A Site Exploring the Physics of the Paddle/Ball Collision
Mapping the Sweet Spot - part 1
11/4/25
Most players are vaguely familiar with the term PBCOR (Paddle Ball Coefficient of Restitution). It's a term used by USAP (USA Pickleball) relating to a test indicating the power of a paddle. Paddles that pass the test display a logo indicating the paddle is certified for tournament use.
The test consists of propelling a ball toward the paddle at various locations with a known speed (50 or 60 mph) and recording the rebound speed after impact. The inbound speed, the rebound speed, the location on the paddle face and several other factors are entered into a complicated equation. The equation spits out a number for each location. The maximum number becomes the paddle's PBCOR score and must be less than 0.43. If the PBCOR score is over 0.43 the paddle is disqualified for USAP tournament play.
Better yet, is a plot of rebound velocities Vre vs impact location. Rebound velocity Vre in miles per hour will be used as it's a metric familiar to all and is an integral part of determining COR. Notice the steep increase in Vre as the impact location moves from the tip of the paddle to the neck.
We always try to hit the ball at the paddle's sweet spot which is usually located about 4" from the tip of the paddle. But we're not always successful. Ball impacts away from the sweet spot can lead to unwanted vibration and rebound velocities that are different - both less and more as shown in the graph. There is quite a variety of shapes.
One might guess that a flat shape would be best. What is the best shape? Flat? Dome? and what's the size of the sweet spot and how should it be measured? The performance of a Ronbus Quanta R2 will be explored by quantifying the rebound velocities for a block, serve, punch and dink at different impact locations along the paddle face.
Coefficient of Restitution (COR) for various paddles (Vinbound = 50 mph).
Rebound Velocities (Vre) for various paddles (Vinbound = 50 mph).
Core Crushed Paddle Performance
10/19/25
Two "hot" Pickleball Apes Pulse V "core crushed" paddles are compared to a stock Pulse V to explore the differences in performance. Many players have noticed their paddles (multiple manufacturers) becoming more responsive and powerful with use. Balls seem to pop off the face with more velocity. Probably the sound has changed to a more bass tone. You've got a "hot" and probably illegal paddle.
Three Pulse Vs were obtained. One, a fairly new, stock Pulse. Two, a gently used Pulse V from Bob M. Three, a heavily used Pulse V from Keith K. Keith's and Bob's paddle had the distinct crackle sound when pressing in on the face indicating core crushing.
Each paddle was measured for KKCOR (Keith K Coefficient of Restitution) and rebound velocity using an air cannon and speed gate. The performance differences and disadvantages of core crushed paddles are discussed.
Core Crushed or Delaminated?
There's some confusion about the causation of "hot" paddles - paddles that, after use, become more powerful. Some websites blame delamination - the breakdown of the glue between the carbon fiber face layer and the polypropylene core. Others blame core crushing - the weakening of the polypropylene core due the stress of multiple ball hits. This article will use the term core crushed as shorthand to describe "hot paddles".
KKCOR v PBCOR v PEF
All three metrics are similar in that they measure the coefficient of restitution (paddle power) by shooting a ball at a paddle and recording the resultant rebound speed. The differences are the brand of ball used and the inbound velocity of the ball. USAP calls their metric PBCOR (Paddle Ball Coefficient or Restitution) and shoots a holeless Franklin X40 ball toward the paddle at 60 mph. UPA calls their metric PEF (Performance Efficiency Factor) and shoots a Vulcan Pro ball toward the paddle at 50 mph. I call my metric KKCOR and shoot a Penn40 ball toward the paddle at 50 mph.
So, why create a third metric? Why not duplicate USAP's or UPA's metric?
Reason: USAP's ball is impossible to purchase. UPA's ball goes out of round and breaks easily.
Guide to Peripheral Weighting
9/20/25
Most serious players will add weight to their paddle. It could be for more power or to decrease vibrations or to lessen the impact of off-center hits. Adding weight has many benefits, but comes at the cost of "slower hands" due to the added static weight and swing weight.
How much weight should be added and where? How much is gained vs how much is lost? One example is pictured to the right. Two 3 gram lead strips are added to a Ronbus R2.16 Quanta.
