What Size Frame Gravel Bike Do I Need?

What Size Frame Gravel Bike Do I Need?

GRAVEL BIKE FRAME

Gravel Bike Size Chart is the best way to get a gravel bike that is comfortable to ride and fits your body. Like other types of bikes, there are many materials that can be used for gravel / all-road frames. It could be carbon, it could be steel, it could be aluminum, it could be titanium (and so on).

The difference is, this type of frame is not required to be very light. Toughness is the main thing. So, even if you use carbon materials, usually the type of carbon is not the most expensive. So that the price becomes more affordable.

Don’t be surprised if the price of the gravel frame set can be way below most road bikes. Although recently started to appear “luxury” gravel frames (which buyers may be afraid of dirty roads).

GRAVEL BIKE GEOMETRY

Perhaps the most important aspect of any gravel bike – is the geometry of the frame. Although much of the geometry of the bike has been mastered in the past few decades, the gravel frame is a wide segment with some feel of geometry and fit.

In general, gravel bikes tend to have a longer wheelbase and higher handlebars than road bikes – often paired with wide handlebars for better handling during rough terrain. Keep in mind that while the head tube of a gravel bike may not be longer than that of a road bike, the longer the axle-to-crown fork size means that your handlebars will almost certainly be slightly taller than that of a road bike.

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Perhaps the biggest debate in gravel bike geometry is regarding the height of the bottom bracket – usually measured as the vertical distance between the wheelbase and the bottom bracket. Some get low, like the Special Diverge with an 85mm drop, and some get high, like the Trail Donkey 3.0 from Rodeo Adventure Labs, which only features a 65mm drop.

How do you know what’s best for you? Lower bottom bracket height provides better stability and bend, at the expense of ground clearance. The tall bottom brackets clean the gruff better, at the expense of stability. Remember that tire size will affect your effective BB height, so don’t deviate too far from the diameter of the stock tire unless you really know what you’re doing (and it’s okay with the effect you’re having on tire handling on a bicycle).

BIKE FITTING FOR A GRAVEL BIKE

what is stack and reach and how to choose frame size is one of the most asked questions we get. Here’s why it’s so difficult.

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GRAVEL BIKE SIZE CHART

Gravel and cyclocross bikes are similar to road bikes when it comes to fit. The size is often numerical, in centimeters, measured from the center of the bottom bracket to the top of the safety post clamp. The length of the top tube will be one of the main measurements to consider. A gravel bike will most likely have a higher head tube than a comparable road bike, to provide a more upright position.

If you already have a drop-bar bike, that’s a good starting point for finding the right size. If a friend owns a bike of the same size, it can be helpful to ride a little to get a feel for it. Unlike road bikes, gravel bikes are usually designed to fit shorter stems, often 80-100mm, so it’s best to avoid buying bikes that are too small in hopes of making them fit very long stems, and vice versa with -big frames as well.1

Gravel frames are designed for long-distance riding, necessitating geometry that is stable and well-mannered. Usually, this means a slacker head tube angle, longer wheelbase, lower bottom bracket, and taller stack. Plus, gravel frames often afford more tire clearance, additional mounts for bottles and bags, and sometimes even incorporate aerodynamic features for battling across the windswept prairie.

Bicycle Frame Dimensions

Gravel Bike Size Chart

How necessary to understand the dimensions of the bicycle frame

For most people knowing gravel bike size chart is important, perhaps the most important thing is the right size, the feet can touch the surface when on a bicycle, or the straight foot position when pedaling, a balanced sitting position, but actually that’s not all.

Two racing bikes with different dimensions, will have different tastes, coupled with the difference in frame sizes that have different dimensions, making choosing a racing bike that matches what we want even more difficult actually.

understanding the dimensions of the bicycle frame geometry will be very useful for:

  • the right size: top priority.
  • bicycle character: bent, upright, long, short will make a different character of the bike.
  • bicycle handling/steering/control: the position of the handlebars, the slope of the handlebars, and others affect the ease of controlling the bicycle.
  • component compatibility: the size of the part of the bicycle frame determines the size of the other components that can be mounted on the bicycle.

We don’t just sit on a bicycle, sometimes we also have to stand up, and the cycling style can also be aggressive, in an aero position (race position), a more relaxed position (touring), or an endurance position. Likewise, the position and distance of the seat, the handlebars, and the width of the handlebar and crank will affect the position of the body and the character of the bicycle.

Bike fit specialists will usually measure and analyze the details of the body and bike to see if there are biomechanical problems that can cause injury, fatigue, and muscle performance to the shape of the bike.

Head tube length

The head tube length is measured from the bottom to the top of the bicycle head tube. In general, bicycles with short head tubes lower the front of the bike, placing the rider in an aggressive position to reduce wind and air resistance, improving aerodynamics. Bikes with long head tubes make the front of the bike look up, and have a wider view.

Racing bikes usually have a head tube length of 12-15cm, while touring bikes are around 20cm. Modern bicycles tend to use short head tubes, but with tapered head tubes that are more sturdy, and use threadless stems so that the handlebar position is more flexible in adjusting the height.

Head tube angle

The head tube angle is the angle or inclination of the head tube to the road surface. Bikes with a more upright head tube angle have faster steering control. It takes a little effort to steer the bicycle handlebars.

