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Using Tungsten Ballast to Set Weight Distribution in Race Cars

September 21, 2026 · Reviewed September 26, 2026

Race cars run at or near a minimum weight set by the rulebook, and teams add ballast to reach that minimum in a way that also improves handling. Where that ballast goes, not just how much of it there is, is often the bigger lever. Tungsten heavy alloy ballast lets a team place mass in a smaller footprint than steel or lead allow, which matters when the mounting points are fixed by the chassis and the rulebook.

Why weight distribution matters more than total weight

Most classes set a minimum total weight, and cars below it fail scrutineering. Reaching that minimum is easy with any dense material bolted anywhere there is room. The harder problem is where the mass sits relative to the wheels. Front-to-rear and left-to-right weight distribution changes how the car turns in, how it transfers load under braking, and how tires wear across a run. Teams tune this by shifting ballast between mounting points as the setup changes from track to track, sometimes within a single race weekend.

The mounting points on a race chassis are fixed by the rules or by the practical limits of the tub, the floor and the roll cage. A team cannot always add a bigger box in a better location. What it can do is put more mass into the box that is already there, which is the entire case for tungsten over steel or lead.

The density argument in a fixed envelope

Tungsten heavy alloy runs roughly 17.0 to 18.5 g/cm³ depending on grade (ASTM B777 Class 1 to 4), against steel at about 7.85 g/cm³ and lead at about 11.3 g/cm³. In a ballast block of a given volume, heavy alloy carries more than double the mass of steel and around 1.6 times the mass of lead. For a team working against a fixed mounting envelope, that difference is the entire point of choosing tungsten: it lets the same block reach a target mass that would need a much larger, and often impossible to fit, steel or lead block.

Material	Typical density	Ballast mass in a 1000 cm³ block
Steel	~7.85 g/cm³	~7.85 kg
Lead	~11.3 g/cm³	~11.3 kg
Tungsten heavy alloy	~17.0 to 18.5 g/cm³	~17.0 to 18.5 kg

Lead is the traditional low-cost ballast material and remains common where space is not the binding constraint. Tungsten heavy alloy earns its higher cost specifically where volume, not weight, is the limit, or where a lower center of gravity is worth paying for by shrinking the ballast block’s height.

How ballast blocks are specified and machined

A ballast block is a comparatively simple machined part, and the engineering is mostly in the drawing rather than the process. Heavy alloy machines much like hard cast iron and turns and mills well with standard carbide tooling, so this is not a demanding part from a cutting standpoint. What matters is getting the specification right:

• Target mass and tolerance. State the finished mass the block must hit, with a tolerance, not just nominal dimensions. Heavy alloy blanks vary slightly in density between lots, so a shop machining to a fixed mass, trimming a face or drilling small relief holes to land on target, is more useful than one machining to fixed dimensions alone.
• Mounting hole pattern. Match the bolt pattern and hole sizes to the chassis mounting point exactly, including counterbore depth if the block sits flush or recessed.
• Corner and edge treatment. Chamfers or radii on exposed edges, both for handling safety in the pit and to avoid a stress riser if the block is drilled for mounting.
• Finish. A plain machined finish is normal. Some teams request a coating for corrosion resistance or to mark the block visually, which is a separate step from the machining itself.
• Quantity and grade. State whether W-Ni-Fe or W-Ni-Cu is acceptable. Standard W-Ni-Fe carries mild magnetism, which is irrelevant for a ballast block in nearly every case.

Sourcing ballast versus sourcing shielding or counterweight parts

Ballast blocks share their material and machining process with tungsten counterweights used in other industries, but the design goal is different. A counterweight is usually sized to balance a known rotating or moving mass against a fixed target. A ballast block is sized to a total vehicle weight target that a team adjusts between events, so many teams order a family of blocks in a few standard masses rather than one fixed size, then mix and match blocks at each mounting point to reach the distribution they want for that track.

If you are sourcing a set of ballast blocks, provide the mounting drawing once and the target mass list separately. A shop can then quote a batch of blocks at different finished masses from the same base drawing, which is usually cheaper than treating each mass as a separate part number.

When your ballast drawing and mass targets are ready, send your RFQ and we match it with shops that machine heavy alloy to a certified finished mass. For the general mechanics of machining this material, see tungsten heavy alloy machining. For how the same density argument applies to a different kind of fixed-mass part, see designing a tungsten counterweight.

Frequently asked questions

Sources

• Wikipedia - Tungsten
• Wikipedia - Tungsten heavy alloy

Keep reading

• MIL-T-21014 vs ASTM B777: How to Convert an Old Tungsten Heavy Alloy Callout
• How to Source Machined Tungsten Shielding and Counterweights