This post compares the differences between lugged and TIG welded bicycle frames.
Definitions
Before comparing the two types of frames, it’s necessary to describe their main properties and the technology behind them.
Lugged Frames
Lugged bicycles frames (image below) are built of steel tubing connected via external steel fittings known as lugs. Each tube is inserted into an opening of the lug.
Then, the tubes are permanently attached to the lug and the tube next to it via a method known as brazing.
Brazing is a metal-joining process using a filler metal to connect two separate pieces of metal.
The filler metal (usually silver or brass) has a lower melting temperature than that objects that have to be joined (in this case steel tubes and steel lugs).
The frame builder heats the tubing via a torch and melts the filler metal which then flows underneath the lug and forms a strong joint.
Frames can be brazed with or without lugs. The process of brazing a frame without lugs is known as fillet brazing.
The advantages of lugs are:
- The joint is hidden (aesthetic gains).
- The filler material spreads over a very large surface.
The result is a very strong and beautiful frame. The downside? The process is very time-consuming.
Note: During brazing, the materials that are joined together are never melted. Only the filler material is. You can look at brazing as gluing two pieces of metal by melting a rod that has a lower melting temperature.
TIG Welded Frames
As the name suggests, TIG-welded frames have tubes connected via a process known as TIG welding.
TIG welding stands for Tungsten Inert Gas welding. In this case, two pieces of metal are joined via an arc welding process using a non-consumable tungsten electrode. Inert shielding gas is used to protect the welded elements and the electrode from contaminations.
Simpler Explanation of the Process
The above may sound a bit complicated to someone who isn’t familiar with the basics of welding.
Below is a simple explanation:
- TIG welding is done with a torch that has a tungsten electrode sticking out.
- The torch heats the electrode and melts the two pieces of metal that have to be joined (in this case the bike’s tubes.)
- The melted area forms a pool of metal. As a result, the two pieces bond.
- In the other hand, the welder holds a filler rod which melts too and adds strength to the bond.
You can think of the welded pieces as two separate chocolates. If you put them next to each other and melt the neighboring ends, the two chocolates will melt into each other.
The melting process deforms the ends. But if you lay liquid chocolate (e.g., Nutella) on the affected area, it will fill the gaps and make the bond stronger.
The main difference between brazing and welding is that during brazing the pieces joined together are NOT melted. Only the filler material is. During welding, the welded elements melt too.
The Advantages of Lugged Frames
- Aesthetics
Many cyclists consider lugged frames aesthetically pleasing and stylish. In different, a welded frame appears generic and doesn’t have the elegant lines of a lugged frame even when the welding is perfect/robotic.
Lugged frames gain aesthetic points because:
- The connection is hidden.
- The lugs themselves represent a piece of art and can be shaped and painted in many different ways.
People who are into classic road bikes often go for lugged frames simply for the appearance.
- No Welding Needed
Since the brazing process is done with a torch, there’s no need for expensive welding equipment or welding experience.
Most of the time brazing is done with an Oxyacetylene torch because it heats the area incredibly fast. That said, some people use less powerful torches because the melting temperature of silver isn’t that high.
Since brazing doesn’t involve electricity, it can be done at locations that do not have an electric outlet.
That said, brazing isn’t easy and has a long learning curve.
- Kinder to The Tubes
During brazing, the tubes aren’t melted. Only the filler rod is. Thus, the tubes are less likely to overheat and lose structural integrity.
For that reason, brazing is considered kinder to bike tubes.
- Easier to Repair
Lugged and fillet brazed frames are easier to repair. If a tube is damaged, the frame builder can heat the joint to melt the brazing material, take out the faulty tube and braze a new one.
In the video below, Paul Brodie replaces the chainstays of a brazed frame:
Technically, welded frames can also be repaired, but the process is more difficult and expensive to the point where most people prefer to simply buy a new frame.
The Disadvantages of Lugged Frames
- Time-consuming Manufacturing
The production of a lugged frame is a very time-consuming process because:
- Lugs are an additional element that has to be fabricated.
- Lugs from one frame cannot be used on another unless the geometries of the frames are identical. Thus, each geometry change requires a different set of lugs.
- Brazing is slower than welding.
For the reasons above, mass producers stay away from lugged frames. The additional labor, the extra costs, and the slower process make little sense when the targeted demographic doesn’t even know what a lugged frame is.
Thus, lugged frames are considered an exclusive product.
