Driver Head Weight and Club Length

Dave Tutelman -- October 28, 2012

Evidence, Anecdotal and Otherwise

We have a problem here! Some studies don't agree with others, nor with some reality-check data that we have. Why not? Here are a few possible explanations I can come up with. The evidence is common-sense but mostly anecdotal.

Let's start with the fact that the model showed lighter clubheads superior at less than 150 grams, for variable length with constant MOI. But most real-world experience does not bear this out. Few clubmakers report success with clubheads under 190 grams. Why should this be?

Construction of really light clubheads may be difficult.  I am used to seeing quotes like the following:

Bernie Baymiller (a good golfer and clubfitter, mostly for seniors) posted in Shoptalk, May 4, 2011
... most of the guys for whom I build long drivers, seem to prefer and do better with the 190 than the 175 when they demo them side by side.
Again Bernie Baymiller, June 3, 2011
... I'm using a UL-45 R on a 10.5° BOM right now at 47" club length and getting good results. A DTG 190 9°on an SKF PE A also produced good results with a slightly lower trajectory. I don't like the 175 gram heads much, though. They don't have as much "pop" for me as the DTG 190. For me, at a 47" club length, I still think a 190-195 gram head on a low 50s gram shaft delivers the best distance. My BOM weighs 193 grams.
For reference:
  • UL-45 R is an ultra-light shaft weighing between 45 and 50 grams, in an R-flex. It is made by Diamond Tour Golf.
  • BOM is a Bang-O-Matic head, weighing about 195 grams, made by Bang Golf.
  • DTG 190 is Diamond Tour Golf's lightweight head (190 grams).
  • SKF PE is a lightweight shaft called the Pure Energy, made by SK Fiber.
David Dugally (a component designer and clubfitter) posted in Shoptalk, May 3, 2011
There is a trade off between speed and mass, the lighter head increases speed, but reduces mass.
In working with arguably the Jack Nicklaus of long drive Gerry James, we worked with heads from about 179 grams to about 207 grams and got the best Ball Speed with a head at 193 grams, now his swing speed at the time was about 138 mph, I do not know how this would fall off or increase as swing speed decreases, but it seems to be consistent with your results so maybe it doesn't fall off with swing speed, maybe that's the ticket.
Perhaps Dave T knows the math, I don't, I only know the results.
This is counter to the computer studies, which show that long drivers continue to hit the ball significantly farther as the weight decreases. Perhaps the answer is contained in this post to Spinetalk by Danny Seng (a clubfitter from Australia), October 26, 2012:
There are heaps of Titanium driver heads these days and especially the lighter 175g heads tends to generate less mass and as a result the lack of distance is always the complain.
Japanese driver heads does comes in the same 175 to 180 gm weights but they are far more superior and the results are there.
Driver heads in the 175 and 180gm that I have huge success are from John Muir products I have yet to come across one that really deliver the distance desired.
In the 190 gm weight the greatest success are from David's Vector series and Tom Wishon. The rest are mediocre at best.
This suggests that not every club manufacturer can build a fully capable driver head at 175 grams. In order to get a high COR and maintain it across the whole face, you need to provide adequate support in the clubhead surrounding the face. If there is not enough rigidity there, a lot of the spring face's effectiveness is lost.

Danny talks about much better heads from Japan at really light weight (175-180 grams) than he sees elsewhere. And he attributes this (in other posts) to the fact that the Japanese adopted longer, lighter drivers much earlier than the US; he cited the 1980s. So they have much more experience with very light clubheads for long drivers.

This may explain why long drivers with heads under about 190g do not continue to improve distance. But Bernie, David, and Danny all have positive things to say about long drivers with head weights around 190g.
  • Bernie says they give him 25-30 extra yards. He also cites a senior lady who got an extra 35 yards[6]. (To repeat, the model predicts around 10 yards -- worthwhile, but nowhere near this.)
  • David cited his work with Gerry James, a well-known long-drive champion. They did extensive testing, and determined that Gerry got his best ball speed with a 193g clubhead and a 48"+ club length.
  • Danny believes there is a tradeoff between accuracy and distance when going to longer, lighter clubs (which I confirmed when I began experimenting; see below). But he feels that there is a real advantage for smaller or less strong players who can learn to swing a longer driver. Which brings us to...
Some real people can make it work, and some can't. Danny Seng explicitly acknowledges that not everyone can or should play a longer, lighter driver. It is harder to control, and costs accuracy. From private email from Danny Seng on November 11, 2012:
There is no question that a shorter length club generates greater accuracy. KZG article derive driving accuracy data from Pros. I do not dispute that either, nor have any objections on other write ups you have pointed on this topic. Working in Asia and Australia we have the best of both worlds to experience. In Asia for years we have Asian golfer with drivers at 48 " longer under the 300 g mark for total weight, and they drive awesome distance. We use to marvel at that. But in that same breath we have Asian customers build like amazon unable to use these type of specifications, and needs to reshaft their drivers.
Also from Danny, November 28, 2012, after relating an experience with Euan Walters, a winner on the Australian PGA tour:
There is a statement to be made here. In the hands of a professional the longer, lighter weighted driver generates greater distance consistently.

