Help figuring out the ERD of this rim.....

Unicycles and Equipment
1

OK, I want to build up my Surly 26" fram with this rim:
http://www.choppersus.com/store/product/690/Rim-Only-26-x-2.5-Black/

I contacted them and they said they didn’t have that info in their database but that it’s a Weinmann rim… I can’t find anything on the web…HELP!

2

For those like me who didn’t/don’t know:

From sheldonbrown.com’s glossary:
E.R.D.
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.