Don Gillies said:
>So if you take an ERD of 622 mm, and intend to have the spoke tip seat
>3 mm below the tire bed, then you could use 616mm for ERD for just
>about all tubular rims in the vintage era, couldn't you?
While there is not as much variation in rim depths among vintage tubular rims, there is some. It is always best to measure. Also, It is probably better to have the spoke tips a little lower than is suggested here. When I build wheels, I like the spoke tips to be through the rim, but not through the spoke nipple, even though you can get away with that when you build a tubular wheel.
Spoke length also varies by the number of spoke holes. Thus, the chart of 16 spoke sizes expands tremendously when one considers 28-, 32-, 36- and 40-hole rims.
I have found that to cover the even the range of practical lacing patterns, I need spokes of every other length from 288 mm to 304 mm. And if I wanted to be dead-on accurate with the spoke length, with the spoke tip coming to the bottom of the slot in the spoke nipple, I would need spokes of every mm length.
And this does not even count for slight differences in hub diameter and flange spacing.
So, for best results, avoid over simplification, measure each rim you use, and run a spoke calculation based on the hub at hand. Then order your spokes to fit correctly.
Regards, Earle Young Madison, Wisc. Offering expert wheelbuilding services for classic and modern bikes.