When it comes to building a roll cage chassis, the choice of tubing is crucial for ensuring safety, performance, and compliance with racing regulations. ERW (Electric Resistance Welded) and DOM (Drawn Over Mandrel) tubing are two popular options, each with unique characteristics that impact their suitability for roll cage applications. DOM is clearly the superior material, this blog explores the differences between ERW and DOM tubing to help you make an informed decision for your roll cage chassis. A lot of this decision is based on the use of your buggy. If you plan to race in a class then you’re probably going to use DOM. If you’re building a weekend cruiser to show off or to use every now and again ERW may be the more economical choice.

Understanding the Basics

Before diving into the specifics, it’s essential to understand what ERW and DOM tubing are and how they are made.

What is ERW Tubing?

ERW tubing is manufactured by welding the edges of a flat steel strip together. This process results in a visible seam along the length of the tube.

• Process: A flat sheet or strip is rolled into a cylindrical shape, and the edges are welded using electric resistance.
• Characteristics: The weld seam can be a potential weak point, especially under high stress or impact.
• Cost: Generally more economical than DOM tubing.

What is DOM Tubing?

DOM tubing starts as ERW tubing but undergoes additional processing to enhance its properties.

• Process: The ERW tube is cold-drawn through a die and over a mandrel, which eliminates the weld seam and improves mechanical properties.
• Characteristics: Stronger, with a seamless appearance and better dimensional accuracy.
• Cost: More expensive due to the additional manufacturing steps.

Key Differences in Roll Cage Applications

Roll cages are critical for protecting drivers in the event of a crash or rollover, making the choice of tubing pivotal. Here’s how ERW and DOM tubing compare in this context.

Strength and Durability

• ERW Tubing: While ERW tubing offers sufficient strength for many structural applications, the weld seam can be a vulnerability. In high-stress conditions, such as a collision, this seam might not hold up as well as the seamless structure of DOM tubing.

Example: During a high-speed impact, the stress concentration on the weld seam can lead to a higher likelihood of failure, making ERW less reliable for roll cages subjected to severe forces.

• DOM Tubing: The absence of a weld seam in DOM tubing means it offers uniform strength throughout. This characteristic is critical for roll cages, which must withstand high forces from all directions without compromising safety.

Example: DOM tubing’s uniform structure allows it to absorb and distribute impact forces more effectively, reducing the risk of catastrophic failure during a crash.

Regulatory Compliance

• ERW Tubing: Some racing organizations and regulations, such as those from the FIA and SCCA, do not allow ERW tubing for roll cages due to concerns about the weld seam’s integrity under extreme conditions.

Example: In professional racing circuits, using ERW tubing may disqualify the roll cage, impacting your eligibility to compete.

• DOM Tubing: Widely accepted by racing bodies and regulations for roll cage construction due to its superior strength and seamless nature.

Example: DOM tubing meets the stringent safety standards set by most racing authorities, ensuring compliance and enhancing safety.

Weight and Performance

• ERW Tubing: Typically heavier for a given strength compared to DOM tubing. This can impact the performance of a race car, where weight reduction is crucial.

Example: Heavier roll cages constructed with ERW tubing can affect handling and acceleration, which are critical in competitive racing environments.

• DOM Tubing: Provides higher strength-to-weight ratios, allowing for lighter and stronger roll cages.

Example: DOM tubing enables the construction of a roll cage that offers robust protection without significantly adding to the vehicle’s overall weight, enhancing performance.

Fabrication and Workability

• ERW Tubing: Easier to work with due to its lower cost and availability but may require additional attention during welding and fabrication to ensure the seam does not become a weak point.

Example: Fabricating complex roll cage designs with ERW tubing might necessitate additional reinforcements at the weld seams, complicating the construction process.

• DOM Tubing: More challenging to work with due to higher material costs and toughness but results in a superior final product with fewer concerns about weak points.

Example: Despite the higher cost, using DOM tubing can simplify the fabrication process by eliminating the need to compensate for seam weaknesses, leading to a more straightforward and reliable roll cage design.

Cost Considerations

• ERW Tubing: Offers a cost advantage, making it appealing for budget-conscious builders. However, the potential for added reinforcement and the need to meet safety standards can offset these savings.

Example: While ERW tubing might seem cost-effective initially, the need for additional materials and potential upgrades to meet safety standards can increase the overall expense.

• DOM Tubing: More expensive upfront but provides long-term benefits in safety, compliance, and performance. This can result in cost savings by avoiding penalties or the need for future upgrades.

Example: Investing in DOM tubing can lead to savings by ensuring compliance with safety regulations from the start, reducing the need for costly modifications or replacements later.

Choosing the Right Tubing for Your Roll Cage

Consider the following factors when selecting tubing for your roll cage chassis:

1. Safety and Compliance: Prioritize tubing that meets or exceeds regulatory standards and provides the best protection in case of a crash.
2. Budget: Weigh the upfront costs against the potential long-term benefits and savings.
3. Performance: Opt for tubing that offers the best balance of strength and weight for your specific racing needs.

Conclusion

For roll cage chassis applications, DOM tubing is generally the superior choice due to its uniform strength, regulatory acceptance, and better performance characteristics. While ERW tubing can be an economical alternative for non-competitive or lower-stress applications, it often falls short in critical areas such as safety and compliance for professional racing. By understanding the key differences and aligning them with your specific needs and regulations, you can make a well-informed decision that ensures both safety and performance on the track.