Does anyone know the spoke tension recommended by the rim manufacturer for the rims that UDC sells (or other sellers)? At least for a 36" rim I could find no spoke tension recommendations on the US or UK UDC sites.
It is recommended by expert wheel builder’s that the rim manufacturer should specify the spoke tension. It does little good to have a spoke tension meter if the required tension is not known. Spokes can easily be tensioned equally by just listening to plucked spokes.
Well yes and no – I’ve only really looked at the manufacturer’s tension values for carbon rims – but to be fair I only bought a tension meter for doing carbon rims and didn’t bother before that.
Mostly it seems that it is the relative tension of the spokes to each other that is important rather than the absolute value, and you are right that listening to the plucked value may be “good enough” in some cases, and you also need to have a good enough ear.
Anyway, here are couple of useful videos, the first is trials rider Ali Clarkson’s second part of his latest wheel building video (the first part is on wheel lacing). Ali builds a lot of wheels for folk, including (as far as I know) Danny MacAskill. The second is Park Tool’s video on using their app to document your wheel build.
I have a Park tension meter, however when you start to read about these things it doesn’t really stack up against ones from the likes of DT-Swiss and Sapim which are much more expensive. It is probably a case of diminishing returns though (and I suppose how much is riding on the quality of the wheel).
I’m tone deaf so I used an app on my phone to measure the tone for my 36" build. I also use a thing like a guitar steel at the spoke cross to get a true measurement on a single spoke with no interference from the adjacent crossed spoke. I’ve also used a small C clamp on the cross to do the same thing. Based on my measurement and calculation I’m putting about 90kg (200lb) of spoke tension on my 36er (brake side Nimbus) but I have no ideal what the rim is rated for. It must be about right because I’ve put several thousand miles on it with no problems.
For regular maintenance I just quickly pluck the spokes around the wheel and listen for any differences. If I happen to have a loose spoke I can tell right away.
First order of business is absolutely to get the super loose ones up to the same tension as the rest. I’d personally just do that and keep a close eye on how it develops over the next few rides, if other spokes keep coming loose the whole wheel needs more tension. Sometimes you just get a random hit on a few spokes and that’s why they untightened, but the overall tension of the wheel is fine.
I’ve built around 100 wheels. When you are building the wheel keep tightning until you hear a pinging sound. The spoke gets twisted and the ping is the spoke untwisting. At that point he spokes are probably tight enough. If you want to go tighter for a heavy load keep tightning 1/4 turn at a time until you round off one of the nipples. Replace the nipple and back off the tension a full turn on each spoke. True the wheel ride it repete until the wheel is perfect. Once I tried to see how tight I could get the spokes. I used a spoke wrench and a screwdriver. As I approached around double tension the wheel buckled. It is possible for a nipple to strip and go shooting off so wear some Lexan lenses. I bicycle tour with 165 to 190 pounds on the back wheel and have hit 53 mph on wheels I built. I’m still here after 120000 miles so I think my wheel building advise is sound.
Now that your wheel is true lay it on it’s side. Thump one of the spokes with your fingernail. Now thump the one closest to it on the opposite side. Spokes are laced so if you thump the one on the outside on one side thump the one on the outside on the other side. Decide which one has the higher tension and make a note on a piece of paper. Do all the spokes this way. Your results will look something like this. U U D U D U U U If you end up with more of one letter than the other your wheel is off center. Give all the spokes on lower tension side 1/4 turn then repete the process.