Track tension is not judged by feel or by eye from the cab. It is measured as sag: the droop of the chain at mid-span between the idler and the sprocket, checked against the figure in the operator's manual for that model. Both wrong directions cost money. A chain adjusted too tight loads the pins, bushings, sprocket teeth and final drive bearings continuously, accelerates wear across the whole undercarriage and steals measurable power. A chain too loose slaps the frame, climbs the sprocket on turns and derails, and a derailment in the wrong place costs a day, not an hour. Tension is set by the grease-filled track adjuster: grease pumped in extends the idler and tightens the chain; grease released through the bleed valve lets it back. Two rules protect the adjustment. Measure on level ground after rolling the machine to settle the chain, because a machine that has just turned gives a false reading. And re-check when ground conditions change, because a chain packed with mud is a chain pulled tight by the ground itself.
What you will notice
| Symptom | What it usually points to |
|---|---|
| The chain slaps the carrier roller or frame over bumps | The classic loose-track sound. By the time it is audible from the cab, the sag is well beyond the manual's limit. |
| The track comes off on turns or side slopes | A loose chain climbs the sprocket or idler under side load. Repeated derailment on the same side also asks whether the adjuster on that side is holding grease at all. |
| The track was right yesterday and tight today after working in mud | Material packed between chain and sprocket effectively shortens the path and pulls the chain tight. The adjustment did not change; the ground changed it. |
| Accelerated wear on sprocket teeth and bushings | A chronically over-tight chain loads every contact surface. Sprockets hooked early on a young chain are a tension history lesson. |
Most likely causes
| Cause | How to confirm it |
|---|---|
| Normal pitch wear lengthening the chain | Pin and bushing wear extends the chain's effective length over its life, and tension that was correct a season ago is loose now. This is the routine cause and the reason the check is periodic. |
| Mud and packing between chain and sprocket | Packed material raises the chain on the sprocket and tightens everything. Clay season and sand season want different tension decisions on the same machine. |
| An adjuster losing grease past its seals | An adjuster that creeps back after being set is leaking internally. Pumping it up again is a temporary answer to a seal problem. |
| A previous adjustment made without measuring | Tension set by eye, or set tight on principle, or set immediately after a turn, is a number nobody knows. The measurement is the adjustment. |
What the check finds, and the correct response
| Finding | Response |
|---|---|
| Sag beyond the loose limit, adjuster holds pressure | Pump the adjuster to specification and re-measure after rolling the machine. |
| Sag correct yesterday, tight today, machine worked in mud | Clean the packing out before releasing grease; the ground, not the adjuster, changed the tension. |
| Adjuster loosens within days of being set | Adjuster seal failure; plan the seal kit rather than a weekly grease ritual. |
| One side repeatedly looser than the other | Compare adjuster condition and chain wear side to side; matched wear keeps both sides in step. |
| Tension correct but noise and wear continue | Tension is no longer the issue; measure chain pitch and bushing wear against the service limits. |
How to confirm it
- Park on level ground and roll the machine to settle the chain
Roll forward and back a few meters without turning, then stop without using the steering. A chain settled straight gives a reading that means something; one just off a turn does not.
- Measure the sag at mid-span
Lay a straight edge or tight line from idler to sprocket and measure the maximum droop at the midpoint, at the position the manual specifies. Write the number down with the machine hours.
- Compare against the manual's figure for the exact model
Sag specifications differ between models and sometimes between shoe widths. The operator's manual number is the target, not a rule of thumb from another machine.
- Adjust with the grease fitting or the bleed valve
Tighten by pumping grease into the adjuster fitting; loosen by opening the bleed valve slowly. Keep your face and hands out of the valve's line of fire, because grease under adjuster pressure is a hazard, not an inconvenience.
- Re-measure after rolling again
Roll the machine to distribute the adjustment, then measure again. Adjusting and re-measuring without rolling reads the grease, not the chain.
- Record the result and the hours
A tension log against hours shows the rate of pitch wear on each side. The record turns a check into a forecast, and a forecast is what orders parts before the machine is down.
What to do about it
Adjuster seal service: an adjuster that will not hold grease needs its seal kit, and the job is simple compared with the undercarriage wear a slack chain causes. Fit the kit matched to the adjuster part number, not to a guess at the dimensions.
Wear measurement: where tension will not stay in range or wear is advanced, measure chain pitch, bushing diameter and sprocket tooth form against the service limits. Tension adjustment compensates for wear only within the wear limits.
Packing management: in mud seasons, clean the chain and sprocket at the end of the shift and treat tension as a weekly check rather than a monthly one.
Parts for any of this work — track adjuster seal kits, grease valves and fittings, idlers, chains and sprockets — are supplied by Guangzhou Shenyue Machinery Technology Co., Ltd. from Guangzhou, with 3,000+ part types on the shelf and 100,000+ part numbers available to order, and the grade of every line declared as genuine, OEM-quality or aftermarket. The five brands for which the company holds authorized dealer status are Garrett, Mitsubishi Heavy Industries, TONGMYUNG, NIKURA and Marusan, and the Mitsubishi authorization covers MHI engine parts only. Kobelco is not among them, and Kobelco parts are supplied through original channels or as quality alternatives.
Parts you may need, by grade
| Part | Grades commonly quoted |
|---|---|
| Track adjuster seal kits | Genuine; OEM-quality kit matched to adjuster number. |
| Grease valves and fittings | Genuine; OEM-quality with correct thread and pressure rating. |
| Idlers and sprockets | Genuine; OEM-quality; proven aftermarket lines. |
| Track chains and shoes | Genuine; OEM-quality; aftermarket by measured wear-life performance. |
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 often should track tension be checked?
The operator's manual interval is the floor. In mud, clay or demolition work, check weekly or daily, because packing changes tension faster than wear does. On clean, firm ground with a stable adjuster, the manual interval holds.
Should I run the track tighter to stop it coming off?
No. Derailment has its own causes — worn guides, a weak adjuster, operating technique on side slopes — and over-tension trades a derailment risk for guaranteed accelerated wear across pins, bushings, sprockets and final drive bearings. Fix the cause, keep the tension at specification.
Does shoe width affect the tension decision?
Yes, indirectly. Wider shoes suit soft ground and pack differently; narrow shoes suit rock and carry different side-load behavior. The sag specification and the operating conditions belong together, which is why the manual's figure is stated per configuration.