One of the most talked-about terms in golf right now is COR, coefficient of restitution, value of golf clubs. So, here we are going to go into what that is, why it matters and the impact it can have on your golf game.
What is COR?
COR is an acronym that stands for “Coefficient of Restitution, and is a term that originates from the world of physics, but has now been applied to the world of golf.
This is a term that describes the energy transfer between two objects, in the case of golf, it is the energy transference between the face of the golf club and the golf ball.
This is otherwise referred to as the “spring” or “trampoline” effect on the face of the golf club.
Ultimately clubs with a higher COR have less energy that is lost upon impact with the ball which equates to longer golf shots and more distance.
The COR is always expressed as a measure between 0.000, where all energy is lost, and 1.000, where all energy is perfectly transferred from one object to the next.
For example, if you launched a gob of silly putty at another they would collide, stick together and there would be almost no movement forward.
Therefore this is an almost complete loss of the energy creating a COR that is closer to 0.000, while an example of an almost perfect (1.000) COR would be in the game of pool.
When one ball impacts the other the first ball stops and the new ball continues on at almost the same speed, creating an almost perfect transfer of energy.
However, no golf club can every have a perfect 1.000 core value because the clubface and the ball are made of completely different materials.
As a result, there will always be some energy loss in the transference.
This is where the ball and club manufacturers come in to try and make clubs/balls from materials that will transfer energy more efficiently.
However, the USGA and R&A regulate what the core values can be to make sure all players are on an equal playing field, as well as keep current golf courses playable (a topic that has very much been up for debate as of recently).
As of right now the regulation COR limit is .830 and any cub that goes higher than that is non-conforming, making it unable to play in tournaments.
But boy can those nonconforming clubs launch! Check out our experiment where we compared an illegal 750cc driver Vs. The PING G400 Max here.
What is CT?
In 2004, the USGA and the R&A decided to move away from COR values to regulate drivers and instead have decided to use a term called characteristic time (CT).
COR value is still the metric used to regulate all other clubs, however.
The new metric, CT, is the amount of time, measured in microseconds, that the clubface of the driver and the ball are in contact from the moment of impact.
Think of this like watching a boxer get punched in slow motion and counting how many seconds their fist was in contact with the opponent’s face, just at full speed and hopefully no one gets knocked out.
As of right now the CT limit for drivers in 239 microseconds, with an allowable tolerance of 18 microseconds, bringing it to an absolute maximum of 257 microseconds.
For comparison, it takes 350,000 microseconds for the average human to blink, so the driver and the ball are in contact with one another for more than 1000x fewer microseconds than it takes you to blink!
Although they have changed the standard of measurement for drivers, CT and COR values do track very closely so clubs with a high CT will also have a high COR value.
Why Do They Matter?
Now, that you know what these measures are, why do they matter and how do they impact your golf game?
Well, this matters for two reasons:
First, if you are hoping to play in any tournaments or be competitive in any capacity during your golf career, then you need to make sure that all of your equipment is conforming.
Most clubs made by the major manufacturers are within regulation, but it is definitely something to keep in mind and double-check when getting new clubs.
Second, when comparing golf clubs to purchase the COR and CT values have some of the greatest impacts on the distance that you get out of your clubs.
The best way to know what clubs give you the best distance and overall performance is with a trackman fitting, but if you are trying to make a decision based on specs alone then comparing the COR/CT values is super important.
Doing this is one of the best ways to get an idea of the distance you will get out of the club. (Looking for a new driver? Check out our top 11 drivers of 2019 here!)
In the end, the COR value is the spring off of the face of the club that helps you hit longer drives the higher it gets. We hope that this article was able to help you get a better understanding of what it is and how it translates to your success out on the course.
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Check out our entire inventory of drivers that you can purchase and fully customize online at our online store, mortongolfsales.com.