Originally Posted by trek330
Can I switch a double walled 622-15 rim with a 622-17 single walled rim without changing spokes?
Unlikely. 622 refers to the bead seat diameter, basically where the tire meets the rim. There's no fixed relation between the BSD and the requires spoke length. 15/17 refers to rim internal width, which has a so-so relationship to which width of tires you can run on a certain rim.
The value you want to be looking for is (quote from Sheldon Brown) Effective Rim Diameter. This is the rim diameter measured at the nipple seats in the spoke holes, plus the thickness of the two nipple heads. The E.R.D. is needed for calculating the correct spoke length.
A rim with a higher profile will have a lower ERD despite being the same BSD.
Do note that all suppliers measure ERD in the same way, and don't take for granted that values listed on websites are correct.
Sometimes picking another lace pattern can offer possibilities. Going from 3-cross double wall to 2-cross single wall might free up enough spoke length for a successful transplant. Or 3X single-wall to 4X double wall might use up enough spoke for the wheel to tension up properly.
Different nipple lengths can, IME, be used for minor tweaks of spoke lengths. However, not all would agree, and for a first build you want things to line up nicely w/o any extra challenges.