flik9999

Hey so the title says it all. I have a specialised sirrus which I am converting to electric for my job.

However one of the problems I have encountered is that the pedal sensor thing requires a semi sealed bottom bracket and my bike has a sealed bottom bracket. So I was wondering can I take the bottom bracket off this old falcon I have lying around and pop it in or would I need to find a modern bottom bracket which is semi sealed?

Andrew R Stewart 

Not enough info to say yet. First what is a "semi sealed" BB? Do both bikes have the same BB shell design/spec? Are both BBs the same design/spec? Other then fitting a sensor does the E conversion deal with the crank set or BB? Andy.

CliffordK

What do you need for the pedal sensor that your current setup won't work with?

What gearing do you have on the rear of your bike? 8 speed?

Square Taper on the crankset, or something else?

If you have a square taper crankset/bottom bracket, then a good many bottom brackets will work. Just match the threading (probably "English"), length of spindle, and whether the spindle is offset.

Your Falcon BB may work, but the spindle length or offset may be different.

IRD makes sealed cartridge bottom brackets that come apart, with access to the spindle in the middle if needed for something, and you can replace just the bearing cartridges if needed.

SkyDog75

I'm with Andy in that I don't know what you mean by a "semi sealed" bottom bracket.

But answering the original question in a general sense, you can take the bottom bracket off an old bike and mount it on a new bike if the frames' bottom bracket shells are the same type/threading. For example, if the old frame and the new frame both have English threaded bottom bracket shells, you can swap parts. If one frame has an English threaded bottom bracket shell and the other doesn't, you can't swap bottom brackets. (Well, not without an adapter, if one exists for your particular combination of bottom bracket shell types.)

squirtdad

you may also want to see what the electric bike forum has to say also. And put specifics, like what specific conversion kit you are using

3alarmer 

...I've only seen the term used to describe a sort of nightmarish BB spindle arrangement used on the lower end Chinese bikes currently sold at places like Wal Mart and Target. They biodegrade, and are almost impossible to service and readjust correctly...so considered disposable.

Semi Sealed Bottom Bracket Cartridge 115mm Bike Cycle Road MTB New | eBay




To the OP, assuming your old school replacement package of cups, bearings, and spindle meet the same specs as the cartridge you are replacing (threading, spindle length, end taper), it ought to be possible. But there are a lot of spots you can go wrong, especially if you end up with an asymmetric spindle.