Static vs Dynamic Connecting Rod Balancing: What’s the Difference?
Jason LiuShare
When people hear “engine balancing,” they often think about rotating assemblies being spun on a machine. This leads many DIY builders to wonder:
Do connecting rods need dynamic balancing?
Or is static balancing enough?
The short answer: connecting rods are always balanced statically, not dynamically.
Dynamic balancing applies to crankshafts, not rods.
Let’s break down what the terms mean and why rods are only balanced one way.
For a complete step-by-step workflow, see the Complete Connecting Rod Balancing Guide.
What Is Static Balancing?
Static balancing means ensuring that each rod has the same:
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big-end weight
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small-end weight
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total weight
This is the method used by DIY builders, machine shops, OEM engine programs, and race teams.
Static balancing uses:
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a digital scale
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a rod balancing fixture
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consistent measuring technique
A static balance ensures each rod contributes identical forces during rotation (big end) and reciprocation (small end).
If you’re balancing rods at home, the easiest tool is the 3D-Printed Connecting Rod Balancing Jig, which replicates a $300 specialty fixture.
What Is Dynamic Balancing?
Dynamic balancing places a rotating assembly on a spinning machine so the operator can remove material to eliminate vibration. This is used for:
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crankshafts
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flywheels
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harmonic balancers
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clutch assemblies
These components rotate as a unit, so balancing must be done while spinning.
Connecting rods do not rotate as a single continuous mass, so dynamic balancing does not apply.
Why Connecting Rods Are Not Dynamically Balanced
A dynamic balancer measures rotating imbalance across 360°.
Connecting rods experience two different types of motion:
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Big end: rotates with the crankshaft
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Small end: moves up and down with the piston
Because these two ends move differently, they cannot be dynamically balanced as a single rotating piece.
Instead, the rod’s ends are measured separately and matched statically.
This allows:
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consistent rotating mass (big end)
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consistent reciprocating mass (small end)
It’s the only way to make forces equal across all cylinders.
Static Balancing Is the Industry Standard (And Always Has Been)
Machine shops, F1 teams, NASCAR, WRC, and OEM engine plants all balance rods statically. Dynamic balancing is never used for connecting rods themselves.
The only time rods interact with a dynamic balance is indirectly:
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Their big-end weight is part of the crankshaft bobweight
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The bobweight value influences crank balancing
But the rods themselves are not spun on the balancer.
How to Perform Static Balancing (Quick Recap)
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Measure total weight of each rod
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Measure big-end weight
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Measure small-end weight
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Choose the lightest rod as your target
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Remove material only from safe exterior areas:
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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
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Re-measure and confirm consistency
A scale + fixture is all you need.
For DIY accuracy, the 3D-Printed Rod Balancer Jig makes this process repeatable and precise.
When Do You Need Dynamic Balancing?
Dynamic balancing is for:
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Crankshaft machining or rebuilding
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Adding forged pistons or rods
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Changing crankshaft stroke
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Changing rod length
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Changing piston compression height
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Changing wrist-pin material
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Aftermarket flywheels or clutches
If any of these change, the crankshaft should be dynamically balanced.
But again, the connecting rods themselves remain statically balanced, even during a full rotating assembly balance.
Final Thoughts
Static balancing is the correct and only method used for connecting rods. Dynamic balancing applies to rotating assemblies, not individual rods. As long as your rods match in big-end and small-end weight within your target tolerance, your engine will run smoothly, reliably, and without imbalance-related wear.
For accurate DIY measurement, the 3D-Printed Connecting Rod Balancer Jig makes the process simple and cost-effective compared to $300+ metal fixtures.