Shimano BBs

[Neil]

I've just got a UN54 BB (73 x 122), when did they start using plastic for one side?

I've also got a UN51, still in it's greasy bag, from BITD, which has a metal locking ring. Thing is, I wasn't sure of it's dimensions, because although I can measure the spindle, there doesn't seem to be any codes on it that give it away. The axle / spindle seems practically the same length as my newly acquired UN54, but with both lock rings on the body, compared with the UN54, the layout seems different.

Is there any obvious way to find the shell width for my (NOS) UN51, given there's nothing on it that seems to reveal it?

Are there any reasonably priced shimano square taper BBs that have a metal lock ring, these days?

 

[RockiMtn]

i believe started with UN53 (also UN73) with plastic cups. you could always re-use the cups from the BB your replacing. try your LBS and see if they have some spares lying around, or I think you can buy spares ones from Phil Wood or Sheldon Brown.

i'm pretty sure bb shell width are marked on the bb, but the spindle width aren't always. (sometimes on the spindle itself).

 

[RockiMtn]

actually scratch what i just said. i just remembered.

it's the cups that are marked with the bb width. you change them to make up the size.

 

[elite504]

make sure you don't mish-mash cups willy-nilly. Measure the cart diameter and check it with the cups you use, they're not all the same diameter. Not just alloy/vs resin cups, it depends on the model. If you use the lage cup, on a small cart, you'll have a creaky racket-bracket. .

 

[Neil]

make sure you don't mish-mash cups willy-nilly. Measure the cart diameter and check it with the cups you use, they're not all the same diameter. Not just alloy/vs resin cups, it depends on the model. If you use the lage cup, on a small cart, you'll have a creaky racket-bracket. .

I'm looking at the two, now, side by side. the actual cartridge bit looks the same length, although the UN54 has a thicker lip on the fixed (right side). The spindle / axle seems the same length, too, although the tapers look ever so slightly shorter on the (older) UN51, but the spindle does seem as long as on the UN54 (should be 122)

On the label on the middle of the cartridge body, the UN54 has all the details, 73 for shell width, and "BC1.37 x 24", can't see any separate mentioning of the spindle length, though? On the UN51, the cups have the same, stamped on them "BC1.37 x 24", (edit: oh I see, I've read the shimano leaflet, and this is the thread dimensions) and am seeing 68, so presumably for 68mm shell width. The cups seem the same diameter between the two, although the UN51 has a nice metal one, with less thread depth (presumably because it's for 68mm BB shell) compared with the resin one on the UN54.

Just out of interest, given the axle lengths seem to be the same, would using a 68mm BB in a bike with a 73mm BB shell just mean the none-drive crank would be closer to the BB shell?

It's probably all for the best, as one of my bikes has 68mm BB shell (the 95 one, which came stock with a UN51 BB), and the other, 73mm BB shell.

It does seem disappointing about the resin cup on the UN54, though, I guess like you say, I can reuse the one already on the bike - but I seem to remember, BITD, BBs lower than (at least) the UN51 had plastic cups for the non-fixed cup, 'cos I've got one in the loft, somewhere, I guess I just expected that a UN54 would be similarly spec'd to the UN51.

 

[RockiMtn]

i should have said, you MAY be able to swap LH cups to change up the size. but don't quote me on it as i have never done that before. all my bikes have 68mm bottom brackets. also i only have UN5x and UN7x BBs so no experience outside of that either.

regarding replacements, Sheldon Brown discontinued whatever LH cups they were stocking originally but are now stocking ones from Problem Solver. But they are only for 68mm shell application. Scroll down to almost the bottom under "Cups":

http://www.sheldonbrown.com/harris/bottombrackets.html

 

[FluffyChicken]

It's not worth getting replacement cups in my opinion as it will cost you half the price of a UN54. (unless you get the v cheap)

The spindle length would be marked (if anywhere) either on the sticker (I guess not) or on the axle in the part between the tapers and the shell. Stamped in , like BB107 or MM113 or ?
May be not, but a pair of callipers (can get digital for <£9 delivered from of ebay, look for the UK location if you don't wish to wait weeks, come in very handy. Will need 25cm version, not the 15cm one's)
But if they look the same length when you stand them on their end they they'll be pretty damn close, you would notice if it was 118 or less easily.

Don't put the 68 in to the 73 frame, that's a quite a bit of frame thread you would have showing to get damaged and you'll likely get your crank arms rammed on to the chainstays. Just get the proper size
You could try it though just to see.


UN54 are a lighter about 15g than UN52 at best guess.

Why do you want the heavy metal (steel) cups ?

 

[Neil]

It's not worth getting replacement cups in my opinion as it will cost you half the price of a UN54. (unless you get the v cheap)

The spindle length would be marked (if anywhere) either on the sticker (I guess not) or on the axle in the part between the tapers and the shell. Stamped in , like BB107 or MM113 or ?
May be not, but a pair of callipers (can get digital for <£9 delivered from of ebay, look for the UK location if you don't wish to wait weeks, come in very handy. Will need 25cm version, not the 15cm one's)
But if they look the same length when you stand them on their end they they'll be pretty damn close, you would notice if it was 118 or less easily.

Don't put the 68 in to the 73 frame, that's a quite a bit of frame thread you would have showing to get damaged and you'll likely get your crank arms rammed on to the chainstays. Just get the proper size
You could try it though just to see.

I was only thinking out loud, it doesn't really matter, I've got two bikes, one with a 68mm BB shell, t'other with 73 - so I'll find a use, at some point.

UN54 are a lighter about 15g than UN52 at best guess.

Presumably all in the weight saving between a plastic and metal cup? ;-)

Why do you want the heavy metal (steel) cups ?

Well it doesn't feel overly heavy in my hand, but seems more robust.

I'll probably just reuse the metal ones already in the frames, when it's time to use them in anger.

 

[Xesh]

Axle length on the older Shimano cart BBs is marked on the lefthand side of the spindle near the bearing seal. It'll be in the form of 2 or 3 letters (sometimes some numbers).

E.G.: D-NL is 122.5mm, MM107 is 107mm, D-EL is 127mm. There are more but the easiest way is to just use a vernier gauge to measure axle length.

Shell width is usually marked on the driveside BB cup on the outside of the flange: BC1.37 x 24 and then there'll be a 68/70/73 on there somewhere. In the case of the pic below it's a UN90 Italian threaded cup (36x24T and 70mm shell width).

BTW I have both cups going spare if anyone wants them....