The short answer: gear effect. When a drive hits the toe, the clubhead twists open around its center of gravity, so the ball starts right. As the face turns, friction spins the ball the other way, like two meshing gears. That is draw spin, and it curves the ball back toward the middle. A heel hit does the reverse. The curved face of a driver and the deep center of gravity of its hollow head are what make this work. Directions here are for a right-handed golfer.
This article goes with episode 5 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 |
|---|---|---|
| More than 2× | Toe hits compared with heel hits in just under 5,700 drives by 20 golfers | MyGolfSpy (2016) |
| 18.1 yd | Average distance lost on heel hits | MyGolfSpy (2016) |
| Just over 5 yd | Average distance lost on toe hits | MyGolfSpy (2016) |
| 222 vs 203 yd | Carry from the center vs low on the heel, 95 mph robot, average of 25 drivers | GOLF.com (2022) |
| 5.5 yd | How far short of center a high-toe strike carried | GOLF.com (2022) |
| 5,900 g·cm² | Moment of inertia limit, so every legal driver still twists a little on a mishit | USGA Equipment Rules, Part 2 |
More numbers from the series, each with its source: Golf by the Numbers.
Watch the episode: Why Does a Mishit Curve Back? on YouTube.
The head twists around its center of gravity
A driver head is a thin shell of about 200 grams wrapped around mostly air (we cut one open in episode 4). Somewhere in that space is its center of gravity, the balance point of all the mass, and in a driver it sits well behind the face. Hit the ball in line with that point and the head simply slows down. Hit it out on the toe and the head behaves like a book pushed near one corner: it does not just slide, it spins. The toe is shoved back and the face turns open. On a heel hit the heel is pushed back and the face turns closed. Moment of inertia resists that twist, and the rules cap it at 5,900 g cm², so every legal driver still turns a little on a mishit.
The invisible gears
Here is the puzzle. A face pointing right of the swing path normally curves the ball right, and a toe hit turns the face open, yet the ball curves left. The reason is friction. For the brief moment the ball is squashed against the face, the face grips it. On a toe hit the face is turning clockwise, seen from above, so the ball is turned counterclockwise. Counterclockwise spin from above is draw spin: it tilts the ball's spin axis to the left and the ball curves left. So the toe hit starts right because the face turned open, then curves left because of the spin the turning face put on it. Heel hits start left and pick up fade spin. The usual face-to-path rule assumes a centered hit; miss the center and the gears join in. Physicists have measured gear effect in the lab.
Why a driver face isn't flat
Seen from above, a driver face curves from heel to toe. That curve is called bulge. It makes the toe end point a little right and the heel end a little left, so a toe hit launches farther right than it would off a flat face, and the draw spin from gear effect brings it back. Get the curve right and the ball finishes closer to the middle; on a flat face nothing would balance that draw spin. In 2001, physicist A. Raymond Penner worked out the best curve mathematically in the American Journal of Physics and found that typical driver faces were already close to it. He also found that harder hitters need a more sharply curved face and larger heads need less. A second curve, from crown to sole, is called roll: a hit high on the face launches higher with less spin, and a low hit launches lower with more spin.
How deep is the center of gravity?
When the head twists, it turns around its center of gravity. The farther that point sits behind the face, the faster the face at the impact spot slides sideways, and the more spin it rubs onto the ball. A driver's hollow shell puts the center of gravity deep. In irons and wedges it sits much closer to the face, so a toe hit with an iron gets much less of that curve back. Impact height changes spin too: a hit higher on the face takes some backspin off the ball, and a lower hit adds backspin.
What a swing robot measured
GOLF.com tested 25 drivers with a swing robot at 95 mph. From the center they averaged 222 yards of carry, 11.4 degrees of launch and 2,710 rpm of spin. Low on the heel, launch dropped to 8.95 degrees, spin rose to 3,310 rpm and carry fell to 203 yards, 19 yards gone. High on the toe, launch rose by about 2.5 degrees, spin fell by less than 300 rpm, and carry was only 5.5 yards short of center. That fits the curved face: high on the face, roll launches the ball higher with less spin.
