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    All about frame height on a mountain bike

    Sophia Willmes
    Sophia Willmes
    Mar 4, 2024 8 min
    All about frame height on a mountain bike

    The buycycle frame sizes guide

    Previously, anyone who wanted 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 the so-called stride length 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.

    Therefore, it is worthwhile to examine the different dimensions of the frame before buying. The geometry of the bike frame determines the driving behavior, so each area of use needs a slightly different shape. You can find all the important information here to find the right frame height for your dream bike.

    1. What frame height is needed for a 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 measures from the bottom bracket's centre to the seat tube's end. 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. 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 pay attention to the specifications of the respective manufacturer.

    The sizes can deviate due to the manufacturer's 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 influences the riding behavior of the mountain bike. The right fit will give any rider more fun, control, and comfort.

    "A frame that is too small will feel more maneuverable, which will benefit you on technically demanding trails with switchbacks." - Anja Benson @buycycle

    If you choose a slightly too large frame, the bike will behave 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 full-suspension bike, situations often arise on downhill rides where you should be able to swing off your MTB quickly.

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    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 because bodies have individual characteristics.

    Some people have particularly long arms, torsos, or legs. So, according to body size, someone should ride a more petite frame height, 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 in the YouTube video attached below. You need a tape measure, folding rule, loose saddle, spirit level, or book. Stand in front of a straight wall. The legs should have a small distance between them. Clamp the book or the saddle in the crotch.

    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 using 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 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 consider the main area of use. For this, an honest look at the previous driving behavior is necessary. You can purchase an MTB hardtail if you like to ride long tours uphill and downhill without riding trails with deep drops and wide jumps.

    Fullys are designed to overcome larger obstacles. All mountain or trail bikes are true all-rounders, bringing fun on long distances and rougher trails. Enduro bikes cushion jumps even further and are more adapted to downhill riding.

    "Freeride and downhill bikes roll over large screes without any problems, and uphill riding is almost nothing for these models." - Alice Huot @buycycle

    Those 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 the seating position change.

    The desired seating position can also provide information about which bike suits you. Consider whether you want to ride long tours and should thus 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.

    You should remember some terms to look at in more detail regarding the frame geometry. 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 top tube's highest point to the bottom bracket's centre. So, the stack indicates the height of the front of the MTB.

    The higher it is, the more upright the position. The reach is the distance between the center of the bottom bracket and the handlebars. So, a more extended reach leads to a longer wheelbase. Frames with a long reach can benefit people with long torsos or arms.

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    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. You often stand on the pedals when mountain biking, especially when riding downhill. A long reach leads to a more athletic posture, and a shorter reach leads to an upright posture.

    The reach should not be confused with the effective top tube length. The top tube length is the distance between the center of the head tube and the center of the seat post. If, for example, complaints arise when pedaling, the seat post or another stem can help adjust the top tube length.

    Since you can not compare the manufacturers' specified sizes, comparing the top tube length is a better option. Caution is advised here, as the top tube length changes with the seat tube angle.

    "The Reach always has the perpendicular to the bottom bracket fully in focus and is, therefore, more meaningful." - Anja Benson @buycycle

    In conjunction with the steering angle, the wheelbase influences whether the bike is maneuverable or smooth-running. The wheelbase is the distance the wheels are measured from the centre of each other. The steeper the steering angle, the more maneuverable and playful the bike. The flatter, the smoother.

    A flat angle is particularly suitable for fast downhill rides, where the technique plays a subordinate role and obstacles are rolled over rather than driven around. Flat steering angles are used primarily in freeride and downhill bikes.

    All mountain and trail bikes, for example, tend to rely on steeper steering angles 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 ", it wheels, which are also called 650B wheels, this is the French designation. The most popular today are 29" wheels. They roll over scree without problems, run smoothly, and bring stability and grip. Fast trail descents are enjoyable with them. By the way, there are also so-called Mullet bikes. A 29" wheel is mounted in front and 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 occasionally to see if it suits your riding style." - Alice Huot @buycycle

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

    Moving forward

    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.

    Look at buycycle to find your new dream bike or sell your old one. Until then, we wish you, as always, happy browsing and cycling!

    And if you want to sell your mountain bike on buycycle, that's possible too!

    Go to buycycle

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