CDS vs. T45 Roll Cages: What’s the Difference and Why Upgrade?
Roll cages are an essential safety feature in motorsport, designed to protect drivers during high-speed collisions, rollovers, and other impacts. But not all roll cages are created equal. One of the biggest decisions when choosing or upgrading a roll cage is understanding the materials used, specifically T45 and other types of CDS (Cold Drawn Seamless) tubing.
If you’re building or upgrading a roll cage, it’s vital to understand that CDS is a manufacturing process, not a material itself. Below is what CDS tubing is, how T45 fits into the picture, and the differences that actually matter when you come to buy.
CDS vs. T45 Roll Cages
CDS steel is a popular choice for roll cages because it balances affordability, durability, and ease of manufacturing. T45 is a high-tensile carbon-manganese steel with a much higher yield strength than standard CDS, which is why professional race teams and the aviation trade use it.
What Is CDS Tubing?
CDS stands for Cold Drawn Seamless, a manufacturing process that produces high-quality steel tubes. By drawing steel through a die at room temperature, the CDS process creates seamless tubing with consistent thickness and exceptional strength.
This process eliminates the weld seam found in Electric Resistance Welded (ERW) tubing, which gives a more reliable and durable structure. Both the FIA and Motorsport UK specify cold drawn seamless tube for roll cages, so ERW is not an option.
T45: A Type of CDS Tubing
T45 is a specific type of CDS tubing, made from a high-strength carbon-manganese steel to the British BS4 T45 specification. Its strength and weight advantages make it a popular choice in professional motorsport and aviation applications.
The Key Differences Between T45 and Other CDS Tubing
The real comparison lies in the materials used for CDS tubing, such as:
Standard Carbon Steel CDS
- A cost-effective and versatile option.
- Supplied to the right grade, it meets the FIA and Motorsport UK tube specification.
- Commonly used for grassroots and club-level roll cages.
T45 CDS Tubing
- Made from a high-tensile carbon-manganese steel.
- Roughly double the yield strength of standard CDS, so it clears the regulation minimum by a wide margin.
- Bends and welds well, which is why cage builders like it.
- Costs more, and it is still plain carbon steel, so it wants painting or coating like any other cage.
Key Comparison Table
| Feature | Standard Carbon Steel CDS | T45 CDS Tubing |
|---|---|---|
| Manufacturing Process | Cold Drawn Seamless | Cold Drawn Seamless |
| Material | Unalloyed carbon steel | High-tensile carbon-manganese steel (BS4 T45) |
| Yield strength | 370 N/mm² minimum | 620 N/mm² minimum |
| Tensile strength | 510 N/mm² minimum | 700 N/mm² minimum |
| Elongation | 25% minimum | Around 15% |
| Weight | Identical at identical tube sizes. Both are steel. A T45 cage is only lighter where the design uses thinner wall, and that needs FIA homologation or a Motorsport UK ROPS Certificate. | |
| Weldability | Straightforward | Good, but follow the cage maker’s welding procedure |
| Minimum tube sizes | The same for both: 45 x 2.5 mm or 50 x 2.0 mm for the main rollbar, 38 x 2.5 mm or 40 x 2.0 mm for the other members | |
| Cost | More affordable | More expensive |
Strength figures are Custom Cages’ published minimums for their T45 and their high-spec E355 CDS. Other suppliers’ grades vary, so check the certificate that comes with the tube.
What the Regulations Actually Say About Tube
This is where most of the confusion sits, so here is the exact position.
Neither the FIA nor Motorsport UK mentions T45 anywhere. We ran a full-text search of FIA Appendix J Article 253 (the 2026, 2020 and 2016 editions) and the Motorsport UK National Competition Rules 2026 Edition 3. T45 does not appear once. It is a British tube specification, BS4 T45, and not a regulatory category.
What both bodies do specify is the material and the minimum sizes. Cold drawn seamless unalloyed carbon steel containing a maximum of 0.3% carbon. The FIA table (Appendix J 2020, Article 253-8.3.3) asks for a minimum tensile strength of 350 N/mm². Motorsport UK (NCR 2026, Chapter 7 Appendix 3, Article 20.1) asks for a minimum yield strength of 350 N/mm². Those are two different measurements of two different things, so quote whichever document applies to your event and don’t treat them as one rule.
