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Old 08-08-06, 08:07 AM   #1
Sincitycycler
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After market ceramic bottom brackets.

There are a few out there that are sub 90grams.

Assuming English threads, are these compatible with Truvativ GXP or Shimano Dura-Ace 7800 cranksets?
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Old 08-08-06, 10:56 AM   #2
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I'm pretty sure that the Truvativ GXP cranksets use ISIS splined bottom brackets... so if your 90g BB has an ISIS spindle and is the right length, it should work.

The newer Dura-Ace cranksets have the BB spindle built in and are only compatible with the appropriate Shimano BB cups and bearings. I've no idea what pre-2004 Dura-Ace cranks used, frankly. According to Sheldon Brown, there are only 2 types of Shimano Octalink BB splines: http://sheldonbrown.com/gloss_n-o.html#octalink ... the pre-2004 Dura-Ace must use something different, who knows what...
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Old 08-08-06, 11:03 AM   #3
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He is talking about the newer style external bearing design BBs. The mfgs say only theirs will work with their cranks but in the aftermarket they say they work with all (or most) cranksets.
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Old 08-08-06, 01:02 PM   #4
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yep, grasschopper is correct. the outboard bearing bb are cross compatible with integrated type cranks despite what the manufacturers say. You can use a D/A with FSA, bontrager, truavativ, etc. with no problems.
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Old 08-08-06, 03:27 PM   #5
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Originally Posted by steelforme
yep, grasschopper is correct. the outboard bearing bb are cross compatible with integrated type cranks despite what the manufacturers say. You can use a D/A with FSA, bontrager, truavativ, etc. with no problems.
Yeah, what I figured. These companies like Shimano want to force you to keep your money "in the house"...
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Old 08-08-06, 05:10 PM   #6
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By the way, some of the wheel and bearing experts (Jobst Brandt!!!) think that ceramic bearing are a complete waste of money. Read this: http://groups.google.com/group/rec.b...4fbcc870f8a04b

The summary: bearing drag is a negligible part of the power that you exert when cycling at even a moderate pace on moderately good equipment (*much* less than 1% of total power output). So even if ceramic bearings are better (Jobst isn't convinced) it makes no practical difference.

Maybe the fancy-schmancy ceramic-bearing BBs are lighter, but it would be pretty easy to make a conventional steel-bearing BB of nearly the same weight for significantly cheaper. Basically the "ceramic bearing" part is just hype to get your money.
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Old 08-09-06, 08:09 AM   #7
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Ceramic bearings were mostly developed for extremes of speed and temperature in aerospace applications where rotational speeds are in RPS rather than RPM and where temperatures in the bearing might approach the softening points of steel and lube is chancy. They are a bit overkill for rotational speeds below 4000-5000 rpm. It is the rare bicyclist who rides above 60mph, about 800 rpm in the wheels on a 700c tire. 406 bents will be closer to 1200 rpm. Bottom brackets get nowhere near this range.
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Old 08-09-06, 04:35 PM   #8
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Quote:
Originally Posted by steelforme
You can use a D/A with FSA, bontrager, truavativ, etc. with no problems.
Are you nuts? FSA and Shimano may be interchangable, but there's no way either of those will work with Bontrager/Truvativ (same thing). FSA and Shimano use the same outer diameter on their spindles on each side, whereas on the Bonty/Truvativ the non-drive side has a smaller outer diameter.

Quote:
Originally Posted by Sincitycycler
Yeah, what I figured. These companies like Shimano want to force you to keep your money "in the house"...

He has no idea what he's talking about.
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Old 08-09-06, 07:47 PM   #9
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