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28h hub on 20h 0r 24h rim. At all possible?

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28h hub on 20h 0r 24h rim. At all possible?

Old 07-07-13, 09:29 PM
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Estuche
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28h hub on 20h 0r 24h rim. At all possible?

Hi,
I want to lace a 28h Brompton hub to a 20h or 24h super lightweight rim I found. I only have those two hole options for the rim, and the hub is proprietary so no alternative there either. Can I match these together or should I start looking for different rims?

Thanks!
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Old 07-07-13, 09:42 PM
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It is possible Im no help in the math so good luck//

and the hub is proprietary so no alternative there either
pray tell how ?
and Why do you feel so attached to it that you consider this effort worth it , vs just tossing it in a bin
and doing something else with your time?
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Old 07-07-13, 09:55 PM
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Estuche
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Oh this is a very special project so if possible I would like to make it happen What I mean by proprietary is that the hub's OLD is 112-113mm, which is difficult to substitute with anything else that is not heavier!
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Old 07-08-13, 03:55 AM
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I've looked briefly at the math and can't come up with anything that isn't a right PITA to lace. For 28/24 you'd need to use 6 out of 7 holes, for 28/20 you'd use 5 out of 7 holes.
Can't find a way to make the rim spacing match up symmetrically to the hub spacing. (as far as I can see) Any cross pattern would have the spoke angles at a systematic biased angle, and not symmetrical.
It's doable, you can do a 2X to a 24H rim simply leaving every 7th hole empty hole in the flange but you end up needing a lot of different spoke lengths.

It'd eat up a bit of the weight savings, but I'd seriously consider cutting a set of adapter flanges, just a circular band maybe 15-20 mm wide that screws on to the hub flange and can be drilled in any configuration.
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Old 07-08-13, 09:51 AM
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To go with that 28 hole hub, Why not look for a 28 hole rim, grasshopper.. ?

"112-113mm" you talking rear hub then?

narrower than my Brompton rear hub..
Front is 74mm

most fronts are 100mm

Last edited by fietsbob; 07-08-13 at 09:54 AM.
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Old 07-08-13, 10:55 PM
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Thank you all for your insightful responses! It does sound like it would be a PITA... I think I might be able to use the rim with the front hub instead. Any chance that a 16h hub can be laced to a 24h rim?Many thanks!
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Old 07-09-13, 08:22 AM
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Originally Posted by Estuche View Post
Thank you all for your insightful responses! It does sound like it would be a PITA... I think I might be able to use the rim with the front hub instead. Any chance that a 16h hub can be laced to a 24h rim?Many thanks!
If the rim is really stiff, maybe. I tried lacing a 24h rim w/20h hub once, and as I brought up the tension I found I was building a square. (skipped 4 holes, one at each "corner" of the rim)
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Old 07-09-13, 09:18 AM
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You'll need a working knowlege of trigonometry and as many as 12 different spoke lengths for the 24 hole rim. It's a fun project. I built a 36 hole rim onto a 40 hole hub once. Try to keep twisting force off the hub, from the fact that the holes on the opposite flange are offset by 1/56 circumference on the hub and the rim wants 1/48 circumference offset...
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