Motorcycle Frame Tubing Question:
From: BOB ELLIS
Hello CCG: I am building my own bike frame and need to get your opinion on the information that I received from the guy at the local metal supply store about motorcycle frame tubing. I went in asking for DOM tubing, (now according to Luke's article this sounds like ERW tubing)what do you think? Is this safe to use or would you go for the DOM which cost a little more? Here is the email that I received:
Begin Motorcycle Frame Tubing Email:
Hello, Bob. Here's your quote. This is DOM, not seamless. DOM is just as good as seamless and a lot cheaper, fine for a motorcycle frame. They come in random lengths from 17’ to 24’, so we won't know what to charge you until we actually get the shipment. I can get these for you overnight and can deliver to your shop.
1 ¼ x .125…………....$5.91 per foot.
1 ½ x .125……………$6.24 per foot.
2 ¼ x .125……………$8.97 per foot.
2 ¼ x .250……………$12.17 per foot.
Your input on motorcycle frame tubing is much APPRECIATED! This confused me a little. HELP!!
Thank You Kindly,
Motorcycle And Chopper Frame Tubing Answer:
Thanks for your question.
ERW or Electric Resistance Welded tubing is not as strong as DOM or Drawn Over Mandrel tubing. Usually when tube is made, it starts off as a flat sheet and this is rolled up into a tube and welded. DOM tubing is usually made the same way but there is an extra process where this tube is drawn through a die along with a mandrel to control the outer and inner diameters of the tube. This extra process strengthens the steel since it is cold formed by up to 20%. Another type of common tubing is Chrome-Moly also known as Chromium / Molybdnem Steel. This type of steel also uses the same process but has these additional elements within the steel alloy which increase strength even more. Chrome-Moly is usually used in tubing for cars and other applications over 3500 lbs.
Motorcycle Frame Tubing Answer Part 2:
Motorcycle frame tubing: Motorcycle frames are made with both ERW and DOM tubing. For small engines with not a tremendous amount of horse power a 1" x 1/8" mild steel ERW tube should be fine. Modern motorcycle engines with a lot more horsepower as well as stretched frames require at least 1 1/4" x 1/8" wall thickness at a minimum. Bigger choppers even use 1 3/8" x 1/8" walls. More on the overkill side done for design or aesthetics is 1 1/2" tube with 1/8" wall. All applications under 3500 lbs pretty much can get away with using ERW tubing. Roll cages and dune buggies, car frames are almost always made with DOM tubing.
Motorcycle Frame Tubing Answer Part 3:
All three, Chrome-Moly, DOM and ERW weigh about the same but it is important to note that Chrome-Moly is the strongest, followed by DOM and finally ERW being the weakest of the three. You can take advantage of this by replacing a larger diameter tube with a smaller diameter tube of stronger material. For example, you can replace a 1 1/2" ERW tube with a 1 1/8" DOM or Chrome-Moly tube. The advantage here is that you can reduce your bike frame weight by making such a change. It is very critical to confirm that it is ok to make this kind of change on your motorcycle frame. Each frame has a different geometry and different loads that will bend and twist the steel in various ways. Finite Element Analysis (FEA) conducted by a qualified engineer can provide you with correct tube diameters and wall thickness that can be replaced for your specific frame design.
Motorcycle Frame Tubing Follow Up Email From Bob:
This is the motorcycle frame tubing information that I have been studying for months (CCG article not luke's), so when this "SALESMAN" emailed, I new it was GARBAGE!! You guys are on it, and I will not take anymore advice from him. I look forward to doing business with you.
Thank You Kindly