I search every time I change sprockets.
Among consumables, sprockets have a relatively long life and are replaced infrequently. In terms of its role, it is a component that performs the important job of transmitting the "power" output from the engine to the rear tires via the chain.
The sprocket is an essential part of the bike, and by changing the number of teeth (jagged teeth), acceleration performance and maximum speed can be adjusted.
This time we're going to talk about something you may or may not know: sprocket tooth setting!
When do you change the number of dings?
The number of teeth on the sprocket is called the number of teeth, and by changing this number of teeth, you can obtain either the maximum speed or acceleration power.
In reality, the change in the sprocket's hinge number changes the engine speed at the same speed, so that the maximum speed and acceleration force feel as if they are changing.
As an example, when driving a small-displacement car on a fast-flowing road, if the RPMs are too high and noisy, or if fuel consumption is poor, a setting is made to increase the maximum speed.
On the other hand, if the driver feels that the car is slow to start at traffic lights or wants to enjoy cornering, an acceleration-oriented setting should be used.
Also, the shift up timing is too fast due to the gear ratio./The sprocket can also be used to adjust the shift timing of a vehicle that is too slow.
The disadvantages of each are that acceleration is reduced when the maximum speed is required and the maximum speed is reduced when the acceleration is increased.
I want to enjoy winding roads with higher acceleration when exiting cornering.
The engine output has changed since the bore was increased.
The low gear is short, so shifting up is busy.
I want signal dash acceleration.
Increase the number of sprockets/What happens if we reduce it?
Even if you know the effect of changing the number of sprockets, when you actually change the number of sprockets, which one should you increase, the front or the rear? Many people are not sure if they should reduce it.
I am one of those people. I always check to make sure. (Because I replace them only once every few years.)
Therefore, we have prepared a table for easy understanding.
Sprocket Ding Number Change Chart
As shown in the table, if you want to increase the maximum speed, increase the number of dings on the front sprocket or decrease the number of dings on the rear sprocket.
If you want to increase acceleration, reduce the number of dots on the front sprocket or increase the number of dots on the rear sprocket. Each has an inverse relationship between increase and decrease at the front and rear.
Which sprocket to replace?
Another problem that troubles me when changing the number of sprockets is the question of whether to replace the front or rear sprocket. If the purpose is only to change the vehicle characteristics by changing the number of pins, we recommend replacing the front sprocket.
The effect of changing three rear guns is equivalent to a change of about one gun in the case of the front.
(Conversely, fine adjustment is easier in the rear.)
In many cases, it is not necessary to change the length of the chain if the number of pins is changed by one or two pins.
In general, it can be said that the most cost-effective and significant change can be achieved by changing the number of pins on the front sprocket.
On the other hand, front sprocket removal and installation may require very hard bolts depending on the vehicle. Another disadvantage is that unlike the rear, the rear sprocket is not visible from the outside of the vehicle, so it does not have a custom look. If you want to refresh the entire drivetrain, including the chain, you may choose to change the number of rear sprockets.
Why do the maximum speed and acceleration change?
This is because the secondary reduction ratio changes with a change in the number of sprockets.
What is the secondary reduction ratio? Number of pins on rear sprocket divided by number of pins on front sprocket.
The value is calculated by the number obtained in this calculation is the ratio of how many rotations of the front sprocket are required to make one rotation of the rear tire.
For example, the stock number of the well-known Super Cub 110 is 14 at the front and 35 at the rear. In this case, the secondary reduction ratio is 35 divided by 14, which is 2.500. In other words, it takes 2 front rotations to make 1 rear rotation. So it turns 5 rpm. The maximum speed at this time is 87 at 7500 rpm in 4th gear 6km.
Now, let's increase the number of front pins by one in order to increase the maximum speed based on the speed table for changing the number of pins mentioned earlier.
In the case of 15 fronts and 35 rears, the secondary reduction ratio is 35 divided by 15, which is 2.333. The number of revolutions the front must turn to make one revolution of the rear tire is 2.500 to 2. It was reduced to 333 times.
In other words, one revolution of the rear tire can be achieved with fewer revolutions = lower engine speed at the same speed = higher maximum speed.
Incidentally, the theoretical maximum speed at this time was 93 mph at 7500 rpm in 4th gear. The maximum speed can be expected to increase by approximately 5 km to 9 km. Thus, a change in the number of sprockets changes the speed and acceleration.
The ratio of how many rotations of the front sprocket it takes to rotate the rear tire one revolution.
Smaller secondary deceleration ratio values are closer to maximum speed, while larger values are closer to acceleration.
Let's imagine a bicycle for the secondary reduction ratio.
Although it is difficult to put it into a formula, the change in acceleration and speed due to this change in reduction ratio can be easily understood by imagining the acceleration and maximum speed of a bicycle with gears in light and heavy gears.
On a bicycle with a gearshift, you select a lighter gear when you start riding and switch to a heavier gear as you gain speed, right? Even if you are moving your feet at the same speed, you will not go as fast in a lighter gear, and a heavier gear will make it harder to start riding when you start off. It is easy to understand if you imagine that this also happens with bike sprockets.
Also, in many cases, gears are visible in the rear wheel area on sport-type bicycles. The first gear is a large gear with a large number of gears, and the sixth gear is a small gear with a small number of gears. This is also the same as the sprocket on a motorcycle.
In a bicycle, the front and rear sprockets also serve as the transmission and are structured in this way, but in the case of a motorcycle, it is the transmission part that performs this shifting.
Sunstar is recommended for sprocket replacement
The front is made of steel, as strength is of utmost importance, but in addition to steel, the rear lineup also includes aluminum sprockets that are lightweight, highly accurate, and durable. This rear aluminum sprocket is approximately 1.5 times larger than the stock steel sprocket./3, which reduces the unsprung weight.
Hard anodizing not only gives a custom look at a glance, but also makes the entire body of the vehicle look tighter, so we recommend changing the number of cylinders as well as the rear to aluminum.
Material: Chrome molybdenum steel (SCM)
Durability: 10,000 to 30,000 km
Material: Superduralumin (A7075-T6)
Weight: Approx. 1 of steel (stock, etc.)/3
Durability: 10.000 km to 20,000 km
Material: Steel (S45C)
Durability: 20,000 km to 40,000 km