Rollers and idlers guide and carry the track chain, and they wear as a set with it. Replaced at the right time, they protect the chain and sprockets they run with. Left too long, worn rollers accelerate wear on the chain links and can let the chain jump on the sprockets.
Bottom rollers run on the chain rail under the machine, carrier rollers support the chain over the top of the frame, and the idler guides the link and is pushed out by the recoil cylinder to keep the track at the correct tension. Wear is measured as a percentage against new dimensions, bottom rollers should always be changed as a set, and idlers and track adjusters are best replaced together.
What each component does
The idler guides the link and is extended by grease pressure in the recoil cylinder behind it, which keeps the track at the correct tension. Our cast idler assemblies come complete with heavy-duty seal groups, shafts and brackets, so they fit as one unit.
Bottom rollers carry the machine along the chain rail. Carrier rollers, on top of the frame, support the chain's return run. Rollers are supplied in single flange and double flange types, with shaft-type carrier rollers also available. A double flange roller increases guidance of the link, and dozers normally run a mixture of single and double flange rollers.
How quality rollers are built
The differences between rollers are not visible from the outside, which is why the build specification matters. DuraTrack roller shells are forged, joined by friction welding or submerged arc welding, and heat treated by differential quenching or through hardening. The shafts are made from forged alloy or rolled carbon steel and hardened. Top and bottom rollers incorporate reinforced flanges and heavy-duty seals for increased reliability. Roller and sprocket bolts are 10.9 grade, forged from alloy steels and heat treated to OEM specification.
Reading the wear
Roller and idler wear is measured, not judged by eye. A track inspection records the top rollers, bottom rollers and idler as wear percentages against new dimensions, alongside chain stretch, rail height, bushing and grouser height, so the whole system is read together.
Two findings deserve particular attention:
- Pin boss side wear on the chain. If it appears before the links reach 100% wear, replace the rollers.
- Chains jumping on the sprockets. Worn track rollers are one of the causes, along with worn sprockets, a broken track adjuster spring, offset sprockets fitted the wrong way round and the wrong pitch. Track guards help keep the chain in line while the cause is put right.
Replace bottom rollers as a set
It is always best practice to change all the bottom rollers together. A single new roller sits proud of its worn neighbours, so it carries more than its share of the load and the wear rate increases.
Browse the ranges by machine make and model: bottom rollers, top rollers and idlers, all DuraTrack and available from UK stock.
Frequently asked questions
When should track rollers be replaced?
When measurement says so. Roller wear is assessed as a percentage against new dimensions during a track inspection. Pin boss side wear on the chain appearing before the links reach 100% wear is a specific signal to replace the rollers.
Why should bottom rollers be changed as a set?
A single new roller sits proud of its worn neighbours, carries more than its share of the load and increases the wear rate. Changing all the bottom rollers together keeps the load shared and the wear even.
What is the difference between single flange and double flange rollers?
The flanges are what guide the chain link. A double flange roller increases guidance of the link, and dozers normally run a mixture of single and double flange rollers. Shaft-type carrier rollers are also available.
What makes the track chain jump on the sprockets?
Worn sprockets, a broken track adjuster spring, offset sprockets fitted the wrong way round, the wrong pitch or worn track rollers. Track guards help keep the chain in line, but the worn component still needs to be found and replaced.
Should idlers and track adjusters be replaced together?
Yes, wherever possible. The adjuster works directly against the idler, a worn idler can cause a new adjuster to fail prematurely, and the warranty reflects it: 12 months when fitted with a new idler, 6 months without.
Astrak Group develops and manufactures products intended to be compatible with machinery and equipment from various manufacturers. Unless indicated otherwise, Astrak Group has no relationship, commercial or otherwise, with the owners of the trademarks.
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