valueaudio

Measuring a 700c Sun CR-18 rim (with nipple eyelets) for ERD. Two conflicting sets of where to measure from:

Sheldon Brown's technique adds 2mm each for the seated nipple head tops within the rim (2mm each x 2).
"Finally: If you measured over the tops of spoke nipples, you are done. If you measured an empty rim, add twice the height of a spoke nipple -- about 4mm total."
(From section 'Calculation of rim spoking diameter' at: https://www.sheldonbrown.com/spoke-length.html )

DT Swiss's spoke length calculator at indicates ERD to be measured from the deepest part of the nipple's screwdriver slot (diagram photo attached from: https://spokes-calculator.dtswiss.com/en/calculator

Which should I use?

- Sun states the ERD as 612mm.
- Rim O.D. I measured as 635mm.
- My measurements with Brown's technique – with me also measuring to the top of the the nipple head while it's seated into position in the eyelet, is 11mm down from O.D each side. The ERD this gave is 613mm.
- Using DT Swiss's technique - it measures down 12.5mm each side from the O.D.. The ERD this gave is 610mm.

Which is correct to use? My measurements are averaged from slight variations at multiple points on the rim.


While here, I might as well ask about spoke gauge combos for the rear wheel DS & NDS. I'm inclined to be a bit creative on this build, and try Sheldon's suggestion for radial spoking on the Non Drive Side (NDS) – and go 3x on the Drive Side (DS) on a 32 hole rim. It's for my city/commuter bike. I thought I'd use straight 2.0 on the DS, and double butted 2.0/1.8/2.0 on the NDS. Sound good? NDS radial spokes will be about 12mm shorter than the DS spokes. Goal is to help equal spoke tension between the two sides. I'm not sure if I should simply rely on the shorter NDS length to achieve that, or combine that with the thinner NDS spokes which will also increase tension.

Thanks!
Jeff

FBinNY 

As used today, the term ERD refers to the diameter where you want the spokes to end, ie. 1mm short of the tops of the nipples.

Years ago we used to measure the rim's actual at the nipple seat, then add 5-6mm to allow for the nipple heads.

It doesn't matter how you do this, as long as you're consistent, and understand that most online calculators will have the spokes end at the diameter you entered as the ERD.

So, enter the value that reflects where you want the spokes to end.

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BTW - I NEVER use published ERD specs. Besides the possibility of typos or errors, I don't like ERD because it include an assumption about how high into the nipple the spoke should reach. Folks differ on this detail, so I won't use something that depends on the rim maker properly guessing what I want, and/or me knowing what they think I want.

So, if I were king, ERD specs would be replaced with NSD (nipple seat diameter) based on the actual measurement, and the builders wiuld be charged with adding whatever allowance for nipple heads they prefer.

valueaudio

That's a real clear answer, and what I was thinking made sense as well. Basically, I think DT has it right on their diagram.

I AM measuring with some generic nipples, but I'm pretty sure they'll be close enough to the Sapims I'll be using.

Thanks, Jeff

Bike Gremlin

Take two old spokes. Cut them to 20 cm length, as precisely as possible (i used grinding to fine-tune them). Leaving the threaded parts in tact.
Screw one nipple at each spoke, so that the bottom of the nipple screwdriver slot is flush with the spoke end.
Use cable cutters, or pliers to pinch the nipples in place. Some thread locking glue is also a good solution (one doesn't exclude the other ).

Place the spokes in two opposite holes in the rim (12 and 6 o'clock) and measure the distance between the spoke ends, then add 40 cm, of course.
Repeat the measuring 3 more times (1.5 and 7.5 o'clock, then 3 and 9, finally 5.5 and 10.5). Write all the measurements down and calculate the average (add them all, then divide by 4). That way you will compensate for any rim imperfections. Even two measurements are often good enough (12-6 and 3-9).

