Our current bicycle evolution direction has become more and more technological, and it can even be said to be the prototype of future bicycles. For example, a seat post can now use Bluetooth for wireless control to lift. Many non-electronic components also have elaborate designs and more fancy looks. In terms of non-electronic components, our technology and craftsmanship have been improving. For example, the soles of our lock shoes used to be made of rubber as the main material, but now most of the lock shoe soles use carbon fiber or glass fiber as the main body. Made of high-quality materials, which can greatly enhance the hardness of the sole, so that it has excellent force transmission and greatly improves the transmission efficiency. But there is one part that, despite the attempts of many engineers, still cannot shake its status: the spoke nipple.

   Of course, some brands of wheels have unique custom made nipples that fit their wheels better. Most of the nipples will have screw glue applied to the spoke threads at the factory, which can effectively prevent the spokes from loosening due to vibration during the bike’s use, but the actual material that makes up these nipples is aluminum or brass.

For more than fifty years, brass has been the primary material of which spoke nipples are made. In fact, brass is a very common material around us. For example, most of the materials of tools such as door handles and nautical sextants are made of brass.

So why can’t the nipples be made of stainless steel like the spokes? And almost no parts on our bicycles are made of brass as a material. What magic does brass have to make spoke nipples made of it? Brass is actually a copper alloy, mainly composed of copper and nickel. It has high strength, good plasticity, and can withstand cold and hot environments well. However, the material of the spoke nipple is not 100% pure brass, there will be a layer of white or black oxide on the surface, of course, after the surface coating is worn off, the true color of the brass will be revealed.

Brass is naturally a softer material than stainless steel, so it allows more stretching when a load is placed on it. When a spoke is working, it is always in varying degrees of tension. Whether you’re riding a bike, or building a wheel, nuts and bolts are held together because there’s some very slight distortion in the threads as they’re tightened. The material’s pushback against this deformation is why bolts tend to stay tight, and why split lock washers are sometimes needed to help. Especially when the spokes are under unpredictable stress levels, the extra deflection provided by the brass stabilizes the friction a bit.

In addition, brass is a natural lubricant. If the spokes and nipples are stainless steel, there is a good chance that there will be wear issues. Abrasion means that a certain amount of one material is scraped off and attached to another material, leaving a tiny crater in the original material and a tiny bump in the other material. This is similar to the effect of friction welding, where extreme forces are combined with sliding or rotational motion between two surfaces, causing them to bond.

When it comes to bonding, brass and steel are different materials, which should be a no-no if you want to avoid corrosion. But not all materials have the same qualities, and putting two different metals together increases the likelihood of “galvanic corrosion”, which is what we mean when we talk about corrosion when dissimilar metals are put together, depending on the “anode” of each material index”. The more similar the anodic indices of two metals, the safer they are to be kept together. And cleverly, the anodic index difference between brass and steel is much smaller. The anode index of materials such as aluminum is quite different from that of steel, so it is not suitable for the nipple of stainless steel spokes. Of course, some riders will be curious, what if some manufacturers use aluminum alloy spokes with aluminum alloy nipples? Of course, this is no problem. For example, Fulcrum’s R0 wheel set uses aluminum alloy spokes and aluminum alloy nipples for better corrosion resistance and lighter weight.

After talking about stainless steel and aluminum alloy, of course I have to mention titanium alloy. In fact, there is not much difference in the anodic index between titanium alloy and stainless steel spokes, and they are also quite suitable to be installed on bicycles as spoke caps. Unlike the replacement of brass nipples with aluminum alloy nipples, which can greatly reduce weight, compared with brass nipples, titanium alloy nipples can basically reduce the weight basically negligible. Another important reason is that the cost of titanium alloy is much higher than that of brass, especially when it is added into a delicate component such as a spoke cap, which will further increase the cost of the bicycle wheel set. Of course, titanium alloy spoke nipples have many advantages, such as better corrosion resistance and beautiful luster, which is very pleasing. Such titanium alloy nipples can be easily found on platforms such as Alibaba.

It’s refreshing to see tech-inspired designs on our bikes, however, the laws of physics apply to everything, even the “future” bikes we ride today. So, unless some more suitable material is found in the future, or until someone actually makes a less expensive full carbon bicycle wheel set, this bike is made of carbon fiber including rims, hubs, spokes and nipples. Only then do brass nipples get beat.