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vcnz
PostPosted: Sat Dec 24, 2011 4:46 pm 
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Location: The Netherlands
I have a chance to change my bb on my cx bike from standard to bb30 to increase stiffness

Does anybody know the weight difference between Sram Red BB30 (or FSA K-Force BB30) and the standard Shimano DuraAce 7900 ?
I'm referring to the whole setup, considering bearings, shell etc

Thanks
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Weenie
Posted: Sat Dec 24, 2011 4:46 pm 


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simonj
PostPosted: Sat Dec 24, 2011 10:50 pm 
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Um, as far as I know, you can go from BB30 to standard via an adapter, but not the other way around. Your bike needs to have a BB30 shell
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vcnz
PostPosted: Sun Dec 25, 2011 4:34 pm 
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Location: The Netherlands
simonj wrote:
Um, as far as I know, you can go from BB30 to standard via an adapter, but not the other way around. Your bike needs to have a BB30 shell

It's a Ti frame and I can change the standard bb with a bb30, any Ti frame builder can do this.
That's why I wonder if the new setup (Sram RED BB30 of FSA BB30) is lighter than the current one (Shimano Dura Ace 7900 crank).
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simonj
PostPosted: Sun Dec 25, 2011 9:08 pm 
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Ahh, I see, my apologies.

Well according to SRAM, the BB30 version is 30% lighter than its GXP counterpart. Although I'm not sure how that compares to a 7900 setup.
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monty dog
PostPosted: Mon Dec 26, 2011 7:22 pm 
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Cutting-and-shutting the BB shell from threaded to BB30 is a whole lot of aggravation for a few grammes - I wouldn't consider this to be a viable option and would probably be as expensive as a whole new frame.

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tomikasa
PostPosted: Tue Dec 27, 2011 4:37 pm 
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Location: belgium
I think rotor has a bottombracket for "normal "frames so you can use a bb30 bottombracket.They also have one for the other way around...
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monty dog
PostPosted: Thu Dec 29, 2011 5:02 pm 
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Standard English BB shell has internal diameter of 34.8mm - putting a BB30 shaft through there leaves 4.8mm of 'space' for the bearings - just exactly where do the bearings go? FWIW Rotor BSA 30 uses a 30mm spindle but bearing are placed external to the shell - but this won't work with a regular BB30 crank.

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captainclarko
PostPosted: Wed Jan 18, 2012 11:24 pm 
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GXP Sram Red : 760g
GXP FSA K-Force Light :736g

BB30 Sram Red : 630g
BB30 FSA K-Force Light : 675g

Dura-Ace 7900: 725g

All weights are for standard crankset and taken from manufacturer's websites as of 01/18/2012.

The weight difference is there, but you could still do pretty well with another GXP style crankset. KCNC, THM, S-works, and Hollowgram all come to mind.
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jaup
PostPosted: Wed Jan 18, 2012 11:32 pm 
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http://www.rotorbikeusa.com/products/bs ... acket.html

This?
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rahman
PostPosted: Fri Feb 10, 2012 8:32 pm 
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Sram's BB30 weighs about 34 grams and Duraace's 7900 90 grams precisely, hope this helps :D

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mlchang
PostPosted: Sun Feb 12, 2012 2:48 pm 
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jaup wrote:
http://www.rotorbikeusa.com/products/bsa_bottom_bracket.html" onclick="window.open(this.href);return false;

This?


Takes 30mm spindle, but a true BB30 crankset spindle will be too short to work with these BB cups.
Rotor BBRight has 30mm spindle but is much longer which is what these cups are designed for.
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Weenie
Posted: Sun Feb 12, 2012 2:48 pm 


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rockdude
PostPosted: Mon Feb 20, 2012 5:44 pm 
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Location: Boulder, Colorado
I see no need in a bb30 and for cross and they have be problematic with keeping the bearing from seizing. I have now put a conversion shell in all my bb30's and run standard BSA.

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