Cycling gradient – guide to take a comprehensive look at it

Cycling gradient - guide to take a comprehensive look at it.

Le Tour de France 2023 is in full swing, and those who like to watch Le Tour de France must always check out the intense climbing in those steep alpine stages.

The cycling gradient referred to in the race commentary is actually a percentage of the bike’s climb, rather than the number of gradients we talk about in everyday life.

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    What is called cycling gradient?

    In cycling terms, cycling gradient is the degree of steepness of the surface unit, usually the ratio of the vertical height and horizontal distance length of the slope surface is called cycling gradient.

    Percentage and degree are expressions of it.

    The formula for percentage is: Vertical height/Horizontal Distance length* 100%

    Specific degree is: tanα = Vertical height/Horizontal Distance length.

    e.g.① The maximum gradient for a highway is 5%, 3°.
          ② The maximum gradient of a parking garage is 15%, 8°.
          ③ A car’s ability to climb a slope is 36%, 20°, and certain off-road vehicles can climb a 60% slope, almost 30°, which is the slope of a staircase in an ordinary building.
          ④ A 100% gradient is 45°, which is almost like a cliff.

    cycling gradient

    When we talk about gradient, then we need to understand some related concepts. What is the difference between “degree” and “gradient” as we often refer to them?

    Although they sound similar, there is a big difference between the two.

    As shown in the picture, we can describe cycling gradient as:

    c – the length of the slope is considered to be the surface of the road, which is the part of the road on which we are actually riding;
    b – the distance travelled horizontally;
    a – the height is the elevation gained.
    The angle of the a-side is θ, in degrees.
    Angle: the value of θ in °, with 0° being horizontal and 90° being vertical.

    Standard slope, as a/b, the standard definition of slope calculation, expressed in %, 0% of course means horizontal, the standard slope at an angle of 45 ° is 100%, and the standard slope for vertical is infinity.

    Definition of cycling gradient

    Approximate slope (average slope): a/c, also expressed in %, when the angle is lower than 20 °, the value is similar to the standard slope. 0% also means horizontal, vertical for 100%. This is the so-called gradient for normal riders.

    Usually, because the distance of b is difficult to measure, and the gradient will change a lot due to different road sections and conditions, resulting in a large error in the estimated value of b, the actual riding distance will usually be used as c to project into an approximate gradient (average gradient).

    The two values will be very close when theta angle is low.

    Difference between angle and cycling gradient

    When describing the steepness of a slope, we often use the words “degree” and “gradient” to describe it.

    When we describe how steep a slope is, the word “degree” here means the angle (angle = θ value) and the unit used is ° (degrees).

    When describing the steepness of a surface slope, we usually use “%” of cycling gradient instead of the angle.

    Difference between angle and cycling gradient

    And we often use the average slope as a proxy for the actual standard slope, often omitting the words “gradient” or “slope ratio.”

    Because the data required to obtain this data is the easiest to obtain, and in the case of a smaller angle, there is almost no difference between the two.

    So we usually use a ratio of the “climbing height” and the “length of the ramp ride.” That is, climbing gradient/ramp length*100%.

    Angle vs. cycling gradient

    If the cycling gradient is 3%, it means that for every 100 meters of horizontal distance, the vertical direction rises (fall) by 3 meters.

    1% means that for every 100 meters of horizontal distance, the vertical direction rises (fall) by 1 meter.

    If the gradient is 15%, the horizontal distance per 100 meters, the vertical direction rises (falls) 15 meters, but the actual angle is only 8.5 degrees.

    Therefore, the difference between the values of the same slope expressed in two different units is very different.

    cycling gradient categories

    Cycling gradient categories

    Knowing how the cycling gradient is calculated, UCI will calculate it according to a certain formula ((average gradient (%))^(3/2)*elevation gain (m))/100).

    And then divide all the gradient into five grades, of which grade 4 cycling gradient is the lowest and grade HC cycling gradient is the largest.

    Grade 4 cycling gradient ≦ 20 5 kilometers of climbing below 2 kilometers with a gradient of 5% (2.86 degrees), or 5 kilometers of climbing with a cycling gradient of 2% - 3% (1.145 degrees - 1.67 degrees)
    20<Grade 3 cycling gradient ≦ 50 Climbing with a gradient of 10% (5.7 degrees) for up to 1km, or cycling gradient of 5% (2.86 degrees) for 10km
    50<Grade 2 cycling gradient ≦ 120 8% (4.6 degree) climb for 5km, or 4% (2.29 degree) climb for 15km
    120<Grade 1 cycling gradient ≦ 200 8km 8% (4.6 degree) climb, or 20km 5% (2.86 degree) climb
    HC cycling gradient > 200 A climb that combines length and steepness and is more difficult than a grade 1 climb
    Limits of cycling gradient

    Limits of cycling gradient

    Theoretically, if the bicycle gear ratios are sufficient, the rider can climb any steep hill even with less power as long as he/she has a high enough pedaling frequency.

    However, there is another issue to consider when cycling, which is balance.

    After testing and calculation, the rider’s contact between the front wheel and the ground is already decreasing at a gradient of 86.9% (41 degrees).

    In other words, when the gradient reaches 40%, the gradient will be reduced to 40%.

    In other words, when the cycling gradient reaches 40%, the rider and the bike are already showing signs of tipping backwards.

    cycling view

    Professional riders have been tested climbing 40% (about 22 degrees) of a hill as hard as they can at 422 watts and 7 kilometers per hour, which is about the speed of a healthy male brisk walk.

    If the gradient continues to increase, cycling becomes far less efficient than walking.

    For cycling climbing, a cycling gradient of more than 12% (about 7°) requires riders to pedal very hard, and a slope of more than 20% is already considered super steep, and is not a slope that ordinary riders can just ride up.

    Hi, I'm an experienced writer about mechanic and an expert on bike and e-bike tech who appreciates practical, beautifully-engineered things. And of course, I love cycling.
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