Originally Posted by
steppinthrax
Thanks for you reply.
1). What is Slot bottom or top. I used two calculators.
There's a 1mm deep screw driver slot for starting nipples. The closed end near the rim is the bottom. The top is the tire side where the nipple ends.
The second one has the mfg of both my wheels and hubs.
It has one example of your rims measured at an unknown time using an unknown method. You can't count on it. Measure yourself adding twice spoke length to the distance across their elbows with nipples threaded on in opposite holes. Measure again 90 degrees away because some rims are oval shaped. If that doesn't match, do the 45 degree angles too. Add up the total and divide by the number of measurements to get ERD.
Drop that into the spocalc.xls spreadsheet which makes no assumptions.
Published ERD should only affect which way you round. If your rim is a little bigger than the published numbers, round down if you can so you won't run out of thread swapping a new rim that doesn't run big. If it's smaller favor rounding up.
Get that right and when you bend or wear out the rim, you tape a new on to it in three places, move spokes over one at a time, remove the old rim, tension, and true.
2). The first hub has a 2.0 mm spoke hole. However the rear hub has a 2.6mm spoke hole. This is actually a question I missed. Does the extra 0.6mm matter? I'm not really seeing 2.6mm but I do see all 2.0mm spokes. All my spokes will be J-bent spokes.
Spoke threads are rolled so they're larger in diameter than the spoke shafts, nut cut which would weaken the spokes. The holes are correspondingly bigger than 2.0mm.
3). I'm figuring that I should round up because I read that usually they give you 8 - 10 mm of spoke thread. So if I have spoke sticking out I can grind/cut each spoke down by a bit?
No. When you run out of thread the nipple won't go on any farther if you don't drill it out. It's like threading a nut on a bolt past the head - not physically possible.
If the nipple has 8mm of thread and spoke has 9mm, it's physically impossible for the spoke to extend more than 1mm past the top.
That's a standard 12mm DT nipple on the bottom. It can't thread any farther on to the spoke. If you end up in that situation, you'll need to settle for whatever tension it's at which might not be enough to keep the wheel true, or remove the nipples, drill them out for more clearance, and start over.
This is what happens when the spokes are too short. They need to be long enough to go all the way through the rim bed, so they're squeezing the nipple into it not putting it in tension.
You need to avoid both problems.
I think nipples should be made with less thread now that quality bikes all use double walled rims. Dropping to 6mm of thread on a 12mm nipple would give you an extra 2mm of tolerance. With only 1-1.5 bolt diameters required for full strength, 4mm of engagement would be plenty when a spoke was as short as it could be without risking nipple breakage.