I had a set of DT Swiss RR 415 rims on DT Swiss 240 hubs come in to me for a rebuild. Here’s what had happened to the rim:
The tensions were all over the place, up to 1300 N on the rear drive side (the rim is rated to 1100 N maximum). It was a good example of how hard it can be to judge tensions by “pinging” the spokes – it wasn’t immediately obvious until the tension meter was brought out. I see many debates on forums about whether a tension meter is essential. The debate seems to split along pretty binary lines – “never used one, I can tell from experience” on one side, “totally essential” on the other. I’m in the “totally essential” camp – good luck to you and congratulations if you can build a hand built bicycle wheel with accurate tensions, evenly balanced without a tension meter. As it happens, I can get very close by ear alone, but I positively welcome the ability to measure, check and confirm. Why would anyone have a problem with that? Feels kind of Luddite / stubborn to me.
To add to the problems, the rear wheel had been laced incorrectly, with spoke holes not being laced to the correct flange. Confusingly enough, the front wheel had been laced correctly (I would have thought at that point someone would spot the difference…?). The incorrect lacing will have also added to the stress on the rim, likely accelerating its demise.
A pity, as there was plenty of life left in the braking surface (measured with Iwanson Caliper), and the RR415 is a nice light rim (actual measured weight 28h 405g) and is no longer available.