Where real golfers miss
In 2016, MyGolfSpy had 20 golfers hit 25 drivers, just under 5,700 shots, and tracked where each one struck the face. Anything within 4.5 millimeters of center counted as a center hit. More than twice as many balls were hit on the toe as on the heel. Toe shots started farthest right with draw spin; heel shots started more to the left with fade spin, just what gear effect predicts. Heel shots lost 18.1 yards on average, toe shots just over 5. So the most common miss, out on the toe, was also the cheaper one.
Illustrations by HYTON. Directions are for a right-handed golfer; face curvature and head rotation are exaggerated. Not affiliated with or endorsed by Titleist, GOLF.com, MyGolfSpy or the USGA.
Sources
- Titleist Learning Lab, Gear Effect: toe contact rotates the face open and the ball counterclockwise (right-handed golfer), heel contact the reverse; irons and wedges have the CG much closer to the face than drivers; drivers and metal woods use bulge and roll with gear effect
- R. Cross and A. M. Nathan (2007), Experimental study of the gear effect in ball collisions, Am. J. Phys. 75, 658-664: laboratory measurements of gear effect (listed on R. Cross's publications page)
- A. R. Penner (2001), The physics of golf: The convex face of a driver, Am. J. Phys. 69, 1073-1081; Science News, October 30, 2001: typical driver curvature is near the mathematically determined optimum; harder hitters need more curvature; larger heads need less
- GOLF.com (October 14, 2022), driver miss robot test: 95 mph, average of 25 drivers, six balls per location: center 222 yd carry, 11.4 degrees, 2,710 rpm; low heel 203 yd, 8.95 degrees, 3,310 rpm; high toe about 2.5 degrees higher launch, under 300 rpm less spin, within 5.5 yd of center
- MyGolfSpy Labs (October 19, 2016), Horizontal Impact Location Study: 20 golfers, 25 drivers, just under 5,700 shots; center within 4.5 mm; more than twice as many toe hits as heel hits; heel -18.1 yd, toe just over 5 yd; toe shots start right with draw spin, heel shots start left with fade spin
- Kris McCormack, GOLF.com (May 10, 2025), Bulge and Roll: Why that curved driver face isn't just for looks: bulge is the heel-to-toe curve and roll the crown-to-sole curve; high strikes launch higher with less spin, low strikes lower with more spin
- GOLF.com (September 3, 2024), How impact location affects spin rate: Andrew Rice, GOLF Top 100 Teacher: hitting higher on the clubface lowers spin, hitting lower raises it
- Tucker, Kenny, Byrne and Anderson (2009), The Effect of Varying Club Head Mass on Velocity and Kinetic Energy, ISBS Conference Proceedings: a standard driver head mass of approximately 0.2 kg
- USGA Equipment Rules, Part 2 (Clubs), Rule 4 (Clubhead): moment of inertia no more than 5,900 g cm2 plus a 100 g cm2 test tolerance
Sources last checked October 2026.
Frequently asked questions
What is gear effect in golf?
Gear effect is the spin a clubface puts on the ball when contact is off-center. The head twists around its center of gravity, and friction makes the ball rotate the opposite way, like two meshing gears. For a right-handed golfer, a toe hit gets draw spin and a heel hit gets fade spin.
Why does a toe hit curve back to the left?
On a toe hit the face turns open, so the ball starts right. At the same time the turning face spins the ball counterclockwise seen from above, which is draw spin, so the ball curves back to the left. Directions are for a right-handed golfer.
Why is a driver face curved?
The curve from heel to toe is called bulge. It makes the toe end point a little right and the heel end a little left, so off-center hits start out to the side and gear effect spin can bring them back toward the middle. The curve from crown to sole is called roll.
Do irons have gear effect?
Much less than drivers. In irons and wedges the center of gravity sits much closer to the face, so the face slides sideways less as the head twists and puts less spin on the ball.
Is a toe miss or a heel miss worse with a driver?
In a 2016 MyGolfSpy study of just under 5,700 shots, heel hits lost 18.1 yards on average and toe hits just over 5 yards. In a 2022 GOLF.com robot test, a low heel strike lost 19 yards of carry and a high toe strike 5.5 yards.
More from HYTON Golf
The gear effect drawing from this episode is also a shirt. The Gear Effect T-Shirt ($24.99, 2XL $26.99) shows a driver head from above, the face twisting open on a toe hit and the ball curving back, with the line "Most misses find the toe. The face fights back." It is printed to order with free US shipping. More designs from the series are in the Wear the Science collection, and every episode is on the HYTON Golf Videos blog.