Crankshaft Balancer: from Passenger Cars to Heavy Trucks

Q: Does the V-angle (60°, 90°, etc.) affect the balancing method?

No. The V-angle affects the crankshaft geometry, but it does not change the dynamic balancing procedure . Whether it is a V6 at 60° or a V8 at 90°, the process is the same: bobweights are fitted to the rod journals and the crankshaft is balanced dynamically. The bobweight mass calculation follows the same formula regardless of the V-angle.

Q: If I replaced the pistons or connecting rods, is re-balancing required?

Yes, it is mandatory for V-configuration engines. The bobweight mass used during balancing is calculated for the specific connecting rods and pistons in that engine. Replacing those components — even with parts that differ only slightly in weight — invalidates the original balance. For inline 4- and 6-cylinder engines this is less critical, but a balance check is recommended after any major engine overhaul.

Q: Why should the flywheel be balanced separately from the crankshaft?

The professional approach involves a three-stage procedure : balance the crankshaft independently, then balance the flywheel independently, then verify the complete assembly as a unit. This provides two key benefits: first, if the flywheel is ever damaged, it can be replaced without fully dismantling the engine; second, higher final balance accuracy is achieved because each component is first brought to its optimum condition independently.

Q: Why does the assembly weight matter more than the bare crankshaft weight when selecting a machine?

Because the final balancing step is always performed as a complete assembly: crankshaft + flywheel + harmonic damper . A heavy truck flywheel weighs 40–80 kg; a passenger car flywheel 5–20 kg. A machine rated only for the bare crankshaft weight may not handle the load once the flywheel is mounted. This is why our machine specifications state the load capacity for the full assembly, not just the crankshaft alone.

Segment 1 — Passenger Vehicles

Passenger Cars: Inline 4- and 6-Cylinder Engines, VR6, V6

The 9A714 is designed for balancing crankshafts in passenger cars and light commercial vehicles. It supports the most common engine configurations on the European market.

Horizontal Balancing Machine

0.03 to 60kg

9A714

Industrial belt-driven balancer for lightweight rotors up to 60 kg

Inline 4- and 6-Cylinder Engines

The most widespread configuration in the European passenger car market. These crankshafts do not require bobweights during balancing: each rod journal has a symmetrical counterweight positioned at 180°. Balancing is carried out using the standard metal removal method.

Examples: VW Golf TDI, Audi A3, BMW 318i / 330i, Renault Mégane, Peugeot 308, Ford Focus, Opel Astra

V-Configuration and Narrow-Angle Engines (VR6, V6)

VR6 Volkswagen/Audi, V6 Alfa Romeo, V6 Renault and equivalents require the installation of bobweights on the rod journals during balancing. Bobweights simulate the combined dynamic effect of rotating and reciprocating masses. Their weight is calculated individually for each engine based on the actual mass of connecting rods and pistons. Any change to piston or rod weight during the overhaul requires re-balancing.

Examples: VW Passat VR6, VW Golf IV VR6, Audi A6 2.8, Alfa Romeo 156 V6, Renault Laguna V6, Ford Mondeo ST220 3.0 V6

Crankshaft

8–35 kg

bare crankshaft

Full Assembly

up to 50 kg

crankshaft + flywheel (5–10 kg) + harmonic damper (1–3 kg)

Segment 2 — Light Commercial Vehicles & SUVs

Vans, SUVs, V8: Inline 6-Cylinder Diesels and V-Configuration Engines

The 9D715 is designed for heavier crankshafts found in commercial vehicles, minivans, large SUVs, and high-performance passenger cars with V8 engines.

Horizontal Balancing Machine

60 to 500kg

9D715

Hard-bearing balancing machine for medium-weight rotors up to 100 kg

Inline 6-Cylinder Diesel Engines

The dominant configuration in European light commercial vehicles. Balancing is performed without bobweights. However, diesel crankshafts are noticeably heavier than petrol equivalents due to higher combustion pressures and thicker journal walls — this directly affects the weight of the final assembly.

Examples: Mercedes-Benz Sprinter OM651 / OM642, VW Transporter TDI, Ford Transit 2.0 EcoBlue, BMW 530d (M57)

V8 and V6 — Petrol and Diesel Engines

BMW X5 V8, Mercedes-Benz E-Class V8, Audi Q7 V6 TDI, Porsche Cayenne V8, Land Rover TDV8 — all of these engines require the mandatory use of bobweights. The bobweight mass is calculated based on the specific connecting rods and pistons used in that engine. Any change in moving part weights makes re-balancing obligatory.

Examples: BMW X5 4.8i V8, Mercedes E55 AMG V8, Audi Q7 3.0 TDI V6, Porsche Cayenne 4.5 V8, Land Rover Range Rover TDV8

Crankshaft

35–70 kg

bare crankshaft

Full Assembly

up to 100 kg

crankshaft + flywheel (10–20 kg) + harmonic damper (2–5 kg)

The 9D714 is not suitable for this engine class: the crankshaft + flywheel assembly of a light commercial diesel will easily exceed 50 kg — even without the harmonic damper.

