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question about measuring single speed hub

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question about measuring single speed hub

Old 06-28-08, 01:35 PM
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pax139
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question about measuring single speed hub

Hi all. I have read the forums and different websites about building wheels. I have figured out how to measure the front hub, but my rear one I am having difficulty with. I am using a single speed Gipiemme hub that is shown in the picture. For the OLD (over locknut distance) i am measuring from the end of the black bolt on the left to the end of the black bolt on the right. When I do that, I get 127mm, which seems correct. But then when I go and calculate the spoke length it comes to 315mm, which seems way too long.

So my question is, am I measuring the correct way or should the OLD be measured some other way. It seems wrong to measure from black bolt to black bolt since then the middle would not be in the center of the hub and this wheel will not be dished as it is going on a single speed. But the websites (such as http://sheldonbrown.com/rinard/spocalc.htm) seem to imply otherwise.

picture: http://picasaweb.google.com/pax139/B...16062569712370

Thanks

Last edited by pax139; 06-28-08 at 01:38 PM.
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Old 06-28-08, 01:58 PM
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bikemoner2k
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By black bolt you are referring to the black locknuts?
In that case you are measuring OLD correctly, but you probably want to change the spacing before you build it. You will probably want to space it to get a good chainline, and bring the hub body closer to the center.
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Old 06-28-08, 02:27 PM
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dabac
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Originally Posted by pax139 View Post
... For the OLD (over locknut distance) i am measuring from the end of the black bolt on the left to the end of the black bolt on the right.
Yeep, that's the way to do it

Originally Posted by pax139 View Post
... When I do that, I get 127mm, which seems correct.
Sounds close enough, old standard is supposed to be 126 mm.

Originally Posted by pax139 View Post
...But then when I go and calculate the spoke length it comes to 315mm, which seems way too long.
Can't rightly answer that w/o crunching the numbers for your hub, rim and intended lace.

Originally Posted by pax139 View Post
... It seems wrong to measure from black bolt to black bolt since then the middle would not be in the center of the hub and this wheel will not be dished as it is going on a single speed. But the websites (such as http://sheldonbrown.com/rinard/spocalc.htm) seem to imply otherwise.
You're measuring OLD right but maybe you're getting the left flange/right flange offset right. Flanges for a dished hub aren't symmetrically placed around the hub centerline. AFAIK spocalc pretty much assumes that you're using the hub for its intended usage, which in this case is with a chunky freewheel and significant dish.
Lucky for you spocalc allows you to tweak the numbers. My suggestion for you would be to stick a SS freewheel on the hub, swap some spacers (on the axle) around and figure out your chainline. After that you can determine YOUR left flange/right flange offset, add those numbers to spocalc and get some corrected spoke lengths out of it.
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