Tips · THE GEAR EFFECT · RIGHT-HANDED

Hit a driver off the toe and the ball curves back.

A toe hit twists a driver's head open around its centre of gravity, well behind the face. The face swings sideways across the ball and friction spins the ball the other way, like meshing gears. Driver faces bulge, so a toe hit starts right and draws back. Irons show much less of it.

The one to remember

Driver faces bulge so a toe hit starts right and draws back.

Facts and sources

  • On a toe hit the head rotates open about its centre of gravity (clockwise seen from above, for a right-handed golfer). Friction between the turning face and the ball spins the ball the other way, so it curves right to left; a heel hit does the opposite (Titleist; Dave Tutelman; A. Raymond Penner).
  • It takes a centre of gravity well behind the face, as in a driver, for the face to move sideways across the ball. In irons the centre of gravity sits close to the face and the effect is much smaller (Titleist; Penner). In robot tests at Ulster University, a cavity-back 5-iron showed a gear effect and a blade 5-iron did not (Wallace and others, 2021).
  • Dave Tutelman's model of a typical driver (150 mph ball speed, an 11° driver hitting about 240 yards, a 12-inch bulge): a strike half an inch toward the toe gets about 1,100 rpm of hook spin from the gear effect. Off a flat face it would finish about 38 yards left; with the bulge, about 6 yards left.
  • Driver faces bulge from heel to toe, so a toe hit starts right and the gear effect's draw brings it back (Titleist). Modern drivers' bulge radii run about 11 to 13.5 inches (LA Golf's Jeff Meyer in Golf Digest, 2025); Tutelman's 2009 survey of catalogues found 10 to 13 inches, most often 12. Most drivers also curve from crown to sole, which is called roll.
  • The bulger, a driver with a convex face 'like a cricket bat', dates from about 1884. Penner's 2001 analysis found the curves on commercial drivers close to the calculated optimum, though the shape was found by trial and error.

Illustration: the strikes are slowed right down, and the head's twist, the gears, the spin axes and arrows are drawn to explain, not measured; the toe strikes sit further out than half an inch so they read, and the twist is exaggerated. The drives, the dawn tee and the ride alongside the ball are illustrative, as is the 1897 table: its manual, the engraving and the club are not a particular book or maker's.

Sources

  1. Gear Effect (Learning Lab) · Titleist (Internet Archive copy of 12 April 2026; the live page refuses automated requests) checked 11 October 2026
  2. Bulge and Roll in the Clubface of Metalwoods (Learning Lab) · Titleist (Internet Archive copy of 10 June 2026; the live page refuses automated requests) checked 11 October 2026
  3. All about Gear Effect · Dave Tutelman (20 February 2009, last modified 3 April 2009) checked 11 October 2026
  4. All about Gear Effect, part 1: horizontal gear effect · Dave Tutelman (19 February 2009) checked 11 October 2026
  5. Physics Question #2419 (gear effect) · science.ca Ask a Scientist, answered by A. Raymond Penner, professor of physics, Malaspina College (11 December 2004) checked 11 October 2026
  6. The influence of 5-iron clubhead mass distribution on clubhead presentation and initial ball launch conditions, Part I: Golf robot tests · E. S. Wallace, T. W. Corke, K. M. Jones, N. F. Betzler and S. R. Otto, Proceedings of the Institution of Mechanical Engineers, Part P 235 (1), 36–45 (2021; Ulster University) checked 11 October 2026
  7. LA Golf Face ID drivers: What you need to know about the new Bryson-designed big stick · Golf Digest, Mike Stachura (24 March 2025; read on the Internet Archive copy of 8 October 2025) checked 11 October 2026
  8. What is Spin Axis? · TrackMan, Trackman Editorial Team (23 September 2024) checked 11 October 2026
  9. Curve on golf club sends ball straight · Science News, Peter Weiss (30 October 2001), on A. Raymond Penner, The physics of golf: The convex face of a driver, American Journal of Physics 69, 1073 (2001) checked 11 October 2026
  10. Bulger n. · Dictionary of the Scots Language, Scottish National Dictionary (2004), quoting R. Forgan, Golfer's Manual (1897), pp. 9 and 11 checked 11 October 2026

The narration is AI-generated. Sources last checked 11 October 2026.

Script

Hit a driver off the toe, and the ball curves back toward the target. A toe hit twists the head open around its centre of gravity, which sits well behind the face. The face swings sideways across the back of the ball. Friction spins the ball the other way, like two meshing gears. For a right-handed golfer, that's draw spin off the toe, and fade spin off the heel. Irons carry their weight close to the face, so the gear effect is much smaller. Their faces are flat. A driver's face bulges, heel to toe, on a curve about 12 inches in radius. So a toe hit starts out right, and the draw brings it back. In 1897, a golf manual promised that heel or toe, the bulger sends it always straight.