Other Heft Issues

Backweighting

"Backweighting" is the practice of putting weight in the butt of the club. The weight is usually not more than 30 grams for full-swing clubs. (Let's leave putters out of the discussion for now.)

It does help some golfers, and does nothing for others. In fact, experimenters who have tried it with careful testing, find that it may help for some clubs and hurt for others.
  • One of the better tests of backweighting that I have seen was done by Jeff Summitt of Hireko Golf, and is available on their web site. Summitt found that, for the same golfer, a 27g backweight could add 8mph of ball speed, subtract 6mph of ball speed, or almost anything in between. He saw nothing in his fairly extensive one-golfer data to hint at whether backweighting would help or hurt for any particular driver.
  • Tim Hewitt of MyOstrich Golf, one of the more experienced people at fitting for backweight, has posted to SpineTalkers his experiences and methods. His conclusion: "I don't know of ANY science that has been able to predict which clubs will benefit which player, or been able to find the commonality in finished clubs that can predict the combination for the  next club. I have even had single length iron customers benefit in odd clubs throughout a set - with clubs that were virtually IDENTICAL club to club."
This is a very curious phenomenon that just about begs for explanation. So here goes...
  • Doesn't affect MOI -- We know that weight at the butt of the club is not going to affect the moment of inertia. So that isn't what is going on.
  • Computer simulations -- I investigated the effect of backweight, using Max Dupilka's "SwingPerfect" program. It showed only a tiny effect from backweighting -- even with backweights as high as 100 grams -- and less than a 0.1% effect from the sort of backweights that are normally used. So there is nothing in the physics to support backweighting a club.
  • Wristwatch analogy -- If there were any physical validity to backweighting, then a wristwatch or weighted bracelet should have the same effect. A metal men's wristwatch weighs between 50 and 80 grams, quite a bit more than most backweights. And a wristwatch has just about the same effect on the equations of motion that a butt weight would. Both would show up as extra mass very close to the hinge; which side of the hinge it was on would make almost no difference in the equations of motion that govern the swing. (That's true for any physical model of the swing, not just Jorgensen's model.)
    But, in fact, informal experiments have shown no effect due to the weight of a wristwatch on the wrist.
  • More wisdom from Jeff Summitt -- In an email discussion with Jeff, I mentioned that robot testing does not show any effect from backweighting. He responded, "You are right, a robot will not tell any difference in counterbalancing, but a human can (well at least some will).  While at Dynacraft, we had a very special test club that was counterbalanced by 30g (2g), can't remember exactly since it was so long ago.  It was a heavy club, but not when you picked it up and tried to waggle it.  There was an identical club sans counterbalance as a control.  Inevitably the students would swing the counterbalanced club faster and change their swing from outside-in to inside-out.  It was truly amazing how it would work on somepeople but not all. "

My conclusion from all this is that backweighting is completely subjective. It is a feel issue, with no basis in the actual mechanics of the swing. The feel must occur through the hands' grip on the club, not the arms nor shoulders. (If it were arms or shoulders, then a wristwatch would have the same effect as a backweight.) The golfer who responds to the feel of a backweight does so by making a different swing -- that is, apply more or less force, perhaps at different times. This, and not any physics phenomena, is responsible for the effectiveness of backweight for some golfers. This is the only explanation I can come up with that is consistent with the facts.

So it is some kind of internal human feedback mechanism. It differs from person to person and, within a single person, from club to club. So far, we have not discovered any correlation that allows us to do much better than trial and error in fitting a golfer for backweight. And any science that can help the situation will not start with physics (a better model of the swing) or technology (a better backweight system). It will be number-crunching or eyeballing a lot of human test data ( probably like Jeff Summit's), looking for correlations. So far, nobody has tried that with any persistence. Perhaps some day a graduate student doing a thesis project will attack the problem. I don't see any other party with both the resources and the motivation to do it.

None of this denies the effectiveness of backweighting for some golfers for some clubs. It just precludes any way to fit a golfer for backweight except old-fashioned trial and error. Maybe some day we will know enough to do better.

