First, I will briefly explain the importance of the size of the bicycle frame tubes. The size must be suitable for your body. If it is too large or too small, it will affect your riding posture, making it more difficult to ride a bicycle compared to others, and prolonged use may lead to movement disorders. However, this is not absolute. For example, if you often go downhill, you should reduce the frame size. If it is only used for traveling on flat roads, a slightly larger size is fine. But the experience in choosing the frame size should be "prefer smaller over larger". Then, let's learn about the method for choosing the size of bicycle frame tubes. 

For our amateur enthusiasts, although we can't customize cars or use complex formulas to convert things, some important parameters of bicycle frame tubes need to be mastered. 
First, let's talk about the length of the riser. The C-C value (the length from the center of the tee to the junction of the riser and the upper pipe) and the C-T value (the length from the center of the tee to the front end of the riser), some manufacturers use C-T while others use C-C. 
Another important parameter for the size of a bicycle frame tube is the length of the upper tube and the standing height. Of course, it is quite difficult for beginners to understand this. Fortunately, the length of the upright tube and the length of the upper tube correspond to each other, so it is not too absurd. It is also good for beginners to figure out the relationship between the length of the upright tube and their height (especially the length of their feet), so for mountain bikes, the frame size is almost always correct. 
Returning to the previous question, due to the manufacturer's definition of the size (some use C-C, while others use C-T), there is a problem with choosing. So, let's start from the practical aspect. 
We specifically measured the 18-inch and 16-inch pipe lengths (C-T values) of the Merida Warrior. The 18-inch and 16-inch are the terms used by Merida. Let's see if the manufacturer uses C-T or C-C. 
18-inch Duke straight pipe length (C-T value) 46CM, upper pipe length 55CM 
16-inch Warrior straight pipe length (C-T value) 41CM; upper pipe length 52CM 
So, let's calculate it now. 46 divided by 2.54 equals 18.11 inches. 41 divided by 2.54 equals 16.14 inches. This is consistent with the dimensions noted by Merida, and it is obvious that Merida used the C-T value. 
So, now let's start choosing the frame. Suppose the height is 1.67 meters and the foot length is 73 centimeters. How many frame should we choose? 
There are several formulas and websites circulating online. Additionally, there are also several categories based on height and frame size. Let's see how they made their choices. 
On the other hand, the size of the mountain bike frame = (I * 0.67 - 11.0) * 0.394 inches. I is the foot length. This is a well-known formula. Calculated based on my height, it should be 14.93654 inches, approximately equal to 15 inches. 
The calculation comes out to be 14.90, which is approximately 15 inches. 
There are also general statements as follows. Cyclists are classified based on their height: approximately 14 inches corresponds to a height of less than 155 cm, 16 inches to a height between 155 and 170 cm, 18 inches for heights above 170 cm, and those taller than 180 cm should try to opt for bicycles with a size of 20 inches or larger. "According to this statement, based on my height, I should choose a 16-inch one." 
The above content describes the method for selecting the size of bicycle frame tubes. If you want to know more, please feel free to contact us at any time! Our company has many years of experience and is always looking forward to your participation.