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Understanding the Grading Charts

If we examine the chart to the left it is immediately obvious that it is valid for ride distances between 0 km and 120 km and moderate gradients, say between 6% and 7.5%.

Looking at the ride grades in bold integers ranged above the top diagonal axis, we see that it encompasses ride grades between 1 and 11. Note that grade 12 rides (beyond grade 11) are not annotated, and have no upper limit. The grade boundaries are delineated by straight lines descending to the right.

We also notice annotations for the percentage of the ride that is level ranged down the right hand edge of the chart. These annotations terminate a series of straight lines ascending from the left, each delineating a percentage of the ride that is level. In the wedge between these lines a separate annotation describes the same percentage in terms of the fraction of the ride that is climbing and descending.

The horizontal axis sets out the ride distance. It also represents the straight line delineating all-level riding.

Example

A ride of 50 km has a steepest gradient of 6% with more shallow kilometres than steep ones. 50% of the ride is level. What is it's grade?

Solution.

• We locate the 50 km point along the horizontal axis at the base of the chart. A vertical red line has been drawn at that point.
• We move up that red line until we meet the 50% level point. (We may sometimes need to interpolate between tabled values).
• The intersection is in a right-descending panel. At the head of this panel we see the bold figure 6. So the ride is grade 6.
• Drawing a line diagonally down to the horizontal axis we note that it intersects the distance line at the 63 km mark. So this ride is the same difficulty as a 63 km level ride. A red line has been drawn to show this step.
• Now check the level speed for this grade by clicking here. You can actually calculate it yourself as 15 + a tenth of the ride distance in kilometres.

That's all there is to it!