The name of this bicycle gear type is a "derailleur gear system." This type of gear system uses a mechanism to move the chain from one sprocket to another, allowing the rider to change gears and adjust the resistance while pedaling. Derailleur gear systems are commonly found on modern road and mountain bikes, providing a wide range of gear options for different terrains and riding conditions. **

No, it is not possible to convert a 7-speed gear system to a 21-speed gear system. The number of speeds in a gear system is determined by the number of sprockets on the rear wheel and the number of chainrings on the front crankset. A 7-speed system has 7 sprockets on the rear wheel and one or two chainrings on the front crankset, while a 21-speed system has 7 sprockets on the rear wheel and 3 chainrings on the front crankset. Therefore, to convert a 7-speed system to a 21-speed system, you would need to replace the entire drivetrain, including the rear wheel, front crankset, shifters, and derailleurs. **

The Shimano 7-speed gear shift may crack in every gear due to a few potential reasons. One possible cause could be that the gear shift is not properly adjusted, leading to misalignment and causing the cracking sound. Another reason could be wear and tear on the gear shift components, such as the cables or the shifter itself, which can lead to issues with smooth gear changes. Additionally, the gear shift may crack in every gear if there is dirt or debris built up in the gear mechanism, causing friction and noise during shifting. Regular maintenance and proper adjustment can help address these issues and prevent the gear shift from cracking in every gear. **

The name of this bicycle gear shifting type is "trigger shifters." These shifters are typically located on the handlebars and are operated by using the thumb or index finger to push or pull a lever, which then shifts the gears up or down. Trigger shifters are popular for their ease of use and quick, precise gear changes, making them a common choice for many cyclists. **

It is not recommended to use fifth gear when driving uphill, as it may strain the engine and cause it to work harder than necessary. It is better to downshift to a lower gear, such as third or fourth, to maintain a steady speed and prevent the engine from overworking. This will also provide better control and power when driving uphill. **

From 5th gear, the next gear in most manual transmission vehicles is 6th gear. However, some vehicles may have additional gears beyond 6th, such as 7th or 8th gear. The higher gears are typically used for cruising at high speeds on highways to improve fuel efficiency and reduce engine strain. **

The speed of each gear in a vehicle depends on the specific gear ratios of the transmission. Generally, first gear has the lowest speed and highest torque, making it ideal for starting from a stop or climbing steep inclines. As you shift up through the gears, the speed increases while the torque decreases. The highest gear, typically fifth or sixth in a manual transmission, allows for the highest speed and lowest engine RPM, making it suitable for cruising at highway speeds. Automatic transmissions also have different gear ratios, but the specific speeds for each gear can vary depending on the make and model of the vehicle. **

From the 5th gear, you can shift to the 6th gear in most vehicles. The 6th gear is typically the highest gear in a manual transmission, providing the best fuel efficiency at high speeds. It is important to shift smoothly and at the appropriate time to ensure optimal performance and fuel economy. **