How Do Aftermarket Sprockets Compare to OEM for the PC300?

On a PC300, the difference between an aftermarket sprocket and an OEM one is not usually the steel - it is the paperwork. Both are machined, heat-treated parts, and the ones that fail early fail for reasons you could have checked before ordering: a tooth profile cut slightly wrong, a bore that does not seat on the final drive, or no stated hardness at all. The brand on the box is the least useful information on it.

Last updated: October 5, 2026

This guide covers the dimensions an aftermarket sprocket has to match, what separates a durable one from a cheap one, how the price difference is actually made up, and what to have in writing before you buy.

The dimensions that have to match

Three numbers decide whether a sprocket belongs on the machine, and all three are checkable.

Tooth count and pitch. The teeth engage the track links; the pitch has to match the chain exactly. A sprocket with the right bolt pattern and the wrong pitch will bolt on and then climb the links, stretching the belt out of tolerance. The bore. The bore has to fit the final drive hub precisely - this is the measurement buyers most often assume rather than measure. The mounting geometry. Bolt count, hole spacing and the face that seats on the hub all have to match, because a sprocket that does not sit flat runs out of true and wears the belt's links unevenly.

Confirm all of them against the parts book for your machine and serial number rather than against the model name. Komatsu changed sprocket part numbers across the PC300 range, which is why a listing has to be read from the number you have - as the product in the photograph illustrates, these are listed by part number and machine class.

What separates a durable sprocket from a cheap one

Four features do the work, and each one is worth a question.

Feature	Why it matters
Hardened teeth	The tooth surface is what wears against the link; hardness here decides how long the profile survives
Heat treatment of the body	A body without proper treatment distorts or cracks under torque rather than wearing out predictably
Machining tolerance	Bore and tooth profile are cut, not cast to shape; tolerance is what makes the part fit and run true
Coating or corrosion protection	Matters where the machine works in wet or salty conditions, and where the sprocket sits unused for periods

The honest test is that a supplier can state the material and the treatment, not just the dimensions. "Hardened" without a specification is a word; a stated material grade and heat treatment is a part you can compare with another.

Where the price difference comes from

An OEM sprocket costs more for reasons that have nothing to do with the steel: research and development amortised across a catalogue, brand licensing, dealer margin, and a warehousing network. An aftermarket sprocket avoids most of that overhead, which is the real source of the saving - and it is also the source of the risk, because the same channel that removes overhead can also remove inspection.

So the useful comparison is not "OEM versus aftermarket" but "documented versus undocumented". A documented aftermarket sprocket with a stated material, treatment and warranty is a known part. An undocumented one that happens to be cheaper is a bet on the seller's supply chain - and on a PC300 the cost of losing that bet is a stretched track, not a sprocket.

What to have in writing

Four items, and they take one message to ask for. The part-number cross-reference to your machine's model and serial number. The tooth count, pitch and bore as supplied. The material and heat treatment. And the warranty terms as a period plus an operating-hours cap, whichever comes first, with freight responsibility named for a claim - on a part this weight, who pays freight is the difference between a warranty and a gesture.

Where the machine's own warranty is still in force, confirm with the dealer how a non-OEM sprocket affects coverage on the final drive it mounts to, before ordering rather than after a failure. And where the sprocket is being replaced because it is worn rather than broken, note what the teeth said: uneven wear around the sprocket is a symptom of alignment or a track running off line, and a new sprocket will wear the same way unless that is corrected. The same failure pattern shows up on track loaders, which is why drive sprocket wear on CTL machines is worth reading alongside this - the mechanics do not change with the machine type.

Telling when the sprocket is finished

The wear on a sprocket is progressive and readable, and the point to act is before the teeth stop carrying the load properly.

Teeth that have rounded, or that lean toward the drive side into a hook, are climbing the links rather than seating in them - which stretches the chain and wears the bushings with every revolution. Wear that is uneven around the sprocket points to the track running off line or to an alignment problem, and a new sprocket fitted without correcting that will wear identically. Broken or chipped teeth indicate impact damage and warrant a look at the final drive and the mounting face before anything new goes on. And a track that skips under load means the pitch no longer matches, which can be the sprocket, the chain, or both.

Two practical rules follow. A sprocket belongs in the same job as the track, because the two parts wear against each other and a mismatch in either direction shortens both. And a sprocket is measured against the machine's own service limits rather than judged by eye - the difference between "worn" and "finished" is usually a measurement you take before the teeth start hooking.

This article is part of the drive sprockets guide, which covers how a sprocket is identified, how it wears and when to replace it with the chain.

FAQs

Do aftermarket sprockets meet OEM tolerances?

They can, and the way to verify it is by asking for the tooth count, pitch, bore and mounting geometry as supplied, plus the material and heat treatment. Those four statements are what "meets OEM tolerance" actually means on a sprocket.

Why is an aftermarket sprocket cheaper?

Mainly overhead: no research and development to amortise, no brand licensing, no dealer margin. That is a legitimate saving - and also the reason the documentation, not the price, is what you should judge the part on.

How do I know when a PC300 sprocket needs replacing?

Teeth hooked or rounded toward the drive side, wear uneven around the sprocket, broken teeth, or a track that skips under load because the pitch no longer matches. In practice the sprocket belongs in the same job as the track.

Can I run an aftermarket sprocket with an OEM track?

Yes, provided the pitch and tooth profile match the chain. What you should avoid is pairing a new sprocket with a stretched track, or a new track with hooked teeth - either mismatch wears both parts.

Should I replace the sprocket and track at the same time?

Where either is worn, yes. A new belt on hooked teeth is damaged by the teeth, and a new sprocket on a stretched belt sees the same mismatch from the other direction. Doing them together is what keeps the pitch matched.