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    All about frame height on a mountain bike

    Sophia Willmes
    Sophia Willmes
    Mar 4, 2024 7 min
    All about frame height on a mountain bike

    The buycycle frame sizes guide

    In the past, anyone who wanted to buy a bike usually went to the nearest specialty store. The bike whose looks were most convincing was test ridden. The only quality criterion was often whether you could still reach the ground with the tips of your feet. Today, most people know that there is the so-called stride length, which should provide information about the appropriate frame size. Whether road bike, city bikes, cross bikes, trekking bikes, cyclocross bikes or gravel bikes, BMX or mountain bike: the body's own stride length gives a good first clue to the optimal frame size, no matter what type of bike. Especially for MTB, many manufacturers try themselves with different frame geometries. The frame geometry influences the range of use for which the MTB is suitable. It is therefore worthwhile to also take a look at different dimensions of the frame before buying. Depending on the main area of use, the geometry of the bike frame determines the driving behavior. So each area of use needs a slightly different shape. To find the right frame height for your dream bike, you can find all the important information here.

    1. What frame height is needed for mountain bike?

    It should be said in advance that frame height and frame size mean the same value. As a rule, the "center-to-top" method is used to measure from the center of the bottom bracket to the end of the seat tube. The determined frame height is given in centimeters or inches. Many manufacturers nowadays specify the frame size like clothing sizes in S, M or L. Major brands such as Cube, Santa Cruz, Cannondale or Trek have years of experience and give reliable guide values. To the respective data ranges of body sizes are called. Information on the respective stride length is also often provided. All of this provides an initial indication of which bike fits your body. You should really pay attention to the specifications of the respective manufacturer. The sizes can deviate due to manufacturer-own construction methods under the marks of each other and are with one another with difficulty comparable. If you were satisfied with an M frame size on your last bike, you can't simply transfer that to another model. The right size has an influence on the riding behavior of the mountain bike. The right fit will give any rider even more fun, control and comfort. A frame that is too small will feel more maneuverable. This will benefit you on technically demanding trails with switchbacks.

    If you choose a slightly too large frame, the bike behaves more smoothly. It is more comfortable on fast downhill rides, where obstacles are generously rolled over. Unlike other types of bikes, what matters is that there is plenty of space between the top tube of the frame and the rider's crotch. Whether you're riding a hardtail or a fully, situations often arise on downhill rides where you should be able to swing off your MTB quickly. This distance between the top edge of the top tube and the crotch is called protrusion. It can not be compensated by retrofitting other components. So if the top tube already clamps between your thighs the first time you get on the bike, the frame height is too small or the bike is generally unsuitable for your body. The fact that the stride length and height can only serve as a guide for sizing is also due to the fact that bodies have individual characteristics. Some people have particularly long arms, torsos or legs. So it can happen that someone should ride a smaller frame height according to body size, but the particularly long legs speak for a larger frame. By the way, frame height is not usually specified for children's bicycles. Instead, the wheel size in inches provides information. Children's bikes are often advertised with age specifications as a recommendation for the correct size.

    2. How to measure the stride length?

    Just determine the stride length yourself, Nic explains it you in the YouTube video attached below. For this you need a tape measure or a folding rule and a loose saddle, a spirit level or a book. You stand in front of a straight wall. The legs should have a small distance between them. In the crotch you now clamp the book or the saddle. Measure from the tip of the saddle to the floor. In the case of the level or the book, it is measured from the top of the book or the level to the floor. The step height determined in this way can be calculated into the correct frame size. To do this, multiply the stride length by a factor of 0.574. A value between approx. 33 cm and 56 cm should be the result. Alternatively, you can of course go to a bike store and get professional help with measuring.