- Expensive
Lugs aren’t cheap, especially when made by a popular builder.
- Aluminum Cannot Be Used For Brazing
Aluminum frames cannot be brazed for the following reasons:
- The filler brazing rod has a higher melting point than aluminum. The long exposure to heat will irreparably damage the aluminum tubes.
2. There are filler rods designed to melt at lower temperatures so that aluminum can be brazed, but they don’t provide enough strength to build a strong frame.
Thus, the user is limited to steel only. Normally, this isn’t a problem because most people who want a lugged frame prefer steel in the first place. Steel is denser than aluminum and can therefore provide just as much strength in a slimmer and more elegant package.
Note: Lugged aluminum frames exist, but they’re not brazed. Instead, the builder uses a very strong epoxy to connect the tubes to the lugs. In some cases, there’s also a threaded connection for additional security.
Currently, this process is not in fashion due to the low demand for lugged frames, to begin with.
- Extra Weight
Lugged frames tend to be heavier because:
- The lugs add weight to the frame.
2. The tubes’ ends have to be thicker at the locations covered by the lugs. If the ends are thinner, the torch may burn through them (destroy their integrity). Consequently, the frame tubes cannot be butted as aggressively.
FAQ: What is frame butting?
Frame butting is a process producing lighter and yet strong frames.
This goal is achieved by doing the following:
- The least stressed sections of a tube are made thinner.
- The sections undergoing extra stress are thickened.
The Advantages of TIG Welded Frames
- Faster and Cheaper
TIG welding is not only faster than brazing but also cleaner and requires less effort to finish/smoothen the area.
A factory with well-trained workers and high-end equipment can manufacture a massive amount of welded frames per day.
To produce the same number of lugged frames, the employees will have to invest a lot more time into each unit.
- Easy Geometry Changes
A new set of lugs is needed when the geometry of a frame is changed. With TIG welding this isn’t the case because the welder isn’t restricted by a lug and can alter the angle as needed right away.
- Aluminum Can Be Used
TIG welding can be used to weld aluminum tubing. The setup for welding aluminum isn’t cheap, but the accelerated mass production process makes up for the extra price.
- Lighter
TIG-welded frames do not use lugs and can have more aggressively butted tubes because the welded area is smaller than the lugged one. Thus, the ends of the tubes can be thinner without fear of burning through the tube.
- The Frames are Cheaper
Welded frames are cheaper to make and thus the final price could be lower too.
The Disadvantages of TIG Welded Frames
- Generic Look
A welded frame has a “nothing special” look. A lugged frame, on the other hand, is rare and thus considered luxurious.
- The Welding Setup Is Expensive
Many independent frame builders use brazing because it’s cheaper on an individual level.
If you want to weld frames, you will have to invest 1000s of dollars into welding equipment. Thus, the barrier to entry is higher, and many people who build frames as a hobby don’t find an incentive to buy the needed gear.
FAQ: Is There a Difference Between The “Ride Feel” of Lugged and TIG Welded Frames?
The process used to connect the joints of a frame does not have the greatest influence on the bike’s ride feel.
How the frame feels depends on the following properties:
- Tube Material
- Design
- Tube length
- Tube thickness
- Geometry
A skilled frame builder can make a frame that performs as needed by the client via both methods.
Truth be told, most people won’t feel a difference between a brazed or a welded frame.
FAQ: Are lugged frames stronger than TIG-welded frames?
Many people consider lugged frames stronger because:
- The tubes aren’t overheated.
- The ends of the tubes are thicker.
- The lugs add a lot of support.
Conversely, TIG-welded frames are considered weaker because:
- The tubes are thinner (potentially).
- The tubes are heated to melting temperatures.
- There are no lugs supporting the joint.
If everything is equal, a lugged frame may be stronger than a TIG welded one, but in practice, the strength of a frame is dependent on a number of factors, not just the joining process.
Here are some of the factors that affect a frame’s strength:
- Tube material and quality
- Tube thickness
- Craftmanship
- Design
- Geometry
A TIG-welded frame can be made brutally strong and fairly light by using oversized tubing. In fact, most MTBs are built this way.
A TIG-welded MTB frame with oversized 7075 aluminum tubing will be notably stronger and more durable than a thin road bike frame with lugs.
Therefore, it would be inaccurate to conclude that one method is stronger than the other.
If a frame is of good quality and used as intended, it will provide more than enough strength whether it’s fillet-brazed, lugged, or welded.