Bill Kapaun

I use the same method, but found it much easier to just get a couple pairs of "calibration spokes".
I think I have 250 & 300mm. I found that the wider the gap to span with the caliper, the more inconsistent my measurements. I'll probably buy a couple more sizes to fill in the "gaps" a bit, next time I buy spokes.

davidad

I have not had a problem using the manufacturer's spec on ERD. If I can't find one then I measure.

nfmisso

Contrary to Francis; I have had no issues following the manufacturer's ERD on Sun CR18 590, Alex DP18 559, Velocity Dyad 622, Velocity Aeroheat 559, Velocity Aero 622 and Velocity NoBS 622 rims; with Spocalc Express and Wheelsmith spokes and nipples. But everyone's results may vary.

I'd suggest 2.0/1.8/2.0 on both sides for a 622 wheel.

For my 559 rear wheels, I am using Wheelsmith DB14 on DS and DB15 on the NDS; 3X both sides. For my 622 rear wheels DB14 on both sides.

valueaudio

Well, on the Sun CR-18, I ended up using an ERD of 610, measured to the bottom of the nipple's screwdriver slot. Sun's ERD is 612, so it will be interesting to see if I end up 2mm short, right on the money, or if in-between is the bee's knees.

Explaining my interests in building this wheel, a lot of this is an experiment in trying to apply my recent learning about wheel builds into a sensibly applied rear wheel. This experiment – including the radial-laced NDS while staying with 32 spokes – is to see how my own combination of these build theories work out. If I dig it, it may end up working it's way up into building more expensive wheels for my flat-bar road bike...a rather racey Giant Fastroad.

I'm getting my spokes from Dan's Comp – https://www.danscomp.com/search/sapim+spokes.html – who offers awesome prices on custom cut Sapims - 25 cents for straight 14g, and 40c for DB 14/15s, plus $6 shipping. It must be a loss leader for them, to bring in a national following for their shop and website. It includes nipples, though she said the are generic rather than Sapim (she didn't know the brand). They offer racier models as well, but they all seemed too slinky for a city commuter bike.

Because my NDS spokes are only 4% shorter than those on the DS, and I didn't want to go lighter than 14/15 gauge anywhere, I ordered DubButt 14/15/14g for the NDS, so that I can increase the tension on that side of the dish to be closer to the DS. If I had the options of DT Swiss, I might have gone single butted 13/14g for the DS.

I couldn't find the DB15 on the current Wheelsmith website. Only an SS15 (straight 15g). Did they perhaps drop it from production? Not sure I like the idea of a straight 15g – seems it might be prone to breaking at the ends without a stretchier middle. I'm not too concerned about that problem with a straight 14g.

Bike Gremlin

I'd recommend using DB spokes on the drive side as well - those spokes take the most load, and DB are more durable (if built well). If you want to equalize tension, you could go 1.8-1.6-1.8 on the NDS and 2-1.8-2 on the DS.

nfmisso

eBay. Walt's in Milwaukee has a large quantity, maybe they bought Wheelsmith's inventory when the stopped offering DB15 - I do not know for sure.

I will no longer build wheels with straight gauge spokes; the cost difference is insignificant to the value of my time to me.

I also use Velocity rims for the same reason - they are easier to build.

nfmisso

ERD to spoke length is not a 1:1 relationship, and gets further away from 1:1 as crosses increase. Spokes ±2mm from nominal will work just fine a double wall rim application like a CR-18. On single wall, you might want to grind the end off longer spokes.

SquidPuppet

Are you sure? They've come with Sapim brass Polyax 14mm nipples in the past. Let us know what gets delivered, please.

Drew Eckhardt 

Or use two new spokes. Thread nipples on to your target depth, measure across the elbows with calipers, and add total spoke length.

Drew Eckhardt 

Spokes over 1mm short of the nipple slot can break alloy nipples.

With DT spokes and nipples you run out of thread when the spokes reach 1.5mm above the nipple tops.

That's -1, +2.5mm aiming for the nipple slot; or -2, +1.5mm aiming for the top.

