sced

I'm trying to figure out what lengths I need for older (silver) Campy 10spd hubs, Sun SL1 rims, 3x 14-15-14 double butted.

I measured the ERD to be 565mm between the tops of the nipple flats + 2 x 16mm for the nipples = 597mm

I used SPOCALC with a surrogate 597mm rim because it lacked and entry for the Sun SL1's. It calculated Front = 292.5mm, Left Rear (non-drive)= 291.9, Right Rear (drive) = 289.8.

I assume SPOCALC assumes use of 12mm nipples. I spun 12mm and 16mm nipples onto some spokes and it appears that the internal threaded length of the 16mm nipples is only 1mm longer than the 12mm nipples.

So should I use
Front = 292.5 rounded down to 292 minus the 1mm extra internal threaded length of a 16mm nipple = 291mm?
Left Rear (non-drive) = 291.9 rounded down to 291 minus the 1mm = 290mm?
Right Rear (drive) = 289.8 rounded down to 289 minus the 1mm = 288mm?

Thanks, Ed

Ronno6

I would not use shorter spokes due to longer nipples.
The strongest point of spoke/nipple/rim system is in the nipple head itself.
The spoke end should at least make it to the bottom of the cross slot when properly tensioned.
Much shorter than that and you risk breakage of the nipple at the base of the head.
I have had that happen...........

FBinNY 

This shows a fundamental misunderstanding. If you measured to the tops of the nipples, why would you add the nipple length? Take some time to think about and get it straight in you head before reading on.

The key issue in nipple length isn't the overall length of the nipple, it's the length of the thread within the nipple and how it compares with the spoke's thread length. If the two are the same, the spoke will top out at the top of the nipple. If the nipple thread is longer the spoke can't reach the top, and if the nipple thread is shorter it allows for some overrun beyond the top of the nipple.

sced

This is how I understood it to be and why I posted. What I'm calling the "tops of the nipples" is the start of the wrench flats nearest the rim center. Adding 2 x 16mm nipple lengths to the distance from top to top across the rim is the ERD"

I'm looking for advice on how to adjust the SPOCALC calculated spoke lengths for the 16mm nipples.

FBinNY 

Let's start with some basics.

1- the spoke has to end at the top (head end) of the nipple. Most consider the ideal length to be such that spoke ends 1mm short of the top, or about the depth of the screwdriver slot.
2- spoke calculators (most) give you a spoke length which brings the ends to the ERD entered, meaning that the ERD is the diameter of the circle of spoke tips.
3- as for the effect of nipple length, read the 2nd paragraph of my prior post.

I suggest you draw a sketch to help you get it all straight in your head, or re-read the supporting text for the spoke calculator you plan to use. You might also visit some sites on wheelbuilding and read about calculating ERD.

Ronno6

I understand the OP's method and logic as far as ERD measurement is concerned, just have never seen it expressed that that manner.
I have seen the Swift SL1 rims listed with an ERD of 595mm so he is not far off.

I generally take a couple of broken spokes (at the J-bend) of known length and thread onto the nipple to bottom of slot,
then insert into opposing holes pointing toward each other and measure the gap using a spoke ruler. Add gap to spoke lengths for an accurate ERD.

FBinNY 

Other than the nomenclature (most people call the button end the top of the nipple) he's actually spot on if he subtracts 1mm from each side for an ERD to the slot rather than the top of the nipple.

Dan Burkhart 

Some 16mm nipples have a deep enough skirt so the threads won't bottom out before the tip of the spoke is through the nipple, but many do not. When this is the case, you should not adjust with shorter spokes, as this leaves the nipple head unsupported and risks shearing the heads off.
I like to build with 16mm nipples in some applications, but I'm equipped to roll 13mm of thread on the spokes so they don't bottom out. If you have not ordered your spokes yet, and you really want or need to use 16mm nipples, see if you can find someone to roll 13mm of thread onto them.
If it comes down to it, I could help you with that.

Soil_Sampler

Some 16mm nipples have the same amount of threads, like my black brass Sapim nipples.

sced

Thanks all for the help and confirming my analysis.

I subtracted the slot depth (mic'd at 1.36mm) from the measured ERD used in SPOCALC and subtracted 1mm from the calculated spoke lengths to account for the extra threaded length of the the 16mm nipples.

When I posted I had already ordered from 72 Custom Length 14g 2 0mm Double Butted Silver Stainless J Bend Bicycle Spokes | eBay
and had already asked if he could increase the threaded length. He replied that his machine could not do this.

Dan Burkhart 

Not knowing what machine he has, he is probably correct that in it's usual configuration it can't. I have a Morizumi spoke machine, and as delivered, it only threaded at 9mm. I had to adapt the machine myself for the longer threads.

Ronno6

He uses Phil Wood machines.
https://philwood.com/products/tools/spokemach.php
FWIW, I have done much business with him and he is excellent.
Great customer service and great Sapim spokes.

FBinNY 

FWIW, a nipple needs only 3-4mm of thread to achieve maximum engagement strength in the head. The threads in the shank don't add structural strength. They're a convenience for the builder because it's harder to start the last few spokes when the nipple doesn't have extra thread.

Based on experience, 6-8mm nipple thread length is about the right balance between (hand) building ease and tolerance for overrun with spokes threaded the typical 10mm. As I posted earlier, the builders concern isn't the length of the nipple, but the length of the thread.

Even if the thread is a bit longer, that's not a reason for shortening the spoke, because it still has to reach the head which is in the same place. All it means is reduced margin for error for spoke overrun.

Dan Burkhart 

All that is true. If we could only get the nipple manufacturers to make the skirts deep enough so standard spokes wouldn't bottom out in longer nipples,we wouldn't be having this discussion.

FBinNY 

You have to understand their objectives. The number of rims that require long nipples, namely filled double wall rims where the nipple sits on the upper (tire) side, is very small (if any are still made), so today's long nipples aren't made for that application.

Long nipples today exist to satisfy the needs of the women using semi-automatic machines to hand lace wheels in production facilities. These women lace upward of 40 wheels per hour and the longer nipples allows the wheel to be laced 3 turns while still slack. With shorter thread length, the wheel starts to have a bit of tension as it's being laced and that makes the job slower and harder on the fingertips.

When I can't find the right nipples, I'll set a 2mm drill, or burr up in a Dremel clamped in the vice. I fit a depth stop, and hand feed nipples to bore out 2-3 threads. It's a very fast process once you develop the touch.