Total indicat…

Islandix truing tools use the acronym TIR to describe wheel alignment. Originally TIR stood for Total Indicated Runout but over time became Total Indicator Reading. Technically runout is a measure of concentricity, which applies to radial wheel alignment but not lateral alignment (instead a measure of flatness). Wheelbuilders often say runout when referring to both and that’s fine.

Regardless TIR is a Total measure, that is the maximum reading minus the minimum. On a rim brake wheel, for example, lateral TIR is the difference between shortest and longest spans from rim to brake through a full rotation of the wheel. That’s intrinsically useful.

For various reasons some wheelbuilders prefer to describe alignment in plus-minus terms. In this nomenclature alignment is given as the difference between minimum/maximum readings and the midpoint.  If you prefer thinking about alignment in plus-minus terms, divide TIR by two.

Visual wheel centering

The Target Plot is a unified visualization of lateral and radial alignment, which helps reasoning about both dimensions at once. From version 1.2.2 it can track wheel centering too (the term centering is used because it translates better than the word dish).

How does it work? Wheel Analytics needs to learn the ideal/centered position of the rim. This can be established two ways, either (i) using a single lateral reference as you would with the Centrimaster v-block or (ii) checking two lateral references by flipping the wheel in the stand. The second method is universal so it’s the default and discussed here.

Initiate setup with the ‘c’ key on the keyboard or click/tap the scale in the bottom corner of the graph. A dialog opens waiting for the first lateral reference. Rotate the wheel so the valve hole is at the lateral indicator and press the left foot pedal to record lateral position. Flip the wheel in the stand, rotate to the valve hole and press the foot pedal to record again. That’s it. Now when you snapshot the visualization, direction and magnitude of any centering error is displayed.

How accurate is it? Accuracy hinges on repeatability of wheel position spanning removal and re-insertion. Technique plays a role — aim to tighten the wheel in the truing stand to the same degree with the same force every time. Do not overtighten. Better truing stands do a better job of resisting twist and deflection, which reduces the importance of technique. More will be written on this topic in a future article.

The image at the top of this article depicts a real wheel built in the Islandix lab. With a bit of luck the wheel landed 0.01mm off center to the left. The wheel was built using a Park Tool TS-2.2 and Wheel Analytics 1.2.2. This result was externally verified with a digital dishing gauge.

Radar re-homed

The free spoke tension graphing tool I’ve hosted online since 2013 has been re-homed to Please update your bookmarks.

This tool is also available with Wheel Analytics under the name Tension Radar. When used with the Islandix ecosystem, you are independent of the cloud (functions without internet access). It works with your Islandix FP-2 foot pedal and supports custom tensiometer calibrations.