    3. Tips for frame geometry.

    Before purchasing a new mountain bike, it is important to think about the main area of use. For this, an honest look at the previous driving behavior is necessary. This provides information about which type of mtb with which geometry fits best. If you like to ride long tours uphill and downhill without riding trails with deep drops and wide jumps, you can purchase an MTB hardtail. Fullys are designed to overcome larger obstacles. All mountain or trail bikes are true all-rounders and bring fun on long distances as well as on rougher trails. Enduro bikes cushion even further jumps and are somewhat more adapted to downhill riding. Freeride and downhill bikes roll over large scree without any problems, uphill riding is rather nothing for these models. Those who are happy to do without the shuttle service, but still want to race down trails several times in a row, can consider an e-mountain bike. Reaching high places with great views can also be made easier with the help of an e-bike. These considerations about the range of use are very profitable. Depending on this, the geometry of the frame and thus also the seating position changes. The desired seating position can also provide information about which bike suits you. So also consider whether you want to ride long tours, and thus should rather sit upright. Frequent visits to the bike park require a different seating position. A detailed look at the dimensions allows you to assess the riding behavior of the new bike.If you want to look at the frame geometry in more detail, you should remember some terms. These include the stack to reach ratio. It provides a good insight into the seating position you will have on the bike. Stack means the distance from the highest point of the top tube to the center of the bottom bracket. So the stack indicates the height of the front of the MTB. The higher it is, the more upright the position when standing and sitting. The reach is the distance between the center of the bottom bracket and the handlebars. So a longer reach leads to a longer wheelbase. People with long torsos or arms can benefit from frames with a long reach. So the reach generally says something about how tall the frame is. A smaller reach leads to more maneuverability, a larger reach provides more stability. When mountain biking, you often stand on the pedals, especially when riding downhill. A long reach leads to a more athletic posture, a shorter reach leads to an upright posture.

    The reach should not be confused with the effective top tube length. The top tube length means the distance between the center of the head tube and the center of the seat post. With the help of the seat post or another stem, the top tube length can be adjusted if, for example, complaints arise when pedaling. Since you already can not compare the specified sizes of the manufacturers, the top tube length comparison falls as a better means into consideration. Here, caution is advised, as the top tube length changes with the seat tube angle. The Reach has the perpendicular to the bottom bracket always fully in focus and is therefore more meaningful. The wheelbase, in conjunction with the steering angle, has an influence on whether the bike is maneuverable or smooth-running. The wheelbase is the distance that the wheels have measured centrally to each other. The steeper the steering angle, the more maneuverable and playful. The flatter, the smoother.

    A flat angle is particularly suitable for fast downhill rides, in which the technique plays a subordinate role and obstacles are rather rolled over than driven around. Particularly in freeride and downhill bikes, flat steering angles are therefore used. All mountain and trail bikes tend to rely on steeper steering angles, for example, to be able to steer around tight corners better. In addition to the frame geometry, the wheel size is also relevant. Whereas 26" wheels were predominant on mountain bikes in the past, 27.5" or 29" wheels dominate today. Larger wheels make it easier to roll over obstacles. Wheels in 27.5" are mainly installed on bikes with frame size XS or S. They bring a playful, agile behavior and can be advantageous on technically challenging trails.

    Often, instead of 27.5 "is also called 650B wheels. This is the French designation. The most popular today are 29" wheels. They roll over scree without any problems, are smooth running, bring stability and grip. Fast trail descents are particularly fun with them. By the way, there are also so-called Mullet bikes. A 29" wheel is mounted in front, 27.5" in the rear. This is to combine the advantages of both sizes. This also changes the geometry, the front of the bike moves up and the steering and seat angles become flatter. It's best to try out the Mullet bike on occasion to see if it suits your own riding style.

    In summary, you can follow this procedure: Determine frame height based on body size and stride length, define range of use, view geometry. This way, you are on the safe side even when buying used bikes online or ordering from a dealer, without having to test ride. In the end, no matter how perfectly the bike fits, it's primarily the rider's skills that make every ride an experience. So instead of getting too lost in the science behind a frame, get on the saddle and get going.

    That's it! If you have further questions about frame heights or about the topic of bicycles in general, you can always continue on the blog or contact our team team. And take a look at buycycle if you want to find your new dream bike or sell your old one. Until then, we wish you, as always: Happy browsing, happy cycling!