Bike Gremlin

I prefer to have a sharp cut to measure from, rather than a spoke's twisted elbow. That's why I used two old spokes, you could cut two new ones too, of course, but it's two spokes wasted. Cut them roughly to length, then ground them down to precisely 20 cm. That fits both larger and smaller wheels nicely, as well as my toolbox.

valueaudio

That spoke combo will be a consideration when I build a racier wheel. Also, when I'm willing to spend 3-4 times as much on spokes. Here are the offerings and prices at Dan's Comp:

https://www.danscomp.com/search/spoke.html

Bill Kapaun

My PARK spoke ruler works really well.

valueaudio

Not sure I'll be able to find an indication of the manufacturer on the nipples. For spokes, I know to check the spoke head for identification.

AlexCyclistRoch

FWIW, I've built my last 3 rear wheels semi-radial. I'm a bit hard on climbs, and got tired of replacing NDS leading spokes. Haven't broken a spoke since...

BTW, prowheelbuilder.com filled my order quickly last week when coloradocyclist didn't have my spokes in stock

SquidPuppet

The heads are shaped like this.

FBinNY 

I agree that most published specs are OK,

BUT

I'd still be playing the newlywed game, trying to guess the nipple height that they had in mind.So, preferring not to waste my time reworking something I could have had right the first time, I take Admiral Hopper's advice (see below), and measure myself.

I should add that I'm finicky and insist that the spokes each within a hair of the top of the nipple. On some brands, there's very little overrun possible, so a mistake of only 1mm can mean starting fresh.

nfmisso

Francis; and a corollary to Admiral Hopper's quote is that measurements need to be consistent (repeatable). Staying with one quality rim manufacture (Velocity in my case) improves that consistency .

For others in the audience, https://en.wikipedia.org/wiki/ANOVA_gauge_R%26R

nfmisso

Spoke cost and rim costs are a very small percentage of the total cost of a wheelset; it makes little sense to go with anything less than what you really want.

FBinNY 

I agree, and will add hat one should also use the same calculator, because there are small variances in some of the fudge factor assumptions.

Once you settle on how you measure, use a calculator, and built a pair of wheels or two, you'll see how the reality matches the expectation, and can add your own fudge factor (if needed). It will be the same every time as long as you stay consistent.

I typically add 1-2mm to the calculated results and end up with spokes that end just about flush with the tops of the nipples.

The problem is that the people we see asking here, aren't the ones who've built a number of wheels and dialed things in. They're people building their first or second pair, and lack the history that you and I can count on.

valueaudio

Just going by what Christina, the order taker at Dan's Comp told me. When the order arrives, I'll try to answer your question. It would be good to know.


Nigel - I agree with your philosophy, but I do have a budget on this particular set of wheels, proportional to the value and sensitivity of this particular bike to exacting equipment. I don't really want to spend around $80 on spokes alone between these two wheels. These are 'practice' wheels for me, both in building and functionality on a less critical bike, before I attempt a serious set. I've built wheels and did rebuilds before. About a half dozen total. They've all came out well, but it's been quite some time. I'd give myself an A- on my wheel truing skills. Just wanting to get my feet wet again with wheel building, and get a sense if these days it's still worth the effort instead of buying quality pre-built.

I'm nearly 59, and just getting back into cycling after a long bought with severe hip arthritis and a problematic hip replacement, and still feeling out my limits. Feeling grateful I seem to do well with road/fitness cycling now, as I can't usually walk with or without a cane for more than about an hour without a lot of pain. I did road, switched to mountain biking for about a dozen years, but I'm not ready for mountain now, and fitness cycling is now where I'm at.

If and when I feel I can make a significant enough upgrade to what's stock on the road bike, and not be too out-of-proportion to the value of the bike and the use I make of it, I'll be more interested in getting the parts I feel it deserves, rather than cutting corners such as not getting the best spokes for the build, even if the cost is 4x as much as I can get certain Sapims for. On the city bike, the parts chose should be just fine.