The stock specs are:
-
Static weight: 7.8 oz
-
Swing weight: 102
-
Twist weight: 6.34
-
Testing with an air cannon puts the rebound velocity of a 50 mph inbound ball at 8.8 mph (equivalent to a 58.8 mph serve)
The specs with two 3 gram strips located 11.5" from the butt are:
-
Static weight: 8.0 oz
-
Swing weight: 105.5
-
Twist weight: 6.94
-
Testing with an air cannon puts the rebound velocity of a 50 mph inbound ball at 9.1 mph (equivalent to a 59.1 mph serve)
Most players would not notice the change in performance. The improvements in speed (0.3 mph) and twist weight (0.6) are modest. The extra weight (static, swing, twist) is modest. But what happens when the weight is increased (2.5x or 5x) and placed at different locations. How are pro players weighting their paddles? When does extra weight make the paddle too hard to swing?
The Ball's Surprising Behavior
8/28/25
As kids, we've all thrown a rubber ball against a wall and caught the rebound. We've come to expect that if we throw the ball faster toward the wall it will rebound back to us faster. But a pickleball ball's behavior is unusual and surprising. There is a point where throwing the ball faster results in a rebound speed that is slower! It all depends on how much the ball deforms as it impacts the wall.
The article explores -
-
the "fold over" of the rebound velocity
-
the behavior of four different balls
-
the time the ball is in contact with the wall (or ground) during impact
-
the force profile developed by the impact
-
implications for paddle design
So, why are we concerned with how a ball bounces off a wall or the ground? Shouldn't we be more concerned with how the ball bounces off the paddle face? The explanation is that it's easier to understand the complex behavior of a two element collision (ball & paddle) once both of the elements are understood separately. Future articles will isolate the paddle's performance by exploring the response to a steel ball impact. Eventually the ball/paddle impact will be explored. Issues such as power, pop, dwell time and plushness will be addressed.
This graph depicts the rebound velocity of a Franklin X40 ball as a function of the inbound velocity. If the X40 behaved as a typical rubber ball the plot would follow a straight line as depicted by the blue arrow. Below inbound velocities of 20 mph (dinking speeds) the X40 follows the straight line mimicking the behavior of a rubber ball in that limited region with the rebound velocity being 66% of the incoming velocity.
However, above 20 mph the rebound velocity deviates away from the ideal line. Above 45 mph the rebound velocities "fold over". Surprisingly, the rebound velocity of a 60 mph ball (~12 mph) is less than that of a 25 mph ball (~14 mph).
The ball is shot at a marble slab using an air cannon. Both inbound and rebound velocities are recorded using a speed gate.
End Caps (Speed Caps)
Less Power, Larger Sweet Spot, Better Feel
7/2/25
Several manufacturers (Flick Weights, Slyce, Gamma, GRYP) offer weights that fit on the paddle handle. Resourceful players have glued quarters to the butt cap or wrapped lead tape around the handle to improve performance. According to one manufacturer adding weight to the handle will "improve paddle sweet spot, control, balance, spin, and power".
One insightful quote from a user: "I was worried at first that the added weight would slow down my hand speed, but I didn't notice any slowdown at all, in fact, it may have been better (or maybe the paddle just felt better in my hands?)." And that sums it up: It just feels better with end cap weight.
The use of an air cannon and vibration measurement equipment reveals the effects of handle weighting for two popular paddles.
Ruby paddle with hole drilled in the butt cap to facilitate the insertion of various weight bolts. A 1.65 oz weight is shown.
Off Center Hits & Perimeter Weighting
6/5/2025
We instinctively know to hit the ball somewhere along the center line of the paddle. But we're not always successful. The downside of off-center hits - a loss of speed and off angle rebounds - is explored. Perimeter weighting (6 grams on both sides) helps mitigate the downside effects at the expense of higher swing weight and less maneuverability.
Impact locations marked with an "X" at the center line , 1" off-center and 2" off-center.
The Power Era is Ending
5/27/25
Over the past few years players have been demanding more powerful paddles and manufacturers have responded. But both governing agencies have recently moved to rein in paddle power and ball speed to save the integrity of the game. By mid 2026 all paddles that carry the USAP Approved logo will have to pass PBCOR testing. By March 2026 all paddles approved by the UPA will have to pass PEF testing. In addition, Accelerated Break In (ABI) testing is being conducted to weed out paddles that initially pass testing specs, but over time exceed (sometimes wildly) those specs.
