Originally Posted by
thehammerdog
How do I know what type I have ? Is the any standard size to a modern BB. I do have external BB I think. But I do not know what size it is?
There are multiple standards, both for the frame's bottom bracket shell and for the crankset/spindle. It's sort of a case where "the more things change, the more they stay the same". In the old days, your frame could be English/Italian/French threaded, or even Raleigh's proprietary threading. Today it's English threaded, BB30, etc. Back in the day, you needed to know if your crank needed an ISO or JIS spindle and what length. Today, it's the spindle diameter or type like Hollowtech II (24 mm) or BB30 (30 mm).
You may be able to visually ID your bottom bracket from markings on it; otherwise you'll need to cross-reference your bike frame and crankset to look up the specifics. We can often help with that if you were to post the brand/model/year of your bike and the brand/model of crankset, or if you post pictures.
Originally Posted by
thehammerdog
Are they serviceable or just replace the entire BB unit.
Most current bottom bracket designs have sealed cartridge bearings that aren't meant to be serviceable.
Originally Posted by
thehammerdog
I need to replace chainrings and figured BB would need new bearings or to be replaced as well.
If the bottom bracket spins smoothly, there's no need to disassemble and service/replace. Just keep on riding 'til it gives you trouble,
then replace it.