Bikes with a gentler head tube angle have slower steering control. More power is required to steer the bicycle handlebars. Slower and stiffer steering controls increase the stability of the bike when moving at high speeds. Bikes designed for forward carry usually have a gentler head tube angle, such as bicycles with front baskets or touring bicycles.

Likewise with mountain bikes, which have a smaller head tube angle in order to maintain a stable center of gravity during sharp descents on bumpy roads.

Effective Top Tube (ETT)

Effective Top Tube (ETT) is the horizontal length from the highest position of the head tube to the seat post (the support pole under the bicycle saddle).

The Effective Top Tube (ETT) provides a better measure of how much space is sitting on the bike. Coupled with the length of the stem and the height of the saddle (seat) will indicate how far the arm extends forward from the sitting position to reach the bicycle handlebars.

Stack

Stack is the height (perpendicular vertical distance) from the center point of the bottom bracket to the center point of the highest position of the head tube. Which states how high the foot distance when on the pedal with the position of the hands on the handlebars.

Reach

Reach is the horizontal distance from the center of the bottom bracket to the center of the highest position of the head tube. Which states how far the foot distance when on the pedal with the position of the hands on the handlebars.

Stack and reach are important dimensions that indicate the comfortable position of the feet and hands on the bike when choosing the right bike, even without having to try the bike directly.

If we know the stack and reach sizes that are comfortable on the bikes we’ve used, without trying we can know if other bikes are comfortable or not by looking at the dimensions of the stack and reach.

Due to the size, shape and length of the legs and arms, the comfort position and riding style of each person may vary.

If the bicycle specification does not provide stack and reach information, then you can use the calculator at bikegeo 2 to calculate the stack and reach by entering other dimension parameters.

Mountain bikes and racing bikes have different characters and also have different stack and reach ratios. Racing bikes, for example, usually have a short stack and long reach, while more relaxed bikes have a longer stack and shorter reach.

  • As the stack value increases, the sitting position usually becomes more relaxed and upright (if reach remains). The stack value that is closer to the reach value is usually found on bicycles that require long-term comfort.
  • If the reach increases, the sitting position becomes more bent, aerodynamic and the body stretches (if the stack is fixed). Reach values ​​that are much greater than the stack are usually found on racing bicycles or bicycles that aim for speed.

For professional cyclists, knowing the ideal stack and reach (whether for power or speed) is important. This makes it easier for frame designers or bike fitters to set up the ideal shape and position to get maximum results.

From the stack and reach values, we can also compare the character of the cycling position. Of course, the comparison must be on frames of the same size, because the larger the frame, the greater the stack and reach values.

Seat tube length

Seat tube length may not be necessary for most people, except for cyclists who need a certain height to be able to stand to balance a bicycle (usually short ones). Again, it is better to compare and calculate the stack and reach.

Seat tube angle

The seat tube angle doesn’t give much information about the feel of the bike.

Because the height of the bicycle mount can be raised or lowered, the greater the angle of the seat tube, raising and lowering the seat will provide a significantly longer or shorter distance than those with a steeper seat tube angle.

The size of the seat tube angle can be ignored, and it is better to use the effective seat tube angle number.

Effective seat tube angle

The effective seat tube angle or commonly called the Effective Seat Angle (ESA) is the angle from the center of the bottom bracket to the center of the saddle at the ideal seat height.

The ideal bicycle seat height is in a position where your feet can still enjoy the lowest pedal position and don’t bend your legs too much.

The effective seat tube angle is a true indicator of the ideal position between the waist and the pedals. forward and backward the saddle on the rail can reduce or increase the angle by up to 3 degrees.

The higher the ideal seating position, the smaller the ESA angle will be. So for a cyclist with a tall stature, it must have an ESA that is steeper or smaller than a cyclist with a shorter body on the same bike.

Dimension measurement 

In measuring the detailed dimensions of a bicycle, we often come across the terms C-C or C-T and others.

Terms that can be used for detailed measurements:
– C = Center (central point)
– T = Top (the very top)
– B = Bottom (the very bottom)
– I = In (deepest part)
– O = Out (outermost part)
So C-C means Center to Center, C to T means Center to Top, and so on.

Often the measurement of dimensions produces different numbers because they use different calculation methods. The shape of the tube or pole on a bicycle frame that has space, must be ascertained whether measuring it from the center point, the outermost point, or the deepest, to produce accurate and appropriate calculations.

Fork rake/offset

Fork rake is the difference between the vertical line at the center of the wheel and the projected extension of the fork to the surface. This fork rake is an imaginary line, which on a racing bike is called a fork rake and on a mountain bike it is more commonly called an offset fork.

Has the same effect as the head tube angle, only in different units. The fork rake is expressed in length, while the head tube angle is expressed in degrees. Increasing the length of the fork rake will result in faster handling, while shortening the fork rake will result in slower handling.

Extending the rake/offset fork, and lowering the head tube angle, will result in the same fork trail length.

References

  1. https://www.theproscloset.com/blogs/news/buyers-guide-pre-owned-cyclocross-gravel-bikes
  2. https://bikegeo.muha.cc/