In the linked article, several paddles were tested that fall below and above the PBCOR limit of 0.43 and the PEF limit of 0.385. The test results are translated into ball speeds measured in miles per hour to make it easy to imagine what will be experienced on the court. Today's power paddles such as the TA-15 and the Gearbox Power Pro Elongated will be gone. Expect "bazooka" paddles to disappear and maximum ball speeds to be significantly reduced.
The Ronbus Ripple is one of the first paddles to sport the PBCoR.43 Certified logo.
Fire Fights
We all enjoy watching fire fights at the net. At the CIBC Texas Open the teams Johns Tardio v Alshon Staksrud participated in a 9 hit sequence. Just how fast are those balls moving? How much time do the players have to react to the incoming ball? How fast do you have to swing the paddle ? What happens if an illegal paddle is used?
Dinks
Paddle power has been dialed back with the advent PBCOR testing, Dinking has become more prevalent. How fast is the ball moving? Why do players swing the paddle from the shoulder or elbow rather than from the wrist when dinking? Video from the CIBC Texas Open with Johns Tardio v Alshon Staksrud is analyzed.
Analyzing the Serve
How fast is a Jack Sock serve? How long does it take to reach the opponent? What's his paddle speed? The ball's initial velocity? The velocity when it reaches his opponent Quang Doung?
Video from the PPA Tour, the equation of motion and projectile motion give us some answers.
The Paddle-Ball Impact
Here's a taste of what happens in my basement. A paddle is hung vertically on a pivot so the paddle can rotate when struck by the ball. The wires attach to a small accelerometer on the paddle face to measure the force of the impact. A pickleball is shot from an air cannon (not shown) toward the paddle. Before it gets to the paddle, the ball travels through a speed gate (multiple red laser beams) to measure the inbound velocity. After the collision the ball travels back through the speed gate to measure the rebound velocity.
To the right is a three frame sequence of a paddle/ball collision taken with an iPhone at 240 frames per second. Left: Ball approaching stationary paddle at 50 mph. Center: Collision lasting 2 milliseconds. Right: Ball rebounding back toward the speed gate at 12 mph and paddle recoiling at 7 mph.
Paddle Break-In
A Pulse V Example
I purchased a Pickleball Apes Pulse V paddle in November 2024. It got hot and hotter as I used it! The sound got deep. Opponents noticed my flicks were unusually fast. I heard multiple times, "Is that a legal paddle?"
I measured the collision efficiency and calculated that the PBCOR was far above the UPA-A 0.385 limit and the USAP limit of 0.43. Pickleball Apes replaced the paddle free of charge and explained the problem was isolated to early batches and had been corrected. The performance of my old Pulse V, my new Pulse V on arrival, my new Pulse V after 3 weeks of play and a new Neonic Flare is documented.
Is PBCOR the Best Metric to Limit Ball Velocity?
For safety reasons and to prevent pickleball from becoming a power only sport the two governing agencies have adopted PBCOR as a way to limit ball velocity. If a paddle's PBCOR value exceeds a certain number (0.42 for USAP; 0.385 for UPA-A) the paddle doesn't make it onto the list of tournament approved paddles. Recently, there has been criticism from paddle reviewers and manufacturers that PBCOR has problems. Let's take a look at the data from a PBCOR determination to explore the relationship between PBCOR and ball velocity.
Understanding PBCOR
PBCOR testing jumped into the pickleball news when the Joola Gen 3 paddles were not approved for tournament play by USAP in November 2023 because they were too powerful. USAP, in part, used PBCOR testing to evaluate the power of the Joola paddles. The non-approval was a financial loss for Joola. A lawsuit was filed initiated (still in litigation as of March 2025) against USAP to recover a portion of the loss. Subsequently, both governing bodies for pickleball, USAP and UPA , have universally adopted PBCOR testing to limit paddle power.
Simply stated, a ball, at high speed (50 or 60 mph) is shot at a paddle and the rebound speed of the ball is measured. A few physical parameter of the paddle (weight, etc) along with the rebound speed are entered into an equation which results in the PBCOR number for that paddle.
USA Pickleball PBCOR test equipment
The Equation of Motion
There is one unifying equation to describe the rebound velocity of the ball after a collision between the ball and paddle. The equation covers blocks, serves, dinks, and volleys. The equation is basic to understanding what happens when ball meets paddle.
Vrebound = eA * Vinbound + (1+eA) * Vpaddle
