How Undercarriage Wear Really Happens: A Detailed Guide for Excavator Owners

If you want to understand the true cost of running an excavator, forget the engine, forget the hydraulics, forget the electronics.Your undercarriage is the single most expensive part of your machine — and the most abused.

It can represent up to 50% of your total operating cost, especially in harsh environments. But most undercarriage wear doesn’t happen because of age. It happens because of conditions, technique, terrain, and understanding (or misunderstanding) how the undercarriage actually works.

In this guide, we dig into the physics, the mechanics, the operator habits, and the environmental factors that make or break your tracks.

1. What the Undercarriage Actually Does

Before we talk about wear, we need to talk about purpose.

The undercarriage of an excavator:

✔ Supports the machine’s entire weight

On a 20-ton excavator, every pin, roller, and track link carries extreme forces.

✔ Transfers power to movement

Final drives turn the sprockets, which turn the tracks — allowing the machine to move, steer, climb, and counter-rotate.

✔ Keeps the machine stable during digging

A well-maintained undercarriage means smoother digging, lifting, and rotation.

✔ Absorbs ground shock

Rocks, uneven terrain, slopes — the undercarriage takes the hits.

If this system weakens, the entire machine becomes inefficient.

2. Components of the Undercarriage (and What Wears First)

Let’s break it down piece by piece:

1. Track Chain (Track Links + Pins + Bushings)

The “spine” of the tracks.Wear points:

• Pin–bushing joints

• External bushing wear

• Link rail surfaces

2. Sprocket

Drives the track chain.Wear points:

• Teeth tips

• Valley between teeth

• Alignment surfaces

3. Bottom Rollers

Carry machine weight.Wear points:

• Roller surfaces

• Seals (loss of oil → failure)

4. Top Rollers (Carrier Rollers)

Guide the chain.Wear points:

• Flat spots

• Seized bearings

5. Idlers

Guide the track and maintain alignment.Wear points:

• Rim wear

• Bearing failure

6. Track Shoes (Grouser plates)

Provide traction.Wear points:

• Grouser height

• Bolt holes elongating

• Shoe bending

7. Track Adjuster (Grease Tensioner)

Controls track tightness.Wear points:

• Leaking tension cylinders

• Broken springs

Each component wears differently depending on usage.

3. The Real Reasons Undercarriage Wear Happens

Undercarriage wear is NOT random. There are clear causes.

Below are the top 12 contributors, backed by field experience from mining, forestry, construction, and demolition sites.

1. Incorrect Track Tension (the #1 killer)

Running tracks too tight increases friction and accelerates wear on:

• Pins

• Bushings

• Sprockets

• Idlers

• Rollers

A tight track can destroy a chain 30–50% faster.

Running tracks too loose leads to:

• De-tracking

• Slapping wear

• Shock load on rollers

Proper tension is a cheap fix with massive savings.

2. High-Impact Job Sites

Rocky terrain, demolition, and forestry operations cause:

• Roller dents

• Chipped sprocket teeth

• Bent shoes

• Compacted material between components

Sharp stones also grind between the chain and sprocket — chewing both out.

3. Constant Turning and Counter-Rotating

Excavators are not dozers.They were not designed for tight, repeated counter-rotation.

This operator habit accelerates:

• Bushing wear

• Sprocket wear

• Link side wear

• Track shoe wear

Best practice: Make wide, sweeping turns.

4. Working on Slopes

Undercarriage wear increases dramatically on slopes due to:

• Uneven load distribution

• Side loading

• Track drift

• Weight bias on one side

The downhill track always wears faster.

5. Packed Debris (Mud, clay, rocks)

Material stuck in the undercarriage causes:

• Restricted movement

• Increased friction

• Uneven roller load

• Forced alignment issues

Clay and wet sand are the worst offenders — they dry like cement.

6. High-Speed Travel

Traveling long distances at full rabbit mode heats the pins and bushings.

This especially kills:

• Bushings

• Carrier rollers

• Sprockets

Excavators are built for digging, not racing across the site.

7. One-Sided Digging

Digging only from one side of the machine causes the same track to carry most of the stress — wearing it out much faster.