So it takes skill and consistency to make a longer driver work. There is formal research confirming that enough skill and consistency can make it work. Bernie Baymiller has pointed out to me a scientific paper from  the journal Sports Biomechanics, "Influence of shaft length on golf driving performance" by Ian C. Kenney, Eric S. Wallace, and Steve R. Otto of the University of Limerick. They tested seven Category 1 golfers (handicap index less than 5), most in their early twenties, using drivers of length 46", 48", and 50". Here are some of the results that I think are important:[7]
  1. There was some gain of distance going from 46" to 48". The average gain was 6.3 yards. If we assume that same rate of gain over the whole 45" to 48", that is 9.9 yards, very close to the 10 yards that our computer model predicted.
  2. When you think about it, the gain is even less than what the computer model predicted. The computer model was based on a 100mph clubhead speed. The golfers in this study were young, near-scratch golfers. I have to believe they had clubhead speeds between 110 and 120mph. So they might expect an additional yard or two, compared with the computer model.
  3. There was no further distance increase in going to a 50" driver. Well, at least not on average. Some could make it work, and others did worse with it.
  4. One of the test subjects got considerably more distance gain: about 23 yards going from 46" to 50". This is outlier data, but still it is actual, measured fact.
  5. Most surprising to me was that there was no falloff of directional accuracy as they went to longer drivers.
Again, remember that the test subjects are elite golfers. Many clubfitters feel that a long driver is a mistake for most golfers. Tom Wishon has been the most vocal proponent of this position, and I have supported it for years. From Tom's web page on driver fitting:
It’s time to be blunt.  The standard driver length of 45.5 to 46.5 inches offered by the majority of golf club companies is too long for the majority of golfers and will prevent at least 75% of all golfers from achieving their maximum potential for distance and accuracy.  For men with an average to fast tempo with an outside/in swing path, 44” should be the maximum length; women, 42.5” to 43” should be the limit.  There’s a very good reason the average driver length on the US PGA Tour since 2005 has been 44.5” and not 45.5” to 46.5”.
Tom has a great anecdote about the difficulty of hitting a long driver in his booklet, "The Search for the Perfect Golf Club".

How can we account for the sort of distance changes that Baymiller reports, Seng implies, and Kenney's research finds as an outlier? In the first place, it can only be accounted for by a different swing, a difference that favors the longer driver. Something had to happen to increase the distance so much more than the 10 yards that physics gives it. A few possibilties:
  • The particular golfer is just better suited to the longer driver. Perhaps their swing benefits considerably from a flatter plane, or perhaps the increase in swingweight regulates their swing better. (The computer model kept the same MOI, but Baymiller's experiences are all with a considerable increase in MOI going to the longer driver.) Perhaps there was a shaft with a very different flex profile, better suited to the golfer's swing.
  • The particular golfer was doing something very wrong with their shorter driver. In other words, the large gain comes from the fact that their old driver was not a hard act to follow.
  • The measurement and reporting of the gain is flawed. (Read on, and you will find out how easy it is for this to happen. I did it myself for my first cut.)
Bear in mind that these other factors must also account for the need for repeatable accuracy that Wishon cites and I certainly experienced (see below).

How do you keep score?

In the game of golf, score is kept by strokes. But not everybody plays golf to minimize their total strokes. As the club manufacturers well know, many (probably most) of their customers want to remember a really long drive or two from each round, or they want to out-drive their buddies. If they have that, a high stroke count will not bother them.

If you don't believe this phenomenon, compare PGA Tour statistics with commercial sales of golf clubs. In 2005, the average driver length on the Tour was 44.5". Depending on whom you listen to, it may still be there, or it may have crept up close to 45". But no higher than that. In any event, it is nowhere near the 48" allowed by the Rules of Golf. Yet off-the-rack drivers from the major manufacturers are in the 45.5" to 46.5" range. It would appear they are selling to people who don't keep score by strokes. Think about it; the Tour players collectively have as much skill and consistency as any golfers on the planet, and they are not using 48" drivers.[8]

But there is a golf sport where score is kept by driving distance! The LDA (Long Drivers of America) have a competition circuit and even a world championship (the ReMax Long Drive Championship) based on how far you can hit the ball. Moreover, consistency does not win; you get six tries, and only your longest drive (in a very wide "fairway") counts. Not surprisingly, those guys use the longest shafts they are allowed to. They have the skill to find the sweet spot, and get six chances to find it once -- so they can afford to trade consistency for any increase in distance.

