Undercarriage & wear parts
Track pad bolts: torque, pattern, and why they keep coming loose
Why bolts loosen: the four mechanisms
1. Stretch. A bolt torqued beyond its elastic limit does not return to its original length. A stretched bolt cannot hold preload, regardless of how carefully it is re-torqued. This is the most common cause of repeat loosening.
2. Reuse. Track pad bolts are commonly specified as single-use. Reusing them is normal practice in the field and is also the second most common cause of pads coming loose.
3. Embedment. Paint, dirt or corrosion under the head beds down over time. The bolt loses preload without anything moving, and the joint that felt tight on installation is loose weeks later.
4. Hole wear in the link. The bolt hole in the chain link enlarges. The bolt can then move, and once it moves, preload is gone. At this point new bolts do not fix it — the link is the problem.
Reading the failure pattern
Where the bolts fail tells you which mechanism is at work:
- All bolts on one pad loose, others fine — embedment or that pad's holes are worn.
- Bolts on many pads loose — reuse or stretch, or under-torquing.
- Bolt heads sheared off — over-torque or a hard impact, not under-torque.
- Pads gone entirely — the first bolt went unnoticed for long enough that the remaining ones carried double load.
Tightening sequence, stated plainly
Cross pattern, two stages. First pass at roughly half the final torque to seat the pad evenly, second pass at full torque. A sequential pass around the pad leaves the last bolts carrying a disproportionate share, and those are the ones that fail first.
Track pad bolts loosen for a reason. Retightening them repeatedly without fixing that reason is how pads get lost on site and chains get damaged.
Why they loosen
- Stretched bolts. A bolt torqued beyond its elastic limit does not hold torque. Once stretched, it will keep loosening no matter how often you retighten.
- Reused bolts. Track pad bolts are often specified as single-use. Reusing them is the most common cause of repeat loosening.
- Dirt or paint under the head. The bolt beds into it over time and loses preload.
- Worn bolt holes in the link. The hole enlarges, the bolt moves, and preload is lost.
Torque: get the figure from the manual
Correct torque is machine-specific and depends on bolt grade and diameter. It is not interchangeable between machines. Take it from the manual for your model — do not apply a figure from a forum post.
The tightening pattern matters
Tighten in a crossing pattern, not sequentially round the pad. Sequential tightening leaves the pad cocked, and the last bolts carry uneven load. Two stages — an initial pass at part torque, then final torque — is standard practice.
When pads need replacing rather than retightening
- Bolt holes in the pad are ovalised
- The pad is cracked at a bolt hole
- Grouser height is worn below the limit
- Multiple bolts have failed on the same pad
Repeated bolt failure on one pad usually means the pad or the link holes are worn — not that the bolts were badly made.
Ordering pads and bolts
You need: pad width, thickness, bolt hole count and spacing, bolt grade and diameter, and the machine serial number. Send to alfrun@gmail.com for fitment confirmation.
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.
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.
Reviewed by Zhonglei M&E parts desk — export trading partner for undercarriage and wear parts. Last updated 2026-11-13.