bikerbobbbb

If my spoke calculation gives me 291mm, but I can only buy 290 or 292mm, which way is better to go, too high or too low?

Or does it not really matter?


Too high would leave more jagged edge of the spoke sticking out, but I'll have a double-walled rim, so it's not a huge concern unless the spoke breaks. I could also probably file that edge down when it's sticking out of the nipple.

Too high also means I might run out of thread to pull the spoke in more.
- Is it possible to buy a spoke with more then 10mm thread on it? Or is 10mm plenty, even for being 1mm off?

Too short means the spoke end might still be in the threads of the nipple, not sticking out. Plenty of thread on the spoke left. Is that a concern if there's spoke lock lube on it?

I'm kind of leaning towards 1mm too short being better. Or it might not really matter for a 1mm difference either way.


Another possibility might be to take a 292mm spoke and file off 1mm, then rethread it if needed. But then I'd need a threading tool which is over $100.

sch

Makes no difference really with a double walled rim. On a rear wheel you could use both, with the shorter ones on the drive
side and longer ones on the non-drive side

See also: https://www.bikeforums.net/bicycle-me...confusion.html

Jiggle

I usually round down because the spokes I use will stretch about 1mm at full tension.

However, I have almost 5mm of extra nipple thread with the nipples I use, so it really doesn't matter. If my spoke lengths are within 4mm for the whole wheel, I just order one spoke length.

dabac

Well...
Do you know where in the nipple you're aiming for?
Bottom of screwdriver slot - 1 mm extra is fine.
slight risk of trouble with an 1.5 mm spoke on the DS.
Flush with nipple head - still likely to be fine for 2.0 and 1.8 spokes. Almost guaranteed trouble with 1.5 mm DS spokes.
OTOH If your aim is flush with nipple head, then -1 won't be a problem.
If a spoke is a little long its always possible to add a washer under the nipple or drill out a few turns of thread.

trailangel

Depends on the spoke manufacture. Have you actually measured the spokes?
Some run short and some run long.

andr0id

A spoke 1mm lower than the slot is much easier to deal with than an a spoke that protrudes into the slot if you ever need to use a screwdriver later down the road.

Bill Kapaun

On a double wall rim, I round up, since a "bit" long won't matter.

You have about 2mm more above the screw driver slot before running out of threads.
The NDS spoke will protrude less, but it also has less tension, so IF it's a TINY bit short, that's the side you want it on.

bikerbobbbb

Thanks.

"So if your objective is to have at least that protrusion, you would always round up. "


It's looking like it's not going to matter either way. Personal preference.

I'm leaning towards rounding up.

If the calcuations give me this....
290.8 NDS
289.4 DS
... then 290 and 292mm. That happens to be what I already bought for the 32 spoke wheel I'm on now. I did think the spokes for a 36 wheel would be slightly shorter. It's less of a difference than I thought, maybe 2mm (whatever it is, I don't care what the current wheel perfect spoke length is now since my current wheel is on death row).

I think a lot of my spokes already protrude just a little. That's been fine. For the inner tube getting punctured, I was thinking a spoke would have to go through the second rim (doubtful? but possible if it's all lined up) but then it also has to go through the rim tape. I imagine the most a broken spoke would do is tap on the rim tape. And then I shouldn't have any broken spokes if it's a wheel build with all new parts and everything is trued and dished.

That could give me the option of using a washer too if I really didn't like how it stuck out.

L134 

Do yourself a favor and get ONE of the several different wheel building guides that are out there and follow it step by step. You will wind up with a fine wheel.

Jiggle

The slotted nipples are so 1980. DT, Sapim, Pillar, and CN all make square drive or torx nipples that will work on all but the shallowest of rims. They will let you go about 4mm past the minimum, which is 8 turns, and are only limited when the unthreaded portion of the spoke bottoms out on the nipple threads.

Ronno6

Why not purchase from a source that will cut to order in 1mm increments??
Rounding to the next mm is seldom a problem.

Kimmo 

If using brass nipples, round down. If using ally, round up.

The two bad things you're trying to avoid are, being too short to make it through the head so the nipple doesn't break, and running out of thread.

A brass nipple is less likely to break if the spoke's a little short, and if you run out of thread in an ally nipple, you can just mash it for a thread or two, which will help them stay tight.

Drew Eckhardt 

The one which isn't so long it will bottom if the wheel has a low spot, and not so short it doesn't reach through the nipple head which leads to broken nipples. Consider both your current rims and examples of the same type with slightly larger or smaller ERD.

You're probably better off with longer spokes if you measured your rims, your calculator is aiming for the bottom of the nipple slot, and either you aren't using 1.5mm spokes or the calculator accounted for 1mm of stretch.

In that situation, 1mm extra means they'll end at the top of the nipple with 1.5mm of thread remaining before they bottom, and leave almost 2mm extra so you don't break nipples because they don't reach the head.

With a high spot in the rim (like at the joint), 1mm short of the slot can break nipples especially when they're made of alloy.

OTOH, with 1.5mm cross section drive side spokes you'll get about 1mm of stretch. If the calculator didn't account for that you'll only have 0.5mm before running out of threads drive side and front and would want to go 1mm shorter so with stretch they end at the slot bottom.

If you want to be spot on to accommodate variations in ERD or whatever, order your spokes in custom lengths for a small upcharge.

CerveloMad

I always go for the higher length spoke, then extend the thread if it starts to stiffen up with just the Cyclo rolling head I bought for GB£35 (Amazon Cyclo Rolling Head). I didn't buy the whole tool, as it isn't really needed for the amount of spokes I become involved with and it works a treat without it by holding the spoke in a vice with 2 thin wooden blocks. OK, you can call me a cheapskate if you like.........

mpetry912 

I agree. round up. Spokes that do not have full thread engagement in the nip will cause the nip to fracture. True, the brass ones are less fragile. but I round UP to the next MM.

and I measure ERD and spokes. Don't trust published measurements you found on the internets

/markp

ted_major

This looks like the best advice in the thread. I’ve used Roger Musson’s wheel building ebook and found it reasonably priced and easy to follow. (In fact, I’m just about to lace up a pair of wheels with a new dynamo hub this morning.)

FWIW, he recommends rounding to the nearest 1mm, which would round both your 289.4 and 290.8 to 290.

janthenat

Based on the discussion here I'm assuming it would be unreasonable to think I could use 290mm spokes based on the following 2-cross & 3-cross calculations? By the way, I'm using 12mm brass nipples.
Thanks for any input!


Front 2-cross

Rear 2-cross

Front 3-cross

Rear 3-cross

ThermionicScott 

^ I wouldn't use 290mm for any of those, you can do better.

janthenat

Yea, that's kind of what I suspected... dang. I did my original calculations using 28 spokes instead of 32, duh.

In that case does anybody have a box of 100 14g 286mm j-bend spokes to trade me for my 290mm's? ;^)

sweeks

Agree about Musson's book. I've used this one for several years, and it's very clear and easy to follow.

About "rounding to the nearest 1 mm"... 289.4 rounds to 289, and 290.8 rounds to 291.

ShannonM

True, but the parameters of the question rule out odd-numbered lengths, so "rounding to the nearest 1 mm" should be read as "rounding to the nearest even 1 mm," even though that phrase doesn't make literal sense.

This generalizes. The most common way to arrive at the wrong answer is to start from the wrong question.

--Shannon