Bottom bracket confusion
 

Hi, I am looking into the new-to-me external BBs for the first time. I'm trying to sort it out but confused. I'm reading a lot about press fit bearings creaking. Are all of these external (looking at shimano xt stuff) BBs press fit or not?
Thanks

Press Fit depends on your frame.

Is your current bottom bracket threaded? English threads?

Or, does it have a press fit bottom bracket (BB30, PF30, etc).

Shimano uses a 24mm tubular spindle fused into the drive side crank arm..

threaded, screws into the frame, sits outboard..

frame designers then widened the frames to use bearings that pressed in rather than screw on.

but the bearings themselves are the same width apart, so as to use the same crankset.





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Threaded bottom bracket standards listed and explained.
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Press fit bottom brackets standards listed and explained.
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Shortlist of press fit BBs - with dimensions.

Hey, thanks for the replies, sorry for late reply here. Newbs here have very limited posts initially and I got locked out.
Yes, I have threaded english standard. I think I'm getting the picture of these things now. Thanks for the info and links.
I see I was reading about pressed bearings in two regards: pressed into the frame and pressed into some sort of screw-in holder. Confused me a bit.
have been totally out of the loop regarding BB developments for quite a few years. It's the thing I touch least often on a bike. I have been lucky with BBs; they seem to last me 5 to 10 years even with huge mileage.
I found a good deal on a shimano xt m-770, lightly used, so grabbed that last night. New bearings are very cheap. I hope it goes well. Looking forward to what looks like easy bearing swaps in the future. Hope they don't creak and do hold up well!

Great articles on the standards. I've been totally confused by it all over the years and now understand where my MegaExo fits into it all. This brings up my question, how do I replace the bearings in my MegaExo BB? Is it something I can do myself or is this a specialized tool kind of job? I had always thought I couldn't replace the bearings in my wheels, but then found instructions and it was easier to replace the sealed bearings than cup/cone loose bearing, and didn't require special tools, just a hammer.(really, you use the axle to lightly tap the old out with a rubber mallet, and the quick release to press the new ones in.) Is it a similar job on a BB?

I think it depends on the brand.

Campagnolo presses their sealed bearings onto the crank spindle, and the bearing cups on the bike stay in place. You need a puller to free the bearings from the cranks.

I think Wheels Manufacturing also uses a type of bearing cups with replaceable bearings.

Some of the internal press fit bearings are mainly just bearings that must be removed and replaced.

I think the MegaExo bottom bracket is usually a sealed unit that must be removed and discarded, often screw-in for English threads. Get a special wrench to unscrew it.

With the proper wrench, the repair can be done by anybody.