Undercarriage & wear parts
How to check track tension — and why over-tension is worse than under-tension
Track tension is the most adjustable variable in undercarriage wear, and the most commonly set wrong. Over-tensioned tracks wear rollers, idlers and sprockets faster than any amount of normal use.
The measurement
Track sag is measured at the middle of the track frame, between the sprocket and the idler, on a level surface. Lift the track slightly with a jack or a bar, measure the maximum gap between the track shoe and the track frame, then let it settle and measure again.
The correct figure is machine-specific — take it from the manual, not from a general rule. Machines with different track frame lengths and shoe widths have different specifications.
Why over-tension is the more common error
Under-tensioned tracks are noisy and obvious. Over-tensioned tracks look fine and quietly destroy the undercarriage: every component carries load it was not designed for, seals fail earlier, and the track pins wear faster.
What changes tension
- Packing material between sprocket and idler — the most common cause of apparent "loosening"
- A leaking track adjuster seal, which loses grease over time
- Temperature — tracks tighten in cold weather and slacken in heat
- Worn pins and bushings, which effectively lengthen the chain
Check tension before ordering replacement parts
If rollers are failing repeatedly, check tension first. Replacing parts without correcting the cause guarantees the same failure again.
Questions about undercarriage wear patterns: alfrun@gmail.com
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Send machine make, model, serial number and a photo of the casting mark. We confirm the part number and fitment basis before any price discussion.
Symptom to cause: tension problems
| Symptom | Likely cause | What to do first |
|---|---|---|
| Track needs re-tensioning every week | Adjuster seal leaking | Look for oil at the adjuster cylinder |
| Sag stays above spec at maximum adjustment | Chain stretched beyond limit | Measure pitch; a stretched chain cannot be tensioned back |
| Track derails on one side | Tension too loose, or alignment | Check both before buying anything |
| Rollers failing repeatedly | Over-tension | Over-tension wears rollers faster than use does |
| Loud clatter over hard ground | Tension too loose | Measure sag, do not guess by eye |
A symptom is not a diagnosis. Confirm with measurement before ordering a part — a new component on an unfixed cause fails the same way.
Track sag calculator
Enter your machine's operating weight class and track frame type. This returns the sag range that most manufacturers of that class publish — it is a starting point for checking your manual, not a substitute for it.
How to measure: on level ground, at the midpoint between sprocket and idler, lift the track slightly and measure the maximum gap between the shoe and the track frame. Measure cold, after the machine has been standing.
Why a range: track frame length and shoe width both shift the figure, and manufacturers publish different limits for the same weight class. Treat this as a sanity check, then use your manual.
Trademark notice
Machine brand names and part numbers are used only to describe fitment and application. We are not an authorised dealer of any machine manufacturer.
Reviewed by Zhonglei M&E parts desk — export trading partner for undercarriage and wear parts. Last updated 2026-11-13.