What is a Chain Sprocket in Bike and How It Works?

A vehicle's performance depends on the coordination of all its components, even the smallest ones. Most bike enthusiasts look to increase the engine's power output to enhance its efficiency. An easy way to do this is to change its sprocket. 

A sprocket is a chain controlling the movements of a bike’s wheel. 

Keep reading this article for a detailed overview.

Among others, most bike enthusiasts consider sprockets a major motorcycle component. These are toothed metal wheels designed to engage the final drive chain. Chain-driven motorcycles, therefore, feature two sprockets with a chain connecting them.

The front one is mounted on the transmission output shaft and is smaller in size. The bigger one, on the other hand, is attached to the rear wheels of a bike. The teeth of both sprockets are slotted into the gaps in a motorcycle drive chain. Sprockets contribute to providing engine power to the rear wheel. 

Now that you know the significance of chain and sprocket in a motorcycle, it is important to understand the way it functions within a vehicle. As the throttle is applied, a bike’s engine uses combustion to turn the input into power. 

Then, this power transmits to the countershaft sprocket using the motorcycle’s transmission. 

There are various types of bike sprockets available in the market. They are usually classified based on the following factors:

• Size

• Diameter

• Dimension 

• Teeth width and depth

Sprockets are classified into four shapes. These are as follows:

1. Type A

This type of sprocket is flat and free of hubs. Usually, they are mounted on the flanges or hubs of the equipment. These sprockets help a vehicle drive through a series of plain and thin holes.

2. Type B

These sprockets come with hubs on one side. This allows the sprocket to fit the machinery on which it is mounted. Such sprockets stand out for reducing a large overhang load on equipment bearings.

3. Type C

You will find hubs on both sides of the plate in such sprockets. They have a larger pitch diameter with more weight to support the shaft. Bigger hubs are required for heavier loads.

4. Type D

These sprockets use a solid or split hub, with a Type A sprocket mounted on the hub. The best part of such sprockets is that they can be easily splinted for removal. Other equipment like bearings is not required to be removed for this. 

Here are some different types of sprockets in a bike:

1. Multi-Strand Sprocket

You will need this type of sprocket in cases of high torque and power conditions. Such sprockets use taper-locked, finished, or QD-style hubs.

2. Double-Pitch and Single-Pitch

Single-pitch sprockets come with spaced teeth. This allows the chain’s roller pins to come under every tooth. On the other hand, double-pitch sprockets come with spaced teeth, which allow roller pins to fall into every other gap.

3. Duplex, Triple and Simplex Sprockets

Duplex sprockets are usually made of double-strand sprockets. These can be single hubs or double hubs based on specific requirements. Besides that, triple 18-tooth taper bushed type sprockets are the triple sprockets. Made of mild steel, these sprockets offer heat-treated hardened teeth. Simplex sprockets, finally, are made of teeth and smooth pulleys and do not have a flange.

4. Chain and Drive Sprockets

Chain sprockets are the most common ones. They use chains designed by rollers, which are further interconnected by pins. Drive sprockets are also common. However, they have smaller diameters and come with shaft import power.

5. Industrial and Shaft Sprockets

Industrial sprockets are usually made of stainless or mild steel and sometimes of cast iron. They offer high tensile strength and efficiency. On the other hand, Shaft sprockets come with replaceable tooth segments, and people mostly use these for ash-handling applications.

6. Drum, Steel-Split, Idler and Bushed Sprockets

Drum sprockets come with wider teeth, plates and hubs to reduce contact pressure. On the other hand, steel-split sprockets come with two parts that are split through the centre and bolted back together. Idlers come with a long chain, preventing uneven load distribution. Finally, bushed sprockets offer additional supports, such as anchor bolts. 

Now that you have a better understanding of bike sprockets, you must be curious to know about their applications and uses. Currently, sprocket assemblies are commonly seen in the following applications: 

• Automotive equipment 

• Chain-driven vehicles, like bikes and bicycles 

• Equipment for farming and agriculture 

• Chain-driven machines, like conveyor belts

• Power transmission equipment, like pulleys, shafts, etc. 

Generally, the chain and sprocket should be changed every 20,000–30,000 kilometres, or less based on your driving. However, many factors determine if the sprocket needs to be changed, including:

1. Sprocket Condition

Check the sprocket for any visible signs of wear like hooked or pointed teeth, excessive chain slack, or grinding or squealing noises, as these suggest it may be time to replace the sprocket.

2. Regular Maintenance

If you regularly go for bike maintenance and get sprocket inspection and replacement done, you will not have to change it for a long time.

3. Performance Issues

If the chain starts skipping, slipping, or making unusual noises, it means that the sprocket might be worn out and it's time to change the sprocket.

4. Manufacturer Recommendation

Check the manufacturer's guidelines in the provided manual or on the website for suggested sprocket replacement intervals.

5. Professional Advice

If you’re not sure, it is best to consult a mechanic familiar with sprockets. 

Now that you know when you need to change your bike’s sprocket, follow these steps actually to change a sprocket.

1. Start by loosening the sprocket nut.
2. Now remove the rear sprocket's bolts using a wrench or allen key.
3. Fit the new sprocket on the output shaft.
4. Put the spacers or shims back in the same order as before.
5. Tighten up the two small retaining bolts.
6. Now wait until the new chain is on and chock up the singular center nut.
7. Correct the torque setting using a thread-locking compound.
8. Refit the rear wheel and install the new sprocket.
9. Tighten up the bolts and reassemble the chain.
10. Install the master link and lube it.

Remember, it's essential to use the appropriate tools and techniques when inspecting and replacing sprockets to avoid injury and ensure proper installation. If you're unsure about any aspect of the process, consult a professional mechanic.

Here are a few factors to consider in this regard:

1. Gearing Ratio

The sizes of front and rear sprockets constitute the sprocket ratio. Usually, you can find the OEM gearing ratio on your bike’s manual, which will help you choose an ideal sprocket ratio for your vehicle.

2. Size

You need to check the size of the stock sprockets before finalising a model. This is important as the degree of adjustability of a bike usually depends on its size.

3. Material

Sprockets are mostly made of either steel or aluminium. Steel sprockets stand out for being more durable and long-lasting. On the other hand, aluminium sprockets are much lighter and thus more efficient. You need to choose the material based on your preference.

4. Pitch and Width

The pitch of a sprocket mainly represents the distance between the sprocket's teeth. On the other hand, the width of a sprocket considers the thickness of the teeth measured from the outer to the inner face in cross-section.

5. Speed

People who are expecting good speed from their vehicles usually go for a large countershaft or front sprocket. Smaller rear sprockets will be ideal if your vehicle is suitable for moderate speed.

Hopefully, that gives you a clearer understanding of the role of a sprocket and its importance in the functioning of vehicles. Besides, this component is also crucial for ensuring the speed and efficiency of the vehicle.