HREW vs DOM
Let’s talk steel.
Let’s face it, we are all tired of trying to find solid answers about what we need for our armor. The HREW and DOM debate is one that has been around for a while, and some tests were done in a way that allows a lot of misunderstanding and confusion. So, let's try and clear things up to the mud level shall we?
First off, HREW (hot rolled electric welded) and DOM (drawn over mandrel) are not types of steel, they are processes. How do you tell them apart? If you are looking at your material, HREW should have a visible seam on the outside defined with a different color, with a matching physical seam on the inside. DOM will be smooth and consistent inside and out. Once part of a structure, and finished in paint or other coating, there should be no discernible difference between the two to the naked eye.
DOM is not a seamless steel; it has just undergone another step in the manufacturing process, drawing over a mandrel. This cold working of the material aids in making it more consistent, both in wall thickness and ID (inner diameter), as well as the crystal lattice (atomic arrangement) of the material. These changes and consistencies are part of what makes DOM material ‘stronger’ and more resilient than HREW. How does this strength relate to you and your parts? DOM will generally take more abuse and hits before deforming, aka, dent.
That last bit of information is what most know to be the undoubtable truth. However, it is not that simple. The steel rating, and manufacturing process/tolerances play a large part in the steel’s strength. High quality, American made steel, even in a HREW finish, will outperform a large majority of the imported tube, even the DOM, it is also generally a fair bit more expensive. As much as HREW vs DOM is a point of interest, steel rating should be as well. Most American suppliers use 1020/1026 rated steels (nominal size and thickness dependent), while imported steels can vary, even from the same plant. Simply put, not all HREW or DOM is created equal. That is why some manufacturers can offer their DOM products at competitors HREW prices. (this is not always the case but is something to consider. Does not hurt to call and ask where they source their steel.) This is also why some products in HREW hold up great for some folks and not others. Product design, fit up, and steel quality/grade are more likely to affect your experience with them, than just HREW or DOM difference.
Now, let's toss another wrench into the mix. We talked about steel manufacturing process and rating; but what about size - wall thickness and outside diameter, or O.D.? Strength is determined by two dimensions of tube of a given material: Wall thickness, and O.D. A thicker walled tube means more resistance to dents or other damage from impacts, like rocks. However, when it comes to bending, the distance of O.D. to the center axis determines the relative strength. A larger diameter tube, even with a moderately thin wall, can be more rigid than a heavy walled, smaller O.D. tube. Meaning a larger tube can be lighter and stronger than a smaller, thicker option. This is important to know. Looking at a variety of parts made of different materials, you may not realize DOM from one part may be weaker than the HREW of another part. 2" O.D. .120 wall tube is going to hold up longer than 1.5, or even 1.75", tube of the same thickness. Even if it is HREW to DOM. It is important to think about where the parts are located, and what kind of load they will see, realistically, from your use. Think of a half ton truck's drive shaft. Large diameter, light weight, plenty of strength to transfer power to the wheels. Just don't hit it on a rock or it is going to cave in on itself. Keep in mind, some parts are meant to crumple and give way in order to protect other parts, or even you the occupant.
But what does this all mean? Well, that part is up to you. Knowing how you plan to use your rig, and the parts you put on it, will really help you determine what you need material wise. If you are a weekend warrior, where getting to camp might involve some rocks and the occasional tree stump, HREW or cheaper DOM options should serve you just fine. Wheel frequently, but don’t get too crazy because it is your ride to work tomorrow? Depending on your vehicle weight and terrain, HREW is likely fine for you as well. If “full send” and “hold my beer” are in your common wheeling vocabulary, or your rig is a bit overweight, DOM might be more up your alley. A lot of manufacturers will push for DOM as the end all answer. In short, that’s not inaccurate. Just keep in mind, for most folks, QUALITY HREW parts will work great for what you need. Style, design, fitup, bracing, O.D., wall thickness, and purpose are all things to think about. Don't just buy into the hype.
Have fun, stay the trail, tread lightly, and do it for you not the gram.