I am currently eyeing Mike's Ultegra / Rigida Chrina wheels in For Sale. If I acquire them I'll be wanting to swap over my existing SON from a very worn Open Pro rim into the Chrina. I have seen the 'tape rims together and transfer spokes' method and wonder if the spokes on my existing SON / OP will fit for a SON/Chrina build.
Can anybody advise please?
One of the frustrations with wheel building is the difficulty of calculating spoke length because their so much wrong and contradicting info on rim ERD, a crucial number when calculating spoke length. Eg. Mavic Open Pro ERD is often stated as 602 mm or 605 mm. The Rigida Chrina as 603.5 mm or 608 mm.
If you are very unlucky this may mean that the spokes may be too long, especially if they are protruding above the nipple slot in the present SON/OP build.
Too long spokes can't be salvaged, but slightly too short spokes aren't a problem: Some thread showing beneath the nipple shank may look wrong but really isn't a problem. If there is too much thread showing, then 14 mm or 16 mm DT Swiss brass nipples can be used to "extend" the spokes 1 or 2 mm.
Personally I don't really trust any wheel data unless I measured myself. That said, I suspect that the spoke length will be practical identical between Mavic the Open Pro and the Rigida Chrina. The best ERD data for the Mavic Open Pro I have seen is from a wheel builder who not only build wheels but also actually measured the Open Pro ERD himself as 603 mm using Wheelsmith rods.
This pdf
http://www.cycleservicenordic.com/product-images/Filer/Teknik/Rigida/Rigida_Rim_Type_and_ETRTO_2012.pdfstates that the Rigida Chrina (double eyelet version) has an ERD of 603.5 mm.
It would make a lot of sense that Rigida would make a box rim that matches the spoke length of a very popular Mavic rim. So, no guarantee, but I suspect that the Chrina rim will fit perfectly on the spokes from the SON/OP wheel.
Some other advice. Spoke wind-up is the wheel builders enemy number one, so; lubricate both threads and nipple wells/eyelets, and when you tighten the nipple, turn the spoke key eg. 1/2 turn forward and then back off a 1/4 turn.
Be systematic; put a piece of tape on a spoke near the valve hole so you know when you have worked through one side of the rim. A Q-tip or a tooth pick or something similar can be helpful to insert the nipple if the eyelets are deep.
Technically you don't need to stress relieve the spokes since you reuse spokes that hopefully was stress relieved when the wheel was build, but it doesn't harm either and may improve spoke the spoke line; so when the slack is taken of spokes but they aren't so tight they can yield, grab two parallel spokes with one hand and squeeze hard. You can't wreck the wheel by squeezing too hard. Use work gloves or a some cloth around your hand when squeezing. Work through all the spokes.
Put the rim tape on before the spokes are too tight, the forces involved are surprisingly large, so a nipple popping off can (at least in theory) achieve a nasty speed. To paraphrase a manual to a laser device; don't look into the nipple well with your remaining eye.
