Originally Posted by
Al1943
Another case of why I say to always round down.
Agree 99%
Some manus like Mavic aim exactly for the screwdriver flat. So as-is is fine with their ERDs. But most others aim somewhere between the screwdriver flat and the top of the nipple - so rounding down gets you right back to the screwdriver flat.
Recently when Sun-Ringle put out their MTX33's, they reported on the rim labels ERD's of 536 and 598. I knew right away when measuring and after building a dozen that someone had measured all the way to the top of the nipple. Called 'em, they already knew and had already corrected their documentation. (They still insist on 597mm for the 700c though...)
Luckily, rounding down on the first set of rims kept me out of trouble by a hair. I use 534 and 596 - as-is - perfect result everytime.
Also, rounding down makes the use of 14mm nipples more feasible as an option...
=8-)