Reusing DA 7850 straight pull hub

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athos
Posts: 43
Joined: Fri Apr 11, 2008 8:40 pm

by athos

I have a DA 7850 straight pull rear hub from a broken c50 wheel. The hub is fine and I would like to use it again. Some questions:

1. Is the hub is compatible with standard (DT or Sapim for example) straight pull spokes? I think it is but I'm not 100% sure.

2. How do I calculate the correct spoke length? Any pointers on how to do this? I read the post from ergott to 'reverse engineer' this by checking the old spokes and old rim ERD. (viewtopic.php?f=3&t=89693#p774717) Is this the best way?

3. What (cheap?) rim would be strong enough to accommodate a 70 kg rider on a 20 spoke rear wheel?
An option I found is this: http://www.cnc-bike.de/product_info.php ... ts_id=9694
The seller told me that is it suitable for a 70kg rider and that it isn't a H Son Plus SL42 (I thought it might be)

Thanks!

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Zen Cyclery
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by Zen Cyclery

These aren't standard spokes that you could simply replace with a DT or Sapim. You will have to rebuild with Shimano rims/spokes seeing as the nipples thread into that rim, instead of the traditional style where the nipples thread into the spoke.

by Weenie


jooo
Posts: 1504
Joined: Wed Feb 02, 2011 3:48 am

by jooo

@Zen Cyclery - Nope, you're probably thinking 7800/1 or the 7850 C24's (except for the full carbon tubular).

@athos - 7850 C50 use normal spokes so there are no issue reusing the hub with another rim. The 'blade' dimensions are the same as CX-Ray (pretty sure I remember reading somewhere they were even made by Sapim). ergott's method for finding the spoke length sounds good provided you've still got the original rim :thumbup: The original spoke length is 278mm according to Shimano tech docs.

Are you trying to find a replacement rim to match the height/appearance of the Shimano front, or will anything do provided it's strong enough for you?

athos
Posts: 43
Joined: Fri Apr 11, 2008 8:40 pm

by athos

I think jooo is right, this is the more traditional style wheel. Difference I think is that the thread and nipples are larger as compared to standards.

jooo wrote:Are you trying to find a replacement rim to match the height/appearance of the Shimano front, or will anything do provided it's strong enough for you?
It doesn't really matter what it looks like, just a rim that is strong enough and isn't very expensive. I may also redo the front wheel. (16 spoke)

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F45
Posts: 855
Joined: Wed Jun 08, 2011 6:08 am

by F45

I'd look into Kinlin XR380 or one of the 38mm carbon clinchers from light bicycle.

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