The short answer: backspin, and the friction that makes it. A wedge face is tilted back so far that the ball starts to slide up it at impact. Friction fights that slide, grabs the ball's surface and spins it backward. How much spin you get depends on the spin loft, on the ball's cover, and on whatever is trapped between the ball and the face. Water and grass act like a lubricant, and that's when grooves matter most.
This article goes with episode 6 of HYTON Golf, our video series that cuts golf open in 3D. Every fact below is linked to its source at the end.
Key numbers
| Number | What it means | Source |
|---|---|---|
| 8,300 vs 5,600 rpm | Urethane vs ionomer-covered ball, 75-yard shot with a new 58° wedge | Team Titleist (2019) |
| About 35% | Average spin a wedge lost in wet conditions (18 wedges, 17,000+ shots) | MyGolfSpy (2022) |
| About 10,000 vs 5,300 rpm | Sand wedge spin from a dry lie vs the rough (modern ball, U-grooves) | Second Report on the Study of Spin Generation (2007) |
| 0.0030 sq in per in | 2010 limit on groove area divided by groove spacing | USGA notice to manufacturers (2008) |
| 0.010 in | Minimum groove edge radius on clubs with 25° of loft or more | USGA notice to manufacturers (2008) |
| 9,612 vs 9,082 rpm | Pitching wedge spin off a fairway mat, older U-grooves vs 2010 grooves | Burnham, Wilkinson and Goodall (2013) |
More numbers from the series, each with its source: Golf by the Numbers.
Watch the episode: Why Won't Your Wedge Shot Stop? on YouTube.
How a wedge makes backspin
When a wedge meets the ball, it doesn't just push it forward. Because the face leans back so much, the ball also starts to slide up the face. Friction resists that slide where the ball touches the face, and that twists the ball backward. Physicists who model the impact say the ball doesn't simply slide or roll up the face: for a moment, it grips it.
TrackMan calls the angle that sets this up spin loft: the gap between the direction the clubhead is moving and the direction the face is pointing. All else equal, more spin loft means more spin, and a close estimate is the loft on the face at impact minus the attack angle. The numbers get big. In one lab study, ten low-handicap golfers spun pitching wedge shots off a fairway mat at more than 9,000 rpm.
The cover sets the friction
Spin loft sets up the spin, but friction has to deliver it, and the first place friction lives is the ball. Tour balls usually have a thin, soft urethane cover; most other balls use a harder plastic called ionomer. Titleist tested both off a new 58-degree wedge from 75 yards: the urethane ball spun at 8,300 rpm, while a popular two-piece ball with an ionomer cover spun at 5,600 rpm and launched five degrees higher. Same wedge, same shot, about a third less spin, which Titleist attributes to the cover. In a 2007 groove study for golf's ruling bodies, the lab found that with an ionomer ball, changing the shape or sharpness of the grooves didn't seem to change spin at all. At the time, that type of ball made up about 70 percent of balls sold at U.S. retailers.
What grooves are for
It's tempting to think grooves bite into the ball. A better picture is the tread on a tire. On a clean, dry face, the ball can grip the metal directly, but golf is played with dew, rain and grass. Anything trapped between the ball and the face acts like a lubricant: the ball can slide instead of grip, and spin drops. Grooves give that water and grass somewhere to go. Researchers have used the tread comparison since at least 1990, though the authors of a 2013 groove study noted that the idea that newer grooves leave more water and debris on the face had yet to be shown in peer-reviewed work. What has been tested is groove shape: in the 2007 lab work, with wet paper between the ball and the face, boxier U-shaped grooves with sharper edges and more volume produced more spin than V-shaped ones.
The 2010 groove rule
In 2008 the USGA announced new groove limits for clubs made from January 1, 2010. On every club except drivers and putters, groove cross-sectional area divided by groove spacing can be no more than 0.0030 square inches per inch; on clubs with 25 degrees of loft or more, groove edges must also be rounded to an effective radius of at least 0.010 inch (0.254 mm). The limits applied at the U.S. Open and its sister championships from 2010 and at the USGA's other championships from 2014. The stated goal was to limit the effectiveness of grooves on shots from the rough. A 2013 study comparing older U-grooves with 2010-style grooves found the same golfers spun the ball about 500 to 1,000 rpm less with the newer grooves and finished a little farther from the target.
Rough and rain
From the rough, grass gets between the ball and the face first. In the 2007 study's launch data, a sand wedge with a modern ball and U-grooves started at about 10,000 rpm from a dry lie and about 5,300 rpm from the rough: nearly half the spin gone. With old V-grooves and a balata ball, spin fell from about 10,600 rpm to under 4,000, and across the clubs in the study's model, the older setup's total bounce and roll from the rough was about 60 percent greater than the modern one's, on a flat green. Oddly, with longer irons, the study found the modern setup could spin even more from the rough than from a dry lie. With a wedge, the rough wins.