Here are a few more relevant points, added March 17, 2011:
  • Wisdom from Leith Anderson -- Leith Anderson probably has more experience fitting backweights than almost anybody. He says that they are almost universally helpful, but at different weights for different golfers. Also, bear in mind that he focuses just about exclusively on good golfers who are willing to work and practice to get better. That puts his clientele in a small minority to begin with. Anyway, Leith told me, "I have done that hundreds of times.  I use the Achiever.  I set the benchmark with no weight.  Then, I swap 5g, 10g, 15g, and 20g weights and look for improved patterns in swing path, face angle at contact and launch angle.  The Achiever has one terrific report that shows all that on one page with the average deviation numbers.  I have literally sold hundreds of customers counterweights.  They stay installed.  I have taken out two or three sets of counterweights and an occasional one with a driver.  I'm not saying it's 'pure science' because I slip in a little swing advice - most players don't know what they ought to be trying to do." So Leith's approach is organized trial and error, augmented by a lesson while he fits.
  • How about negative backweight?  Since the helpfulness of backweight varies from golfer to golfer, it is reasonable to ask if some golfers need negative backweight -- that is, less weight in the butt of the club. It would be a huge coincidence if only positive backweights help, given that the best weight varies markedly, and many golfers are not helped at all (at least if we believe Jeff Summitt's testing). And indeed, apparently there are a lot of golfers who prefer a negative backweight. How do we know? Winn grips makes a lot of money selling lightweight grips, maybe 10-25 grams lighter than normal. But that is exactly the opposite of adding 10-25 grams of backweighting.
  • The TaylorMade Bubble -- In fact, negative backweighting predates the popularity of backweighting by several years. When TaylorMade came out with their Bubble shaft in the mid-1990s, there was a lot of mystery and "magic" about what it did. Those clubfitters who did their homework figured it out fairly quickly, and it was both simple and surprising. By far the biggest difference the Bubble shaft introduced was the ability to add a very light grip. Very light! In fact, it was 30-35 grams lighter than a standard grip. This suited a large number of golfers, and the clubs were popular for years. And their unique feature is a negative backweight of 30-35 grams. (Note that a positive 30-35 grams is the very high end of conventional backweighting.)
  • The Heavy Club -- Steve Boccieri of Boccieri Golf pioneered a club named the Heavy Putter in 2004. He came up with a putter head that was by far the heaviest on the market, then countered the extremely head-heavy feel with a huge backweight (over 200 grams). Since then, he has concluded that the same approach (albeit less extreme) works for full-swing clubs, too. His company now makes the Heavy Driver, Heavy Wedges, Heavy Irons, etc. He goes with a heavier head (to make the golfer hit with the body rather than the hands) and a slightly shorter overall length of club, then counters the extremely head-heavy feel with a much bigger backweight than you would expect from a typical Balance Certified fitting. For instance, the Heavy Driver has a standard backweight of 50 grams. The trick in all the Boccieri clubs is to add enough backweight so the balance point of the club is actually significantly higher than the balance point of a "normal" club of the same designation. For instance, the modern driver has a balance point of about 12", while the Heavy Driver's balance point is closer to 15".

Total weight

Total weight is yet another measure of heft. That it can make a difference is undeniable. In fact, Tom Wishon has said in many places over the years that total weight has a substantial effect on distance. In particular, reducing total weight increases distance. I have been a skeptic for a long time. Here's why:
  • Tom is completely committed to the importance of MOI as opposed to swingweight. I also believe that MOI is fundamental, and swingweight is not -- and I went to some pains to make the case for that belief earlier in this chapter. So let's just assume for this argument that MOI matters and swingweight does not.
  • The only ways to make a large difference in overall weight are the shaft weight (e.g.- ultralight graphite to standard-weight steel), or backweighting (see above).
  • Changing the shaft weight also affects the MOI of the club, so it has other effects besides just changing the total weight.
  • Changing the grip weight or adding butt weight does not affect the MOI, so only the total weight is affected. But, as we saw above, butt weight has no effect on clubhead speed by itself. It may have an effect for some golfers, but that is a feel issue that causes the golfer to change his swing.
This suggests that it matters how and where you reduce the total weight of the club. For instance, you can make major changes in the total weight of the club by backweighting, with no predictable change in distance. In Tom's classic book on clubfitting,  he makes it clear that he is talking about total weight based on the shaft material. Since he also believes in MOI as an important factor, I would have thought he might agree that the MOI reduction may indeed be as important as the total weight reduction. But no; he maintains that total weight can increase distance even at the same MOI.

