COR is one of a few acronyms that golf equipment manufacturers use when describing their latest products - but what does it actually mean?
First, the 'science-y' stuff. COR stands for coefficient of restitution and is the ratio of the final to initial relative velocity between two objects after they collide.
Sir Isaac Newton first developed the mathematics in the late 1600s. The ratio normally ranges from 0 to 1, with 1 being a perfectly elastic collision.
In layman’s terms, COR is a measure of how efficiently the clubface transfers energy onto the golf ball. However, it wasn’t until the late 1990s that COR gained prominence in the golfer’s vernacular.
At this time, manufacturers were beginning to use new materials and discovering new manufacturing techniques and technologies that could help significantly increase COR in their drivers. In just a few years, the industry norm went from around 0.7 to above 0.85 thanks to new, ultra-thin, fast faces.
It was at this stage that the R&A and USGA stepped in. In 2003, they set the universal limit for COR at 0.83 (meaning 83% of the energy in the collision of the driver head with a golf ball is transferred from the head to the ball).
With this new limit, golf’s governing bodies felt they could limit the increases in distances that were prevalent at the time and put a stop to escalating ‘trampoline effect’ of most drivers.
Pretty much every driver available today is engineered as close to the legal limit as possible to help promote maximum distance.
In recent years, thanks again to new materials, manufacturing techniques and technologies, COR has become no longer the reserve of the driver market. Today’s fairway woods, hybrids and even irons are engineered to achieve maximum COR and get as close to the 0.83 limit as possible in order to deliver maximum distance throughout the bag.