Measuring ERD

vala

Hello all,

I'm about to measure the ERD of my rims and am using a couple of spare spokes and nipples I have about.
For my wheel build I'll be using 12mm nipples however the nipples I have to use as the measuring tools are 14mm.
Does this matter?
I'm thinking not as it shouldn't affect the lengths of the spokes but just wanted to be sure.

Thanks

Monty Dog

If the measurement you used for ERD is the actual measurement rim bed - rim bed then you'll be OK. Make sure that you entered the correct length of nipple in Spoke Calc otherwise your spokes will be 2mm too short. If you Google your rim make and tyre, you should find be able to find the ERD - or at least worth checking.

vala

Checking online has resulted in 3 different ERD's for the Open Pro's.
602mm, 604mm and 605mm. After speaking to a few wheel builders all advised it would be worth just measuring the actual rim I'd be using.
Aside from the DT Swiss calculator none of the others ask for the nipple length information.

Monty Dog

+/-1mm spoke length difference makes no difference structurally to the wheel as the load of the spoke thread is only taken by the first 6 or so turns, any remaining nipple length is effectively redundant. This used to be more of a problem in the days of shallow / single-wall rims, where protruding spokes = punctures. The rim bed on the Open Pro is deep enough that protruding spokes don't really create a problem.

cycleclinic

Most calculators assume 12mm nipples that why. Yes measure your rim yourself. Did we speak on the phone?

Some 14mm nipples have thread extending further than others. I think Spaims 14mm nipples have the same thread length as the 12mm nipples so your spoke length is unaffected. DT Swiss 14mm nipples have a longer thread length I think than the 12mm nipples so nipple length is important.

The only problem with letting the spokes stick out is you might and I say might run out of spoke thread before the spoke is at the required tension. It has to stick out a fair bit for this to happen though. Monty's right +/- 1mm make little difference but I measure the rim bed ERD of open pro's to be 602mm and I often round up lengths but with Lasers I may round down is I am only rounding down no more than 0.4mm. The wheels I build with that rims all semm fine and spoke reach the rim when everything is assembled. Being a bit anal I don't like spokes sticking out of the nipple head but if they do a little bit is not a problem.

You can get too hung up of spoke lengths.