I've built 5 wheelsets now, all with all new rims and hubs. Now I'm working on rebuilding a rear wheel (Race Face Affect SL 24 rim) for a friend, intending on reusing the wheel but with a new hub. I'm trying to calculate spoke lengths needed and I don't know what the "++" means after the ERD measurement. Picture shows the rim dimensions.
by carlew
3 Comments
ERD is effective rim diameter, which is very nice to know when getting new spokes, which I’d advise doing in this situation. If your replacement hub is the same as the old one, you can reuse spokes but I’d rather get new.
Not sure what the ++ means.
I was building a Spank wheel a few weeks ago and asked myself the same question, so directly from the Spank website…
”ERD and “++” – It’s important to note that the “++” callout in Spank published ERD measurements for all our rims, refers to the height of the nipples you are using in your wheel build. You must add 2X nipple head height (specific to the nipples you have chosen), to the ERD when calculating spoke lengths. In the past ERD was usually communicated as a calculation including a standard nipple head height, (Inner Diameter of the Rim + 2x Spoke Bed Wall thickness + 2x Nipple Head Height = ERD). However, in recent years many new standards of nipples have been introduced, and nipple head heights vary. For example a standard external nipple has a 2mm head, while a DSN type nipple has a 4mm head. For this reason, Spank communicates ERD without including nipple head height, so the user can add the exact height of the nipples they have chosen for their build, (Inner Diameter of the Rim + 2X Spoke Bed Wall Thickness = ERD ++).”
For erd++ (ususally spank) i just add 3.5mm and it works out fine.