What do the 21 and 27 variants mean on a shifting bike?

It is obtained by multiplying the number of wheels at the bottom foot pedal by the number of tower wheels (flywheels) at the rear wheel.

For example, the middle wheel is 3 pieces, the tower wheel is 7 pieces (7 fly), then it is 21 speed (21 changes), the middle wheel is 3 pieces, the tower wheel is 9 pieces (9 fly), it is 27 speed (27 changes), and the middle wheel is 2 pieces, the tower wheel is 8 flies, and it is 16 speeds.

The middle wheel is 3 pieces, and the tower wheel is 6 flies and 18 speeds.

The middle wheel is 3 pieces, and the tower wheel is 8 flies and 24 speeds.

Bikes are usually available in 18-speed, 21-speed, 24-speed, and 27-speed, but don't really think that you can use 21, 24, and 27-speed.

The car shop didn't lie to you, your car is so many gears, but considering the safety and wear factors of actual use, the 21-speed car actually uses only about 15 speeds, the 24-speed car is of course only 18 speeds, and the 27-speed car only uses about 21 speeds. It's not that you can't use all gears, it's that you won't use them either. For example, if you use the largest crankset against the biggest fly, you can, but you have to take into account that the chain has been tilted very much, and your crankset, fly, and front derailleur are worn badly.

When you ride, you make a kara-kara sound, can you bear to hear it? There is also a situation where the chain is tilted so badly that it will fall out of gear :)

I don't quite understand, copy, I'm honest

A 21-speed gearbox bicycle is a bicycles that can change 21 gear ratios, usually a 3-piece crankset and a 7-piece flywheel to achieve 21 gear ratios. (Known in the industry as a 7-speed).

A 27-speed gearbox bike is a speedshift bike that can change 27 gear ratios, usually using a 3-piece crankset and a 9-piece flywheel to achieve 27 gear ratios. (Known in the industry as a 9-speed).

21 speeds = 3 cranksets x 7 cassettes There are 21 combinations (also known as 7 speeds) 21 speeds = 3 cranksets x 8 cassettes There are 24 combinations (also known as 8 speeds) 27 speeds = 3 cranksets x 9 cassettes There are 27 combinations (also known as 9 speeds) Mountain bike cranksets are generally 3 pieces AM DH will have 2 or 1 cranksets on road bikes and 2 cranksets is generally 2 pieces If both the crankset and the cassette are 1 piece, it is called a single-speed car.

Now there's also a 10-speed -- which is a relatively new technology for SRAM -- two cranksets with a 10-speed cassette -- Himano has its own 10-speed technology -- it's a three-piece crankset with a 10-speed cassette.

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1. Change the hub, 27 speed is a cassette flywheel, 21 speed is generally a rotary flywheel. These two types of flywheels are not the same, and the hubs are not universal. Hubs can be considered Shimano.

The M510 hub, about 150 yuan a pair, other buy Shimano M390 kit, including finger dial, front dial, rear dial, crankset, flywheel, chain, in the finch shaft.

It should be noted that the number of hub holes should be the same as the number of rim holes you are now, otherwise you need to change the rim.

2. You only need to change the number of rear gear pieces (the specific need depends on whether the width of your rear wheel frame shaft is allowed), and the line disc brake.

Change the oil disc brake - if it is usually well maintained, it is not recommended to change it (the handlebar needs to be changed and the oil disc brake needs to be changed regularly.)

Hello, a 21-speed gearbox bike refers to a shifter bike that can change 21 gear ratios, usually a 3-piece crankset with a 7-piece flywheel to achieve 21 gear ratios. A 27-speed shifter bike is a 27-speed shifter bike that can be changed and replaced with 27 gear ratios, usually using a 3-piece crankset and a 9-piece flywheel to achieve 27 gear ratios. Sheltered.

1. The number of teeth of Zhongqing's 21-speed flywheel is 7, the number of teeth of 24-speed flywheel is 8, and the number of teeth of 27-speed flywheel is 9.

2. With the increase of speed, the accessories of the vehicle are also raised, the transmission and the front and rear derailleurs are upgraded, and the gear is increased after the Huqing transmission positioning needs to be more accurate.

3. The number of teeth of the crankset decreases with the increase of speed, making it more convenient for the force to be transmitted. The central shaft is generally upgraded to a one-piece type.

4. The fixing method of the flywheel is generally changed from spinning to flying, which improves the strength and facilitates the replacement of the gears.

In the transmission bicycle, the 21-section (21-section) shift, and the 27-section (21-section) shift refer to the shift class of the shifting bike.

The 21-speed shift, also known as the 21-speed, is a 3-piece crankset and a 7-piece tower wheel with a transmission mechanism, which can be combined with each other to obtain 21 gear ratios. That's why it's called 21-speed.

The 27-speed shift, also known as the 27-speed shift, is a 3-piece crankset and a 9-piece tower wheel, which can be combined to obtain 27 gear ratios. That's why it's called a 27-speed.

Compared with the 21-speed, the 27-speed has 2 more tower wheels and 6 more gear ratios, making the shifting smoother and more delicate.

Overspeeding, there are three ** in front of the pedal that are fixed. That's the third verse. Then the rear wheels have a set of flywheels.

After verse 21 are seven flywheels. The front big wheel three times seven is twenty-one... Twenty-seven is that there are nine flywheels in the back.

Hope it helps. Forget to adopt.

The first three sections are shifted, the last nine sections are shifted, and three times nine is twenty-seven sections!

That is, how many kinds of combinations there are in total, how many knots of speed change.

The first 3 and the rear 7 are 21 speeds, and the first 3 and the rear 9 are 27.

To put it simply, what we call 21 speed or 27 speed is the product of the chainring of the front flight and the rear flight The chainring of the front flight is generally three, and the back is more or less No matter how much speed We generally use one matching mode when riding on the flat ground, so these three shifts are basically the same and do not affect the speed Then when climbing, the difference between 21 speed and 27 speed is shown The so-called shifting is more delicate, that is, you can choose from several shifts, so that you can climb more effortless, more comfortable, more in line with your riding style.

As for the height of the saddle, the most suitable and comfortable is that the saddle is the same height as the handlebar You stand on the ground and the handlebar to the armpit Just If you require labor-saving, then you can properly pull the saddle higher The higher the person on the saddle, the greater the transmission force, the more labor-saving the relative The highest should not exceed the vehicle management cordon Otherwise, there will be an accident It is also uncomfortable The speed of the car has nothing to do with the height of the saddle The comfort of the saddle is the most important It is also related to your frame model If you have any questions, you can ask me again.

21 24 27 large cranksets are 3 gears, 21 24 27 correspond to the rear wheel gear has 7 8 9 gears, 3 times 7 and so on 21 3 times 8 etc. 24 3 times 9 and so on 27 , 21 24 27 are the number of kinds of collocation.