BB installation question

Back off the drive side a couple of turns and seat the non drive side, then seat the drive side again.

capwater said:

Back off the drive side a couple of turns and seat the non drive side, then seat the drive side again.

I just tried the exact same thing today .. although the drive side will have the same gap if the non drive side gets flush first

ieandro said:

I had installed a square type BB on a friends MTB and I was curious if the non drive side cup should be flush with the shell.

I had installed a Shimano UN-53 type and i installed the drive side first and then the non drive side second. Thing is the drive side is flush, giving it a perfect chainline. As for the non drive side, there is a 1.2 mm gap from the cup to the shell. The cup is plastic and I'm afraid any more torque would possibly damage the splined teeth or worse. It's as tight as torque specs will allow. It just has a small gap. I don't want to mess with the drive side as the length is already good.

Is this something I should be worried about ? I thought about a spacer, but the cup has no lip. Maybe an O-ring queezed in between just to keep the moisture and [censored] out ?

I am assuming that you have the proper BB size for the frame.

It is probably OK. Do as you did the first time. Tighten down the drive to the proper torque, then do the non-drive. It is no problem if a few threads of the non-drive cup are showing as long as everything is properly tight and the chain line is appropriate. The non-drive cup locks down onto the BB cartridge shell, not the frame, whereas the drive side (with the lip) locks down onto the frame. What capwater was suggesting was a way to make sure that the non-drive got started well and seated properly. His method would not affect the final position of the drive side.

ieandro said:

I had installed a square type BB on a friends MTB and I was curious if the non drive side cup should be flush with the shell.

I had installed a Shimano UN-53 type and i installed the drive side first and then the non drive side second. Thing is the drive side is flush, giving it a perfect chainline. As for the non drive side, there is a 1.2 mm gap from the cup to the shell. The cup is plastic and I'm afraid any more torque would possibly damage the splined teeth or worse. It's as tight as torque specs will allow. It just has a small gap. I don't want to mess with the drive side as the length is already good.

Is this something I should be worried about ? I thought about a spacer, but the cup has no lip. Maybe an O-ring queezed in between just to keep the moisture and [censored] out ?

If it isn't too tedious, remove the crank & BB from the frame ...

Put the non-drive side cup on the bare BB ... and, hold it up against the BB shell. THAT is the easiest & (almost) fastest way to determine how deeply the adjustable cup can maximally snug up against the BB cartridge.

DON'T FORGET TO PUT A SMALL AMOUNT OF GREASE ON THE INSIDE OF THE CUP.

If the loose cup is "designed" to extend beyond the shell, and if it bothers you (be sure it is labeled something like UN53-73), then scrounge up an old/vintage (from the loose-type bottom brackets) lockring and put it in place.

alfeng said:

If it isn't too tedious, remove the crank & BB from the frame ...

Put the non-drive side cup on the bare BB ... and, hold it up against the BB shell. THAT is the easiest & (almost) fastest way to determine how deeply the adjustable cup can maximally snug up against the BB cartridge.

DON'T FORGET TO PUT A SMALL AMOUNT OF GREASE ON THE INSIDE OF THE CUP.

If the loose cup is "designed" to extend beyond the shell, and if it bothers you (be sure it is labeled something like UN53-73), then scrounge up an old/vintage (from the loose-type bottom brackets) lockring and put it in place.

It's not so much that it bothers me (it's not me whos riding it), it's really just a curiosity as to wether it's fine just the way it is. I also tried the lockring earlier, but since the cup has no lip, it will not hold.

and just to show what kind of gap we're talking about here:
[IMG]i20.photobucket.comDSC01324.jpgOpen ↗[/IMG]