Are they just have to have a wider bearing, which equates to more stiffness? Is that the only real difference?

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lighter, stiffer, better looking, you can use Hollowgram SL cranks with a good q-factor.

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/jonas l
http://cerrol.wordpress.com (my cyclingblog)

not lighter or stiffer but lets them use bigger down and seat tubes to make the frame stiffer

The BB30 bottom bracket axle is 30mm diameter, compared to most which are 24mm (or smaller, in the case of square taper about 17mm). Makes the axles stiff enough they usually use aluminum instead of steel, which gives back some of the stiffness but often saves weight (depending on the reference crank of course.)

The frame's BB shell is still 68mm wide, so there's no more room for bigger down or seat tubes than threaded frames, also 68mm wide.

Stiffer, but not lighter.

According to this it is lighter:

http://www.totalcycling.com/index.php/c ... ights.html

I had my eye more on stiffness though.

According to this it is 130gr lighter:

http://www.sram.com/sram/road/products/ ... d-crankset

It is complicated, but when comparing apples-to-apples as closely as is possible, BB30 does come out a little stiffer and lighter, and with more ankle clearance.
The downside is the slight increase in difficulty of having to press-in/press out your own bearings. After press-out it is recommended that they be replaced. Hollwtech can be cleaned, regreased, reused indefinitely and seems to work perfectly adequately. I have both, so I don't have strong feelings either way. Hollowtech is definitely more easy and convenient. I also enjoy the weight reduction of BB30.

Same width, yes, but the BB30 has a lager diameter BB shell which makes for a better mating of large diameter down tubes letting them maintain more of their roundness. PF30 is even better. I think BB30 and PF30 is best suited for aluminum and Titanium frames that use very large diameter down tubes. If going carbon it seems that the BB86/90/386 would be better unless you are bent on running a real BB30 crank.

Don't forget about the noise. Every bb30 bike I know makes some kind of bb noise. So much so I sold the frame and bought one with BSA.

Having owned several BB30 frames none have made noise.

Two frames under my belt. No creak.

my xcr is bb30, no creaking here either

Is it possible to run a BB30 crank on a frame with a standard English 68mm threaded BB? (specifically a BB30 quarq sram s975 on a felt AR) I had a Hive fifteenG crankset on my mountain bike that had a huge aluminum spindle and special cups. Looked like the special BB it came with was designed to accept spindles of BB30 diameter.

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