Which Bike Frame Size Do I Need?

The question of how to determine the correct frame size of a bicycle is one of the most common questions beginner ask. And unfortunately, they usually get a not quite right answer from those people who travel only a few times over the summer and do not have the information completely.

Beginners, therefore, buy a bicycle with a frame that is unsuitable for their height and that suffers from knee and back problems. The wrong frame size is an uncomfortable ride that can be felt as your mileage increases to 30-50 kilometers per day. Worst of all, if the frame is small.

That’s why I decided to give some advice to my readers, who are in the early stages of cycling. According to the usual tradition, the size of the bicycle frame is indicated by the length of the seat tube (size ST in the following drawing). Here’s a very conditional table that lets you determine the right frame length for your height.

Frame size (inches)Height (cm)Frame height (cm)Size
15140 – 15038XS
16150 – 16540S
17160 – 17543M
18170 – 18045M
19177 – 18348L
20180 – 18650L
21185 – 19353XL
22186 – 19755XL
23190 – 20558XXL

The place where the size is specified – usually the seat tube – is indicated there either with a letter (S, M, L, XL) or digitally in inches or cm. The size of the mountain bikes in inches. It is due to the fact that the road bike first gained popularity in southern Europe and the mountain bike was invented in the United States.

Well, friends, remember one thing – if someone says it suits you, for example, an 18-inch frame, then this is very average information because that size says very little today. In the past, when the frames were almost the same, the 18 “(457.2 mm) seat tube length could say that this frame size would be 175 cm tall. Today, bicycle manufacturers offer a variety of frames with different geometries for different directions of travel Let’s get to the examples.

What is ETT and why frame geometry is so important?

Here is a drawing of a frame. Pay attention to only two sizes: ST (seat post length) and ETT (Effective top tube, top tube horizontal) – an imaginary line from the center of the steering sleeve to the point of intersection with an imaginary axis that runs through the seat post. In fact, ETT is the length of the bike, the most important factor in choosing a bike, and the novices never look at it.

Note that these two frames apply to the same person, although the size of ST (the one specified as the size of the frame) is different in this case. That is, because of the different geometry, a person who was advised to frame 18 inches without looking can make a big mistake.

Bicycle Geometry ST + ET

This example shows the differences in geometry between the highway and the mountain frame, but do not think the frames are the same within their class. For example, I have a mountain bike – 21 “and it’s a bit short for me while the other is only 19”, but it’s longer than the first one. The difference is that the second top tube (size ETT) is longer, but the seat tube (ST) is shorter.

When choosing a bike for height, first pay attention to its length, since, as I said, what stands on the frame means only the size of the seat tube and this is not a very important parameter.

ETT table for different cyclists height

Specifying the size of a bicycle (18 inches, 20 inches, L, XL, etc.) gives a very limited idea of the size since the frames have different geometries. In the description of a bicycle, on the website of the manufacturer or in the online shops is often a geometry table. There you will find the parameter ETT.

Please note that mountain bikes now use a modern forward geometry for athletic purposes – the frame is longer and the extension is shorter. This makes the bike more stable on the trails.

Your height (cm)Effective Top Tube (ETT)
150 – 165580-590mm
165 – 175590-605mm
175 – 185605-630mm
185 -195630-650mm

I emphasize that these figures are suitable for mountain bikes that are used in aggressive sports areas and whose frames are longer than usual. If your new mountain bike is not sporty but rather relaxing, you should subtract 5% from the above ETT values.

Of course, these are subtleties that a beginner can push aside, but I still advise you to be very careful when choosing a bike size. A wrong frame length could cost you the purchase of a new bike.

Wheel dimensions and frame dependence on height

There is an opinion that you need to choose the size of the bike for your height, eg. For example, if you’re 190 cm tall, you should never take a bike with 26-inch wheels, just 28 or 29 inches.

Now everything is determined by the geometry, it is impossible to say that the diameter of the wheel is suitable for a certain height. For example, a 26 inch and 29 inch frame is equally well balanced for any adult size.

Or, for example, take folding bikes for adults – there are usually wheels from 16 to 24 inches. And imagine, the frame is designed so that even a tall person feels comfortable.

