Ronno6
Bottom line - it's always best to measure your own ERD's - even for the same rim.
See my spreadsheet at:
http://www.mrrabbit.net/wheelsbyflemingapplications.php
Open "rimchart" tab...
Scroll down to Mavic section - and you'll see that the Open Pro varies all by itself quite a bit.
Hub changes as FB pointed out - relatively minor. ERD changes - deal killer.
=8-)
__________________
5000+ wheels built since 1984...
Disclaimer:
1. I do not claim to be an expert in bicycle mechanics despite my experience.
2. I like anyone will comment in other areas.
3. I do not own the preexisting concepts of DISH and ERD.
4. I will provide information as I always have to others that I believe will help them protect themselves from unscrupulous mechanics.
5. My all time favorite book is:
Kahane, Howard. Logic and Contemporary Rhetoric: The Use of Reason in Everyday Life