Originally Posted by
davidad
I rebuilt a wheel with a power tap for a friend. He is about 225lbs and strong as an ox. Can generate over 800 watts for a short time on a climb. He actually broke 2 Mavic OpenPro rims.
I rebuilt the wheel the second time with a Sun rim and had to up the drive side tension to 130kg because he was breaking the NDS spokes at the nipple.
The power tap has a little extra dish because of the design of the hub which makes for lower NDS tension.
You bring up a good observation. Often times, the spoke tension isn't what breaks a spoke, but abnormal stresses that suddenly occur at the ends of the spoke. And it's often counter intuitive that the spoke tension at rest is simply a pre-tensioning that allows the wheel to shift stress on-and-off spokes as the wheel rotates without sudden changes in tensile direction. And the non-drive side of the wheel is where the problems often are and either loosen unexpectedly or break at hub or nipple. And that's because they aren't tight enough.