Why Do BMX Bikes Have Small Sprockets? (Explained)

Why Do BMX Bikes Have Small Sprockets

The sprocket is the main unit responsible for the propulsion mechanism of a bike. It holds the bike’s chain as the back wheel moves in a rotary motion.

Although we have different sprockets, you will notice that the BMX bikes have smaller sprockets.

Hence, you may wonder if it is designed by chance or deliberate action. And also whether smaller sprockets on BMX bikes have positive or negative impacts.

The small BMX bike sprocket helps generate more force, move the bike through parts with obstacles, make the bike feel lighter, and provide efficient pedaling. With the small sprockets, there is faster acceleration and an increment in the frame-to-ground clearance. Another remarkable reason for small sprockets is to minimize the occurrence of shin hits.

As the article progresses, you will see if a small sprocket is best and whether it is standard for all BMX bikes or if there are other available alternatives. 

Do All BMX Bikes Have Small Sprockets?

Why Do BMX Bikes Have Small Sprockets

Not all BMX bikes have small sprockets. The reason is that the old BMX bikes have a 48T (teeth). But this is different from the standard still in use in the modern BMX of today.

If you carefully look around, you will find out that the BMX of today uses 25T or 28T and a bore of 23.7mm.

Furthermore, there are two different sprocket sizes: the bolt drive and the spline drive. 

Using a bolt, you can attach the bolt drive sprocket to the crank arm. The 48-spline spindle usually has the spline drive sprocket placed directly into it. 

If the bolt sprocket has more than one tightening bolt, then the lifespan of both will be almost the same (last longer).

The spline drive socket appears to be a steel insert that is hardened for a 19mm or 22mm spindle and has it placed on the 48-spline spindle. The sprockets do not make use of a tightening bolt.

#1. Advantages of Big Sprockets

“The larger the sprocket size, the lesser force exerted on the chain,” says the world-renowned bicycle company Odyssey BMX. 

Bikes with big sprockets will have fewer rear cog teeth or broken chains than ones with much smaller gearing.

Additionally, larger teeth also make contact with the surface of the chain less frequently, which is why it wears longer than small ones.

#2. Advantages of Small Sprockets

The advantages associated with small sprockets are so many that it is why you will not be able to find a BMX with big sprockets anywhere today. 

For one thing, the smaller sprockets do not bend as easily as the big sprockets and receive less damage than the big sprocket during stunt performance.

Are Small Sprockets Better for BMX Bikes?

If you ask me the question above, my answer will be an obvious yes. But saying yes will not be enough, so below are the convincing reasons small sprockets are better;

#1. Faster With Better Acceleration:

The smaller sprockets can move much faster than the bigger sprocket, which means they can carry you to your destination within a shorter period.

And today, nobody wants to do things the long way when they know they can achieve it in a shorter time.

#2. Pedaling Efficiency:

The small sprocket improves your pedaling at a considerable and unprecedented rate. 

This feature brings the chain so low that it gets into direct contact with the brakes.

With this setup, struggling to steer a bike from one direction to the other will not be a matter of concern, saving you a lot of energy.

#3. Improves Force Generation:

As I said earlier, the small sprocket doesn’t bend easily. It allows you to generate much force while expending less energy. 

This applies to you after riding far distances or taking a steep slope.

#4. Endurance Capacity:

You find obstacles you must avoid or navigate through when using a trail. 

The obstacles on these trails not only damage your bike but can also reduce the lifespan of your bike. However, your BMX will prove to be more enduring with smaller sprockets.

#5. Suitable for Use in Racing:

Smaller sprockets stand out in terms of being light and maneuverable. 

And these factors are essential for a good racing bike. You will have no interference during your ride.

The small sprocket will allow your BMX to take the harsh and winding terrain. And will allow you to use the sprocket for a very long time.

#6. Turning Will Require Less Torque:

Turning around and about a sharp bend with your bike requires some torque. However, the torque amount differs when you use small sprockets.

The torque you expend when using the small sprocket is less than the torque you require for a big sprocket. It will spare your body the stress that comes with it.

#7. Provides More Contact Surface:

More contact between your feet and the pedal surface will help you steer your bike well. 

Compared to the big, the small sprocket provides a more contact surface. Hence pedaling becomes comfortable and fulfilling.

#8. Efficient for Taking Off-road Rides:

No matter the bike you are taking for off-road riding, you will be placing your eyes in search of bikes with small sprockets.

Bikes with small sprockets have built a reputation for handling off-road conditions more efficiently and easily.

#9. Less Stress on Your Legs and Lower Muscles:

It is no news that cycling calls for a continuous engagement of the legs and lower muscles extensively. 

And this requires less effort and power for a small sprocket than a big one.

#10. Maneuverability and Lightweight:

Being light and maneuverable makes the small sprockets not put so much stress on you. 

It makes them appealing for prolonged bike riding and navigating dangerous terrains.

#11. Agility and Smoothness:  

One thing for certain is that you will use less effort because the small sprocket will be smooth and agile.

It will also result in less stress for your chains and a more fulfilling and worthwhile experience.

However, whatever has advantages must have its disadvantages.

Below are two disadvantages of smaller sprockets and the reasons.

Disadvantages Reasons 
Pedaling is harderLess rotational mass (more resistance while pedaling)
Quick to wearLess surface area for the chain to grip onto so it slips off easily

What Sprocket Size Is Best for a BMX Bike?

Regarding the sizes of sprockets being used today, we have the 25T, 28T, and 30 T. Where T stands for “number of teeth.” However, the most commonly used today are the 25T and 28T.

#1. 25T Sprockets

The 25T is the most common sprocket among BMX bikes. If you need to improve at pedaling.

25T is also the best to use if you want to perform a few park tricks or stunts, as it will prevent you from accidentally clipping your sprocket’s coping.

Acceleration is also quite easier with this particular sprocket.

#2. 28T Sprockets

Although harder than 25T, it is still the perfect size of the sprocket to use for riding on dirt. You will go faster and with more acceleration. 

It is true because pedaling two times on 28T will give you the same speed as pedaling three times on 25 T. 

If you are a dirt rider who likes to go fast without worrying about what is hitting on your sprocket, then the 28T is far more suitable for you.

Josh Matthews

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