2005: USGA adds new twist to drivers
Tuesday, October 11, 2011
By James Achenbach
In the past seven years, the U.S. Golf Association has limited the design and performance of drivers in three respects: spring-like effect of the face (.830 coefficient of restitution), clubhead size (470cc) and overall length (48 inches).
Now the USGA wants to add another limit to drivers: resistance to twisting. In other words, drivers will be required to twist a certain amount on off-center hits.
In a letter to golf club manufacturers dated Aug. 31, the USGA proposed that moment of inertia (resistance to twisting) in driver heads be limited to 4,800 grams per square centimeter under specified test conditions. All currently conforming drivers would pass the MOI test, the USGA said.
This 4,800 number for MOI includes a 50-gram tolerance (4,750 plus 50). Many other USGA measurements also have a tolerance (clubhead size, for example, is 460 plus 10). Manufacturers typically manufacture their clubs extremely close to the total limit.
MOI is all about forgiveness on off-center hits. The higher the MOI, the less twisting and the more forgiveness.
According to the USGA, MOI in drivers “has approximately tripled over the past 15 years.” The proposed MOI limit pertains only to drivers and not to fairway woods, hybrids or irons.
Manufacturers, though, are alarmed about the future.
“What are they trying to do to the golf industry?” asked Ping chairman John Solheim. “The (club) development we do in a few years – will it mean anything? Will there be room to move?
“They’re taking the advantage away from the companies that do the work to produce good golf clubs. They’re giving the advantage to companies that mass-produce. That scares me a lot.”
Don Wood, owner of custom clubmaker For Golfers Only! in Temecula, Calif., was more direct. “This ends the driver market as we know it,” Wood said. “We are now completely constrained (in design). Drivers can’t go farther, they can’t go straighter, they can’t be bigger. Now the main differences will be quality of construction and better fitting.”
Movable weights have created a buzz this year in the golf industry, and the USGA proposal said a driver must pass the MOI test in all weight configurations.
The USGA is accepting responses to its latest proposal until Nov. 30. The rule is scheduled to go into effect on March 1.
Meanwhile, no new drivers will be ruled as conforming until the MOI rule goes into effect.
“The box is now going to be tighter,” said Chip Brewer, president of Adams Golf. “In drivers, that will create some challenges. We have bright people (club designers), so hopefully we will continue to innovate around that.
“I’ve been a USGA supporter, but I’m not sure I agree with them on this one. There’s more gray area here. It makes me wonder what will happen with the MOI of irons and hybrids. There are no relevant boundaries there.”
Manufacturers, saddled with restrictions on spring-like effect, clubhead size and overall length, have been focusing on reductions in MOI. They accomplish this with different weight distributions in the shell of the head and different weighting schemes inside the head.
The result of this antitwist campaign has been a generation of titanium drivers that, in theory, hit the ball straighter than older drivers.
In the Aug. 31 letter to golf club manufacturers, USGA senior technical director Dick Rugge quoted another letter that had been sent to manufacturers on March 30, 2005:
“The USGA is concerned, however, that any further increases in clubhead moment of inertia may reduce the challenge of the game. It is possible that current head size restriction could serve as an effective cap over further increases. However, future materials with greater strength and lower weight than materials currently used in clubheads could potentially enable significant further increases in moment of inertia. There may be other means of further increasing moment of inertia as well. The USGA is conducting this research to determine if a limit on moment of inertia should be implemented. It is possible that a proposal regarding such a limit could be made in the future.”
The future arrived on Aug. 31.