Segment 3 — Heavy Trucks & Commercial Machinery

Trucks, Buses, Special Machinery: Large-Displacement Inline 6 and V8 Diesels

The 9D715US is designed for professional repair shops that specialize in the major overhaul of engines for heavy trucks, buses, and construction equipment.

Special Balancing Machine

9D715US

Crankshaft balancing machine up to 300 kg with integrated drilling module

Large-Displacement Inline 6-Cylinder Engines

The defining configuration of European heavy commercial transport. Balancing is performed without bobweights. However, the mass and length of these crankshafts place stringent demands on the load capacity and structural rigidity of the balancing machine — requirements that cannot be met by equipment designed for the light or medium segments.

Examples: Volvo FH D13, Scania R440/G420, MAN D2066, Mercedes-Benz Actros OM473, DAF XF MX-13

Large-Displacement V8 Diesel Engines

Scania V8, Mercedes-Benz OM502, Volvo D16 are less common but require bobweight calculation and installation. The compensating mass is considerably larger than in the light and medium segments. Imbalance in crankshafts of this class critically affects the service life of main bearings and generates excessive bending loads under high operating conditions.

Examples: Scania R500/R730, Mercedes-Benz Actros OM502, Volvo D16G

Crankshaft

80–200 kg

bare crankshaft

Full Assembly

up to 300 kg

crankshaft + flywheel (40–80 kg) + harmonic damper (5–15 kg)

Only the 9D715US provides the load capacity required for a correct final balance of the full assembly in this engine class.

Why Is Balancing Always Done as an Assembly?

The final balancing step always includes the flywheel and harmonic damper. First, the bare crankshaft is balanced independently. Then the flywheel is balanced independently. Finally, the complete assembly is verified as a unit. This approach means the flywheel can be replaced in the future without requiring the crankshaft to be removed from the engine.

This is precisely why selecting a balancing machine must be based on the total assembly weight — not just the weight of the bare crankshaft.

Frequently Asked Questions

Yes, in most cases it does. Factory balancing of production crankshafts is performed to broad tolerances — sufficient for standard operation, but not optimal after an engine overhaul. A rebuilt engine with new pistons and connecting rods has a different mass distribution, and the original factory residual imbalance is no longer compensated. Professional balancing after overhaul reduces vibration, lowers the load on main bearings, and extends engine service life.

Bobweights are precision compensating masses clamped onto the crankshaft rod journals during balancing. They simulate the combined weight of the connecting rods and pistons that rotate with the crankshaft. Bobweights are required for all V-configuration engines (V6, V8, V10, V12) as well as for inline engines with an odd number of cylinders (1, 2, 3, 5). Inline 4- and 6-cylinder engines do not require bobweights — their geometry is inherently symmetrical. Bobweight mass is calculated individually for each engine based on the actual measured weight of its rods and pistons.

No. The V-angle affects the crankshaft geometry, but it does not change the dynamic balancing procedure. Whether it is a V6 at 60° or a V8 at 90°, the process is the same: bobweights are fitted to the rod journals and the crankshaft is balanced dynamically. The bobweight mass calculation follows the same formula regardless of the V-angle.

Yes, it is mandatory for V-configuration engines. The bobweight mass used during balancing is calculated for the specific connecting rods and pistons in that engine. Replacing those components — even with parts that differ only slightly in weight — invalidates the original balance. For inline 4- and 6-cylinder engines this is less critical, but a balance check is recommended after any major engine overhaul.

The professional approach involves a three-stage procedure: balance the crankshaft independently, then balance the flywheel independently, then verify the complete assembly as a unit. This provides two key benefits: first, if the flywheel is ever damaged, it can be replaced without fully dismantling the engine; second, higher final balance accuracy is achieved because each component is first brought to its optimum condition independently.

Because the final balancing step is always performed as a complete assembly: crankshaft + flywheel + harmonic damper. A heavy truck flywheel weighs 40–80 kg; a passenger car flywheel 5–20 kg. A machine rated only for the bare crankshaft weight may not handle the load once the flywheel is mounted. This is why our machine specifications state the load capacity for the full assembly, not just the crankshaft alone.

No. Even if the bare crankshaft of some lighter truck engines is within 100 kg, the assembly with flywheel and harmonic damper will inevitably exceed that limit. For heavy commercial vehicles (Volvo, Scania, MAN, Mercedes Actros, DAF), the 9D715U with a 300 kg capacity is required.

For a complete and accurate balancing job, the following must be provided: the flywheel, the harmonic balancer (crankshaft damper), any timing gears or sprockets attached to the crankshaft, and new fastening hardware. For V-configuration engines, the actual measured weights of connecting rods and pistons are also required in order to calculate the correct bobweight mass. Balancing the bare crankshaft alone without these components does not produce accurate results.