BB shell facing

bgodkin
bgodkin Posts: 28
edited November 2008 in MTB workshop & tech
Can anyone clarify for me if it is really necesarry to have the BB shells faced when installing an external bearing BB? LBS say yes (If it is going to make them a couple bob they would say yes to anything) but from speaking to a few other people I am being told that it isn't really needed as long as your shell isn't damaged on the face.

Thanks in advance,
Brad

Comments

  • nicklouse
    nicklouse Posts: 50,675
    yes it is if it has not already been done.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
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  • -liam-
    -liam- Posts: 1,831
    When my lbs fitted my hollowtech2 bb/crankset the other day, they said mine didn't need doing. They said, and it makes sense to me, that the shell is faced up on modern bikes prior to assembly, and like you said, they only face it up if a) It is an older frame and b) The shell is damaged.
  • Vegeeta
    Vegeeta Posts: 6,411
    Probably a good indication as to weather it needs doing or not is to see if the area the BB will be sitting against is painted or not!
    At work I always chase the threads when I'm fitting someone a new BB and if I'm in any doubt I'll face the shell off for external BBs.

    On my own bike I'd get it done just to be on the safe side, even really expensive frames can be out! Someone I met who worked in a Litespeed shop said that once they had a frame come through without any threads in the BB shell so if they can miss that.....
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  • dennisn
    dennisn Posts: 10,601
    I asked the same question a while back. Their was a bit of debate but never any real consensus about yes or no as I recall. I was of the opinion that the BB threads held
    the BB solid once it was tightened against the shell, even if after it was tight it didn't rest
    totally on the shell and only touched in a few, or one point. Others thought differently
    but like I said, no real consensus. I ventured to guess that the head tube needed facing
    more than the BB shell because the headset bearings needed to be parallel for a smooth turning fork, yet the BB bearings would only be as parallel as the threading would allow
    and not necessarily depend on the BB shell faces. I'm pretty sure though that most
    headsets and BB shells are given a facing before they leave the factory, as a quality control issue, on most all decent frames.

    Dennis Noward
  • I didn't bother with my cheap xt BB which arne't renouned for longevity anyway but when I eventually get my hope ceramical one it'd be sill ynot to. I think it's about how much you value the BB.
    Train hard, ride easy