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PostPosted: Tue Jul 24, 2012 9:04 am 
Dirt Disciple

Joined: Sat May 26, 2012 11:00 am
Posts: 15
Location: Maui, Hawaii
Aloha to all. I posted this on another thread but did not want to hijack the OP so I figure start a new discussion. I am rebuilding a 1996 Kona Humuhumunukunukuapuaa and I want to install a new internal speed hub. I was looking at the SRAM. i-motion 9 speed internal hub with disc brake (if possible this would be my first choice. I would go the coaster brake version as my second choice) or the Shimano/Nexus 8 speed internal hub with coaster brake. If anyone here has experience with these internal hubs, could you please tell me if these hubs will fit my bike frame. My bike has a Shimano 7 speed internal hub and the wheel size is 26". Frame is 20". If anything, what dimensions do I need to look at on the bike to make sure the hubs I'm looking at will be compatible with my bike? [/code]


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PostPosted: Wed Jul 25, 2012 5:43 pm 
Dirt Disciple

Joined: Sat May 26, 2012 11:00 am
Posts: 15
Location: Maui, Hawaii
BTT


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PostPosted: Thu Jul 26, 2012 9:06 pm 
Retro Guru
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Joined: Sat Mar 28, 2009 6:10 pm
Posts: 921
Location: Hampshire
The distance between the rear drop outs is the critical thing. I believe they would be 135mm on your kona. The axle of the new rear hub should also be 135mm long. If that is the case then I would expect all to work ok. Probably best to take your complete old wheel to your wheel builder or shop so they have a reference for building the new wheel. This will ensure the wheel "dish" is correct when the new wheel is built. I assume you intend to buy a new hub and get a new wheel made with it. Dish refers to position of rim relative to hub (i.e side to side position when looking down at the back wheel). When building a new wheel it is probably best to use new spokes and let the shop select them for you to get the appropriate length. You may be able to re-use your old rim if it's in good condition though.


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PostPosted: Fri Jul 27, 2012 12:00 am 
Dirt Disciple

Joined: Sat May 26, 2012 11:00 am
Posts: 15
Location: Maui, Hawaii
Thank you RLY for your reply. I will take my rear wheel off the bike and do some measurements this weekend. I already have the rims and will be looking at dimensions of the hub I want to install to make sure it will be compatible. I wanted to buy the spokes too but I'm not having good luck with the online calcs.


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PostPosted: Mon Jul 30, 2012 2:02 am 
Dirt Disciple

Joined: Sat May 26, 2012 11:00 am
Posts: 15
Location: Maui, Hawaii
I was able to take some measurements on my Kona Humuhumunukunukuapuaa today. The actual width of the rear frame is 120mm. The 7 Shimano speed internal hub OLD is 128mm. I've decided if I am able to incorporate it, the Shimano Nexus 8 speed internal hub OLD is 132mm. So it isn't much difference between the two original and new hubs.
I am concerned about the chainline measurement though and was wondering if that could be adjusted. I don't think there is an 8 speed internal hub that will fit this bike exactly but I'm sure what is available could be used. I hope.


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PostPosted: Mon Jul 30, 2012 6:58 am 
Retro Guru
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Joined: Sat Mar 28, 2009 6:10 pm
Posts: 921
Location: Hampshire
That's a weird frame dimension - 120mm !! Almost all mtbs since the erly 90s have been 135mm. Esrlier ones were 130mm. I can only assume this frame is designed specifically for a different hub design.


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PostPosted: Mon Jul 30, 2012 8:30 am 
Dirt Disciple

Joined: Sat May 26, 2012 11:00 am
Posts: 15
Location: Maui, Hawaii
Thanks RLY for your post. You guys know more about these bikes and I appreciate the help.

To get the wheel back on the frame, I had to pull the rear apart to get it back on. I am thinking maybe the previous owner had messed with the frame maybe? My understanding is that the Shimano 7 speed hub is an original option on the bike? In another thread http://www.retrobike.co.uk/forum/viewtopic.php?t=191713&postdays=0&postorder=asc&start=15 a member did mention a 120mm hub and I just assumed he meant the rear frame opening.

I really would want to put the new Shimano Nexus 8 speed hub with coaster brake on my Humu. I will try to call Shimano and see what they have to say about the install.


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PostPosted: Mon Jul 30, 2012 8:31 pm 
Retro Guru
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Joined: Sat Mar 28, 2009 6:10 pm
Posts: 921
Location: Hampshire
Sounds like your frame was originally meant for 3-speed or single speed maybe, and the 7-speed hub has been wedged in. I'd go for another 120mm hub if possible or get a frame builder to have a look at the frame and see if it can be tweaked to take a larger hub. That other post you linked too was interesting .....see one of the posters had cold set the frame...i.e. bent it. I'd only advise this if you really know what you're doing.
If you stick with the 120mm hub then you shouldn't have trouble getting a wheel built or using cantis or vee brakes. If you for a larger size then the coaster brake option would be sensible so you are no longer relying on the wheel to sit perfectly (needed to get cantis or vee brakes working well).
Not sure I've really been much help....clearly I didn't know much about this bike as I was surprised it wasn't a 135 or 130mm space frame!


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