Yosemite Decimal System - YDS Class

YDS Class

The system was initially developed as the Sierra Club grading system in the 1930s to classify hikes and climbs in the Sierra Nevada. Previously, these were described relative to others. For example Z is harder than X but easier than Y. This primitive system was difficult to learn for those who did not yet have experience of X or Y. The club adapted a numerical system of classification that was easy to learn and which seemed practical in its application.

Guidebooks often append some number of stars to the YDS rating, to indicate a climb's overall "quality" (how "fun" or "worthwhile" the climb is). This "star ranking" is unrelated to the YDS system, and varies from guidebook to guidebook.

The system now divides all hikes and climbs into five classes: The exact definition of the classes is somewhat controversial.

• Class 1: Walking with a low chance of injury.
• Class 2: Simple scrambling, with the possibility of occasional use of the hands. Little potential danger is encountered.
• Class 3: Scrambling with increased exposure. A rope can be carried but is usually not required. Falls are not always fatal.
• Class 4: Simple climbing, with exposure. A rope is often used. Natural protection can be easily found. Falls may well be fatal.
• Class 5: Technical free climbing involving rope, belaying, and other protection hardware for safety. Un-roped falls can result in severe injury or death.

The original intention was that the classes would be subdivided decimally, so that a class 4.5 route would be a climb halfway between 4 and 5. Class 5 was subdivided in the 1950s. Initially it was based on ten climbs of Tahquitz Rock in Idyllwild, California, and ranged from the "Trough" at 5.0, a relatively modest technical climb, to the "Open Book" at 5.9, considered at the time the most difficult unaided climb humanly possible. This system was developed by members of the Rock Climbing Section of the Angeles Chapter of the Sierra Club.

Increased standards and improved equipment meant that class 5.9 climbs in the 1960s became only of moderate difficulty for some. Rather than reclassify all climbs each time standards improved, additional classes were added. It soon became apparent that an open-ended system was needed and further classes of 5.11, 5.12, etc. were added. It was later determined that the 5.11 climb was much harder than 5.10, leaving many climbs of varying difficulty bunched up at 5.10. To solve this, the scale has been further subdivided above the 5.9 mark with suffixes from "a" to "d". As of 2005, several climbs are considered to have a difficulty of 5.15a. Akira, climbed by Fred Rouhling, is claimed to be a 9b (French grade) which translates to YDS 5.15b. Chilam Balam climbed by Bernabé Fernández was rated as 9b+ or 5.15c YDS. Both were controversial, with 'Chilam Balam' downgraded to 9b (5.15b) by Adam Ondra in April 2011.

The original Sierra Club grading system also had a Class 6, for artificial, or aid climbing. This sort of climbing uses ropes and other equipment where progress is made by climbing directly on equipment placed in or on the rock and not the rock itself. Class 6 is no longer widely used. Today aid climbing uses a separate scale from A0 through A5.

Classification of climbs between indoor gym, sport and traditional climbing can also vary quite a bit depending on location and history.