01 Jan 2015

Doing digital dishes


A few times a year I get a query about the digital dishing tool I have in the image slider on my homepage. It’s something I came up with myself though I’d be surprised if I was the first.

You’ll recognize the base tool as the standard Park Tool WAG-4. It’s a decent tool with sliding blocks that lets you check dish even with tires mounted. Checking dish with the analog indicator probe is fast and easy. The problem is it’s not quantitative and that doesn’t jive with my process. I record a ton of stats about every wheel including tension at every spoke and three kinds of alignment. To record dish alignment with a conventional gauge you need feeler gauges and that’s a bit slow.

I had a spare digital gauge in my toolbox so I mounted it up with no fuss. The lug back on the gauge can rotate 90° so I oriented it perpendicular to the shaft. I re-used the existing hole on the WAG-4 so no drilling required — I simply removed the existing screw and replaced it with a slightly longer one to accommodate the thickness of my gauge mount plus a washer. It’s a wood screw and I was able to find a longer one of the same diameter and thread pitch at Home Depot. That’s it.

The issue with my gauge is the throw of the indicator — the range isn’t appropriate for all axle lengths. I could find an indicator with more throw but this was a project done on the cheap (the cost of a screw if you discount the bits on hand). I deal with this problem by installing indicator contact points of different lengths, suitable to the axle in question. Actually I do gross dishing using the regular analog probe and then install the correct tip to record final dish. When using the regular probe it’s handy to remove the contact point altogether so the digital indicator is out of the way.

How does it work? Pretty well. Having the accuracy of a digital gauge makes you realize the limitations of the underlying tool. I balance the digital dishing tool over the wheel and hold it with the lightest touch otherwise the tool flexes and tilts, distorting values. This amount of distortion wouldn’t lead to bad wheels but it doesn’t hurt to sweat the small stuff when it comes to measurement.

Happy New Year!