Choosing steel tubing for go kart frame builds is one of the first real decisions a DIY builder makes, and it shapes everything else: weight, strength, welding method, cost, and how the kart handles. Most home-built karts use mild steel round or square tube around 1 inch in diameter, while racing chassis use thin-wall chromoly tube in metric sizes. This guide explains the main steel grades and tube types, common diameters and wall thicknesses, how to choose tubing for your design, typical USD prices, and how to cut, bend, and weld it. It focuses on material choice rather than frame design.
Part of our Build a Go-Kart guide — explore the full guide →
What Steel Tubing Is Used for Go-Kart Frames?
Kart frames are built from tube rather than solid bar because tube offers high stiffness and strength for its weight. The two big choices are the steel grade and the tube shape. Mild steel, often a low-carbon grade, is the default for recreational frames because it is cheap and easy to weld. Chromoly, an alloy steel containing chromium and molybdenum, is stronger for a given weight and is the norm on racing chassis.
Tube is sold by outside diameter (OD) and wall thickness, often given as a decimal inch or as a gauge. For example, 1-inch OD with 0.065-inch wall is a common size in DIY plans.
If you are still choosing a layout, our guide to go-kart frame plans shows how designs specify tube sizes.
Types of Steel Tubing for a Go Kart Frame
ERW mild steel tube. Electric resistance welded (ERW) tube is formed from flat strip and welded along a seam. It is the cheapest and most common, and it is fine for yard karts. The internal seam can make bending slightly less predictable.
DOM mild steel tube. Drawn over mandrel (DOM) tube starts as welded tube and is then drawn to size, which improves dimensional accuracy and consistency. It bends more evenly and is a popular upgrade for roll cages and higher-quality frames.
Chromoly (4130) tube. Seamless or drawn alloy tube with higher strength. It allows thinner walls for the same strength, which saves weight. It requires more care when welding and is more expensive.
Square and rectangular tube. Square tube is easy to cut, measure, and join with flat surfaces. It is common on simple DIY frames and engine plates. It is heavier for the same stiffness and harder to bend than round tube.
Metric racing tube. Sprint racing chassis commonly use round chromoly tube in sizes around 28 mm to 32 mm OD. These are specific to chassis builders and rarely used in home builds.
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Tubing Options Compared
| Tube Type | Strength-to-Weight | Weldability | Bending | Relative Cost |
|---|---|---|---|---|
| ERW mild steel (round) | Good | Easy | Fair | Low |
| DOM mild steel | Good | Easy | Good | Medium |
| 4130 chromoly | Excellent | Needs care, often TIG | Good | High |
| Square mild steel | Fair | Easy | Poor | Low |
Common Sizes and Wall Thickness
Most recreational DIY frames use round or square tube between 3/4 inch and 1-1/4 inch OD. One-inch tube is the most common main-rail size. Wall thickness often falls in the range of about 0.065 to 0.120 inch, with thicker walls used for heavier, off-road, or two-seat karts and for roll cages.
Roll cages on off-road karts typically use larger and thicker tube than the main frame. If you are building a cage, follow the dimensions in a proven plan or the requirements of any organization whose events you will enter. Our go-kart roll cage guide covers cage design.
Avoid thin conduit, fence post, or galvanized tube for structural frame parts. These products are not made to structural standards, and galvanizing releases toxic fumes when welded.
Cost of Steel Tubing
Mild steel ERW tube is the cheapest, often a few dollars per foot for 1-inch sizes. DOM tube usually costs noticeably more per foot. Chromoly typically costs several times the price of mild steel. Prices change with steel markets and region, so get quotes from local metal suppliers, which are often cheaper than hardware stores for full lengths.
A simple single-seat frame might use roughly 30 to 60 feet of tube, so material for a mild steel frame often comes to $100 to $300. A chromoly frame or a frame with a full roll cage can cost far more. Our guide to the cost of building a go-kart places tubing in the context of a full budget.
How to Choose Tubing for Your Frame
Follow your plan. If you are building from proven plans, use the specified tube size and wall. Substituting thinner tube saves weight but may compromise strength.
Match the use. A light yard kart can use thinner wall. Off-road karts that jump and hit obstacles need thicker wall and bracing.
Match your welding skill. Mild steel is forgiving. Chromoly needs proper technique and filler. If you only have a flux-core or MIG welder, mild steel is usually the practical choice.
Consider bending. If your design uses bends, round DOM tube bends more consistently. Square tube suits designs with straight cuts and flat joins.
Plan for mounting. Brackets, seat mounts, and steering mounts attach more easily to square tube or to round tube with tabs. Think about this early.
Cutting, Bending and Welding Tips
Cut tube square with a chop saw or band saw for tight fit-up. Use a tube notcher to cope round tube ends where tubes meet. Deburr all cuts and remove mill scale near the joint with a flap disc before welding.
For bends, use a proper tube bender with dies sized for your OD. Conduit benders can kink structural tube. Mark bend locations carefully, accounting for the bend radius.
Tack the whole frame on a flat surface and check diagonals before fully welding. Weld alternate joints to spread heat and limit warping. Our sibling guide to the go-kart welding kit covers equipment and safety.
Buying Tube From a Supplier
Metal suppliers usually sell tube in full stock lengths, commonly around 20 feet, and many will cut it into shorter lengths for transport for a small fee. Ask for a quote by OD, wall thickness, material grade, and process (ERW, DOM, or seamless). If you need chromoly, specify the grade and ask whether the supplier can provide a material certificate.
Inspect tube before you leave. Look for dents, heavy rust, and bends along its length. Roll it on a flat floor if you can. Buy at least 10 to 20 percent more than your cut list, because mistakes and practice welds use up material quickly.
Store tube indoors or under cover, off the ground. Light surface rust can be removed before welding, but deep pitting weakens thin-wall tube and should be cut away.
Corrosion and Finishing
Bare steel rusts quickly. Once the frame is complete, clean it and apply paint or powder coat. Seal open tube ends with caps or welds to keep water out, or drill small drain holes in low points if water could collect inside.
Pros and Cons of Steel Tube Frames
Steel is the standard for kart frames, with trade-offs between grades.
Pros
- Mild steel is cheap and widely available
- Easy to weld with home equipment
- Chromoly offers high strength with less weight
- Steel can be repaired and modified easily
Cons
- Mild steel frames are heavier than chromoly
- Chromoly is expensive and harder to weld well
- Bare steel rusts without paint or coating
- Wrong tube choices can create weak or flexible frames
Frequently Asked Questions
What size steel tube is best for a go-kart frame?
Is square or round tube better for a go-kart?
Should I use chromoly or mild steel?
Can I use electrical conduit for a go-kart frame?
How much tubing do I need for a go-kart frame?
What is DOM tubing?
Final Thoughts
The best steel tubing for go kart frame builds is usually 1-inch mild steel tube in an appropriate wall thickness, with DOM or chromoly reserved for cages and lightweight performance builds. Use proven plans, buy from a real metal supplier, and invest in clean fit-up. For the full build process, see our how to build a go-kart guide.