The minimum dimensions are the same in both documents:
- Main rollbar: 45 x 2.5 mm or 50 x 2.0 mm
- Lateral half-rollbars and the other members of the cage: 38 x 2.5 mm or 40 x 2.0 mm
Those minimums apply whatever the tube is made of. Picking T45 does not let you drop to a thinner wall on a cage built to the published specification. A lighter, thinner-walled T45 cage is legal only where that specific design has been homologated by the FIA or holds a Motorsport UK ROPS Certificate, because homologation and certification approve the design as a whole instead of measuring it against the generic table.
The FIA text has also moved on. For cars homologated from 1 January 2021 the build-it-yourself route has gone altogether. Those cars need a cage that is homologated by the FIA or homologated or certified by an ASN, which in the UK means Motorsport UK.
Why Choose T45 for Your Roll Cage?
If you’re wondering whether upgrading to T45 is worth it, here is the honest picture.
1. More strength at the same tube size
Build two cages to the same dimensions, one in standard CDS and one in T45, and the T45 one is the stronger structure. Custom Cages quote a minimum yield strength of 620 N/mm² for their T45 against 370 N/mm² for their high-spec CDS. Both clear the 350 N/mm² figure in the regulations, T45 by a long way.
2. Weight saving, but only on an approved design
T45 is the same density as any other steel, so an identical tube in either material weighs the same. The saving comes from running a thinner wall, and you can only do that where the cage design itself is FIA homologated or holds a Motorsport UK ROPS Certificate. On a cage built to the published specification the minimum tube sizes apply whatever the material.
3. Bending and welding
Custom Cages describe T45 as having excellent properties for bending and welding, and cage builders generally agree. What the regulations care about is the quality of the work. The FIA asks for full penetration welds, preferably gas-shielded arc, and both the FIA and Motorsport UK warn that poor fabrication can leave brittle heat-affected zones and end up weaker than the material you started with. A cage is only as good as the welds holding it together.
Why Standard Carbon Steel CDS Might Be Right for You
Not every motorsport enthusiast needs the advanced properties of T45. For grassroots racing, track days, or budget-conscious builds, standard CDS tubing offers an excellent balance of affordability and safety.
Choosing the Right Roll Cage Material
The decision between standard CDS tubing and T45 comes down to your specific needs:
Choose T45 if you want the extra strength margin at the same tube sizes, or if you’re chasing weight on a homologated design that uses thinner wall.
Choose standard CDS if you want a cage that meets the same regulations for less money. That covers most club racing and track day builds.
Both materials build a legal cage. Neither is named as a requirement by the FIA or Motorsport UK.
Who Offers CDS and T45 Roll Cages?
At GSM Performance, we partner with some of the best roll cage manufacturers in the business to ensure you get the perfect fit for your vehicle and goals:
Safety Devices Renowned for precision-engineered roll cages, Safety Devices offers both CDS and T45 options tailored for Vauxhall, Ford, and Subaru models, among others. These are ideal for club-level and professional motorsport.
Custom Cages Specializing in T45 roll cages, Custom Cages cater to professional race teams with lightweight, high-performance designs.
JP Cages Offering a versatile range of CDS and T45 roll cages, JP Cages focuses on quality and affordability, making them perfect for grassroots racers and track day enthusiasts.
Installation Matters
Regardless of the material you choose, proper installation is critical to ensure your roll cage performs as intended. Our experts at GSM Performance can guide you to the right cage for your car and help you understand the installation process.
Final Thoughts: Is T45 Worth the Investment?
T45 is worth the money if you want the strength margin, or if the cage you’ve chosen is made in it. It isn’t worth paying for on the belief that a scrutineer will turn away a standard CDS cage, because the regulations do not name either material.
Check your championship’s own regulations before you order. Series rules sit on top of the national and FIA requirements and can be stricter about cage type and specification than the tables above.
At GSM Performance, we’re here to help you choose the right roll cage for your needs. Our range from Safety Devices, Custom Cages and JP Cages covers both materials, and we can talk you through what your class actually asks for.