By Chuck Connell,
This article describes how to assemble an inexpensive, but very accurate, wheel building stand for bicycles. The stand uses a dial gauge indicator that is accurate to 1/1000th of an inch, but the complete stand can be finished for about $100. The low price is achieved by using inexpensive options for the primary parts: the overall platform of the tool, the wheel holding mechanism, the dial gauge, and the magnetic base for the gauge.
With some practice, you can build or adjust wheels to within +/- .005 inches, for both roundness and trueness. Wheels with this accuracy ride nicely. With good wheel parts, and a little luck, you can create a wheel that is +/- .002 inches, in both measurements. These finished wheels are so straight that the rims look like a mirror when you spin them.
Because this tool is so inexpensive, you might want one even if you are only purchasing wheels. For example, a racing team might use it to check that all wheels they buy are within +/- .005, and then discard any used wheels that are worse than +/- .020 out of round or true.
My thanks to Peter Askin of Specialty Mechanics for helpful design discussions about dial gauges and magnetic mounting.
Dial gauge kit | Assembled stand | Initial work, no gauge | Gauge mounted | Truing close-up | Rounding close-up | Cheat sheet
· Minoura Workman Pro portable wheel stand ($39 at Nashbar.com). You can also use any other wheel stand you might already have, as long as it has mounting holes on the bottom.
· Grizzly dial gauge set with magnetic base. ($19 for just the parts needed for this project, $29 with a useful 6-inch dial gauge caliper also.) Model G9849 or Model H3022. Also carried by Amazon.com.
· Particleboard, ¾ inch think, 12 inches wide (actual is 11 ¼) by 24 inches long. (Do not use a plain wood board; it will warp.)
· Two one-inch long bolts, with flat washers and nuts. Used to attach wheel stand to particleboard. Diameter of bolts should fit the mounting holes in the wheel stand.
· Six self-stick non-scratch feet, for the bottom of particleboard. Must be taller than the nuts above.
· Steel plate, .060 inches thick (16 gauge), approximately 8 x 18 inches. (About $15 at larger hardware stores and MetalsDepot.com.)
· Five ¾ inch wood screws, to hold metal plate to particleboard.
One-inch diameter hardwood dowel, ½ to ¾ inches
long, used on dial gauge shaft as a rim follower.
· Before cutting or drilling, set up everything loose on the base, copying the photos above. Put a wheel in the stand. Make sure the dial gauge can be used for side and end measurements on the rim. Mark the positions for the wheel stand and metal plate. (If you are left handed, you may want to mount the metal plate on the right-hand side of the base. This will allow the gauge to be on the right side of the wheel, and your left hand to hold the spoke wrench.)
· Drill two holes in the particleboard to mount the wheel stand. The holes should be at least ½ inch from the edge of the particleboard, to prevent it from splitting. Use the bolts to mount the stand on the board. The bolts should be just long enough to hold the nuts, but not longer. If you plan to remove the stand for storage, make the nuts finger tight only.
· Drill four holes in the corners of the metal plate large enough for the wood screws. Again, keep each hole at least ½ inch from the edge of the particleboard. Drill small starter holes in the particleboard for the screws. Mount the plate to the particleboard with the wood screws.
· Notice that there is another wood screw through the metal plate immediately next to the wheel stand support bracket. This screw helps hold the plate firmly so it does not bounce when you spin the wheel. Remember that the dial gauge will measure movements of 1/1000 inch, so you want the wheel stand and plate to be as stable as possible. For even greater stability, you can replace this 5th screw with a small U-bolt over the support bracket and through the plate/particleboard.
· Drill a hole in one end of the dowel, halfway through. The diameter of the hole should be just large enough for the shaft of the dial gauge. Don’t force the shaft into the hole, since you want to remove it easily to store the dial gauge. Sand the other end of the dowel (without the hole) until it is flat and smooth. The purpose of this dowel is twofold. It prevents the annoying sound of metal-on-metal when you rotate the wheel against the gauge. It also prevents the gauge from slipping off the edge of the rim when checking out-of-round measurements.
· Attach a “cheat sheet” to the particleboard, which reminds you which way to adjust the rim, based on the measurements you see on the dial gauge. This is important, at least for me, because it is not intuitive how to translate a number on the dial gauge into a rim adjustment. The first two lines of the cheat apply to making the rim true, the next two lines apply to making the rim round. The first line of the cheat means “If you are seeing a lower number on the dial gauge, compared to the rest of the rim, move the rim to the left to correct the problem.” The text of the cheat sheet is below. (If you mounted the metal plate on the right side of the base, because you are left-handed, reverse the left/right cheats.)
Low number – move left
High number – move right
Low number – move out
High number – move in
· Attach the rubber feet to the bottom of the particleboard. This allows you to put the entire tool on your coffee table, without any damage to your marriage.
You should perform all initial steps of wheel building and adjustments without the dial gauge. Rotate the whole tool so the metal plate is away from you. Use the wheel stand’s regular eyesight gauges at first, since these are easier until the rim is fairly close to true and round. After the spokes are moderately tight and the rim is somewhat straight, turn the tool so the metal plate is closest to you, and mount the dial gauge as shown in the pictures.
To use the dial gauge, slide the magnetic mount toward the wheel until the shaft of the gauge is pressed in about half-way, and then lock the mount in that position. Rotate the wheel slowly. You will see the indicator needle moving as the wood dowel follows the rim. Measuring out-of-true and out-of-round are identical, except that the wood touches either the side of the rim or the outer edge of the rim.
Most dial gauges come with a removable tip that is screwed on. I found it easiest to remove the tip, since the gauge is normally used with the wood dowel attached.
If you are truing a wheel with a tire mounted, you can leave the metal tip on the gauge and measure the out-of-true by placing the gauge tip directly against the side of the rim. You cannot measure out-of-round with the dial gauge when a tire is mounted on the wheel.
As Jobst Brandt has pointed out many times, it is more important that a wheel stay true, than that it start out true. You are better off with a wheel that will stay within +/0.010 inches all racing season, versus a wheel that starts out perfect and quickly deteriorates to +/- 0.1. The way to get a wheel to stay true is tight and even spoke tension.
As you tighten a wheel, the spokes are under quite a bit of tension. If a spoke breaks, it can shoot out of the wheel at high speed, possibly into your eye. Do not look directly into the ends of the spokes (where the nipples are) while you work.
A full discussion of the art of wheel building, including lacing patterns, is in the classic book The Bicycle Wheel by Jobst Brandt. I will note that I disagree with Jobst somewhat about spoke tension. He is certainly correct that you should build a tight wheel. The book advises though that spokes be tightened until the rim begins to deform, then loosened a bit. In my opinion, this is too tight. While Jobst has far more engineering background than I do, I am not comfortable taking a perfectly straight rim and causing it to warp. So I adjust spokes until they are quite tight, but without deforming the rim.
A quick overview of wheel truing, if the spokes are already laced: www.cyclingnews.com/tech/fix/?id=howfix_truing.
A technical discussion of spoke tension, if you want to take your wheel building to the advanced level: www.cyclingnews.com/tech/fix/?id=tm_1.
Please write to me with suggestions, improvements, or problems you run into.