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Eccentric bottom brackets for 'normal' frames.....anybody make one?

kidwoo

Celebrating No-Pants Day
Aug 25, 2003
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Not so much to tighten chains on SS bikes, but more to mess with BB heights (and chainstay measurements if you really want to I guess).

There's this for a BB30 shell

http://www.universalcycles.com/shopping/product_details.php?id=41682

They state 16mm of fore/aft movement, so theoretically, you could use one of these to drop your bb height 8mm. Not huge, but couple that with some selective headset and tire combos you might be able to get an appreciable measurement out of it.

Any reason why this wouldn't work?


And is there anything comparable for a threaded BB shell?
 

kidwoo

Celebrating No-Pants Day
Aug 25, 2003
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that is why I've asked about CS length :)
I was thinking about making one for myself
I don't think your deal is CS length but yeah, something like this would at least let you play with it and find out.

i wouldnt imagine there is much room for manouver with a conventional bb shell
Yeah, you're probably right. I was just curious. Those spindles really don't take up much room in there in an external, threaded BB setup. It would be interesting to try. In my ideal world, I'd just use the existing shell for a mount point and have the spindle hanging below the BB shell. Now that's change you can believe in.


edit:
About 2.5mm off axle maximum, not really worth it IMO.
Is that all? What kind of/brand spindle is that based off of?
 

kidwoo

Celebrating No-Pants Day
Aug 25, 2003
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phones and human interaction?

I don't know man......sounds sketchy.


1/4 inch 'eccentricity'. So if I understand that correctly, 1/8" or 3mm offset max. Definitely not worth it. Thanks y'all!
 

frorider

Monkey
Jul 21, 2004
964
11
cali
those forward components EBB's (for std BB shells) were something i looked into years back but it appears their site stopped working last year. at any rate, the amt of eccentricity was not enough (I was hoping to lower BB height, in combination with other things as woo is proposing).
 

xy9ine

Turbo Monkey
Mar 22, 2004
2,847
237
vancouver eastside
In my ideal world, I'd just use the existing shell for a mount point and have the spindle hanging below the BB shell. Now that's change you can believe in.
that sounds rad, actually. ~1.5" bb drop. could effectively shorten the cs & slam the bb in one fell swoop. i'm currently playing with my old pdc 8.25 in slammed mode (bb @ 12.5" w/ 6.75" travel f&r), and love the geo.
 

LMC

Monkey
Dec 10, 2006
683
0
I don't think your deal is CS length but yeah, something like this would at least let you play with it and find out.



Yeah, you're probably right. I was just curious. Those spindles really don't take up much room in there in an external, threaded BB setup. It would be interesting to try. In my ideal world, I'd just use the existing shell for a mount point and have the spindle hanging below the BB shell. Now that's change you can believe in.


edit:

Is that all? What kind of/brand spindle is that based off of?
I was working it out with a 24mm spindle and assuming the BB cup would have to have 3mm wall thickness. If you have 19mm axle profile style cranks you could get 5mm eccentricity.
 

kidwoo

Celebrating No-Pants Day
Aug 25, 2003
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Cool thanks. I was going to bust out the calipers when I got home but with those kinds of 'gains' this seems kind of pointless to pursue.

That BB30 setup seems like it might just barely be worth it. Not happening on the bikes I have right now though......
 

buckoW

Turbo Monkey
Mar 1, 2007
1,600
376
Champery, Switzerland
Cool thanks. I was going to bust out the calipers when I got home but with those kinds of 'gains' this seems kind of pointless to pursue.

That BB30 setup seems like it might just barely be worth it. Not happening on the bikes I have right now though......
On a 7000 series alu frame, I got my buddy to cut off the BB shell and weld on a new one from doner frame making my frankenframe 25mm lower. He heat treated it and I rode it a lot for testing and it didn't move at all. He told me it would not have worked if the frame was 6000 series aluminum because the heat treating would have been a lot more complicated. It wasn't pretty but it was solid and worked very well for my purposes.

I imagine this is to get your hard tail bb height lower like on the old P bikes?
 

kidwoo

Celebrating No-Pants Day
Aug 25, 2003
22,567
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In my pants
On a 7000 series alu frame, I got my buddy to cut off the BB shell and weld on a new one from doner frame making my frankenframe 25mm lower. He heat treated it and I rode it a lot for testing and it didn't move at all. He told me it would not have worked if the frame was 6000 series aluminum because the heat treating would have been a lot more complicated. It wasn't pretty but it was solid and worked very well for my purposes.

I imagine this is to get your hard tail bb height lower like on the old P bikes?

Nah my hardtail sits at around 11". It's awesome. This would be for every other bike I own :D

Not sure I want to go the full detatchment route, just kicking some ideas around.
 

Udi

RM Chief Ornithologist: “I Brake for Birds”
Mar 14, 2005
4,785
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Is there an option to do this that doesn't cost so much yet?
From what I can see the three products available are the Exzentric, the Philcentric, and the now discontinued Forward Components EBB. The Exzentric and Philcentric are unreasonably expensive for the 3mm of adjustment you can get.
 

jonKranked

Press Button, Receive Stupid
Nov 10, 2005
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Is there an option to do this that doesn't cost so much yet?
From what I can see the three products available are the Exzentric, the Philcentric, and the now discontinued Forward Components EBB. The Exzentric and Philcentric are unreasonably expensive for the 3mm of adjustment you can get.

engineering: functional, strong, cheap.

pick 2.
 

trib

not worthy of a Rux.
Jun 22, 2009
1,172
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I was going to suggest what Buckow did.

Lop the bottom off the existing BB shell, get fabricator to weld in new one. Helps if bike is steel.
 

trib

not worthy of a Rux.
Jun 22, 2009
1,172
101
even better, cut off old shell, weld in larger size shell to allow a proper eccentric hub. BB options galore.