Wheel diameter and destination of the bicycle

Another thing is that a great person looks much more harmonious on a bicycle with big wheels from a purely aesthetic point of view. The size of the bike and its dependency on the bike type can be found in this table:

16-24Folding, for city and good asphalt
26 inchesMountain, with outdated size wheels
27.5 inchesMountain, modern, high maneuverability
28 inchesRoad, city, touring
29 inchesMountain, modern, good coasting

Keep in mind that modern bicycles do not adjust the steering wheel height (except for city bicycles). So if you’re the wrong size, you do not have the ability to “play”. Unfortunately, no size chart can be given as it will, in any case, depend very much on the specific geometry of the frame and its anatomical features. Therefore, only tips for choosing a mountain bike or a hybrid.

Tips to choose a mountain or a hybrid bike

  1. If possible, try the bike yourself. If you can not ride, at least sit on it.
  2. When standing with both feet on the ground (the bike between the legs), the distance between the perineum and the top tube should be at least 5-7 cm. A shorter distance is associated with injuries when falling or an emergency stop.
  3. If you are buying a bicycle over the Internet, use the tips on frame length (ETT) above. The longer the bike, the sportier the landing. For a fast and effective ascent, it is very important to “flatten” the frame. So if you buy a bike for the sport, I recommend long and low frames.
  4. Vice versa, short frames are recommended for a leisurely and comfortable ride. Look at sit-bikes: The landing is almost vertical, a person sits on a stool and only holds the steering wheel. Even in this case, rolling over long distances is not so pleasant: the entire body weight falls on the spine.
  5. The ideal frame for advanced non-athletic cyclists is a medium-length frame that does not require you to transfer weight to your hands but does not need to sit on the tailbone. On a bike like this, you can cover dozens of miles on the right saddle without feeling uncomfortable when landing.

What can I do if the bike size does not fit?

Assuming the bike has already been bought, but what if it does not fit? It is possible that the bike can be easily adjusted to its height, even if the frame does not quite fit. Read the following guidelines.

Adjust the seat in the horizontal plane

The saddle should be parallel to the ground. Sometimes novices and already well-trained cyclists tend the saddle forward or backward for comfort. This is completely wrong, because in this case, the weight distribution of the driver is interrupted, hence the stiff hands, which hurt backwards and so on.

The back should ideally sit in place and not slide forward or backward. Try to lower the saddle a bit, literally 5-7 mm. This most likely provides the opportunity to straighten the saddle.

Correctly fit saddle

Many inexperienced cyclists, especially teenagers, have brought the saddle significantly below the desired level due to fitness exercises we call “knee-highs”. Not only does it look funny, it is also very dangerous for the knee joints.

The height of the saddle should be such that the leg is slightly angled when mounting at the lowest point of the pedal when adjusting the toe (or fully extended when you pry the pedal out from below).

Also place your foot on the pedal with your heel. In this case, the pedal is completely upright. This is a very important point! At first you may be uncomfortable that in case of a sudden stop you will not be able to touch the ground with your feet without leaving the seat, but trust me, the health of your knee joints is more important than comfort.

Ideally, your foot should rest on the pedal so that the axle of the pedal is just below the knee joint. This can be achieved by moving the saddle in the longitudinal direction.


Bicycle Seatpost

If even after the maximum longitudinal adjustment of the seat back, you do not leave the feeling that the bike is a bit short, then the seat can help with the displacement back. This will give an additional 3-5cm, which you lacked for a comfortable fit. You can find it on Amazon starting from as little as $ 20

Grips with horns on the handlebars

Bicycle Handlebar

This is a very important element at long distances, allowing you not only to change the position of the hands but also the entire body. Install them almost parallel to the ground, with a very small rise. You should be able to place your palms on the grips and bring the center of gravity to the front.

As a bonus, this attitude improves your aerodynamics. Cyclists often use this technique when driving against the wind. A good complement may also be handled with flat platforms on which you can put your palms. I used the Ergon GP5 Grips for a long time until I found the perfect bicycle size for me.

Bicycle Stems

Bicycle Stem

As I said, in modern bicycles, the steering wheel is not height adjustable, but something can be done. The execution of the steering wheel (short joystick, which is attached to the steering wheel) has an angle and a length. There are carry-outs of different sizes, and when you buy the right one, you can significantly improve the driving experience. If the bike is too big, take the take-out shorter if it is too small, then longer.

The removal can be installed with both lifting and lowering. There are also supports with adjustment. This only slightly changes the height of the steering wheel. You can buy them for little money on Amazon

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    • Andrej

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