Hi. The bottom bracket cones on my trusty 1984 Peugeot P-something have worn out. I'm thinking it might be time to replace it with a sealed BB. Thing is, I've never actually seen one -- all my bikes are pretty old. So, tell me: what do I need, both in parts and in technique?

The shell is, as near as I could measure it with the cups on, 72mm wide (maybe 73?), and the threading is English. The current spindle is (I think) 121mm. Is this a good choice? What else will I need? Thanks!

Yup. And the tool for install. This:

https://www.niagaracycle.com/categori...m-bracket-tool

Thanks for the tool rec. There're about a million bottom brackets out there in the sub-$30 range. Any opinions on the best one?

If your shell is really 73mm (usually mountain bike specification), and the cranks are JIS taper, then that's probably what I would go with.

All you'd need would be an appropriate Shimano-type BB tool (buy, borrow, or coop?)...plug & play.

Probably want to verify those measurements, though - markings on the old BB might give a clue to confirm?

EDIT: Guess fender1 beat me to it on the tool recommendation!

The shimano bbt-22 will outlast the topeak, only $4 more.

The shell is measured edge to edge, not including the width of the cups. BB get a Shimano UN-26, about $12-$15, best value.

The original poster advised that the BB was 73 mm wide With the hardware, so my guess is it is 68 mm wide without. Which is the way to measure them. 68 is standard road bike save the Italians.
Knowing the brand of crank and the spindle length will get you close to what you need with dimensions. I would also measure the stub length that extends beyond the cups, this info will tell you if it is symmetrical or asymmetrical (which I think is the case) Many cartridge bottom brackets advise the dimensions if asymmetric.
Harriscyclery has in the Sheldon Brown pages much info which may or may not help, you need a vernier caliper if you don;t have one, some serviceable ones are quite cheap.

The way I read it, I assumed that "as near as I could measure it with the cups in" was indicating that the cups make it a bit tougher to get a precise measurement of the shell (e.g. when measuring with a caliper). Certainly one wants to measure the shell, not shell + lip of the cups, so probably worth picking up on this ambiguity...as I said, need to be sure to verify the measurement. I might've guessed offhand that a "P-something" was a road bike, and so likely not 73mm, but really can't say much without more info. Perhaps the OP can clear that up...

EDIT: Actually, looking at the pics linked in the OPs sig, it certainly is a road bike (as I would've assumed offhand) - and so you're probably right about that measurement, and the more likely shell width being 68mm.

Lost me at Peugeot, Brian....

Hal at the Bike Post across from Chico's would know, and he's got the tools to measure it.
You'd probably pay $10 more for the BB there, but at least you'd avoid any errors.

Not sure if Babit's, or the Bike Post on Arlington would be the place to go. There is a good wrench at both, just not sure how old, as far as knowing what's up.

I got one from VeloOrange, pleased so far, a SNAP to install. All metal, not half plastic like a LOT of the Shimano lower end ones...Don't know how well metal vs plastic stands up....but I have seen some older plastic ones that had a LOT of slop in them....The VeloOrange BB cartridge was also a few grams lighter than a Suntour Supurbe BB set...so, you may actually be shedding a little weight too.

Yeah, I should've measured the shell when I had the adjustable cup and spindle off -- it's my daily commuter these days, so I don't really relish taking the BB apart just to measure it. It might be time to invest in a caliper, anyway -- I'm just using a ruler, with the cable guides in the way, which doesn't allow for an accurate measurement. But the consensus seems to be that the all-metal Shimano UN55 is a good product?

Solid. The 54 and 55 are both solid BB's.

Yep, I use the Shimano UN-54/55 in a couple of my bikes. Smooth and works well for the price. They're my go-to square taper cartridge. I used to be be all about the loose ball BBs, but, after using cartridges in a few bikes, I've gotten to like the ease of them and they seem to stay smooth for a long time.

I invested in a caliper; yep, the shell is 68mm. Thanks for alerting me, y'all.