RPM

    RPM

    RPM - Revolutions per minute

    It is the number of Revolutions of crank produced by the engine.

    

    

The rear wheel(or your vehicle) moves at a differentRPM(or speed) than the engine. ... An RPM meter is a device which can measure the amount of Revolutions per Minute of any rotating object, in this case it is theRPM of the Engine driven Shaft. RPM Meter is the same in Bikes and Cars.

Yes, speed is directly linked with the RPM. As the RPM increases, the speed increases. But the engine is not directly connected to the wheels, the power of the engine is directed towards the wheel by the help of different gears. 

Your bike has 5 gears(assuming, as your bike has an RPM meter!) whose job is to vary the rotation speed of the wheel as per your requirement

1. The 1st gear takes the rotations from the engine, reduces it and sends it to the wheel. The wheels rotate slower than the engine's speed.
2. The 4th gear takes the rotations from the engine and sends the same amount of rotations to the wheel. The wheels rotate at a speed same as the engine's.
3. The 5th gear takes the rotations from the engine, increases it and sends it to the wheel. Now the wheels rotate faster than the engine speed, that's why it takes lesser RPM of the engine to take the bike to faster speeds

Gearing ratios are used in the arrangement of gears to control the final wheel's speed.

As we can see that the first gear is reducing the speed, we have to increase the RPM to take the bike at higher speed. But as the fourth gear is rotating the wheel with the same speed as that of the engine, we do not need to pull the RPM as in the case of lower gears.

Note: Increasing the gears does increases the speed but lowers the torque output.

RPM(rotation per minute) is the unit to measure the rotation of the crank shaft per minute. The crank shaft is a rotating shaft inside the engine that is connected to the gear box with fly wheel and clutch in between.

Rpm is Revolutions per Minute. It indicates the engine cycle per minute or the number of revolutions the crank shift makes in a minute.

It is true that the speed is related to the Rpm, but not to the engine directly. The engine transfers the power through the help of gears.

For example, when we shift to the first gear, the engine shifts the power to the wheels. The first gear takes the rotation from the engine, makes it slower, and then transfers it to the wheels. Hence , the engine speed is higher than the wheel rotation.

Now, when we shift to the 5th gear, the same thing happens, except, the gear takes the rotation, makes it faster, and then transfers it to the wheels. In this case the rotation is faster than the engine speed.

Thus, when you go to higher gear the Rpm drops all of a sudden.