The following points should be noted when choosing an electric bicycle:

1. The screws and nuts of the bicycle should be tightened and should not be loose or fall off.

 2. All rotating parts should be flexible and should not be stuck or stiff. For example, the front and rear wheels should rotate flexibly and should not swing left and right or jump up and down. When the wheels are about to stop, they should be able to swing back and forth briskly and should not stop rotating suddenly. The handlebars should rotate freely and flexibly, and the pedal shaft and crank should be tightened, should not be loose, and should rotate flexibly. 

3. The gear shifting should be correct within the speed range, the speed shifting position should be clear, and there should be no gaps in the middle.

 4. The chain should be of appropriate tightness and run flexibly. Use your hands to shake the crank sprocket repeatedly in forward and reverse directions. The chain should run flexibly and should not jump or fall off. 

5. Hold the front and rear parts of the saddle with both hands, and press down the front end of the saddle with one hand. The front end of the saddle should not collapse. Then use both hands to rotate the saddle horizontally, and the saddle should not rotate. 

6. Selection of brakes and brake systems: Hold the handlebars with both hands, apply the left and right brakes respectively, and push and pull the bicycle forward and backward at the same time. The wheels should not rotate at this time; release the handle, and the brake system should be able to reset quickly. 

7. The surface of each component should be clean, free of stains and rust. The trademark decals should be complete and clear, without sharp edges and burrs. For example, the edges of the mud plate and chain cover should not feel prickly, and the ends of the brake and other steel ropes should be equipped with protective covers. 

8. Observe the brand or label of the components. Generally speaking, good components are marked with obvious trademarks and the patterns are clear and beautiful, while inferior products are rarely marked or rough.

 ◆ III. In addition to the above conditions, the following points should be noted when selecting electric bicycles: 

1. The switches of each part are sensitive and reliable. 

2. The speed regulation is stable and reliable. Slowly turn the speed control handle, the motor should start and accelerate smoothly, and after releasing the handle, the handle can be quickly reset, and the motor decelerates evenly. 

3. The brake power is cut off quickly and reliably. Turn the speed control handle, after the motor is running, squeeze the brake, the motor can be powered off immediately, and if there is a power display, you can see that the display returns to zero. 

4. The battery is easy to disassemble and assemble. The weight of a lead-acid battery is generally about 13.5kg. Since it needs to be disassembled and assembled every day, the position of the battery must be suitable for your body.

 ◆ IV. How to use and maintain: Pay attention to reading the instructions carefully to understand the functions of the bicycle, especially the precautions. First of all, pay attention to cleaning. After contact with water, especially salt water in winter, it should be cleaned in time, otherwise it is very easy to cause metal parts to rust and the paint film to age and fall off. The handlebars and the seat are both adjustable. When adjusting, you must first make riding comfortable and secondly pay attention to the maximum adjustment height. The handlebar riser and the saddle tube should be engraved with a safety line, which is generally 

2.5 times the diameter of the tube from the lower end of the saddle tube. This is the maximum adjustment height. The safety line must not be exposed during adjustment. After riding a new bike for a period of time, the whole bike should be checked and adjusted. At this time, tightening and lubrication are essential. Check that the fasteners should not be loose, the transmission parts should be flexible, and pay attention to wiping off the floating oil after lubricating the chain, and a little oil on the flywheel. The tires should be properly inflated, otherwise it will affect the riding comfort and service life. The brakes are the basic guarantee of safety and should be checked at any time. If any problems are found, they should be adjusted or repaired immediately.