How to use a single caliper truing stand (vs dual caliper)?

Question

I have used a Park Tool TS2.2 on a bicycle course. It has a caliper for each side of the rim. As you turn the dial, both calipers converge evenly toward the rim. This allows you to know which side of the rim has the biggest wobble, and therefore which side needs adjusting next.

Single caliper truing stands measure only one side at a time. Let's say the caliper is on the left. A 'peak' is detected on the left side of the rim, you tighten the right hand side spokes. I get that if you repeat this process the wheel will eventually be true, but you've only tightened right hand spokes. Won't the rim be pulled over to one side and have an imbalance with tense right hand spokes and loose left hand spokes? We were taught not to adjust either side more than 3 times in a row (When needed, the instructor would 'kick out' one of the calipers when he only wanted to use the other one, by wedging a screwdriver underneath the one he didn't want to use)- we would use both left and right caliper, therefore tightening both sides of the spokes, which would be more balanced.

So in my example with the single caliper on the left, the only way to detect 'peaks' on the right hand side of the rim would be to look for gaps on the left hand side, using the caliper as a visual aid. This doesn't strike me as very precise. The only other way being to constantly flip the wheel in the stand. I think there's something critical and probably obvious I'm missing here, help would be very much appreciated.

Answer 1

When truing a wheel (such that the rim lies in a plane perpendicular to the axle) it is only necessary to measure against one side of the rim, as rims have a uniform width around their circumference (assuming there are no dents in the sidewall.

The other aspect of wheel geometry is correct dish (rim lies in a plane exactly halfway between the axle shoulders). Another question here indicates that the Park TS 2.2 needs calibrating to achieve correct dish. I believe most wheel builders use a separate dishing tool to ensure dish is correct.

Answer 2

My truing stand is an old 26" fork clamped in a vise, and I use a stubby cable tie around the fork tine on each side as an indicator.

Its not a high precision solution, but its possible to drastically improve most wheels.

Since the indicators aren't linked, I normally work to identify the high spots that bulge sideways the most. They get tweaked back into line a half-nipple turn in the middle of the bulge, and then the nipple on the other side is released the same amount. Successive nipples around the rim are adjusted by a half-turn for the neighbours, and then a quarter turn for the next pair out.

Sometimes I just use my secondary hand's index finger as the gauge, to feel where the most deflection is.

After a bit of sideways, I'll check for out-of-round using the same methods. Then return to sideways true adjustments.

Normally I aim for the "longest section of rim that needs the least adjustment" as a baseline target, on the basis that is probably pretty good and the aberrations are what I have to fix.

After that I'll ping the wheels looking for high or low tensions, then put the whole wheel on my knee and try to taco it, to relieve any bad tensions. And then spin it in the stand again to check what may have changed.

The tricks are

• Use the right-sized spoke driver. Not all wheels have identical nipples.
• Take your time and don't get frustrated chasing a lump around the rim.
• Allow yourself to realise "good enough is good enough" and utter perfection is not required.