Common Connecting Rod Balancing Mistakes (And How to Avoid Them)
Jason LiuShare
Connecting rod balancing is straightforward, but small mistakes can lead to inaccurate end weights, vibration, and avoidable engine wear. This guide outlines the most common issues builders run into—and exactly how to avoid them.
For the complete workflow, see the
Complete Connecting Rod Balancing Guide.
Mistake #1 — Only Measuring Total Rod Weight
Total weight alone tells you nothing about how the rod affects the engine.
You must isolate:
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Big-end weight (rotating mass)
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Small-end weight (reciprocating mass)
Two rods can weigh the same overall and still be completely imbalanced internally.
Mistake #2 — Using Knife-Edge Balancers With Friction
Knife edges introduce friction, and friction = inaccurate readings.
As the edges dull or the rod shifts:
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Readings drift
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Repeatability drops
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You may remove the wrong amount of material
Modern low-friction fixtures are far more accurate, including:
3D-Printed Connecting Rod Balancing Jig
Mistake #3 — Not Keeping the Rod Perfectly Horizontal (Chain Method)
The string/chain suspension method can be accurate—but only if the rod is perfectly horizontal.
If it’s angled even slightly:
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Weight shifts toward the scale
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End weight readings become incorrect
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You’ll over-grind or under-grind
Always use:
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A bubble level
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A height-adjustable stand
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Shims under the scale if necessary
Mistake #4 — Grinding the Wrong Areas
Never remove material from:
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The rod beam
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The big-end bore
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The wrist-pin bore
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The wrist-pin bushing
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Bearing tang areas
Safe removal zones:
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Big end: exterior of the connecting-rod bolt bores
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Small end: exterior of the wrist-pin bore
Always grind evenly.
Mistake #5 — Inconsistent Support Height
If the rod support height changes even a few millimeters, end-weight readings change.
Common causes:
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Wood blocks
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Books
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Random objects used as stands
Use a height-consistent fixture such as:
3D-Printed Connecting Rod Balancing Jig
Mistake #6 — Removing Too Much Material at Once
Take off too much and you risk:
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Overshooting your target
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Weakening the rod
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Needing to remove material from both ends unnecessarily
Rod balancing should be done in micro-increments, checking the scale often.
Mistake #7 — Not Re-Measuring Multiple Times
Always measure each rod:
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2–3 times per end
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In the same location
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On the same scale
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With the same orientation
Repeatability = accuracy.
Mistake #8 — Using a Low-Quality Scale
A poor scale creates unreliable data.
Avoid scales that:
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Drift
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Bounce
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Have tiny platforms
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Have slow refresh rates
Use a digital scale with:
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0.1 g resolution (good)
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0.01 g (best for race engines)
Mistake #9 — Ignoring Temperature & Surface Stability
Scales are sensitive to:
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Cold temperatures
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Vibrating tables
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Uneven surfaces
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Drafts or airflow
Always measure on:
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A solid, stable table
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Indoors at room temperature
Mistake #10 — Not Matching Everything to the Lightest Rod
You should never add weight to a rod.
The correct process:
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Identify the lightest rod
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Match all big ends to that number
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Match all small ends to that number
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Confirm totals
This guarantees consistency across the set.
Final Thoughts
Avoiding these common mistakes will help you achieve accurate, repeatable rod balancing results that improve engine smoothness, bearing life, and high-RPM stability.
For the easiest, most consistent measurements, use the
3D-Printed Connecting Rod Balancing Jig.