheel with even tension will be much stronger. Now, with these points in mind, it’s time to grab a nipple. Wrench.
If your wheel is out of round, fix that problem first. When attacking high and low spots you will need to adjust all of the spokes in the affected span of the rim, beginning at the section of the rim with the biggest deviation. If the rim jumps away from the caliper gauge—a flat spot, spoke tension needs to be decreased, so the rim is let out away from the hub. If the rim scrapes against the caliper gauge—a high spot, spoke tension needs to be increased, pulling the rim in. Again, don’t try to fix the problem all at once. Work on the worst section of the wheel until it is just barely better than the next worse section, and then move on to that section. Repeat the process while looking for spokes that are grossly out of tension until the wheel is within a millimeter or two from being round.
Side-to-side deviations differ slightly. Since a rim will move toward the tightened spoke, if the wheel is deviated left, tighten the spokes on the right and vice versa. Avoid loosening the opposite spokes simultaneously, which will make them too loose, since they have already lost tension when the rim moved to their side. If the rim has been knocked out of true due to an impact, tightening spokes to bring the rim back over will result in uneven tension, which, unfortunately, is the only option in this case. Remember that even spoke tension is more important than a straight wheel and just do what you can. Work slowly and tackle the biggest problems first. Taper the changes you make out towards the edges of the affected section.
When it comes to truing wheels, frequent inspection and preventative maintenance can go a long way toward protecting your rims. Check spoke tension by squeezing pairs of spokes all the way around the rim, looking for uneven tension. If you discover that spoke tension fluctuates noticeably, use your skills to fix the problem, this will save you lots of time and money later on. Examining your wheel in this way every few rides will also help you to discover potential problems and fix them before they turn into something bigger. Finally, remember that wheels are asked to take more abuse than any other part of our bikes, and that proper care, along with realistic expectations of what they can endure, will keep you and your wheels happy for many rides to come.