nerobro

First, the relevant information.

Rims: 615mm ERD. Sun Vista Cruiser
Front Hub: 100mm, 72mm across the flanges, so 14mm from axle face to flange face. 38mm spoke hole circle.
Rear Hub: 130mm, 57.3mm across the flanges. 50mm drive side, 30mm from the non drive side axle face. 49mm spoke hole circle.

Well, I know there's calculators out there, and I've used them. and well... here's the story.

I bought novatec hubs, and some Sun Vista Cruiser rims.

when I first measured the vista cruier rims I got a ERD of 603mm. .... and I got that answer a couple of times. I ordered spokes based on this. Which means I ordered 3/4 of my spokes 278mm, and 1/4 of them 280mm.

None of those spokes even vaguely come close to working on this combination of parts.

So, I put in my new ERD measurement, and got new spoke length measurements. 285mm for the front wheel, and 284/286mm for the rear wheel. I feer another 14mm of spoke length might not be enough.

Could someone check my work? :-) Please?

nerobro

Oh yeah, i'm doing the wheels 3 cross.

FBinNY 

I didn't run your calculations, but one thing jumped out at me. Generally left rear and front spokes are similar in length, with right rear shorter, yet you bought 3/4 short and 1/4 long.

So I reread the post and found another oddity. You measured locknut to flange distance, but did you forget to subtract it from half the overall width to get center to flange distance, which is what you need to know for a spoke length calculation?

If not that is probably where you made a left turn into the dead end street.

BTW- the front c2f distance is easy it's 1/2 the flange separation, and you can check the rear c2f numbers because they have to add to the flange separation.

mrrabbit 

1. Sun's publication of ERD if too often off - too long in most cases. Have the rim measured such that the ERD is one where you are aiming for the screwdriver flat of the nipple. This is the most critical measurement!

2. You hub flange-center to axle-end measures are way off. Have 'em measured by someone who knows how.

On most front hubs the flange offset is in the 32 -36mm ballpark.

On most rear 130mm hubs the flange offsets are usually 36mm/17mm, 36mm/19mm...

Are you sure you measured the flange hole-hole diameter correctly on the rear hub? 49mm is pretty rare. Usually we see 44, 45, 48, and 52. Double-check just to be sure.

=8-)

https://www.mrrabbit.net/wheelsbyflemingapplications.php

Scroll down and download the spreadsheet...take a peek.

=8-)

3alarmer 

While I would love to clear up your confusion, it appears
to be in the measuring process, thus uncheckable from
a distance. The recommendation to have your hubs
measured by someone who knows what they're doing
is sound if you can find someone. If you cannot,
look here:

https://www.wheelpro.co.uk/spokecalc/hubmeasure.pdf

The comment about not being able to trust manufacturer's
data on ERD is true in my experience, too. So look around
on wheelpro for his handy ERD measuring device made from
two spokes and nipples. You will eventually get this, just
takes some time.

Best,
Mike Larmer

FBinNY 

The OPs problem isn't one of minor inaccuracy in ERD data from sites.

It's that he's using the flange to locknut distance, in lieu of the center to flange distance.

It doesn't matter how precisely you measure something if you're measuring the wrong thing entirely. Doh!!!!

To the OP, take a few minutes to reread the instructions in whatever spoke calculator you're using. There may be minor errors and you may end up off a millimeter or two, but at least you'll be in the ballpark, and not outside in the parking lot.

hybridbkrdr

Uh, let's suppose I did use a spoke calculator and it looks like I need 288mm and 286mm for a rear wheel. Do you think I need to order the spokes shorter? What if I wanted to order just a few spokes just to try them out. What's the minimum number of spokes I could buy to see if they're the right size?

3alarmer 

Nice troll.

3alarmer 

FBinNY:

Really no need to shout, bubba, but I do have
some familiarity with NY conversational styles
from summers in Coney Island as a kid, so if
that's what ya gotta do, that's what ya gotta do.

Regards,
Mike

matilda5

my solution ..as of Yesterday on my wrong buy was : 3x drive side and 3x crows foot non drive side.
2x on the non drive side ended up too long by 5mm rather than short by 5mm. Dishing meant drive side length was exceptable but not perfect.

Central radialspokes for crows foot had to be secured elswhere.

hybridbkrdr

What are you talking about? That I'm interrupting the thread? Or my question doesn't look legit?

Fact is, he said you cannot rely on the manufacturer's ERD. So, my question is, if you cannot rely on that, then could you order let's say 9 spokes for example (if shipping cost was cheap enough) just to verify the correct length THEN make a full order of spokes.

FBinNY 

Usually you'd be right there, but I'm not sure in this case.

I rarely resort to bold and oversize type even though I'm from NY, but all the posts are talking about differences in ERD measurements, and other subtleties, which mike a difference of a millimeter or two, and seem to be missing the point that the OP is getting errors of over 10mm because he is not measuring the center to flange distance properly.

