Spoke sizing help

Oldie

1 mW
Joined
Aug 5, 2020
Messages
16
I am totally new to building wheels, i have never done one before but would love to give it a go.

I have trued and replaced a few spokes in the past and it worked great.

I have entered details onto two different spoke calculators and i get different results, i am sure i am entering some information wrong.

If someone can please take a look and let me know whrre i am going wrong i would really appreciate it.

Attached are the screenshots of both calculators and my motors dimensions.

The rim has an ERD of 603.4
 

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Throw away that manufacture's hub drawing and hand measure your hub.
Enter the dimensions into this calculator (as seen on the right side of the page) and see what comes up.
To arrive at the most accurate dimensions I place a straight edge on the axle lock nut to measure the flange offsets.

https://www.prowheelbuilder.com/spokelengthcalculator
 
Bafang's published data are good, as long as you're looking at the right model.

You put the wrong numbers into "flange offset" into the non-Grin calculator. The correct ones are 26.85mm left, 15.65mm right.

The dishing offset must be put in as a negative number to get you the direction that applies to your hub. I think that's why most spoke calculators use "center to left flange" and "center to right flange" values; it's less ambiguous.

Also, the hole diameter of that hub is more like 3.2mm.

Use the Grin calculator, set the dishing offset to -5.6mm, set the left side elbows "in" and right side elbows "out". Like this:
Screenshot_20220808-111442.png

When I put in all your values, I get 234.4mm left and 234.0mm right. So I would get all 235mm 14ga spokes, with 2.0mm stainless washers to keep the heads from pulling through those oversized holes. It's possible to find that length in 14-15ga double butted, at least in 236mm. A 700c rim with 603mm ERD will be deep enough to allow the spokes to poke through the nipples a little without any complications.
 
I used the grin video to measure my hub. I did it as best as i could.

I got the following figures when i entered it into the grin spoke calculator See picture below

However on the other calculator as Chalo pointed out my figures were wrong so when i entered the figures he gave, the spokes from both calculators were similar.

I had actually marked down that i was going to order 235mm spokes so now this confirms it.

Chalo - I really appreciate the time you have taken to explain and work out what spoke sizes i needed.
 

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Whilst i wait for my spokes to arrive i have a question regarding the build.

The rim that i have has every other hole closer to one side. One hole is closer to the right and then the next hole is closer to the left. I think its about 1mm off the tp of my head. The rim is a Mavic A319

With the wheel flat on the ground with the vavle hole at the 12 o clock position. Assuming the first spoke hole clockwise of the valve is closer to the ground, would this spoke be from the drive side of the hub?

I hope that makes sense.
 
Oldie said:
The rim that i have has every other hole closer to one side. One hole is closer to the right and then the next hole is closer to the left. I think its about 1mm off the tp of my head. The rim is a Mavic A319

With the wheel flat on the ground with the vavle hole at the 12 o clock position. Assuming the first spoke hole clockwise of the valve is closer to the ground, would this spoke be from the drive side of the hub?

When the stagger in the rim holes is small like that, the main concern isn't stagger but rather the tilt that most rims have in their drilling. In the vast majority of cases, the holes will tilt in the same direction that they stagger (if they tilt).

But as to your question, consider that if you flip the rim over, the hole to the right of the valve will still be on the far side of the rim. So there's no distinction between drive and non-drive side there.

In the situation you describe, the first spoke clockwise from the valve will lace to the far side of the hub, and the spoke just anti-clockwise from the valve will lace to the near side of the hub. Flip the wheel over and it will still be that way. But this is conditional on the rim's "handedness" or chirality. Most are made with the far spoke clockwise from the valve, but not all. Some have the opposite handedness, and some have centered, untilted holes that lace equally well either way.
 
