# Golf Balling (DD-695)

> When a driver hits a golf ball, the ball flattens noticeably for a fraction of a millisecond and then springs back. The coefficient of restitution (COR) measures how much speed survives that collision: 1 means a perfectly elastic bounce and 0 means none. Because a livelier ball goes farther, golf's governing bodies cap it. In the USGA/R&A Initial Velocity test, a ball is fired at a rigid barrier at 143.8 ft/s. Its initial velocity is calculated from its COR and contact time, and a sample fails if four or more of 24 balls exceed 255 ft/s. Balls must also meet the 317-yard Overall Distance Standard. From January 2028, that test will be run at a 125 mph clubhead speed instead of 120 mph, which the USGA expects to cut the longest hitters' drives by about 13 to 15 yards.

- Department: Science (also Tech)
- First published: 2026-01-25
- Last updated: 2026-01-25
- Permalink: https://detailenjoyer.com/case/golf-balling/
- Author: Marcus Easterling (DetailEnjoyer), The Detail Department

## On the timeline

- **January 2028**: Revised ball distance testing at a 125 mph clubhead speed takes effect (planned)

Full timeline: https://detailenjoyer.com/timeline/?case=golf-balling

## Quick facts

- **DD-695-F01**: The ball's limit is 250 ft/s initial velocity plus a 2% tolerance. _(Write-up · Exhibit C (How the rules test it))_
- **DD-695-F02**: From 2028, conformance testing uses a 125 mph clubhead speed. _(Write-up · Exhibit E (The 2028 change))_

## Write-up

Squash, then spring. How fast a golf ball rebounds is capped by golf's rules.

1. **What COR measures**: COR is the ratio of rebound speed to impact speed. A value of 1 is a perfectly elastic collision, and lower values mean more energy is lost as heat and vibration.
2. **The whole ball deforms**: The core and cover compress together, not just the 'outer layers'. The ball flattens against the clubface during a contact lasting well under a millisecond, then springs back.
3. **How the rules test it**: The ball is fired at a rigid barrier at 143.8 ft/s. Its initial velocity is calculated from COR and contact time and compared with a 250 ft/s limit plus a 2% tolerance (255 ft/s).
4. **Distance cap**: Balls must also pass the 317-yard (plus 3-yard tolerance) Overall Distance Standard, tested with a mechanical golfer.
5. **The 2028 change**: From January 2028, the distance test moves from 120 mph to a 125 mph clubhead speed. The USGA estimates the longest hitters will lose 13 to 15 yards and most recreational golfers 5 yards or less. Recreational players can keep using older conforming balls until 2030.

## Related case files

- [Print Precision (DD-005)](https://detailenjoyer.com/case/print-precision/): Another case about physics that happens in a fraction of a second
- [Tilted Town (DD-035)](https://detailenjoyer.com/case/tilted-town/): Another physics-you-can-feel case
- [Newtons Cradle (DD-286)](https://detailenjoyer.com/case/newtons-cradle/): I paired it with another close look at a collision

## Reel vs. record

- **Missing rule**: a ball's liveliness is capped. In the USGA/R&A test, a sample fails if four or more of 24 balls exceed 255 ft/s (250 ft/s plus 2%).
- **Precision**: 'higher elasticity, greater distance' holds only in part. Distance also depends heavily on launch angle, spin and the dimple aerodynamics.
- **Mechanism**: the whole ball compresses, core included, not just the outer layers. Contact lasts well under a millisecond.
- **Missing context**: clubfaces are limited too. Drivers have a separate 'springiness' limit (Characteristic Time), which the USGA is testing more strictly against 'driver creep'.
- **Since the Reel**: from January 2028, balls will be distance-tested at a 125 mph clubhead speed, cutting the longest hitters' drives by an estimated 13 to 15 yards (USGA).

## Video: Golf Balling: Squash, Then Spring

- Duration: 24.1 s · Published: 2026-01-25
- File: https://detailenjoyer.com/assets/videos/DT8kO76kk2u.mp4

### Transcript

DID YOU KNOW? The elasticity of a golf ball refers to its ability to deform and then quickly return to its original shape when struck, which directly affects how much energy is transferred from the club to the ball. When the club face hits the ball the outer layers compress, storing energy, and then rapidly rebound propelling the ball forward. This property is measured by the coefficient of restitution, or COR, with higher elasticity producing greater launch speed and distance. NOW YOU KNOW!

## Questions & answers

**Q: What does COR compare?**  
A: Speed after the collision divided by speed before it. _(Source: Write-up · Exhibit A (What COR measures) · Wikipedia: Coefficient of restitution)_

**Q: What initial-velocity limit do the rules set (before tolerance)?**  
A: 250 ft/s, plus a 2% tolerance. _(Source: Write-up · Exhibit C (How the rules test it) · USGA/R&A: Initial Velocity Test Protocol)_

**Q: What is the Overall Distance Standard?**  
A: 317 yards, plus a 3-yard tolerance. _(Source: Write-up · Exhibit D (Distance cap) · USGA (Dec 2023): Revised golf ball testing conditions to take effect in 2028; USGA: The Golf Ball and Distance, Frequently Asked Questions)_

**Q: What clubhead speed will the 2028 test use?**  
A: 125 mph, up from 120 mph. _(Source: Write-up · Exhibit E (The 2028 change) · USGA (Dec 2023): Revised golf ball testing conditions to take effect in 2028; USGA: The Golf Ball and Distance, Frequently Asked Questions)_

**Q: A COR of 1 would mean...**  
A: No speed would be lost. _(Source: Write-up · Exhibit A (What COR measures) · Wikipedia: Coefficient of restitution)_

## Sources

- [USGA/R&A: Initial Velocity Test Protocol](https://assets.randa.org/c42c7bf4-dca7-00ea-4f2e-373223f80f76/a893d16d-5b86-43b8-9259-a954c5e12a56/Initial%20Velocity%20Test%20Protocol.pdf)
- [USGA (Dec 2023): Revised golf ball testing conditions to take effect in 2028](https://www.usga.org/content/usga/home-page/articles/2023/12/revised-golf-ball-testing-conditions-to-take-effect-in-2028.html)
- [USGA: The Golf Ball and Distance, Frequently Asked Questions](https://www.usga.org/content/usga/home-page/advancing-the-game/distance-insights/golf-ball-revised-testing-guidelines--frequently-asked-questions.html)
- [Wikipedia: Coefficient of restitution](https://en.wikipedia.org/wiki/Coefficient_of_restitution)

## Cite this case file

Easterling, Marcus. "Golf Balling." The Detail Department (DetailEnjoyer), case file DD-695, last updated Jan 25, 2026. https://detailenjoyer.com/case/golf-balling/