Bicycle Mechanics - BB's
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01-29-06, 06:21 AM
Very simple and possibly dull question for you bike mechanics and enthusiasts out there.
Quite simply standard BB or the external? Which is better and why?
Many thanks for your time.
Better is a subjective term.
Some people would say external bearing bottom-brackets are a solution looking for a problem.
01-29-06, 09:38 AM
The type of bottom bracket is really determined by the crank you choose. If you buy a 10-speed Shimano or some of the FSA or Truvative cranks, you have to use their specific bottom bracket and it will be an external bearing type. Buy an Octalink Shimano crank, an ISIS crank or any Campy crank and the bb will be an internal bearing type
The external bearing bb's are supposed to solve the "problem" of the small bearings needed to allow a large diameter hollow spindle to fit inside the standard bb shell. Maybe it is a problem and maybe it isn't. I have heard lots of complaints about ISIS bottom bracket failures but very few about Shimano Octalink bb's.
01-29-06, 12:02 PM
I believe it's cheaper to purchase a new external bearing set than it is to purchase an entire new internal bearing BB. Of course there are internal bearing BB's that are said to be rebuildable. I owned a couple high end Race Face BB's, and they claimed they were rebuildable. But I had no luck ordering the special tool and bearing kit to rebuild the things. The shops kept telling me they simply throw them away and install a completely new unit. I guess that's the easy route when you're spending someone else's cash.
There are folks here on the forums who say that it shouldn't be a problem to buy the bearings and install them in high end, internal bearing BB's, and that they will be doing just that when the time comes. Then again, I've never read here of anyone actually doing it.
I've gone to buying mid-priced BB's for my current bikes. They seem to last as long as the more expensive ones. So all things being equal, they make for far more attractive 'throw-aways'. If and when I build another new bike, I'll probably go with the external bearing type BB.
01-30-06, 01:08 PM
I only use external BBs now, and I have noticed a great improvement in stiffness. The problem with this is that I also changed the cranks at the same time so I'm not sure whether or not to attribute the stiffness to the BB or to the cranks or to both.
Put it this way, you won't regret outboard bearings if you get them because all the Shimano ones at least come with quality cranks in my experience. Don't shoot me down here, I just never tried ISIS versions of outboard BBs!
02-08-06, 01:07 PM
Many thanks for your time.
Basically this comes from the fact that I puchased a carbon fibre monocoque frame, supplied with external BB. However the cranks will not turn over due to a lack of clearance on the frame. The manufacturers have told me to replace the external BB with a the standard BB. This with new cranks will give me the clearance I need. Hence the question as to whether I am losing out on what I believe (perhaps wrongly) is a stiffer crank. And my concern(again perhaps unfounded) that standard BB will soon be phased out by manufacturers in favour of the externals...
Any reply to this?
i think the problems with internal bearings occur mostly on mtb's. i have isis on my road bike with no problems, but i've gone through 2 isis BB's on my mtb. this is also what i've seen in the shop. that being said, when I build my touring bike it will either have square taper or external.
02-09-06, 10:27 PM
I had an XT hollowtech 2 crankset. I sold it and put the old race face square taper crankset back on. I can't tell any difference. But then again I'm 190lbs and don't think SID forks are flexy. I guess I'm not sensitive to parts flexing.
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