Can I use a spoke tension meter to fix my uneven pre-tensioning prior to truing?

Question

I've managed to lace up the wheel I’m building, however I think I've managed to unevenly tension the non drive side as a few spokes aren't as tight as others.

If I get a tension meter, I can go round the wheel and more easily fix it, right?

Am I correct in assuming if I get the spoke tension even, it will be easier to true?

Answer 1

You're in the "iterative" part of truing.

Try loosening a tight spoke by 1/4 turn and tighten the spokes either side by 1/8th of a turn. Then spin and find the next tight one. You could use a tension meter to identify tight ones, but touch works pretty well too.

Then move to checking for "out of round" for a bit. Keep making the worst bit better, then move on. Remember to relieve the wheel and check it again.

Don't assume that if all spokes had the same tension that the rim will be true... sadly its not like that at all. There will always be some tension variation around the same side of the wheel.

Even minor variances in the rim and spoke length can cause tension variations in a completely true wheel. I missed putting spoke prep on one spoke thread, and it needed to be significantly different tension to all other spokes in the wheel. That was a puzzler!

Answer 2

Can I use a spoke tension meter to fix my uneven pre-tensioning prior to truing?

Yes, my usual method is:

• ensure that the rim holes and that the spoke threads are oiled. This is important. Otherwise, at some point you'll be twisting the spokes rather than tightening them. You may even break the spokes, though this more likely to happen when truing old wheels.
• screw in the nipples as evenly as you can, by using a nipple driver or a screwdriver to turn the nipple until no thread is seen (if the spokes are not too short) and then getting them to about 3/5 of the final tension.
• go around the wheel and take the average of the tension. With enough practice, this can be done entering the values on a calculator with the left hand and doing the measurements with the right hand.
• go around the wheel twice or three times adjusting the tension of the spokes to the average value. The reason you do it more than once is that the tension of a spoke is affected by the other spokes'.
• the wheel will be a mess at this point, maybe with one half going to the left and the other to the right, even if you got the tension exactly the same at all the spokes. True the wheel while making sure that none of the spokes gets too far from the average. So to correct a deviation to the right, between tightening a left side spoke and loosening a right side spoke, choose the option that minimizes the deviation from the average. Don't just check the spokes closest to where the deviation is the highest; check also spokes 2-4 holes away from it. Alternate between fixing the right and left deviations. Get to less than 1 mm of lateral deviations.
• Tighten the spokes uniformly to the final tension by carefully turing the spoke wrench the same amount (I look at the position of the slot of the nipple; a half-turn should leave it looking the same). In my experience, the wheel will generally be truer after this tightening that before. At this point, the spokes are more difficult to turn, and they twist more easily, so try to get it right on the previous step. If you do so, you'll only need to make small adjustments at this point.
• If the wheel requires a dish, do the tightening in several steps (each with smaller turns) until you get it centered. If lateral or radial trueness requires significant adjustments, it's better to again calculate the average tension on each side to guide the trueing. I measure the dish by resting the wheel atop a flat surface, pressing one side of the wheel against the surface and measuring how far the opposite side is from the table, then turning the wheel over and doing the same. The two values should be the same in a centered wheel.

Now, one can get good results with the plucking method (the higher-pitched the sound, the tighter the spoke) is. I find it much harder and slower — I'm not especially musically gifted and if two spokes get too far apart in terms of tension, I find it difficult to compare the sounds. Plus, you don't get to calculate an average value to compare against.

Answer 3

Your question seems to imply you're trying to build a wheel for the first time and without a spoke tension meter.

As someone who did exactly that, I would discourage you. I built a wheel (first time) and it was pretty true and felt solidly built and I was initially pleased at having saved on a tension meter. Then after about 3 months or 300 miles I had a spoke go. Then another, then another and then another. I ended up re-building a wheel, with a new set of spokes and spending on the tension meter.

Unless you're doing this for a living, I think it's impossible to end up with even spoke tension that is the right value without a tension meter. And that will mean a weaker wheel. You may not be able to notice it at first, but the judders of riding will cause metal fatigue at the weakest point and then it's only a matter of time...

So invest in a tension meter and save yourself the hassle of doing it twice.

As for approach, use the spoke meter to iteratively arrive at about the right tension evenly everywhere, and then true up. You'd think even spoke tension everywhere would result in a true wheel, but in the real world the rim and spokes aren't perfect, hence why you will almost certainly need to true up after arriving at the right spoke tension.