robc02 wrote:While I agree, in general, with the sentiments about square taper BBs, I would also point out that they are not all equally durable. I have had a succession of Campag Chorus ones wear out after just one or two winters, even when they have been filled with a mixture of grease and oil in an effort to keep the seals wet. I've heard similar complaints about some Stronglight units.
interesting.... did you similarly remove the inner seals? Were there signs of water ingress? Was that the kind of chorus with the double bearing in the RHS? If so what did you do with the seals on that one...?
I am currently using a Token equivalent, that I filled with semi-fluid grease after first removing the inner bearing seals. It's now on its second winter and is showing no signs of wear, so hopefully this will be more successful.
one of the few that you can get in the right length; I am doing likewise for campag of that vintage but for me this kit sees neither miles nor weather so it doesn't tell me that much if it carries on working....
I have a feeling that for BBs with some riders you might well need
the EP additives and solid lubricants etc found in some greases, and without them you might well still get wear. The reason I think this is that the BB bearings are the slowest moving and see the highest loads. What kind of SF grease did you use?
The Shimano UN series do seem to be remarkably durable and economical. A good buy if they fit your chainset.
yup, my only quibbles (in which they are not alone BTW) is that the bearing preload is not entirely independent of the installation torque; if you (say) reinstall one that is slightly worn, often the play in the bearing mysteriously disappears as you torque the cups up. The other quibble is that they are somewhat uh, 'economical' with the grease fill. You can normally add about four times as much grease to these units if you pop the seals out.
A small redeeming feature of external BBs that hasn't been mentioned is the predictability of chainline. - It's always the same (though not adjustable). I've had a number of square taper chainsets where the chainline varies significantly between different samples of the same manufacturer/model, making bottom bracket length selection a bit of a lottery.
EBB chainline is adjustable with shimano systems if you are canny; Mountain cranksets and BBs use BB spacers anyway (on a 68mm shell) but if you have a 'road' chainset and you need to move the chainline, the trick is to use a 'Mountain' BB set in which the cups are 1mm narrower each side than a 'Road' set. You can immediately shuffle the chainline +/- 1mm this way on a 68mm BB shell, more than this is the shell is slightly narrower. If you use a (supplied) 2mm spacer then the chainline adjustment is 'permanent' (or at least requires the BB cups to come out if you change it).
If you instead screw the 'Mountain' cups into the frame without spacers, you can add (different) spacers on the spindle (i.e. between the cups and the cranks) to a total thickness of ~3mm or so (the extra 1mm comes from the tolerance of the LH crank to being 1mm further out if necessary). This gives ~+/- 1.5mm chainline adjustment.