H
Hkek
Guest
1999 Shimano LX cranks with UN72 Bottom Bracket:
What is wrong with this picture?
I have been trying to chase down a squeaking noise. After disassembling and inspecting the cranks
arms I have discovered that the crank arm on the drive side, when fully tightened, slides onto the
square taper BB such that it "bottoms out" against a shoulder on the BB.
There is no such shoulder on the non-drive (left) side, so the fit of the left crack is truly
determined by the taper. On the drive (right) side, however, the crank arm contacts the shoulder,
which therefore defeats the purpose of the taper.
How common is this condition?
I will openly admit that I have removed the cranks several times over the years and have always
applied high-pressure (marine) wheel bearing grease to the tapers prior to assembly. I now see that
Barnett's Manual emphatically states not to use grease on taper-fit cranks.
Have I stretched and deformed the taper in the crank arm, or might they have "come from the factory"
with a poor fit?
Should I attempt to correct the fit by removing some material from the crank arm to provide some
clearance (prevent bottoming out) between the crank arm and BB shoulder?
Thanks in advance for sharing your experience/knowledge on the subject!
What is wrong with this picture?
I have been trying to chase down a squeaking noise. After disassembling and inspecting the cranks
arms I have discovered that the crank arm on the drive side, when fully tightened, slides onto the
square taper BB such that it "bottoms out" against a shoulder on the BB.
There is no such shoulder on the non-drive (left) side, so the fit of the left crack is truly
determined by the taper. On the drive (right) side, however, the crank arm contacts the shoulder,
which therefore defeats the purpose of the taper.
How common is this condition?
I will openly admit that I have removed the cranks several times over the years and have always
applied high-pressure (marine) wheel bearing grease to the tapers prior to assembly. I now see that
Barnett's Manual emphatically states not to use grease on taper-fit cranks.
Have I stretched and deformed the taper in the crank arm, or might they have "come from the factory"
with a poor fit?
Should I attempt to correct the fit by removing some material from the crank arm to provide some
clearance (prevent bottoming out) between the crank arm and BB shoulder?
Thanks in advance for sharing your experience/knowledge on the subject!