Undercarriage & wear parts
The one-page identification cheat sheet
Print this. It is the short version of every guide on this site: what to measure on each component, and what to send us so a part can be confirmed rather than guessed.
What to measure, component by component
| Component | Measure | What catches people out |
|---|---|---|
| Bucket tooth | Pin bore Ø (two axes, 90°), opening width, overall length, retention type | Pinless and pinned systems are never interchangeable, even at identical dimensions |
| Track roller | Shaft Ø, outer Ø, overall width, flange spacing, casting number | A leaking roller is more urgent than a worn one — the seal has gone |
| Carrier roller | Same dimensions as a track roller | Not interchangeable with a track roller despite looking similar |
| Front idler | Rim Ø, shaft Ø, flange spacing, casting number | Tread wear is measurable; bearing failure is not — look for grease at the hub |
| Sprocket | Tooth count, chain pitch, tooth section thickness, bolt pattern | Tooth length is the wrong dimension — measure the section |
| Track shoe | Width, thickness, bolt hole count and spacing, grouser height | Count the holes on both sides — asymmetric patterns exist |
| Track chain | Link count, average pitch over 4 links (5 pins) | Measure straight and under tension; a curved chain reads long |
| Cutting edge | Bolt hole count, spacing, diameter, cumulative span, thickness, depth | Width is the one dimension everyone measures and nobody gets wrong |
The four things to send
- Machine make, model and full serial number. The prefix identifies the build series — the last few digits do not.
- A photograph of the casting number on the worn part. Clean it, light it from the side, get close. This one photo resolves more than any written description.
- The key dimensions above for that component. Measured, not estimated from a catalogue.
- Quantity, and whether one-off or repeating. It changes the quote and what we recommend.
If one of the four is missing, send the other three and say which is missing. An honest "cannot confirm" is more useful than a guess.
Why the model name alone fails
Within a single machine model there are usually several part variants, depending on build generation and on the bucket or attachment the machine was supplied with. "Fits PC200" describes a family, not a machine. The serial prefix plus the casting number describes a machine.
Five wear signs worth acting on early
- Grease or oil at a roller or idler end — seal failure, ahead of visible tread wear
- Grease escaping straight after greasing — clearance too large to hold it
- Teeth hooked at the tip — the sprocket is now wearing the chain
- Track needing repeated tensioning — usually a leaking adjuster, not a stretched chain
- One roller worn far beyond its neighbours — the cause is tension or alignment, and it will repeat
Track tension, roughly
Sag is measured at mid-span, on level ground, cold, with the track lifted slightly. Exact limits vary by machine, so use your manual — but as a sanity check, a medium excavator with standard steel shoes typically sits around 20–30 mm of sag. Heavier shoes run tighter, rubber pads run looser.
Before you order
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.
Confirming the part before you order
Use the four items above, then build the email in one go — no back-and-forth.
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.