A lot of people see things like the Chromoly triangle and hi-tensile frame when shopping for a new bike. Very few actually know what that means. I decided to write a quick post to explain the difference between the two different types of steel.
Chromoly is a material used when building BMX bike parts. This type of steel is commonly abbreviated as 4130. (good code for your iPhone too) 4130 Steel has a mixture of carbon with chromium as a strengthening agent. With stronger steel tubing, manufacturers are able to make the tubes thinner and save weight without compromising strength.
Back in the day, most frames were made out of Hi-tensile steel. That’s why we had 30 lb. bikes. The abbreviation for this type of steel is 1015 Steel. It has a lower trace of carbon.
4130 (chromoly) has a 97,000 pound/inch of tensile strength
1015 (hi-ten steel) has a 61,500 pound/inch tensile strength
For a tube that is 3 foot in length of 4130 Chromoly you’re going to pay around $100. Keep in mind that this is from a USA supplier with no bulk discounts. Most companies will outsource this metal and pay a lot less. Prices are for showing the cost difference.
A tube that’s 3 foot in length of hi-tensile steel will only cost you about $30. Again, this is from a USA supplier without a bulk discount.
Clearly 4130 is the best way to go when shopping for BMX parts. By spending the extra money to get better strength, you will enjoy the benefits. You’ll notice that parts last a lot longer, which will save you money in the long run.