Check track tension first, then the wear pattern. A track that repeatedly derails on one side usually has a worn sprocket, a worn idler or a loose chain on that side. A track that derailed once after striking an object is a different situation entirely.
What you will notice
| Symptom | What it usually points to |
|---|---|
| Track derails repeatedly on the same side | Uneven wear or a mechanical defect on that side: sprocket, idler, roller or tension. |
| Track derails when reversing or turning | Tension too loose, or excessive side clearance in the undercarriage. |
| Track came off after hitting debris | An event rather than a wear pattern. Inspect for damage before resuming. |
| Chain visibly slack on top of the rollers | Incorrect tension, or a tensioner that will not hold. |
| Track adjuster will not hold tension | Grease cylinder seal failure or a relief valve that leaks. |
| Sprocket teeth noticeably hooked or sharp | Advanced sprocket wear. Chain and sprocket life are coupled. |
| Rollers not rotating | Seized rollers, which distort the chain path and cause derailment. |
Most likely causes
| Cause | How to confirm it |
|---|---|
| Incorrect track tension | The most common cause. Too loose allows the chain to climb the sprocket; too tight damages the final drive and bearings. |
| Worn sprocket teeth | The chain rides up the tooth profile and steps out of the guide. |
| Worn or seized rollers and idlers | The chain path becomes irregular and lateral guidance is lost. |
| Track frame misalignment or worn guides | The chain is not held in the correct plane. |
| Foreign objects between chain and sprocket | Debris wedging the chain sideways. |
| Excessive undercarriage wear overall | Chain, sprocket, idler and rollers all beyond their limits. Derailment is a symptom of the whole group. |
| Tensioner failure | The adjuster cannot maintain tension because its seal or relief valve has failed. |
| Operating practice | Turning on slopes with a slack chain, or tracking with one side unsupported, both raise derailment risk. |
How to confirm it
- Measure track tension correctly
Measure sag at the specified point with the machine in the specified position, on level ground. Tension measured in the wrong place or with the machine positioned differently gives a meaningless number, and it is the measurement most often done incorrectly.
- Inspect the sprocket
Examine the tooth profile from the side. Teeth that are hooked or worn to a point no longer guide the chain and should be measured against the wear limit.
- Check every roller and idler for rotation
Jack the side and rotate each roller by hand. A seized roller forces the chain into an altered path, and it is a cheap component compared with the chain it destroys.
- Look for the wear pattern
Check whether wear is on one side of the links, one side of the sprocket and one face of the rollers. Asymmetric wear indicates misalignment rather than simple age, and realigning is more valuable than replacing parts.
- Confirm the tensioner holds
Pump the adjuster to specification and re-measure after working the machine. Tension that falls away indicates a failed grease cylinder seal or relief valve.
- Assess the undercarriage as a group
Measure chain, sprocket, idler and roller wear. Replacing one component against three worn ones simply transfers the wear into the new part.
What to do about it
If tension was simply incorrect and the undercarriage is within wear limits, correcting tension is the repair. This is a genuinely common outcome on machines that derail once, and it costs nothing.
If the sprocket is worn, replace chain and sprocket together. A new chain on a worn sprocket is destroyed quickly, and vice versa — the two wear against each other and replacing one alone wastes the new component.
If several components are beyond their limits, plan the replacement as a set. It is more expense now and materially less expense over the next two years.
If the tensioner will not hold, it needs a seal kit or a relief valve. Confirm whether the grease cylinder bore is damaged before ordering, because a scored bore will not seal reliably.
Need the parts this covers?
Send the machine model, serial number and the part numbers you need. We confirm fitment before payment and state the grade of every line — genuine, OEM-quality or aftermarket.
Request a quoteFrequently asked
How tight should my tracks be?
It varies by machine and must be set to the manufacturer's specification, measured in the specified position. There is no universal figure. What matters is measuring it properly, and re-measuring after the machine has worked, because new chains stretch in their first hours.
Can a track be re-fitted or does it need replacing?
A track that has come off is usually refittable if the chain and components are sound, though the cause must be corrected or it will happen again. If the chain is stretched beyond its wear limit it will keep derailing regardless of how many times it is refitted.
Should I replace the sprocket when I replace the chain?
Generally yes if the sprocket is past its wear limit. Chain and sprocket wear each other. Replacing one and not the other reduces the service life of the new part substantially, which is the opposite of saving money.