What is 4130 Chromoly?

This is the most commonly used steel in higher end bicycle frames. Many times it's just referred to as chromoly or chromo. If on a bicycle frame, it's likely 4130 chromoly. 4130 chromoly is an alloy. Alloy simply means, 2 or more metals combined. Some people call aluminum "alloy" as if that is what it is called. Yes, this is true, but misleading. Aluminum is an alloy, but so are all metals that have 2 or more materials combined. A chromoly frame is an alloy of Chromium and Molybdenum, which if you look on the periodic table of elements, you will find both listed. There are many types of steel, such as 1020 steel. This is common in cheaper bicycle frames or frames with mixed tubes. Many times you will see things like, Chromoly Downtube, on a frame description. This means that every tube on the frame is likely made with 1020 steel except for the downtube. The reason companies do this is to keep costs down and they put the chromoly tube as the downtube because that is the most common place for a frame to break. 1020 steel is much heavier and weaker than 4130 chromoly, thus it's not recommended for intermediate and experienced riders.

A little bit of added info about tubing. You often hear the term 'butted' when companies talk about their tubing. All this means is that the tube has a different wall thicknesses throughout. Double butted is most common on top and down tubes. This means that the top and down tube are thicker at the ends, near where they are welded, and thinner in the middle. Butting is a good way to reduce the weight of a tube without losing much strength. Tubes need to be much stronger where the tube is stressed the most during riding and those stress points are within a couple of inches of all the joints (welded areas where tubes meet). Sometimes more expensive tubing will be triple butted or even more. As frames (and other parts such as handlebars) get more expensive, companies can fine tune how a frame, or part, rides and how strong it is by changing the tube thickness throughout.

All that being said, this doesn't mean 4130 chromoly is all created equal. There are many different qualities of chromoly and most of it has to do with how pure the steel is. 95% of chromoly tubing is all the same, but the last 5% is the most important. Companies that sell higher (more expensive) grade chromoly tubing have less impurities in the tubing. This is a HUGE deal when in comes to overall bike quality and strength. Also, strength to weight ratio is heavily effected by impurities in chromoly. Most Taiwan manufactured frames, especially ones that cost less, use genaric and low grade 4130 chromoly tubing. But consumers are unaware of this. They simply see 4130 chromoly labeled on a frame and think it's just as good as any 4130 chromoly frame, but this is untrue. Many companies use lower grade 4130 chromoly to keep costs down. They know they need to use a thicker guage tubing to accomodate the weakness of the lower grade tubing, so the frame ends up being heavier than a frame manufactured with a higher grade of 4130 chromoly. This explains why you can get a mountain bike frame and fork for under or around $500 vs one that costs $800 to $1000 or more. Not only is it because of the cheap labor being used by outsourcing the frame and fork manufacturing to Taiwan or China, but it's also a low grade of 4130 chromoly. These frames will weigh a pound or more than a frame of the same size manufactured with a high grade of chromoly.......both frames being equally strong.

The bicycle industry super powers (yes this includes much of the bicycle industry media too) don't want you to know these fine, and VERY IMPORTANT, details. They want to be able to put the 4130 chromoly sticker on their frame and lead the consumer to believe this is the greatest frame on the market, for only $500 (mountain bike hardtail) or less in most cases!!! BMX frames are even cheaper still, especially on complete bikes that sell for under $400 and claim to have full 4130 chromoly frames and forks. Sorry folks, but it is not possible to have such cheap prices using high grade tubesets and becomming less possible as costs for imported goods rises.

Will an inexpesive 4130 chromoly frame last a long time? Yes, it likely will, simply because they overbuild the frames (adding a lot of extra weight) to make them strong. Many times you see added gussets on the top and down tube near the head tube. This is completely unnecessary if a high grade of chromoly is used and if a top and down tube is double butted so it's stronger internally at the ends.

A lot more factors come into play when it comes to tubesets being used for bicycle parts. But it is important to know that when you buy a cheaper frame, it's cheaper for a reason. Just because it says 4130 chromoly on it doesn't mean it's as good as a more expensive frame using high end tubing. It simply means that a consumer is likely going to see that sticker and believe the frame is something that is may not really be. It's called marketing and the bicycle industry uses it all the time to get consumers to buy their products and make them believe their products are of the highest quality.....when the truth is.....the lower cost is there because corners where cut, likely in more places than one.

The bottom line is, just because a bicycle product, such as a frame, has a 4130 chromoly sticker on it doesn't necessarily mean it's a good frame. You need to dig a little deeper and find out what tube set it is. Most frames that use a higher end tube set will state what the tube set is on the frame. If they do not, you can assume they don't want to brag about it because it is likely a low grade of tubing. If a frame is manufactured in Taiwan or China and doesn't specify a brand name of tubing, it is likely the cheapest and lowest grade tubing available.

Another thing to note. When buying a complete bike vs building one up from scratch, many companies will use lower quality tubing on the complete bikes to keep the costs down. This is why you see complete bikes in the $400 - $800 range......many of the parts are not as well made and high quality as the same part purchased as aftermarket, say a handlebar, fork, or frame. Companies refer to components for complete bikes as OEM (original equipment manufacture). OEM bicycle parts, unlike the auto industry, are usually lower quality and grade than aftermarket parts. A good example of this is an OEM brand name suspension fork that came on a complete bike almost always has cheaper internal parts than the same model fork found on the aftermarket. This is why you see a complete bike with a decent brand name fork on it for under $1000, yet when you price just the fork alone it costs well over $400. All the way from the grade of tubing to the internal parts, including bolts and such, corners where cut to make the same product for the mass market assembly line of complete bikes. The same goes for frames. You will see a riders signature frame on a complete BMX bike that costs $600 or so, yet if you want to buy just the frame and build up the bike, the frame will cost $350 or so. The frame on the complete bike is likely not the same quality as the frame purchased as an aftermarket item. Most bicycle consumers don't know this stuff and probably often wonder why the prices seem so unbalanced.

Be an informed consumer and also help inform others as much as you can. It is important we hold bicycle companies to high standards and that we make informed purchases when we buy bicycles and parts.