What is the correct length(s) to order? Spokes are expensive and, generally, not returnable.

I ran Spocalc and the DT calulator with the following results for four cross lacing:

DT
front hub - 301 mm
rear hub, right side - 299 mm
rear hub, left side - 301 mm

Spocalc
front hub - 299.5 mm
rear hub, left side - 299.8 mm
rear hub, right side - 298.8 mm

Rims - Velo-Orange PBP 700c rims (606 ERD per VO web site)

Hubs - Campagnolo Record, high flange, 36 hole, 100 mm front and 120 mm rear* widths.

* The rear hub is actually a 126 mm width. I believe a spacer can be removed and the axle can be replaced (or possibly shortened) to get down to a 120 mm spacing. Other than that, I believe the hub is interchangeable with the 120 mm hub. Is this correct?

One or two mm won't make a difference, so I usually order on the low side. Given those calcs, I'd say 300mm for the front and 299mm rear. The width of your axle doesn't matter to the rim or the wheelbuild; it's the width of the hub (flange to flange) that's critical (in other words, there's no such things as "120mm rims," only hubs).

Neal

I can't be much help, but I checked spocalc and got the same results for 4 cross spokes. Is that what you intended?

FWIW, all those lengths are close to 300mm and 301mm. The actual size you can get might be limited.

You could just let your LBS build the wheels and let them size the spokes.

Of course, you are correct. It was a typo. I corrected my post to say 120 mm hubs.

Yes, I updated the post to show I meant four-cross lacing.

I thought it would be fun to lace a set of wheels. I haven't done it in so long, it might be fun. If it doesn't work out, although I'm not sure why it wouldn't, I can always disassemble the things and drop them (and some cash) off at the local bike shop and let them do it.

The 120 mm and 126 mm hubs are the same. It's the freewheel that gets wider to require the wider axle, not the hub. There is easily 2 mm of room for error in the lengths of the spokes needed but it's better to have to stretch a bit than to bottom out, so order on the short side if you have a choice. See who will sell you 299 mm or 300 mm spokes and buy either one of those.

While it is important to have the correct length spokes the required precision is often overestimated. You can be 2 mm off from the ideal length and be just fine. But if you're 5 mm or more off there's going to be a problem.

I've read recommendations that you that the results from spocalc and round down to the next smaller size. Sheldon Brown recommended rounding up. I guess it's not that precise.

Be sure to let us know how these turn out. I have a set of old Lambert hubs which were the same dimension as Campy Hi-Flanges. I plan to build these up with wide, strong rims as an alternative for the tubulars and Mavic Open Pro wheels I have now.

So, if I purchased all the spokes at 300 mm length I should be okay, correct? Are there any experienced wheelbuilders out there who can comment on this selection?

I'm purely an amateur as far a wheelbuilding goes, having built up maybe a half-dozen over the past few years. FWIW, though, I find Spocalc to be a rough guide at best. It gets you in the ballpark, yes, but in more often than not I've ended up going up or down from their number to get it to work. The wheel I'm doing final truing on now, for example, was supposed to use 308 mm spokes, according to Spocalc. (It's a four-cross on a 27 inch rim). But they were too long--I ran out of threading and had spoke sticking through the tops of the nipples before I got up to the required tension. Unlaced the wheel and relaced with 305s, which I fortunately had on hand and was in business.
I don't know, in my experience your chances of nailing the right spoke length on the first try are not great. Maybe others have not had that experience, but it's what I've found. The only good thing about it is that eventually you end of with a stash of not-quite-right spokes that might turn out to be just what you need for the next project.

I use the UBI site's calculator, it's always be spot on for me:
https://www.bikeschool.com/spokes/index.cgi

It requires flange diameter and center to flange in addition to the regular info.

I get ~300mm for the rear wheel if the hub flange is 40mm and center to flange is 25mm. I get 301 in the front with 25mm flange diameter and 25mm center to flange. If you make more accurate measurements you may get better results.

I used the inputs from Spocalc and ran the UBI calculator. I got results that exactly matched those from Spocalc - 299.8, 299.7 and 298.8 mm of rthe front, left rear and right rear, respectively.

I suppose I should spend some time measuring my actual hub dimensions to make sure those inputs are correct, although they are a fairly well known commodity. I got the ERD from the VeloOrange web site. GIGO!

I was using these inputs:

FRONT
ERD = 606 mm
OSB = 0
WL = 34.0
WR = 34.0
dL = 67.0
dR = 67.0
S = 2.3
X = 4

REAR
ERD = 606 mm
OSB = 0
WL = 33.0
WR = 24.0
dL = 67.0
dR = 67.0
S = 2.3
X = 4

In my experience (a couple of dozen wheels) spocalc tends to be on the high side, often about 2mm high. Or maybe I just don't measure ERD very well. But I think you could go with 298mm all the way around. And did you say you're lacing the front 4x? If so, why?

Neal

My guess is that both the Spocalc and UBI calculators use the same equations.

The Hi-Flange Campy hubs are well known. BTW, I measured my Lambert hubs and they have the same dimensions as spocalc lists for the Campy Hi-Flange. Not too surprising, I guess.

Because that's the way we used to do it back in the old days.

Thanks for the info.

Heck, the 1935 Raleigh Record Ace had a radial-laced front wheel, so why not go with that?!

Neal