An excavator that throws a track on a Friday afternoon does not just lose a day of digging. It loses the truck that was booked to haul spoil, the crew that was standing around a machine that cannot move, and often the next job as well, because a machine with a track hanging off its rollers cannot be loaded onto a trailer safely. Track problems look like small maintenance issues until they stop a machine dead, and by then the repair bill is usually three or four times what a simple adjustment would have cost.
The worst part is that tracks almost always warn you first. A track that slips under load, a track that keeps drifting to one side, or a set of pins and bushings wearing faster on one side than the other are all early signs that something is wrong with tension, alignment, or the undercarriage itself. Learn to read those signs, and most track failures become planned repairs instead of site shutdowns.
This guide covers the three track problems that cost owners the most money: slipping, derailing, and uneven wear. You will learn what causes each one, how to diagnose it in the field, how to fix it, and when a track is worth repairing versus replacing outright. It applies to steel tracks and rubber tracks alike, and the checks here work on machines from a 1.7-ton mini to a 20-ton crawler.
Quick Answer: What Is Wrong With My Excavator Tracks?If your excavator track slips, the drive is losing grip, and the usual causes are worn sprocket teeth, a stretched track chain, low tension, or mud and debris packed between the track and the sprocket. If the track derails, it has come off the rollers and idler, and the usual causes are loose tension, a worn or damaged idler, a bent track frame, or turning sharply on a slope or over an obstacle. If wear is uneven, one side of the machine is doing more work than the other, or the track is running out of alignment, and the usual causes are constant turning in one direction, travelling on hard surfaces, a misaligned idler, or a worn roller on one side.
Start every diagnosis with the same three checks, because they cost nothing and they catch most problems: track tension against the manufacturer's specification, a walk-around look at the sprocket, idler, and rollers, and a check for packed mud, rock, or debris in the track frame. If tension is correct and the components look sound, the problem is usually how the machine is being used, not a part that has failed. The sections below take each failure in turn, so you can jump straight to the symptom your machine is showing.
1. Slipping Tracks: When the Drive Loses Its Grip
A slipping track is easy to recognise and easy to misdiagnose. The machine hesitates or jerks when it tries to travel, one track moves slower than the other, or the track spins without moving the machine forward, especially on a slope or under load. Operators often blame the hydraulic motors first, but a hydraulic fault usually affects travel speed on both sides or shows up as a loss of power in the boom and bucket as well. A problem that affects one track only, and only when travelling, is almost always in the track itself or the final drive sprocket.
The most common cause is a worn sprocket. Sprocket teeth are designed to mesh with the track chain bushings, and as both wear, the fit becomes sloppy. The chain starts to ride up over the teeth under load instead of seating cleanly, and the track slips a notch at a time. You can check this with the machine parked and the track raised: look for teeth that are hooked, pointed, or visibly shorter than the teeth on the other side, and check for play between the chain and the sprocket by rocking the track by hand.
A stretched track chain causes the same symptom for a different reason. As pins and bushings wear, the chain grows longer, the pitch between links increases, and the chain no longer matches the sprocket. This is a slow process on a well-maintained machine, but it accelerates fast once tension is allowed to run slack, because a loose chain hammers the sprocket teeth with every revolution. If you measure the chain and find it beyond the manufacturer's wear limit, no amount of tension adjustment will fix the slip, and the chain needs replacing.
2. Derailing: When a Track Comes Off Completely
Derailing is the track failure every operator dreads, because it stops the machine where it stands and the repair is dirty, heavy, and slow. A derailed track has slipped off the front idler, the bottom rollers, or both, and the machine is left sitting on its track frame with one side grounded. The good news is that derailing is almost always preventable, and it almost always has a visible cause you can find before it happens again.
Loose tension is the leading cause, by a wide margin. A track with too much sag can climb off the idler when the machine turns, crosses a kerb or rock, or travels across a slope with the loose side downhill. Rubber tracks are especially prone to this, because they flex more than steel and a loose rubber track can roll off the rollers under side load. Steel tracks derail too, but they usually need a worn idler or a damaged roller as well before they will come off.
Worn or damaged idlers and rollers are the second cause. An idler with a worn flange no longer guides the track chain in a straight line, and a seized or collapsed bottom roller lets the chain drop and wander. Both problems show up as a track that keeps drifting to one side, or as a rhythmic thumping as the machine travels. Check the idler flanges for wear, spin each bottom roller by hand with the track raised, and replace any roller that is seized, noisy, or visibly out of round.
3. Uneven Wear: When One Side Wears Faster Than the Other
Uneven wear is the quietest track problem and the most expensive over the life of the machine, because it shortens the life of the whole undercarriage. The signs are subtle at first: one track chain measures longer than the other, the grouser bars are worn down more on one side, rubber track lugs are chunking on the inside edge, or the machine pulls slightly to one side when travelling on flat ground. By the time the difference is obvious, you have usually lost hundreds of hours of track life.
The most common cause is simply how the machine works. A machine that always turns the same way, for example when loading trucks parked on one side all day, wears the inside of one track and the outside of the other far faster than a machine that alternates direction. A machine that travels long distances on asphalt or concrete wears rubber tracks and steel grousers far faster than one that works on soil, and a machine that spends its life on a slope wears the downhill track harder than the uphill one. None of these are faults, but all of them are manageable once you recognise the pattern.