Let's see what a few of them have to say:

Jeff Farley -- I met Jeff through David Dugally in 2011, and David suggested I contact him again for this study. He was very forthcoming about his club choices, and had an interesting and perceptive take on it.
Many LDA guys now believe that a little heavier head is the way to go if you lose the speed in your swing. Many reports have David Mobley using a 210 gram head thus giving him more mass behind the ball which makes up for some of the speed he may have lost in the aging years.

Here are my thoughts. I still believe that I must use a head around 194 grams. I would go lighter if I could still find a way to feel the club head at the bottom. The way to hit the ball further is to create speed which is why you see skinny non muscular guys who can pound it.
I agree with Jeff that clubhead speed is more important than "mass behind the ball". In fact, that is what this whole article is about, the tradeoff between clubhead speed and clubhead mass. We were talking about a constant length here; the LDA competitors all use maximum length drivers.[9] Mobley (according to Farley; remember, this is "many reports", not definitive fact) may have something. The ball speed does not change much for tens of grams around 200g, so a big, strong guy might well make a better swing with a heavier club. A "better swing" might mean higher clubhead speed, more consistent sweet spot contact, or both. Every clubfitter knows that the club's heft must be fitted to the golfer; too light or too heavy, and the swing degenerates to some extent. Apparently, Mobley is best fit to a heavier heft.

Jeff is right that, unless you actually need the weight to regulate the quality of your swing, you'll hit the ball farther with a lighter head. The "skinny non muscular guys" are a better fit to less heft than Mobley.

Then Jeff makes an even more interesting statement.
One can do different exercises to hit the ball further but increasing the driver length will give you instant distance if you can continue to hit the sweet spot and maintain good golf fundamentals.  I use a 48 inch driver in LDA competition and a 45 inch driver for golf. I call this my playing driver because I can control it better when I am swinging well.  The 45 incher limits the errant shots.  There is about a 15-25 yard difference between my playing driver and my long driver.

When I long drive I like a 6 degree loft. When playing golf with the shorter driver I like the loft a good 1.5 degree higher which I believe gives me more accuracy. A key thing here is that I am covering the ball more when playing golf, unlike when long driving -- in long drive I am trying to release the club as hard as possible making me very handsy.
There are a few very telling points here:
  1. He himself uses a 45" driver to play golf and a 48" driver for long-drive competitions. 'Nuff said!
  2. He knows he uses a different swing for long drive competition than he does for just playing golf. So the 15-25 yard difference is only partially explained by the club's dimensions. The rest is in the different swing.
  3. "...Increasing the driver length will give you instant distance if you can continue to hit the sweet spot..." Remember this when you see my own test results below. I found the converse also to be true: If you can't hit the sweet spot with the longer driver, you will not get instant distance.