It doesn't matter how he measures, or what references he uses if he doesn't measure the right thing. It's a classic case of garbage in garbage out. If the OP doesn't grasp the fundamentals and realize that center to flange distance is not flange to locknut difference, what other errors is he committing? And if he's a mile off what difference is a difference of 2 millimeters going to make?

To the OP, I say again, spend some more time learning about the process, re-read the instructions, and know what you're doing before worrying about a millimeter here and there.

FBinNY 

There's your problem. I highlighted the error. You don't enter the outside distance-flange to axle, but the inside distance - flange to centerline.

I stopped there because, if you don't get that right, nothing else matters.

nerobro

Well there's my problem. I was measuring from flange to axle face, not center to flange ;-) THAT, is easy to fix. And it explains why my front and rear spoke lengths were so freaking close to each other despite the taller flanges.

Thank you everybody. :-) Time to recalculate.

Oh yeah, I have been measuring everything myself... I've learned over the years that trusting published measurement data can be.. erm.. problematic? As noted earlier suns published data is off.

FBinNY 

I don't want to hurt your feelings, but the nature of your error shows that you lack a basic understanding of the spoke calculation process. Take some time and read various tutorials and get a feeling for the basic principles involved rather than blindly following a "do this do that" process. If you continue inputting numbers without understanding what they mean you'll continue to be vulnerable to this kind of data error.

mrrabbit 

KISS

1. Measure center-of-hole to center-of-hole for flange diameter.

2. Standard Front: Measure center-of-flange to center-of-flange divided by 2. That's front offset.

3. Rear: 130mm / 2 = 60mm. Measure center-flange-left to left axle nut end. Measure center-of-flange-right to right axle nut end. Subtract each from 60mm. Results are your left and right offsets.

Get those numbers down right...FBinNY will stop using caps. I'll stop picking on you.

FBinNY 

And people wonder why I end up using caps. er, Bold.

BTW- if you didn't see it, half of 130mm is 65mm

nerobro

You're making some assumptions, which I understand, but slow your roll a bit. Believe it or not, I do know my trig!

I did take my time, and I read the various tutorials, specially I spent some real time on sheldonbrown to sort this out.

I got the inputs to the DT calc wrong. Whoops. I came here to find out where I went wrong. My mistake really coems down to a basic misunderstanding of the inputs the DT calc wanted, not a misunderstanding of what is necessary to calculate the hypotenuse of a triangle!

If I had just gone and done all the math raw, on my own, I wouldn't have had this trouble. Shame on me for trying to use a calculator, and thinking I had the inputs it wanted correct.

FBinNY 

I wasn't trying to put you down nor was talking about calculating a trig equation. You're missing my point. You were very clear in saying you were inputting the outside flange to axle distance, but alarm bells should have been going in your head off because it should have been obvious to you that this was irrelevant to the calculation.

I wasn't saying you couldn't build a wheel, but suggesting you conceptualize it better in your head, so regardless of the method you used, you'd have a sense of where things were before going forward.

BTW- I'm from the measure twice, cut once school of carpentry, so it isn't personal but a philosophical issue.

nerobro

Oh, the alarm bells DID go off. Now what should have really gotten me was that it didn't ask for axle length.

I asked a few people other places if I was doing it right. I never got a solid answer. And what it's asking for on the calculator isn't all that descriptive. And at some point I decided "hell with it, other people got the right answer, I'm gonna give this a go."

I have lots of precision measuring equipment just for the reason you have ""One measurement is worth one thousand opinions", unknown" In your signature. However, making good measurements means jack if you do it from the wrong point. ;-) and that's the ONLY thing I got wrong here.

We could also look at it this way. In learning my way around bicycles, I've only cost myself $150 or so. (I bought the wrong seat post. The wrong sort of stem. I bought a bad bottom bracket. I bought shifters I didn't like) Not bad all told.

nerobro

Amusingly, the difference in calculated spoke lengths isn't that great. with the proper ERD, and measuring from hub centerline...

I get 300mm both sides up front, and 299/297 out back.

I suppose it's time to list a whole bunch of spokes on ebay ;-)

hybridbkrdr

lol, I find it hilarious people are ignoring my post. Anyway...

EDIT: Does anyone believe you can file spokes to get them shorter if you order them too long? (not that anyone will ever see this message, hehe)

mrrabbit 

Doh! You got me!

65mm

=8-)

blamp28

No

mrrabbit 

Filing doesn't solve the "too long problem". It doesn't change where the threads end. If the nipple has already stopped...you are out of threads period. Filing won't fix that. It only solves the "underside tube puncture problem."

Furthermore, if you are going to go through the hassle and extra shiping expense to test buy spokes...

...then you might as well buy all one length and head to the local LBS that has a spoke machine.

=8-)