8. Poor Track Shoe Selection

Choosing the wrong shoes for your terrain means:

• Too much traction → high wear

• Too little traction → slipping and stress

• Too wide → bending and stress on links

• Too narrow → unstable machine

Every environment has an ideal shoe width.

9. Bent or Damaged Shoes

A single bent shoe causes misalignment.Misalignment causes:

• Roller flange damage

• Sprocket tooth deformity

• Chain walk

One bent shoe can ruin an entire undercarriage.

10. Lack of Cleaning

Most operators don’t clean undercarriages daily.

But packed debris causes:

• Weak roller seals (leading to failure)

• Chain stiffening

• Forced misalignment

• Accelerated wear everywhere

A 10-minute washdown saves thousands.

11. Operating on Hot Tar or Asphalt

This softens rubber pads and increases chain friction — especially on steel tracks with bolt-on pads.

12. Neglecting Worn Components

A worn sprocket destroys a new chain.A worn chain destroys a new sprocket.A failed roller destroys the chain path.

The undercarriage works as a system — not as isolated parts.

4. How Undercarriage Wear Progresses Over Time

Wear typically progresses in this order:

1. Pins & bushings start wearing (internal wear)

2. External bushings grind against the sprocket

3. Sprocket teeth become sharp

4. Track pitch lengthens

5. Chain becomes stretched

6. Rollers develop flat spots

7. Guiding surfaces weaken

8. Machine starts walking to one side

9. De-tracking happens

10. Catastrophic failure (track breaks or rollers seize)

Understanding this progression is the key to early intervention.

5. How to Measure Undercarriage Wear (The Right Way)

Undercarriage measurement is a science.

Professionals use:

• Ultrasonic gauges

• Calipers

• Wear scales

• Pitch measurement tools

But even without advanced tools, operators can check:

✔ Bushing diameter

Sharp edges = worn.

✔ Sprocket teeth shape

Hooked teeth = time to replace.

✔ Roller noise

Grinding = low oil or failure.

✔ Track sag

Too much sag = loose tension.No sag = too tight.

✔ Uneven shoe wear

Indicates alignment issues.

6. How to Reduce Undercarriage Wear (Practical, Real-World Tips)

Here’s the gold — the habits that save the most money:

1. Adjust track tension weekly

Or daily in muddy sites.

2. Minimise counter-rotation

Use wider turns.

3. Avoid unnecessary tracking

Move the machine less.

4. Clean the undercarriage every day

Especially after clay, mud, or rock work.

5. Inspect rollers before each shift

Look for leaks and flat spots.

6. Replace sprockets and chains together

Never mix old and new.

7. Avoid side-hilling

If possible, work straight.

8. Choose correct shoe width

A specialist can advise.

9. Don’t track at full speed over long distances

It overheats bushings.

10. Monitor for misalignment

Machine drifting to one side = misalignment issue.

These small habits extend undercarriage life by 25–50%.

7. When to Repair vs Replace

Here’s the rule of thumb:

Replace the chain when:

• Pitch is stretched beyond spec

• Bushings are worn flat

• Internal pin wear causes “sloppy” movement

• De-tracking becomes frequent

Replace sprockets when:

• Teeth are sharp or hooked

• The valleys are widened

• You’re installing a new chain

Replace rollers when:

• They leak oil

• They wobble

• They develop flat spots

• They seize

Replace idlers when:

• The rim is worn

• Bearing play is noticeable

• Alignment issues occur

A worn undercarriage never improves on its own — it only accelerates wear elsewhere.

8. Typical Undercarriage Lifespan in South African Conditions

South Africa’s terrain is uniquely hard on undercarriages.

Typical lifespans:

➤ Sand sites

2,500–4,000 hours (abrasive)

➤ Clay sites

2,000–3,500 hours (packing wear)

➤ Hard rock

1,200–2,500 hours (impact wear)

➤ Forestry

1,500–2,800 hours (mixed abuse)

➤ Construction (mixed)

2,000–4,500 hours

Operator skill = the biggest variable.

9. Final Thoughts

Undercarriage wear isn’t a mystery — it’s predictable, measurable, and preventable.

If you understand:

• how the system works,

• what causes wear,

• how to inspect it,

• and how to maintain it…

…you can double the life of your tracks and slash your operating costs.

Whether you’re running a single machine or a fleet, undercarriage knowledge is money in the bank.