Tyler Kellett-- When Rick Malm saw my article, he suggested I get in touch with Tyler Kellett, as Tyler had worked very closely with the experts from Krank in tuning his LDA competition drivers and understands what they do. When I talked to Tyler, one of the most important themes that came through is how different long drive competition is from golf -- and how that colors all the equipment selection decisions. I'd like to do a separate article on that sometime, but here are the things that we talked about having to do with head weight and club length -- the topic of this article.
  • A 1% increase in clubhead speed for your regular golfer is about 1mph, which can give an additional 3 yards. That will not make a difference in score over the course of a round. On the other hand, a 1% increase in clubhead speed for a long drive competitor is about 1-1/3mph, which is worth 4 yards. Not that much more, but in long drive competition it is often "the difference between moving on to the next stage and going home" (Tyler's words). Long drive is about eking every yard out of your drive that you can!
  • Almost every LDA competitor uses a maximum-length driver, and even those who don't will use something pretty close -- certainly a lot longer than commercial drivers or those used on the PGA Tour.
  • Tyler found his own ideal clubhead weight by careful and exhaustive testing. He tested using a maximum-length driver with his correct shaft and a TaylorMade R7 head (which is not the head he uses in competition). Why that head? He was able to use the weight screws to change the head weight over quite a large range; he used some custom tungsten weight screws to get the range up. Note that he was not trying to shape the trajectory with the screws, just vary the head weight until he got maximum ball speed.
  • The weight he found from this exercise is definitely not the lightest possible -- not even under 200g. He pointed out that some LDA guys are very strong and others are very quick. The strong ones get better ball speed from heavier heads (as heavy as 210g, and even more), and the quick ones from lighter heads (in the low 190s).
  • An LDA competition involves a bunch of matches in a day. For instance, the world championships are 14 rounds in two days. That presents a problem with a higher weight; you get more tired more quickly the heavier the driver you use. If your optimum head weight when you're fresh is a heavy head, it may tire you out in a tournament. Tyler says you might do well to go 5-10g less than that.
  • The latest generation of LDA drivers have the placement of the weight designed as carefully as the amount of weight. I was surprised at the trend. Tyler told me that we have gone a little overboard in reducing spin; we have gotten very good at it, perhaps too good for long drive. (This does not question that higher launch and lower spin are a winning formula for stronger amateur and professional golfers, in the 100-120mph range. But this is not the same as long drive competitors.) So long drive clubs are now going to a center of gravity that is higher and closer to the face, which gives more backspin. If you understood my article on vertical gear effect, you know exactly why these changes will remove gear effect topspin. (I have not done any studies to verify which ball speeds benefit from more backspin and which from less. Sounds like an interesting project for the future.)
  • Most people in golf have a higher estimation than I do of how much increased clubhead mass will turn into ball speed through momentum transfer. Tyler is no exception. He disagreed when I said how much (actually how little) a given change in clubhead mass affects ball speed --that a 5% change in driver head mass gives only a 1% change in ball speed. But I stand by it. It goes back to a very basic piece of physics, the equation for ball speed based on momentum and energy transfer. The equation appears in Cochran & Stobbs' classic 1968 book, and in a huge number of research papers in golf engineering. You can set up the equations with stuff from college Physics 101 (first-term freshman physics), though solving the equations may require some tricky algebra. I have no doubt the results of the equation are correct.

My Own Experience

Oftimes, analysis is enlighted by personal experience. By now, I was beginning to feel this was one of those times. So, with a little advice from Bernie Baymiller, I went ahead and built myself a long driver. The components were from Diamond Tour Golf, and Bernie said he had used them successfully more than once. I used their house brand 190g head (12º loft, like my usual driver) and their house brand 48g shaft. The result was 47.5" long, just on the verge of legality. (For reference purposes, it is exactly 3" longer than my usual driver.)

I then set about to gain some insight through experience. I started with a range session, and quickly convinced myself that I didn't need a lot of work learning a new swing. Just keep it smooth, swing by rotating the body, and keep a light grip -- don't make the release happen, but allow it to happen on its own. Those are the same swing keys I find productive with any swing, especially a driver swing. But it seemed to be more important for the longer driver. (Note that this is just the opposite of Bernie Baymiller's advice. I did nothing to advance the release earlier in the downswing, and got bad results when I tried.)

My next round, I didn't go straight to the long driver. Instead, I practiced those same swing keys with my usual driver, in part to establish a benchmark for comparison. (It was a good benchmark; by the back nine, my game was as sharp as it has been all year. I set a personal best for that back nine, and got my first back-to-back birdies in years. One conclusion: even if the long driver doesn't work for me on the course, it seems very effective as a training driver.)

For the following several weeks, perhaps ten rounds, I used the long driver exclusively. I also did some "lab tests" indoors with a launch monitor.

On the course: averages, apples, and oranges.

From the first, I noticed that my best drives were 15-25 yards longer than I was used to at those courses. Maybe there is something to this after all!

Then I realized something. If the point is to compare drivers, the wrong way to do it is to compare your best drives with one driver against the typical drive with your other driver. You must not compare apples and oranges. (After realizing this, I began to wonder if that is how the 'testimonials' for longer drivers get the large gains that they do.)

Basis for
comparison,
both clubs
Longer driver results,
compared with Normal driver
Distance
Direction
Trajectory
Best drives
10-15 yards longer
Similar
Similar
Good drives
Similar, maybe
a few yards longer
Similar
Higher
Typical drives
Definitely
a few yards shorter
Heel fade,
as likely to
finish in play
Higher
Poor drives
Noticeably shorter
More likely to
finish in play
Higher
So let's compare best drives with best drives, average drives with average drives, etc. This table is my summary of those impressions. Again, these are impressions, not controlled measurements. The best I can say in their defense is that they were recorded at courses that I play all the time, and playing with my usual golf partners (so I could gauge how I was doing relative to them). A few interesting points about these observations:
  • The best drives are distinctly better with the longer driver. 10-15 yards is not to be dismissed lightly. Of course, it isn't my original 25-yard impression; that was my best long driver shots compared with my typical short driver shots -- the wrong way to compare.
  • Most of my on-course shots with the long driver were shorter than I have come to expect from my normal driver. The few big winners pulled the average up, but the median was definitely lower. (You'll find the explanation in the launch monitor tests.)
  • To my surprise, I did not lose "straightness" with the longer driver. I probably hit more fairways with it, even most of my not-so-good shots. More of my poor shots finished "in play" than I am used to. I'm not sure how to explain it, but it certainly seems to be the case -- and it is in keeping with the results from Kenney's study.

