The frame is the soul of the bicycle

The bicycle frame refers to the skeleton of the entire bicycle, which determines and affects the correctness and comfort of the riding posture to the greatest extent. Materials Frame materials have evolved from the earliest chromium-molybdenum steel, to aluminum alloys, and then to the use of composite materials such as carbon fiber. Others include scandium alloys, magnesium alloys, titanium alloys, etc. The industry continues to develop new material formulas and improve pipe fittings and structural designs. capabilities and innovative processing technology, just to make the frame lighter, stronger, more comfortable and more streamlined and beautiful.

There have been numerous myths about frame materials that have been wrong for a long time. The reality is that by choosing the right tube diameter, wall thickness, and frame geometry, you can build a frame that meets your ride quality requirements using any of the available frame materials.

Rigidity, strength and weight

Strength and rigidity are two properties that people often make mistakes about. To understand the differences between frames made of different materials, it is necessary to clarify the differences between these two properties. Suppose one end of a metal rod is fixed on a fixture, and a certain weight is added to the other end to temporarily bend the metal rod. When the weight is removed, the metal rod immediately returns to its original shape. When the same weight is added to different materials, different degrees of bending will occur. This is rigidity. Also assume that the weight hanging on the other end of the metal rod is heavy enough to cause permanent deformation of the metal rod. That is to say, when the weight is removed, the metal rod is still bent and cannot completely return to its original shape, which is the so-called yield. ). The force that causes a material to yield varies from material to material. This is called strength.

Stiffness

Rigidity affects the riding quality of the frame, because the frame is most afraid of deformation during normal riding. Rigidity is determined by the elastic coefficient of the material, and importantly, the elastic coefficient has nothing to do with the quality of the metal and the composition of its alloy. For example, all types of steel have essentially the same elastic coefficient.

Strength

Strength is related to the durability of the frame but not to the ride quality. Strength is determined by the yield strength of the material. Yield strength has a great relationship with the quality of frame tubes, heat treatment process and alloy composition (some brands and types).

Weight

In addition to strength and rigidity, weight is also an issue. Like stiffness, weight is affected only slightly by the alloy composition of the material.

Note that stiffness and weight have nothing to do with material quality, heat treatment or alloy composition. For example, all automotive steel pipes, from cheap bikes from the big box store to bikes costing thousands of dollars, have the same elastic modulus of 30, and a weight of 490.

Anyone who tells you that a particular brand of steel (or aluminum or titanium) will be lighter or more rigid is lying. The difference between pipes of different qualities (same material) is the yield strength, not the weight or rigidity. It can be seen from the above table that when the pipe diameter and wall thickness are the same, the rigidity of the aluminum frame is only one-third that of the steel frame, and the titanium frame is only one-half as rigid as the steel frame. Aluminum's yield value is quite fragile compared to steel or titanium, meaning it is more susceptible to damage. In terms of weight, an aluminum frame of the same specifications is only one-third of a steel frame, and a titanium frame is about one-half of the weight of a steel frame.

The above is just a general comparison and does not mean much, because no one will use the same specifications to build frames of these three different materials.

The actual bicycle is added to the calculation according to the characteristics of the material, and the diameter and wall thickness of each pipe that makes up the frame are selected. At this time, the pipe diameter is mainly related to the rigidity of the frame, and the pipe wall thickness is mainly related to the strength (the pipe diameter will also be related), and the pipe diameter and wall thickness affect the weight of the frame.

Frame manufacturers must weigh the relationship between different tube diameters and wall thicknesses and the rigidity, strength, and weight of the frame to make trade-offs.

Steel and titanium

Going back to the table above, you can see that a titanium frame is almost as strong as a steel frame, but only half the weight and half the stiffness of a steel frame. Due to the reduced rigidity of such a frame, it will feel a bit slippery, especially when riding long distances with a load. Frame manufacturers can use larger tube diameters to increase rigidity, which will add a bit of weight but will still be lighter than a typical steel frame.

Steel and Aluminum

Usually the rigidity and weight of an aluminum frame are only one-third that of a steel frame, and the strength is only half. This is why the aluminum frame is obviously thicker and thicker, just to get the right amount of strength. Strength and rigidity, and such a frame is still lighter than a steel frame.

Large and thin pipes

The advantages of large pipe diameter can also be applied to steel, but in fact there is a limit. If you build a frame out of two-inch diameter steel tubes, you can build a frame that's stronger than anyone needs, and as long as the tube walls are drawn thin enough, it can also be very light. So why don’t any manufacturers do this? There are two reasons:

- The thinner the pipe wall, the harder it is to join well. Looking at the general double-drawn pipes, you can find that the middle can be thinner and the two ends can be thicker for easier welding.

- In addition, if the pipe wall is too thin, it will be easily dented, and some wiring end points welded on the surface will not be properly supported.

Stiffness and ride quality

Many people would lead you to believe that frame stiffness has little to do with ride quality. Let’s take a look at some different viewpoints:

Torsional/lateral stiffness (Torsional/lateral stiffness) This is mainly related to the force from the pedal. Any frame will have elastic force at the bottom bracket to resist when pedal force is applied. This elasticity can be felt, and many riders believe it takes away from the power of pedaling. In fact, this is not true, because the metal of the frame is a very efficient spring, and the force will eventually be fed back, and the loss will be quite slight. However, most riders find this elastic feeling unpleasant, and prefer this part of the frame to be more stable. This is especially important for taller and heavier riders or those who like to stand up and pump the bike.

Bicycle frame materials are mainly divided into four types: steel, aluminum alloy, titanium alloy, and carbon fiber. The quick differentiation method is as follows:

1.Aluminum alloy:

The aluminum alloy feels sensitive, lightweight, and highly rigid, but it also conveys every bit of vibration response on the ground, slightly sacrificing comfort. It is relatively cheap and comes in many frame styles, making it a popular choice for everyone to buy.

2.Titanium alloy:

The characteristics of titanium alloy are very similar to the combination of aluminum alloy and carbon fiber. It can have elasticity similar to carbon fiber and enjoy the lightness and rigidity of aluminum alloy. Its special point is that due to the sudden expansion coefficient, it is impossible to paint the metal surface. Fortunately, titanium is not easy to corrode and oxidize, and the color is also unique. But its price is also beyond the reach of the first two.

3.Alloy steel material:

Steel is the most traditional frame material for bicycles. Modern various alloy steels can achieve good results in terms of rigidity, elasticity, transmission, and stability. The only drawback is that steel has a defect in weight, and it is heavier than the above materials. Generally speaking, alloy steel materials are relatively cheap, and Giant Bora series is a typical representative. However, the price of high-quality chromium steel and chromium molybdenum steel frames is not cheap, and it cannot be compared with the alloy steel materials purchased from street stalls.

4. Carbon fiber:

Characteristics of carbon fiber: elasticity, stable riding feel, good sustainability during long-distance cruising, and high comfort. The disadvantage is that the price is little high. while more and more riders choose carbon frames because of its higher performance frameset and good experience riding.