Originally Posted by
Ronno6
...
Thread engagement is indeed way more than adequate, but I have read of nipples popping at the base of the head.
This can be attributed to the spoke not threading all the way up into the head, causing a stress point at that location,
especially if that is the point where the nipple contacts the rim. That would not be affected by nipple length.
Absolutely correct, the only threads that count and provide 100% nipple strength are those engaged in the nipple head. 2mm engagement there, which is typically up to the bottom of the slot achieves that goal. Any more is margin for error.
Originally Posted by
Ronno6
But, now I need to understand how to measure ERD for future reference. This go round I can just add 2 or 3mm to the spoke lengths.
I guess I need to assemble the rear wheel using the spokes I have just to verify. I'll put compound on then anyway, just in case ;-)
ERD is the diameter at the desired end of the spoke. For a typical nipple it'll be about 5mm more (2x 2.5mm thread engagement in the head) than the actual diameter at the base of the hole, ie. top of the eyelet where the nipple sits. There are a few ways to handle this. Measure all your rims to the spoke holes, and calculate to there, then add enough for nipple head when rounding or tweaking to the desired spoke length. Or measure to the base of the spoke hole, and add 5-6mm for two nipples before calculating, or put two nipples at opposite ends, and measure ERD directly to the base of the screw slot.
The first is how I measure so I have all my adjustments in place together. Those who make DIY rim rods, to masure rims usually use the last method, building the nipple into their calibration.
Whatever method you use is fine so long as you remember that the calculator result will bring the spoke out close to the ERD you entered in the first place.