Originally Posted by
dabac
There are a couple of possible culprits, the most probable one being that if you picked the numbers out of a chart, the different calculators may use different ERD values. Some use the value where the nipple meets the rim - which would leave your spokes a tad short, others add a few mm to get full penetration of the spoke into the nipple.
Some take spoke stretch into account if you enter a thin spoke etc.
The recommended way is to buy the rim, and measure the rim to where YOU want the spokes to end up, and use that number. You really shouldn't be seeing 3 mm difference for the same calculations using the same input.
This. Measure rim and hub yourself. I aim for spokes to get to the nipple screwdriver flat, and use spocalc spreadsheet to calculate spoke length. 4 wheels so far, and their numbers work great for me.
I can't stress enough how IMPORTANT measuring everything on your own is. That is if you understand how to measure... I work in optics manufacturing, metrology is no big deal to me. It might not be as easy for some, I'm not picking on anyone, I'm just stating the facts.
Measure it, calculate it, and you will probably see the same numbers spit out