Water does the same thing. MyGolfSpy wet the turf and the ball and hit 18 different wedges, more than 17,000 shots in all. It reported that the average wedge lost about 35 percent of its dry spin and the worst lost more than 60 percent, while 11 of the 18 kept at least 90 percent of their spin. The worst performers also launched about 4.6 degrees higher on average.
Illustrations by HYTON; grooves, slide and water film exaggerated. Not affiliated with or endorsed by Titleist, TrackMan, MyGolfSpy, the USGA or the R&A.
Sources
- TrackMan, What is Spin Loft?: spin loft is the angle between the direction the club head moves and the direction the face points; all else equal, more spin loft means more spin; a close estimate is dynamic loft minus attack angle
- R. Cross and P. Dewhurst (2018), Launch speed, angle and spin in golf, European Journal of Physics 39: the ball grips the club face rather than rolling
- P. Burnham, M. Wilkinson and S. Goodall (2013), The 2010 regulations on golf club groove design, International Journal of Golf Science 2(1): 10 low-handicap golfers, simulator, synthetic mats; pitching wedge 9,612 vs 9,082 rpm from the fairway mat and 9,015 vs 8,277 rpm from the rough mat (older U-grooves vs 2010 grooves); cites Lieberman (1990): grooves work like the tread on a tyre; notes that the claim that newer grooves leave more water and debris on the face is yet to be shown in peer-reviewed work; shots with the 2010 grooves landed consistently farther from the pin
- Team Titleist (October 21, 2019), The Short Game Spin Equation: 75-yard shots with a new 58-degree wedge: urethane-covered ball 8,300 rpm, 26-degree launch; two-piece ball with an ionomer cover 5,600 rpm, 31-degree launch
- Second Report on the Study of Spin Generation (technical staff of golf's ruling bodies, January 12, 2007; copy hosted by the Japan Golf Association): sand wedge launch spin 168 rps dry and 88 rps from the rough (modern ball, U-grooves) and 177 and 64 rps (balata ball, V-grooves); total bounce and roll from the rough about 60% higher for the older setup on a flat green; for the ionomer-covered ball, groove shape and edge radius did not appear to influence spin; that type of ball was about 70% of balls sold at U.S. retailers
- USGA Notice to Manufacturers, New Groove Regulations (August 5, 2008): groove cross-sectional area / spacing at most 0.0030 sq in per inch on all clubs except drivers and putters; edge radius 0.010 in on lofts of 25 degrees or more; clubs made from January 1, 2010; U.S. Open and sister championships from 2010, other USGA championships from 2014
- MyGolfSpy Labs (October 10, 2022), Wet Conditions Wedge Test: 18 wedge models, more than 17,000 shots, moisture on turf and ball; the average wedge lost about 35 percent of its dry spin; the worst more than 60 percent; 11 of 18 kept at least 90 percent; the poorest performers launched 4.64 degrees higher on average
- R&A Rules of Equipment, Supplementary Paper C: 2010 Club Face Markings: groove edges need an effective minimum radius of 0.010 in (0.254 mm) on lofts of 25 degrees and above; the area limit of 0.0030 sq in per inch applies to clubs other than driving clubs and putters
Sources last checked October 2026.
Frequently asked questions
Why won't my wedge shot stop on the green?
A wedge shot stops with backspin, and backspin comes from friction between the ball and the clubface. Anything trapped between them, like water or grass, lets the ball slide instead of grip. A harder ball cover also creates less friction than a soft urethane cover.
Do grooves create backspin?
They matter most when water or grass gets between the ball and the face: in 2007 lab tests with wet paper between them, boxier grooves with sharper edges produced more spin. For an ionomer-covered ball, groove shape and sharpness did not appear to change spin at all.
Does a urethane ball spin more off a wedge?
In a Titleist test from 75 yards with a new 58-degree wedge, a urethane-covered ball spun at 8,300 rpm and a two-piece ball with an ionomer cover spun at 5,600 rpm, about a third less, and launched five degrees higher.
What is the 2010 groove rule?
For clubs made from January 1, 2010, groove cross-sectional area divided by groove spacing can be no more than 0.0030 square inches per inch on every club except drivers and putters, and on clubs with 25 degrees of loft or more, groove edges must be rounded to an effective radius of at least 0.010 inch (0.254 mm). The USGA said the goal was to limit the effectiveness of grooves on shots from the rough.
How much spin does a wedge lose in wet conditions?
MyGolfSpy's 2022 wet test of 18 wedges and more than 17,000 shots reported that the average wedge lost about 35 percent of its dry spin and the worst lost more than 60 percent, while 11 of the 18 kept at least 90 percent.
More from HYTON Golf
To track your own wedge distances, the Range Notes practice journal ($21.99) has a wedge matrix page for 9:00, 10:30 and full swings. Every number from the series, with its source, is on Golf by the Numbers, and every episode is on the HYTON Golf Videos blog.