Bicycle Mechanics - loose bearin bottom bracket to sealed
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03-30-09, 05:00 PM
hi i have a loose bearing bottom bracket and wanted to know if it was possible to convert it to a sealed bb? i dunno the size, but it is a three piece suntour crankset with what i think is a standard bb. i have to tighten the bb and figured i should just go ahead a convert it to sealed. thanks
03-30-09, 07:25 PM
Assuming it has threads inside - of course it does - you could outfit it with a Shimano Octalink. But you'll also have to fit a new crankset on it. Your square-taper old-style bottom-bracket fits certain types of cranks, while Octalink needs a different animal altogether. And you could also go all-out and look into using a Hollowtech II bottom-bracket. These, too, requires a special type of crankset - different from both your square-taper and from Octalink. Lastly there is ISIS. These, though they have a different shape, are similar in how they work to Octalink.
If you decide to go Octalink, have your BB measured by your LBS so you get the right size/length. Also buy the best you can afford. The medium and lower tier Octalink's come out of Singapore, and they have some serious quality-control issues. Go for a Dura Ace if possible. Those are not out of Singapore.
Onwards & Upwards...
03-31-09, 11:47 AM
yes you can , just take your old axle to your lbs and get the same length you'll be fine. on some axle the size is stamp on them and that usually all you need. the shamino UN units will work for you.
03-31-09, 11:59 AM
Assuming you don't have an old french bike, an old raleigh, or something else with nonstandard threading, you'll be fine with a cartridge bb. New cartridge bbs are currently in production for bikes with english and Italian threading. Japanese and asian bikes have english threading, as do most bikes in general. If your bike was made anywhere in asia, the us, or england (aside from many older raleighs), you'll be fine with a standard shimano un-26 or un-54 bb, as long as you get the right spindle length.
03-31-09, 12:25 PM
Assuming it has threads inside - of course it does - you could outfit it with a Shimano Octalink.
This is, of course, a possibility, but you can get a square taper bottom bracket that will work just fine with your current crankset. The important statistics are the width of your bb shell (either 68 or 73), and the length of the spindle. If you want to swap it yourself, you'll need a bottom bracket tool, and you'll need to read up on extracting the fixed cup of your current bottom bracket.
As far as which Shimano BB to buy, I'd put my vote in for the UN - 53/54 level. The 26-level is lower-quality, and I've had them die on me. The 54-level lasts forever.
Take your current spindle to the LBS when you go to buy a new one, and they can match it up.
03-31-09, 01:12 PM
In addition to the spindle length and proper cups threads, you also need to know if the crank requires a JIS or ISO taper. The tapers are both the same angle, but the ISO is smaller. Campy cranks are made to the ISO standard.
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