This video shows how Wheel Analytics can track wheel centering, also called dish. First the tool takes samples from both sides of the wheel using cues from the foot pedal. Then the visualization calculates dish at the same time as lateral and radial alignment. In the example above dish error is 0.10mm, which is a great result. In all it takes about 35 seconds to measure dish accurately and quantitatively. From this point the wheel can be adjusted and dish will be automatically recalculated without further setup (calibration stability depends on the truing stand).
In normal use perfect dish means a dish error of 0.00mm. If you’re building wheels with offset dish, then perfect dish could be some positive value. Cannondale Ai wheels, for example, have 6mm offset dish. Wheel Analytics accommodates these wheels seamlessly and is the only truing tool that can measure such wheels without adapters.
Case study: Park Tool
Wheel Analytics works in mathematical terms but dish accuracy depends on the truing stand and the wheelbuilder’s awareness of its limitations. The essential requirement is the ability to remove and re-install a wheel in the truing stand and get the same lateral reading.
Park Tool makes a terrific truing stand in the sense that it holds the wheel securely with effortless installation/removal. But in spite of these qualities, the Park fixture is subject to twist and deflection. Try it for yourself: install a wheel, touch the lateral indicator to the rim and incrementally tighten the truing stand uprights. Watch the lateral reading shift. This phenomenon affects all truing stands but some are more resistant than others.
In the case of Park Tool (and in general), less tightening torque means less twist and deflection. To optimize accuracy I’ve developed the following procedure: install the wheel by (i) closing the uprights until they just kiss the hub then (ii) tighten the uprights by rotating the knob 1/12th of a turn. There is a six-sided nut on the handle that makes it easy to visualize 1/12th of a turn.
Using a digital dishing tool for reference, I’ve found this method gives good results with the Park Tool TS-2.2 in the Islandix workshop. Unfortunately tightening a wheel so gingerly isn’t very practical — it’s possible to continue truing the wheel but it’s difficult to do any stress relieving in the stand without dislodging the wheel. For this reason I use Wheel Analytics to check dish but I don’t track it continuously/automatically through the build (when using the Park fixture). I repeat the wheel-flip calibration procedure at the end of the build to confirm alignment.