What gadgets spokes are you going to use ? What size holes in the motor ? On my d.d. builds I use brass washers under the spokes heads and I only broken one spoke over 2 years.
Plus I used a #10 can the hold the motor on a table and supported the rim. What's Chalo secrets
 
I'm building my first wheel too. I thought the 12G spokes we're stronger? It's damn hard to find the correct size 12G. What about butted spokes or double butted? Damn the washers, the sounds annoying. Why is chalo always saying the 12G are weaker? I put 6000 km on my hub motor and never had spoke issues. My rim did fail but that's because I brake super hard and am psycho with my stuff.
 
MarkJohnston said:
I'm building my first wheel too. I thought the 12G spokes we're stronger? It's damn hard to find the correct size 12G. What about butted spokes or double butted? Damn the washers, the sounds annoying. Why is chalo always saying the 12G are weaker? I put 6000 km on my hub motor and never had spoke issues. My rim did fail but that's because I brake super hard and am psycho with my stuff.

Remember that spokes like these don't "hold up the wheel" like columns, or like a solid-spoked cast wheel. They act as tensioned "cables" something like a suspension bridge, and if they aren't tensioned sufficiently they won't support the rim correctly. A simplified way of looking at it is that they don't push the hub up from the rim down at the bottom of the wheel, they pull up the hub from the rim at the top of the wheel, essentially hanging the bike from the top of the rims (as I said, simplified ;) ).

Thicker spokes are only stronger if your rim and spoke flange on the hub are both designed to use them, and can take the forces from the spokes when they are tensioned correcttly.

Spokes that are thicker than the rim can support can cause rim damage when tensioned correctly. The nipple is pulled by the spoke so hard that it deforms or even cracks the rim around the nipple hole. This then lets the nipple turn and loosen the spoke, until the nipple falls off inside the rim and the spoke hangs loose (or enough spokes loosen for the wheel to come apart, or for less loose spokes in one section of rim they can then poke holes in the tube).

If you glue the nipples to the spokes so they can't turn, they won't fall off, but the spokes are still loose because the rim is damaged / deformed at the nipple hole from the overtension.

If the spokes are not tightened enough to deform the rim (but require this tension to operate correctly) then they will not support the wheel, and the same problems arise as if they were tight enough and damaged the rim and became loose instead.

Loose spokes may also bend repeatedly at the elbow, and break there, next to the spoke flange of the hub.


If the rim can handle the higher tension but the spoke flange can't, the flange may shear off the hub, or rip chunks out around the elbow holes.



Using the right spokes for the rim and spoke flange prevents these problems and makes a stronger wheel. Usually the right spokes are thinner rather than thicker. 14-15g butted or double-butted spokes would be a good choice for most typical ebike wheel builds. Thinner might work even better, depending on usage and specific rim/hub being used.

Butted just means that the end (elbow) is thicker, double-butted means both ends are thicker. This can be done to fit a specific hole size in a flange (or nipple) but still use thinner long part of the spoke so it tensions correctly.

If you find a well-built wheel with thinner spokes is failing from a very heavy load (hundreds to thousands of pounds), you would need to use heavier duty rims and hubs designed for the thicker spokes in order to use the thicker spokes without wheel failures.

But before moving to heavier duty wheels, looking at the specific failure mode would be good, to see what is breaking and why, to make sure the right fix is applied.
 
MarkJohnston said:
Why is chalo always saying the 12G are weaker?

Thick spokes aren't weaker than thin ones, but they make weaker, less reliable wheels.

The strength of the wheel is in the rim. Spokes are supportive, and to do a good job of that they have to be a little bit stretchy. The thicker the spoke, the less stretchy it is and the less supportive it is to the rim.

It's a mistake to use chonky spokes because it's "easier". It's not. Tightening and truing is easier when you use 14 or 15ga spokes with 3.2mm nipples, because it takes less tool torque to get them tight and because the spoke keys in that size are so much better than those for fatter spokes. That more than offsets the extra work of adding a washer to each spoke when lacing the wheel.
 
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