Lab report: launch monitor results.

My friend Charlie Badami is auditioning launch monitors for his teaching and clubfitting bay. When I called to see if he was interested in the experiment, he was using a Flightscope, a highly respected instrument. I zipped over to his "office" and we did some testing.

Club
length
Head
weight
Shaft
weight
Clubhead speed
Measured Predicted
44.5"
208
48
84.4 84.4*
47.5"
192
48
87.6 88.1
My first question was whether my computer model for clubhead speed was in the right ball park. If not, that would explain (a) the disagreement with Cochran & Stobbs' study and perhaps (b) why the computer model disagreed with the anecdotal experience of people like Bernie Baymiller, Danny Seng, and David Dugally.

That did not happen. When I looked at clubhead speed for both drivers (see the table on the left), the gains due to the longer driver were very close to what the computer model predicted. On the computer I tweaked the torques until I got the same 84.4mph from the computer model that I got from the launch monitor. Then I just changed the club characteristics in the computer model to match my longer driver. The measured improvement was 3.2mph and the computer model predicted an improvement of 3.7mph. That is definitely close enough not to worry about.

On top of that, both the computed and measured difference in clubhead speed corresponds to about a 10-yard gain in distance -- exactly what our earlier computer studies suggest.

So the computer model is not debunked by my own swing applied to a long driver. The model works just fine!

Now let's turn our attention to ball speed, because that is where distance comes from. Here is a scatter plot of clubhead speed vs ball speed, and a tabular summary of what it tells us.[10]

Measured
statistics
Short
44.5"
driver
Long
47.5"
driver
Std.
Dev.
Average
Average Std.
Dev.
Club speed
1.8
84 88 1.8
Ball speed
5.6
113
104 8.7

What we see is a tight grouping of clubhead speed for both drivers (the standard deviation is only 1.8mph), but a much more varied ball speed. Charlie tells me that most decent golfers have a rather consistent clubhead speed; this is not unusual. The ball speed variation is clearly a significant dispersion of "smash factor", which derives from the quality of the ball strike.

In fact, the long driver produced lower ball speed than the shorter driver, and substantially so. We see here why my less-than-best drives on the golf course were usually not as far with the long driver.

In case there is any doubt about the smash factor deficiency, we were using face impact tape during the tests. Here are the tapes.

My driver swing was not very good the day of the launch monitor testing. In all honesty, I tend to lose my swing after a one or two dozen hits in an indoor cage. So this is representative of my performance on a not-very-good driving day. I don't think it contains a single "best" drive (using the terminology from my on-course experience); it mostly reflects "typical" and "poor" drives.

Other than the absence of any "best" drives and few "good" drives, this is consistent with what I observed on the course. The short driver had a reasonable (if not really good) impact pattern. But unless I hit the ball in the middle of the long driver clubface, its shots lost distance compared to the short driver. Poor impact trumped clubhead speed in generating ball speed. We can also see the higher trajectory and predominance of heel fades from the impact tapes.


Charlie is continuing to audition launch monitors. He wants to repeat the tests with the next one when it arrives. If and when that happens, I will update this article.

The bottom line for my own use of a longer driver is sort of interesting:
  • My best drives see a gain of 10-15 yards, definitely worthwhile if it happens more than occasionally.
  • Unfortunately, my median drive goes no farther than my shorter driver, and actually loses distance if I am having an average or poor day with my driver swing.
  • The good news is that I don't give up anything in directional accuracy.
Contrary to Bernie Baymiller's experience, I have no problem squaring the face. Instead, my problem is getting the ball in the center of the clubface. And I fail to do it often enough that, even though I usually get the expected higher clubhead speed, I get lower ball speed than my shorter driver.

One final word about the long driver: it seems to be an excellent training aid. I used it for about ten rounds, then went back to my normal (44.5") driver. I hit my normal driver better than I had in a long time. My best drives rivaled my best drives with the long driver -- close, though probably not quite as big. And I was hitting them rather consistently. Apparently the swing discipline involved in hitting the long driver is very beneficial to the use of a more standard length driver.


Last updated Jan 31, 2013