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Getting Started with a Wheel Build, Have some Questions.

Old 11-21-13, 04:24 PM
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North Coast Joe
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Getting Started with a Wheel Build, Have some Questions.

Thanks for taking a look at this post. I'm planning to build a rear fixed gear wheel as a back-up to the IGH that's on the bike currently.

I've received the hub and have it's dimensions listed later in the post. I'm trying to figure the spoke length I'll need using the wheelpro.co.uk calculator as linked in the Sheldon Brown links in the stickies above this forum.

Is the "ERD" that they are looking for in the calculator the rim ISO diameter (in this case 590 for my 26 x 1 3/8 rim)? Or do I need to have the rim physically available for some other measurement? (it's in transit)

With the flange hole diameter (A & B on the calculator) at 47.625mm, and the hub distances (C & D on the calculator) at 24.606mm, 0 degrees offset on a cross three pattern, I get a spoke length of 284mm. Would you mind taking a look to see if you agree? Thanks! Sure would like to order spokes soon.
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Old 11-21-13, 04:37 PM
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The ERD is NOT the same as the ISO diameter and will vary with the rim's depth, nipple seat location, etc. Using just the ISO rim size will give you a wildly wrong spoke length. If the rim manufactures doesn't provide the ERD dimension, there are ways of measuring it. Do a Google search for "Bike rim ERD measurement" and you should find the method.
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Old 11-21-13, 04:52 PM
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Go to the Sheldon Brown site and down load the spoke calc. program.
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Old 11-21-13, 04:54 PM
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Thanks HR! Doesn't look too hard to get the measurement according to the directions I found; I'll need wait the rim to arrive. Thanks for saving me from wasting money on a set of wrong length spokes!!
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Old 11-21-13, 04:55 PM
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Although many recommend that you measure ERD yourself, maybe if you post WHAT rim you are using, someone may have recently built a wheel using it and can tell you what worked for them.
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Old 11-21-13, 05:13 PM
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Originally Posted by Bill Kapaun View Post
Although many recommend that you measure ERD yourself, maybe if you post WHAT rim you are using, someone may have recently built a wheel using it and can tell you what worked for them.
Thanks, Bill. I've acquired a Sun CR18 rim in the ISO 590 size. I've searched the Sun Ringle website and they have the ERD's for all the other sizes, just not mine.
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Old 11-21-13, 05:15 PM
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R'off showed a simple ERD measurement ,
2 spokes screwed in to the rim and to the nip to the bottom of the slot. like when up to tension.

On opposite sides of the rim.. then you measure the distance between them ,
2 spoke lengths and the gap between them.. [vernier caliper in the hooks] sum of all 3 is close.
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Old 11-21-13, 05:41 PM
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As others, just stick the details of what you have in a spoke length calculator, I prefer http://leonard.io/edd/ as you can just enter the name of the parts and if a common item, it will have the data already stored, if you use spokecalc it will give you the same results with a little more work
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Old 11-21-13, 06:08 PM
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I've built a couple CR-18's in both 622 & 630. In both cases, subtracting 10mm from ISO worked to get the ERD.
However, I use spocalc and round up a bit to get my desired result.

You didn't specify how many holes!
ASSuming 36 holes, I'd use-
281mm or 2nd choice, 280mm

ASSuming 32 spoke-
284mm or 283 2nd choice (very close 2nd choice)

That's ASSuming a 2.4mm hole diameter in the hub.

With a double wall rim, an extra mm long won't hurt, since you don't have to worry about a spoke protruding past the nipple head and poking a tube.
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Old 11-21-13, 06:38 PM
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North Coast Joe
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Originally Posted by Bill Kapaun View Post
I've built a couple CR-18's in both 622 & 630. In both cases, subtracting 10mm from ISO worked to get the ERD.
However, I use spocalc and round up a bit to get my desired result.

You didn't specify how many holes!
ASSuming 36 holes, I'd use-
281mm or 2nd choice, 280mm.
Duh! Sorry, Bill and others....it's a 36 hole set up.

Thanks, since there's too many ASSumptions without it, I'll wait to get the rim in hand before ordering. I will, however, compare the figures from the actual measurement to the results for the ISO minus 10mm just for the fun of it. I've also requested the info via email from Sun Ringle to compare as well. Thanks folks!!
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Old 11-22-13, 07:23 AM
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Suggest you download Roger Musson's "Professional Guide to Wheel Building" book. It explains all very clearly and provides a wealth of info and legit explanations as to the whys and wherefores of wheel building.
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