To try to make some quantitative sense of this, I turned once again to our "virtual robot", Max Dupilka's SwingPerfect program. As usual for studies of this type, I tried a bunch of things before I found a way to look at the data so it told me something interesting. Here's that look:

What's different
about this club?
Head
weight
Shaft
weight
Total weight
(compared to
base club)
Clubhead
speed
Base club
210
90
0
105.1
Change total weight
using head weight alone
220
90
+10
103.5
200
90
-10
106.6
Change total weight
using shaft weight alone
210
120
+30
103.1
210
60
-30
107.1
Change both head and
shaft weight, to keep the
same MOI
200
120
+20
104.6
220
60
-20
105.4
  • All clubs were 45" drivers, with 52g grips, 0.83 COR, and all other parameters the defaults of the program.
  • The time interval used by the program was reduced from the usual 5 milliseconds to a half a millisecond, the minimum the program supports. This gave much more consistent results, given the small differences in clubhead speed we're looking at.
This data is not very conclusive. Yes, the 30g clubs (shaft weight) had the biggest clubhead speed changes. But the 10g clubs (head weight) had changes almost as large, and both were substantially bigger changes than the 20g clubs (constant MOI). What's really happening here?

One thing we ignored in these runs is the fact that distance is a function of ball speed, not clubhead speed. Yes, clubhead speed is a major factor of ball speed, but it's not the only factor. Clubhead weight also matters; a heavier head will provide a little more ball speed. Since we are looking at small changes in ball speed for not-so-small changes in clubhead weight, we ought to factor this in.

Let's take another look at the data, with a couple of changes:
  1. We'll include ball speed.
  2. We'll sort the rows in order of total weight.
What's different
about this club?
Head
weight
Shaft
weight
Total weight
(compared to
base club)
Clubhead
speed
Ball
speed
Shaft weight alone 210
60
-30
107.1
160.8
Constant MOI 220
60
-20
105.4
159.5
Head weight alone 200
90
-10
106.6
158.6
Base club
210
90
0
105.1
157.8
Head weight alone
220
90
+10
103.5
156.6
Constant MOI
200
120
+20
104.6
155.6
Shaft weight alone
210
120
+30
103.1
154.8

And here it is plotted as a graph.

This shows very clearly that Wishon is right
. While the clubhead speed jumps around as we vary total weight, the ball speed progresses smoothly, almost proportionally. In fact, it is nearly a straight line, with a slope of 1mph of ball speed for every 10 grams of weight saved.

As an example of what is possible, look at the two yellow rows of the chart. Each has the same MOI (the same basic heft feel) as the base club. But one is 40g lighter than the other, and gives 4mph more ball speed. That translates into six to ten extra yards of distance. No, it's not going to turn you into a "big hitter". But it's a pretty sizeable increase, among those things that just club design can do.

Of course, there are practical limits to how much you can do by reducing total weight. Here are some of the more important considerations.

1.
Most of this section has been devoted to the importance of MOI as the fundamental clubfitting measure of heft. So we mustn't change the MOI away from a proper fit, while we're trying to get the club lighter.

The basic equation for MOI shows how to manage this. Each gram of change in head weight is worth three grams of change in shaft weight. So, if we go to a shaft that is 30 grams lighter, we need to add 10 grams to the head to preserve the same MOI. (That explains the numbers in the yellow rows of the chart.) So we can't put the full impact of a lighter shaft into total weight; we have to be satisfied with 2/3 of it.

2.
John Ford, president of The Golf Institute in Naples, FL, has probably built clubs for more golfers than any clubmaker I know, from PGA Tour pros to senior beginners. His take on total weight is that many golfers need a lighter weight just to deal with lower strength or fatigue. Golfers with low fitness, especially seniors, find themselves "swinging tired" toward the end of a round. John feels that graphite shafts -- in other words, lower total weight -- may stave off this fatigue and allow the golfer to finish the round reasonably fresh.

3.
On the other side of the coin, the golfer may require a heavier overall club -- not just a higher MOI or swingweight -- to regulate his swing. I don't know how usual this is, but I am certainly one of those golfers. Up until very recently, I used irons with steel shafts. Every year or so, I built an experimental graphite-shafted iron to see if I'm old enough to need the lighter weight. Every time I did, I found that my irons are not as reliable; the good hits flew longer and higher with graphite, but I had too many "yips" where I released the club too early and got a big pull. Since irons are about dependable distance, not maximum distance, this is unacceptable.

The last time I did this (in 2009 at age 68), I kept adding weight to the clubhead and trying again, until the MOI was considerably more than that of my steel-shafted irons. At that point, I was getting pretty reliable impact and a bit more distance than my steel shafted irons. So I have finally made the transition to graphite. But it took a long time, and it still is not for everybody. Younger, stronger players are probably better off using the extra weight of steel to regulate their irons.



Last modified March 17, 2011