User Manual

Adjustments 4
41
41
Figure 4.21
ADJUSTING THE BOTTOM BRACKET
Typically the boom bracket contains four major pieces:
lockring, adjustable cone, bearings, and washers. The lockring
has notches. The adjustable cone will have notches for a
spanner wrench or boom bracket tool. The cones can be
removed and replaced separately. A set of round ball bearings
are found in each adjustable cone. A typical ball bearing is 5/16"
in diameter and contains nine balls. This type of boom bracket
may be cleaned, greased and adjusted.
Bearing Adjustment
The basic concept for bearing adjustments is to get the bearings
adjusted as loose as possible but without play. Start by
purposely beginning with play in the adjustment and then
ghtening in small increments unl play is gone. Note: Extended
use may cause the bearings, cups (or cones) to become worn
and pied. In this case, bearing adjustment will not be possible.
If boom bracket is correctly adjusted, but grinds when spun,
cups and/or cones are worn and should be replaced. Figure 4.21
❶ Loosen the locknut. Turn adjusng cone counter-clockwise
unl it hits the ball bearing, then turn back clockwise to
loosen 1/4 turn.
❷ Secure the locknut.
❸ Grab the end of the crank arms and rock it sideways to
check for play. If play is present, loosen locknut and turn
adjusng cone counter-clockwise slightly to ghten.
Re-secure locknut and check again.
❹ Repeat process of checking for play and re-ghtening cone a
slight amount unl no play is felt. Note: The one-piece crank
systems do not use a polished bearing system. There will be
some roughness to a correctly adjusted boom bracket.
Adjust as loose as possible but without play in the crank
assembly.
Boom bracket shown
with crank arm
removed
Locknut
Ball bearings
Crank arm
Chainwheel
Adjustable cones
Lockring
Crank arm
Washers