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Old 08-20-07, 07:17 PM   #1
BugsInMyTeeth
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1 mm Difference for left/right spoke.. Is it necessary?

Fellas..

Yet another spoke thread. Sorry.

I've worked out my wheel to require 263 mm right, 264 mm left.

Do I really need 2 different lengths? Will 1 mm really make a huge difference?

I'm going to be using DT Swiss Alpine IIIs, and my problem is that I need to buy these spokes by the box. The LBS doesn't stock these, and won't split the box(es) for me. I'm ok with buying 1, but 2 may be a little much.




In case anyone needs to know.

Hub: Shimano fh-m475
wL = 34.5
wR = 20.5
flange diameter (center-to-center of opposing spoke holes) = 60 mm (left/right flange the same)
Spoke hole diameter = 2.7 mm
3 cross pattern


Rim: Rhyno Lite
ERD = 548



I've asked this question before, and have had 2 replies, both conflicting.

Please let me know. I'm about to make the spoke purchase, and I'm sweating a little.
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Old 08-20-07, 07:20 PM   #2
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Quote:
Originally Posted by BugsInMyTeeth View Post
I've worked out my wheel to require 263 mm right, 264 mm left.

Do I really need 2 different lengths? Will 1 mm really make a huge difference?

I'm going to be using DT Swiss Alpine IIIs, and my problem is that I need to buy these spokes by the box. The LBS doesn't stock these, and won't split the box(es) for me. I'm ok with buying 1, but 2 may be a little much.
I've seen machine built wheels done with the same length spokes. It can be done as long as you opt for the longer spokes so that the thread is buried on both sides.

Having said that, I would never do it as a hand builder. Just...can't...do...it...
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Old 08-20-07, 07:27 PM   #3
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Might sound silly.. but couldn't you just cut/file/grind off 1 mm if that was the case? (without ruing the thread of course).
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Old 08-20-07, 07:32 PM   #4
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Providing your Calc is correct (I didn't check) You should be able to do it. If it's just 1mm then you can use longer nipples on one side to help with the lack of difference in spoke length. or you can use the longer ones, but run the risk of spoke sticking out the top of the nipples, (but there's usually some play there, so it shouldn't be an issue), but a good rim tape should help there if it's just a tiny bit.

or you can go short on the one side, and just make sure you use aluminum nipples, because when they strip you won't want to replace the spoke. The nipples are easier to replace, and cheaper.
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Old 08-20-07, 09:07 PM   #5
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I built a wheel recently that the spokes came out to something like 290 on one side, and 292 on the other. I went with 291 all around and it worked out fine. Perfect in fact. I had been a bit skeptical at first, but my old LBS told me it wouldn't be a problem at all...they were right.

I'd go short on one side...but I would not use Al nipples. Use brass, don't strip or overtighten, and know that depending on how tight your calculator did the math, you may have an exposed thread or two on each spoke on the "shorted" side. No big deal.

A neat "feature" of Al nipples is that they tend to round off at the same pressure as proper tension for the spoke. That, at least, has been my very limited experience. Other wheelbuilders have echoed those sentiments though.
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Old 08-20-07, 10:23 PM   #6
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I ran your numbers through the DT Spoke Calculator http://www.dtswiss.com/spokescalc/Calculator.aspx and another calculator and came up with 263.4 for the right and 264.9 for the left, or rounded to 263 and 265. I think 264 all around would probably work.

In my experience, which is admittedly only about 4 wheelsets, 1mm, or even 2mm shorter than calculated is no big deal. However if the spoke is too long by just a mm or so, you really won't be able to tell until the end of tensioning and truing when the threads bottom out, and you have to take them all out and start over. My first (planned) radial spoked front wheel ended up as a single crossed wheel because of rounding up! So, I would err for a shorter spoke. Good luck.
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Old 08-20-07, 10:38 PM   #7
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Most of the rear wheel calculations I've done, and the rear wheel I built had a 2mm difference (drive side was 2mm shorter).

Others have mentioned, but at a higher tension (which you should aim towards), you risk threading past the top of the nipple. That may actually interfere with rim tape in some extreme cases. More practically it'd make it impossible to drive the nipple from inside the rim - which is handy if you ever round a nipple etc.
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Old 08-20-07, 11:20 PM   #8
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As already mentioned, I also would go with shorter of 2 lengths, provided you can get them in that length. Sometimes the distributor/seller skips a mm to cut stock in half.

Also, I recommend you actually measure the ERD on the rims you intend to use rather than relying on published date. Sometimes the SpoCalc data is incorrect, and you end up with wrong size spokes.
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Old 08-21-07, 04:58 AM   #9
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Thanks guys. In fact, I haven't properly measured the ERD, but I will before making the final purchase. I just wanted to get this 1 mm difference notion straight in my head.

I've read a few different techniques for measuring the ERD. But the bottom line is you want to measure the diameter of the rim, starting at where, theoretically, the spokes threads would end (inside the nipple), just a little before entering the body of the rim?

Sorry for the noobness.. but I come by it honestly.

What I was going to do was get two of the longest spokes I could buy, snip off the elbow, measure the long spoke/nipple combo, crank on the nipples, drop them into opposing holes, measure the overlap, and subtract from the length of 2*longSpoke.

What I'm not sure of is, do you include ALL of the nipple in the measurement?
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Old 08-21-07, 05:41 PM   #10
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Grrr.

So I bought some long-@ss spokes (to measure the ERD), and tried my best to measure the ERD for real. I took at least 6 samples throughout the rim.. assuring that I was properly opposed (15 empty holes between measurement spokes).

Turns out, if I'm doing this right...my ERD is 551 mm. Larger than any of the values on the spoke calc databases. (Damon Rinard has the Rhyno lite at 448, DT Swiss calc has it at 550).

So, bottom line.. I'm rounding down to 265 mm for both left and right.

If I'm wrong, I'm done.. and I'm saving up for some Aerospokes.

Thanks for the input fellas...
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Old 08-21-07, 10:43 PM   #11
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http://www.damonrinard.com/spocalc.htm#MeasureHubAndRim
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