press-fit BB question
 

silly question.. but like confirmation. my frame came with press-fit BB installed (shimano sm-bb91-41). the crank i have is an old Shimano Ultegra Fc-6500 Crankset.

will that fit?

No, the 6500 crankset is Octalink. Completely different type of bb system.

oh man... so i'd have to get a ultegra 6600 or 6700 crankset instead? if that's the case, that would still work with my deore RD right?

you need a shimano mtb crank with integrated spindle(ht2)

mtb crank? why would they install a press-fit bb on a SCOTT road bike that only fits a MTB crank?

EDIT: wait... isn't the Ultegra 6700 also a HT2 as well? if so, then it should fit right?

http://bikeforums.net/attachment.php...hmentid=255234

You can use Ultegra 6600 or 6700 HT2 cranks, or any of the other HT2 road cranks (you don't have to stick with Ultegra level stuff if you don't want to).

wow.. that's a sigh of relief... thanks for the clarification. :)

sorry google said the bb was an xtr unit. it is easier for me to id a bb with it in hand so i can measure and see it. most press fit styles use the same bb for mtb and road. the cranks are different though because the spindle length is different. if it is a road bike then you can use a shimano road crank with integrated spindle

The only difference between the road and mountain versions of the Shimano press-in bb's is the length of the plastic, inner sleeve. Both road and mountain versions use the same bearing cups.

ok... ultegra 6700 crank on it's way...

Btw, you've now entered the dark, mostly uncharted world of newfangled bottom brackets with your Shimano pressfit bb. My newest bike is equipped with PressFit 30 bb bearings (essentially nylon encased bb30 bearings that require a slightly larger size bore in the frame than bb30), Ultegra 6700 cranks, and Wheels Mfg adapters (they shim the 30mm spindle hole in the bearings to fit the 24mm Shimano crank spindle).

:twitchy: :D

adapters.. i hope i won't need to use adapters for my BB with 6700

Great a new "standard" and a press fit in the most flexed and abused bearing on the entire bicycle. I'm sure they tested it with high pedal force and many use cycles, but I wonder how much they tested it for holding up to what I call the "Roy Rogers" mount/dismount method, where one tromps one's foot on the pedal at the bottom of the stroke while swinging the other leg over.:rolleyes:

No, you won't need adapters.

The Shimano press fit bb bearings are the same size cartridge bearings that are used in the Shimano outboard bearing bb cups, the ones that are threaded into a conventional bb shell. The press-in bearings are encased in plastic or nylon and pressed into the frame's bb shell, and end up completely inside the shell, unlike the outboard bearings. The frame's bb shell is wider and larger in diameter than a traditional threaded shell so that the entire bearing assembly will fit inside the frame and not be exposed to the elements. Like traditional bottom brackets. :lol: The difference is that the bearings and spindles are larger in diameter now.

We sold a few cyclocross bikes last year that were raced hard in the fall and winter in the worst of conditions, no problems at all with the Shimano pressfit bearings. FSA produces compatible bearings for these systems as well, and we found them to not hold up as well as the Shimano bearings. YMMV.

In the world of industrial bearings, I believe it's very common for machinery to use press-in cartridge bearings, FWIW. The newest press-in bb bearings on bikes are not only pressed in, but sealed very well. Here's a pic of Shimano press-in bb bearings, like the OP's:

http://i414.photobucket.com/albums/p...iked/012-6.jpg

I'm not saying the world couldn't have gotten by without press-in bb bearings, or that in some ways these systems aren't problematic, I'm just posting this to let folks know what's going on with some of these new bb systems.