Bicycle Mechanics - Bottom Bracket help

I am the new owner of an 83 Specialized Expedition.

It came to me disassemble and I have further taken everything off for cleaning and inspection.

The bottom bracket feels rough and I want to put in a new one, but I haven’t a clue which one to buy.

I took out the old one, and some of the text on it was erased by the generator wire rubbing on it. Here’s what I can read, with guesses filled in in parenthesis –

Suntour
Taper: Vx( )size
Type: Tr(iple)
Thread: (1.37) x 24t
Lug Widt(h: 68-)70mm
Chain Lin(e: ).5mm

It is a sealed unit with tapered square axles that is 126mm long with a 30mm spindle on the left and a 35mm spindle on the right.

I have a Sugino AT 48-44-28 (110/74) up front and a Suntour Winner Ultra-6 13-30 in back. The BB width is 68mm and the frame spacing is 125mm.

I know that it’s ‘English threads’ but that’s as far as I can get for searching for a new unit. I can find 125 and 127.5 lengths and the only mention of offset is by Phil Woods.

Obviously I’m a Noob to this; what new BB will fit?

Thanks - Keith

Hey ksbman, since the BB shell is 68mm, you need an English/ISO bottom bracket as you have determined (the standard, used on all bikes made by non-sadists :)).

Bottom bracket spindles tend to be shorter in modern cranksets, and the distribution of spindle on the left and right sides may be slightly different too. To be on the safe side, here's a full selection of sealed bottom brackets with longer spindles at bikeman.com: http://www.bikemannetwork.com/biking/c/COMPBBSQRSHMTN

There's a 127mm UN-53 for $23, or a 122mm UN-73 for $34. The UN-73 is lighter because it has a hollow spindle, and I think the bearings are supposed to be better. But UN-53s have worked very well for me. So I suggest going for the $23 UN-53 since it's the length you need. Hope that helps.

Thanks, moxfyre.

There is no mention of the right spindle being longer. Do they normally come this way? Could it be a problem on my bike with the spindles the same length?

If the BB has spindles the same length, can you shim the BB over to the right to compensate, if needed?

There is no mention of the right spindle being longer. Do they normally come this way? Could it be a problem on my bike with the spindles the same length?
Yes, the right spindle is longer on almost all types of spindles (except for splined ISIS BBs), to accomodate the extra width needed for the chainrings on the right side.


If the BB has spindles the same length, can you shim the BB over to the right to compensate, if needed?
Yep, it's possible to add a few mm of spacers on the right side. Those should be available for a few $ from any LBS. But this shouldn't be necessary if you get the 127 mm BB. Pretty much any square-taper BB spindle of that length will be designed to accomodate the width of 3 chainrings on the right side.

To estimate how much safety margin you have with the spindle length, try reinstalling the right crank on the BB, then measure the distance between the chainrings and the chainstay. As long as the new spindle isn't so short as to crash the rings into the frame, you won't need any spacers.

Yes, the right spindle is longer on almost all types of spindles (except for splined ISIS BBs), to accommodate the extra width needed for the chainrings on the right side.
That was my main worry. Nothing I've read in the descriptions when buying said there was a spindle length difference.

Thanks for the help, moxfyre.

That was my main worry. Nothing I've read in the descriptions when buying said there was a spindle length difference.

Thanks for the help, moxfyre.
Sure thing! It's unfortunately something that gets glossed over by most component sellers. Sheldon Brown's shop, Harris Cyclery, includes detailed spindle measurements on their web site for old-style cup-and-cone BBs that they sell: http://sheldonbrown.com/harris/bottombrackets.html#axles.

As you can see from the chart, pretty much all type-3 spindles (British/ISO) have 30-32 mm on the left side, and the length variation goes into the right side. That's because pretty much all left crank arms are the same, while the right sides vary a lot by the number of the rings, and larger rings need to be put a little further from the frame as well.

Have you tried contacting Specialized?

(Well, okay. Maybe that's a silly suggestion...)

"The bottom bracket feels rough"

Inspect it visually to see if the cones and races are pitted, if not you can keep using it. new grease, ball bearings.

"The bottom bracket feels rough"

Inspect it visually to see if the cones and races are pitted, if not you can keep using it. new grease, ball bearings.
He said it's a sealed cartridge unit... so the BB can't be repacked. That's kind of surprising on a 1983 bike, but maybe it was a later upgrade!