The number of teeth and size of children's mountain bike dental disk need to consider the following key factors:

Age and stage of physical development of the child

1. Young children (generally 4-7 years old) :

Children at this stage have relatively weak body strength and leg muscles are not fully developed. Suitable for the selection of smaller size and fewer teeth disk.

- In terms of size, it is recommended to choose a dental disc with a diameter of about 100-120 mm. This size makes it easy for them to pedal easily when riding, and will not feel labored because the dental disc is too large.

- The number of teeth can be between 20-28 teeth. The smaller number of teeth reduces the resistance of the stampede, allowing them to start and maintain the riding speed more easily.

2. Middle Age children (8-11 years old) :

- With age and gradual physical development, their strength and endurance improve. The size of the disk and the number of teeth can be appropriately increased.

- Size can be selected in the diameter of 120-140 mm dental disc. This size can better accommodate their gradually increasing leg strength, while not placing too much burden on their riding.

- The number of teeth ranges from 28 to 36 teeth. This gear configuration can meet their riding needs on flat roads and light mountain conditions.

3. Older children (12 years and above) :

- The physical development of older children is close to the level of teenagers, with strong strength and good riding skills.

- The size of the dental disc can be selected close to the adult standard of small dental disc, with a diameter of about 140-160 mm.

- The number of teeth can be between 36 and 44 teeth. This configuration can meet their riding needs in a variety of difficult terrain, including climbing and acceleration.

Second, riding use and terrain

1. Daily recreational cycling:

- If the child is mainly riding on flat roads, neighborhoods or parks and other more gentle terrain, then you can choose a relatively small number of teeth and size.

- For example, for daily recreational riding children, it is more appropriate to choose a 28-32 tooth tray with a size between 120-140 mm. This allows them to enjoy a comfortable riding experience while riding easily.

2. Light mountain biking:

- When children start trying to ride on some lightly undulating mountains or small dirt slopes, they need to slightly increase the number of teeth and size of the disc to provide better climbing ability and speed maintenance ability.

- You can choose a disk with 32-36 teeth, the size is about 130-150 mm. This configuration allows them to cope more easily when facing some small inclines.

3. Professional mountain cycling training:

- For those children who have a certain cycling foundation and participate in professional mountain cycling training, they need to choose a more suitable dental tray according to their training intensity and terrain requirements.

- Usually, the number of teeth can be between 36-44 teeth, and the size is about 140-160 mm. This configuration can meet their requirements for high-intensity riding in complex mountain conditions.

3. Compatibility of bicycle frame and transmission system

1. Frame size:

- Different sizes of bicycle frames need to match the corresponding size of the dental tray. If the size of the tooth tray is too large, it may interfere with the frame, affecting the safety and stability of the ride.

- For example, for children's mountain bikes with 20-inch wheel diameters, it is usually suitable to match a dental disc with a diameter of 120-140 mm. For a bicycle with a 24-inch wheel diameter, the disk size can be appropriately increased to 140-160 mm.

2. Transmission ratio requirements:

- The number of teeth of the disc needs to match the number of teeth of the rear flywheel of the bicycle to achieve the proper transmission ratio. The choice of transmission ratio will affect the speed and power output of the ride.

- Generally speaking, if you want to obtain higher speed, you can choose a combination of larger disc teeth and smaller flywheel teeth; If greater climbing capacity is required, a combination of smaller disc teeth and larger flywheel teeth can be selected.

For example, a common kids' mountain bike drivetrain configuration might have a disk with 32 teeth and a flywheel with a range of 14-34 teeth, with different gear combinations to suit different riding needs.