As a winter project, I’ve decided to build up some silly deep rims. I just ordered a pair of Light Bicycle rims ( R88 Disc Road/Track Rim ), which state a 2-3 week transit time. I have also ordered the hubs, which should get to me some time this week. I would like to order the spokes soon so that I have them before Christmas, when I plan on building the wheels. My question is, the rim specs give an ERD of 463, but state “not including nipple head dimension.” My question is, is there a way of adjusting for the nipple head dimension so that I can calculate spoke length and get them ordered before I get the rims? Or is this a case where you can’t rely on how they measured the ERD and I just have to wait and do it myself?
It’s really in your best interest to wait and measure on your own. The largest distributor in the US who builds and sells wheels for shops will show the manufacturer ERD of the rims they stock and sell on their site, but also keep an entire matrix of actual ERD for their own wheel building team. The differences can be slight but even a full mm can make a lot of difference in spoke tension on a built wheel. That’s the thing you are trying to achieve anyway, proper spoke tension, while you may be able to build a wheel with slight longer or shorter spokes, the spoke tension won’t likely be correct. This will lead to issues as the spokes settle and in the long term life of the wheel
Another thing to take into account is the use of nipple washers. They effectively change the ERD of the rim. So make sure you take that into account when calculating spoke length.
Spokes aren’t cheap, so only buy them once.
Good luck!
Ideally you want the spokes to terminate somewhere between the bottom of the slot to the top of the slot. Less than that you aren’t getting 100% thread engagement. More than that and your spoke is poking out and that can lead to other issues. Too too long and the nipple will actually bottom out on the spoke thread and you can’t tighten them anymore.
Bottom line, as stated above, get the nipple dimension and adjust accordingly. I would even sanity check your calcs with the rim vendor. They will likely give you a hazy go/no-go without accepting any liability..
And yes, good luck!