to determine percent worn. For D4 through
D7 tractors, position the bar so that one
probe is over the center of each tread. Use
the largest measurement to determine per-
cent worn.
Wear Charts — For undercarriage systems
where links and track rollers are wearing
at the same rate, you should continue to
use the 100% to 120% destruction guide-
lines. This is due to link pin boss contact
with external roller flanges or, for large
machines, bushing contact with internal
roller flanges.
On elevated sprocket machines, track
roller wear charts extend past 120% worn
to allow you to better estimate ‘destruc-
tion’ point. For these machines, roller
wear charts extend to the point where
tread wear meets the retainer bolts. For
track rollers with end collars, and there-
fore no retainer bolts, wear charts extend
to the same diameter as rollers with retain-
ers. This is useful for machines where
links are less worn than track rollers. Keep
in mind that rollers, depending on applica-
tion, may fail due to structure before they
reach this point.
Roller Swapping — Depending on the
situation, the front and/or rear rollers wear
faster than the middle rollers. A swap may
be necessary to extend roller life to the
link service or destruction point. To deter-
mine whether a swap is necessary, follow
the guidelines on page 64. The larger
machines, D8 and above, have large
diameter (extended wear life) single flange
rollers. For these machines, keep in mind
these single flange rollers can only be
swapped into positions where other single
flange rollers are located.
Roller Flange Sequence
From the chart which follows, you will
note that the rear roller (the roller nearest
the rear idler) is a single flange roller. If a
double flange roller were used as the rear
roller, interference could occur between
the inner flange and the rear idler.
Therefore, a double flange roller should
NOT usually be placed in the rear position.
Wear Chart Design — On elevated
sprocket machines, track roller wear charts
extend past 120% worn to allow you to
better estimate ‘destruction’ point. For
these machines, the wear charts extend to
the point where tread wear meets the
retainer bolts. This is to help you better
estimate when the rollers might destruct if
link wear is very low or if the roller
flanges have been trimmed.
For machines like the D6N, where some
rollers have retainers and some have end
collars, the wear charts for both types of
rollers continue to the same point, even
though there are no retainer bolts on the
end collar rollers.
For undercarriage systems where links and
track rollers are wearing at the same rate,
you should continue to use the 100% to
120% destruction guidelines. This is due
to link pin boss contact with external roller
flanges or, for large machines, bushing
contact with internal roller flanges.