CORNER (L.H.) 8K6456 - Caterpillar

Track-Type Tractor:
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Track idlers can incur several types of external wear during field use. One relatively uncommon type of wear is formation of flat spots where track links contact the idler. Flat-spotting can occur on any Track-Type Tractor undercarriage. This bulletin discusses causes of idler flat-spotting and the best practices to limit this wear pattern.Idler flat spotting does not typically occur under normal operating conditions (light to moderate packing, normal track tension, correctly set idler height).A combination of any of the factors listed below can increase the opportunity for flat spots to begin and perpetuate. However, flat spots can wear back to round again.
Illustration 1 g03748796
Idler flat spotsThe primary causes of idler flat spots are:
Illustration 2 g03748797
(A) Randomized track pin and link position on new idler tread (X) Link pitch
Illustration 3 g03749513
(B) Repeated track pin and link position on worn idler tread (smaller diameter (X) Link pitch
Ratio of track link pitch to idler circumference:
When idler and link components are new, this ratio causes the links to contact the idler tread in slightly different locations with each revolution. This action randomizes tread wear, resulting in a round idler tread. See Illustration 2.
However, the idler circumference gets smaller as the idler wears. Therefore, the link pitch to idler circumference ratio changes. Then track links can begin to contact the idler in the same location at each revolution of the idler. See Illustration 3.
Track tension:
Normal track tension allows a small amount of track slip relative to the idler tread during turns and directional changes. This track slip randomizes tread wear, resulting in a round idler tread.
High track tension increases the load between the track links and idler tread, even while the idler is round. This results in accelerated wear and an accelerated change in the ratio of link pitch to idler circumference.
High track tension can also prohibit the slip between track and idlers. This tension can initiate and perpetuate idler flat spots, particularly if the link pitch to idler circumference ratio is allowing links to contact the idler in the same location, per Illustration 3.
Primary causes of high track tension are excessive packing material in the track frame, and poor monitoring and maintenance of track sag via the track adjuster.
Concentrated loading on the idler
If the idler rise height adjustment is too low, ground load input into the idler can increase. Increased load results in more wear.
Machine balance being too far forward can also increase the load on the front idler, increasing wear.
Machine operational preferences such as dozing downhill or backing uphill can shift more of the machine weight onto the front rollers and idler. This increases load and wear.Best Practices To Reduce Idler Flat Spotting
Track tension – Maintain proper track tension per Operation & Maintenance Manual. In heavy packing, set track tension to the looser end of specifications. Additionally, in heavy packing, set track tension with some packing material already in the undercarriage to account for typical packing conditions.
Track frame & undercarriage clean-out -- In heavy packing conditions, clean-out will prevent accumulation of