4. How to Check and Set Track Tension Correctly
Track tension is the single most important track maintenance task, and it is also the one most often done by guesswork. Too loose, and the track slips, derails, and hammers the sprocket. Too tight, and you overload the idler bearings, the final drive seals, and the track pins, and the machine burns extra fuel just to travel. Getting it right takes a tape measure and ten minutes, and it should be done with the track clean, because packed mud changes the sag reading completely.
Steps to check tension
Step 1: Clean the track frame. Remove mud, clay, and debris from around the rollers, idler, and sprocket, and travel the machine a short distance forward and back so the track settles naturally.
Step 2: Raise one side of the machine. Use the boom and bucket to lift the track off the ground on the side you are checking, and support the machine safely before you work near the track.
Step 3: Measure the sag. Place a straight edge across the top of the track frame and measure the gap between the straight edge and the top of the track chain at its lowest point, following the manufacturer's specification for your model.
Step 4: Adjust with the grease gun. Add grease through the tensioner valve to tighten the track, or release grease carefully to loosen it, then re-measure and repeat until the sag is within specification.
Step 5: Check both sides and re-check after work. Set both tracks to the same specification, travel the machine for a few minutes, and measure again, because a track that has just been adjusted will settle as it works.
Always measure rather than tensioning by feel, and record the measurement so the next check shows whether the chain is stretching faster than it should. A chain that needs frequent re-tensioning is telling you it is near the end of its life, even if it still looks serviceable.
5. Steel Tracks vs Rubber Tracks: Different Problems, Different Fixes
Steel and rubber tracks fail in different ways, and the fix that works for one can damage the other. Steel tracks are heavy, durable, and rebuildable: pins, bushings, sprockets, and rollers can all be replaced, and a steel undercarriage can often be rebuilt rather than replaced outright. Their weaknesses are weight, ground damage on finished surfaces, and the cost of a full rebuild when several components wear out together.
Rubber tracks are lighter, quieter, and far kinder to asphalt, paving, and lawns, which is why they dominate the mini excavator market. Their weakness is that they cannot be rebuilt: once the steel cords inside the rubber are damaged or the lugs wear through, the whole track is scrap. Rubber tracks are also more sensitive to tension, to sharp objects, and to chemicals such as oil and solvents, all of which shorten their life fast. For more on keeping the whole undercarriage in shape, see our guide to excavator undercarriage maintenance, and for the lubrication side of the job, our guide on how to grease an excavator properly.
| Feature | Steel tracks | Rubber tracks |
|---|---|---|
| Typical life | 3,000–5,000 hours with rebuilds | 1,200–2,000 hours, no rebuild |
| Main failure mode | Pin and bushing wear, sprocket wear | Cord damage, lug chunking, derailing |
| Tension sensitivity | Moderate | High — derails easily when loose |
| Surface damage | High on asphalt and paving | Low |
| Replacement cost | High per set, but parts replaceable | Lower per set, whole track replaced |
6. Repair or Replace: Making the Call
The hardest decision in track maintenance is not how to fix a problem, but whether the track is worth fixing at all. Replacing a single roller or an idler on a track chain that is already past its wear limit is money wasted, because the new part will wear fast against the old chain and the next failure will arrive within weeks. Conversely, scrapping a track chain that only needs a tension adjustment and a new idler wastes thousands.
Use wear measurements, not appearance, to decide: chain pitch against the manufacturer's limit, sprocket tooth height, and roller flange thickness. If the chain is within limits and the sprocket is sound, repair the failed component. If the chain is beyond its limit, or the sprocket and several rollers are worn together, price a full rebuild against a new track set, factoring in downtime, because a week in the workshop can cost more in lost work than the parts saved.
| Situation | Usually the right call |
|---|---|
| Track slips, tension was slack | Re-tension and monitor for a week |
| One seized roller, chain within limits | Replace the roller only |
| Track derails repeatedly | Check idler, frame, and tension; replace worn guides |
| Chain past wear limit | Replace chain and sprocket together |
| Rubber track with cut cords | Replace the whole track; do not patch cords |
7. Common Mistakes That Wreck Tracks Early
- Running slack: a loose track feels harmless until it derails, and every hour run slack accelerates sprocket and bushing wear.
- Over-tensioning: a track set too tight overloads bearings and seals, and the machine will tell you with higher fuel use and hot final drives.
- Ignoring packed debris: mud and rock packed in the track frame changes tension, blocks rollers, and hides damage until it fails.
- Turning on the spot at full speed: pivot turns grind one track against the ground and wear grousers, lugs, and rollers far faster than a gradual turn.
- Mixing old and new: fitting a new sprocket to a worn chain, or a new chain to a worn sprocket, wears the new part out in a fraction of its normal life.
- Skipping the daily walk-around: most track failures are visible days before they happen, but only if someone actually looks at the undercarriage every day.
Track problems reward the owner who checks often and fixes early, and they punish the owner who runs a machine until it stops. A ten-minute tension check, a clean track frame, and a quick look at the sprocket and rollers each day will prevent most slips and derailments, and they will give you the wear measurements you need to plan a replacement instead of reacting to a breakdown.
Start with the symptom your machine is showing today, work through the checks in order, and fix the cause rather than just the symptom. For more track and undercarriage topics, browse the repairs and news pages, and the operator guides for the driving habits that protect tracks.
