Trials Bikes For Dummies

By Ron Milam

While checking the spokes in the rear wheel of my bike last week, I was inspired to write an article on wheel maintenance and repair. This is an area that most riders hate to check and they are even sometimes afraid they will make a mess of their wheels. They should be. If you follow a few simple principles, adjusting spokes is quick, painless, and easy. If you do it carelessly you will be rewarded with a wicked wobble that will tell everybody you ride near what an incompetent boob you are.

The first thing you should know is when your spokes are too loose and how tight to adjust them. I would like to give a quotation that Charlie Roberts gave to me that I think he got from somebody else ( got it? ). “ Loose spokes don’t break”. Tight spokes are the ones that break and give you trouble. Obviously, if your spokes are really loose, your rim will be wobbling and you will have a mess. But, the point is that is better to be a little loose than a little tight. If you own a Beta or Montesa or other brand that sometimes develop a habit of breaking rear spokes, you have probably known the frustration of checking all of the spokes before a ride, only to come home with some broken ones.

The basic principle is that all spokes in a wheel should carry an equal part of the load. After a few times of tightening to an uneven tension, some begin to break. Then replacements are installed. The uneven tightening continues and more break. At this point some experts recommend replacing the rim. There is another way.

Take the wheel off the bike and if the spokes have the nipples in the rim, you should also remove the tire. Clamp the axle in a bench vise or other holding device so that you can freely spin the wheel and it is held rigidly. After lacing many wheels I have learned that most spokes are made very uniformly if they all came from the same manufacturer. This means that you can use the spokes as a micrometer of sorts to adjust the position of the rim and remove any bending. I have used this method on wheels warped as much as an inch. You first clean the spokes and nipples and lube them as well as possible. Next totally unscrew one nipple and count how many turns are required to completely remove it. Put it back on so that the spoke doesn’t come all the way out during the next step. Then go around the wheel loosening all the nipples 1 or 2 turns at a time. Keep going around until they are all about halfway off. Next take one all the way off and then screw it back on counting the number of turns until it is about 2/3 of the way back to where the reference nipple ( the one you took all the way off ) was originally. Work your way all the way around the wheel repeating the process on each spoke. When you get back to the first one tighten it 1 turn and go around again. Repeat the procedure until the spokes begin to get a little snug. It will be properly tensioned when it rings if tapped gently with a metal object. If it is touching another spoke, this may prevent it from ringing. Try pulling the other spoke away and tap the spoke again. If it doesn’t ring go around the wheel again and tighten each spoke ¼ turn. Keep doing this until they are all screwed exactly the same number of turns. If the rim has been bent badly some spokes may have to be screwed down a little more to reach proper tension, but in general, they should all tighten up at about the same spot. The spoke should just begin to ring at a low pitch.

The next step is to check for run out. The best way and by far the quickest way to do the final tweaking is to use a dial indicator on the side and periphery as you turn the wheel. A dial indicator is a instrument used by machinists and mechanics to measure movement to a very close tolerance. These days you can buy an inexpensive imported dial indicator for $20 or less. They have a lot of other uses around the shop. The reason this instrument is helpful is that it puts a number on the amount of run out. All you do is to find the side with the most run out and set the dial to zero. Then turn the wheel 180 degrees. Make a note of the change in the reading. Set the dial to read a value halfway between the 2 readings. This way the reading you get all the way around should be zero. Adjust spokes until the run out is .02 in. or less. This is a very low number for a dirt bike wheel, but should be attained quickly. Just remember, if you tighten spokes on one side loosen the ones on the other side so that the tension stays uniform. You will probably find that the wheel has a number of dents or bulges that you can ignore when reading the indicator. If you do not have an indicator you can do the job by attaching a pointer of some type, such as a piece of wire, to a stationary object and bending it to nearly touch the rim. As you rotate the wheel note the change in the clearance between the rim and pointer and adjust spokes accordingly.

If your wheel is in pretty good shape, simply tightening any loose spokes is all that is required. Just remember to make adjustments gradually while checking all the way around the wheel.

Ron