## Tuesday, May 1, 2012

### The “Spin” about Backspin with the Driver w/Tom Wishon

In Tom Wishon's updated eTech newsletter, I thought he had a great article on how golfers over-value spin rate and how to determine the best driver for you based upon certain launch conditions. You can learn more at www.wishongolf.com

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When we scan the various golf equipment forums on the internet to get a feel for topics of interest to golfers, we can’t help but notice a lot of questions asking what driver heads or what shafts will result a lower amount of backspin on a tee shot. It’s amazing to us to read that many golfers never seem to ask as much about the right launch angle or ball speed as much as they are focused about the spin rate numbers they generate with the driver.

From reading the questions and comments on several different forums about driver launch parameters, it is evident that most golfers do not properly understand the role or the cause of backspin as well as what is or is not the proper amount of backspin for their driver shots. The purpose of this article is simply to offer some of the pertinent facts from years of research about drivers, performance, and backspin.

Part 1 – Spin is not as important for distance as ball speed and launch angle

The most important launch parameters for maximizing distance with the driver are ball speed first, launch angle second and the amount of backspin third. If you don’t believe that, then get a copy of one of the golf industry’s competent ball flight modeling software programs and start running different combinations of launch angle and ball speed against spin numbers to see what happens. Here’s some basic numbers for an example golfer with a 100mph clubhead speed and level 0* angle of attack.

PLEASE NOTE that while the Carry distance does not change much from spin, the angle of descent of the shot will increase as spin increases, which will reduce the amount of roll on the ground to reduce the total distance. When launch angle remains the same, the effect of spin differences is pretty small on carry distance. Most golfers who have seen a greater distance loss from higher spin are not maintaining the same launch angle and/or ball speed as the spin changes. In short, if you get the right launch angle with the maximum ball speed your clubhead speed will allow, spin variations will have less effect on your distance.

Launch angle has a medium effect on carry distance per increment of change. Golfers who have seen greater changes in carry distance from different launch angles likely are not maintaining ball speed or spin while the launch angle is changed. Launch angle MUST be modified lower as fairway conditions get more firm and conducive to roll so as to maximize TOTAL distance.

Bottom line – spend more time nailing down the best launch angle for your clubhead speed plus your angle of attack with a driver that will also get you as close to a smash factor of 1.49 as possible. The goal is to have at least 1.47 smash factor driver that will generate the launch angle to give you the very best combination of carry + roll for your fairway conditions before you start worrying about backspin.

Part 2 – How much can you trust the spin measurement in the first place?

From what we have seen there are only four systems available that produce accurate enough spin numbers to make fitting and equipment evaluations. They are Trackman, Flightscope, Vector and GC2. If another system is used they will rely on more algorithms to determine spin rates. The more algorithms that are used, the greater the error will be. Also, if you are hitting driving range balls, your spin numbers from a launch monitor are not likely to be representative of what they will be when you play with normal play ball. Being over concerned about spin numbers that come from range balls can lead you in the wrong direction. If you do have the capability to use the ball that you regularly play with, it is recommended for proper driver fitting. But as we will see further down the page, spin rate is primarily a function of how the clubhead is delivered to impact. As most golfers don’t have regular access to a system that accurately determines spin rate, it’s important that we learn to observe the ball flight shape and trajectory to determine if there really is a spin problem that needs to be addressed.

Part 3 – Analyze the ball flight shape more than the number off the launch monitor

The first step in determining if you have a spin problem is not to look at the launch monitor spin number but instead to watch the flight of the shot. You must learn to VISUALLY IDENTIFY the difference between a shot that has spin problems and a shot that does not.

If you see the flight of the ball taking off on a steadily rising, boring/penetrating type of trajectory, followed by a similar and gradual drop of the ball on a flatter angle to the ground – you do not have a spin problem regardless what the spin number from the launch monitor number is saying. On the other hand, if your typical drive ramps up steeply to its apex, hangs there for a little bit and then drops more steeply to the ground with very little roll, then you are likely looking at a ball flight that very likely is flying with too much spin.

The key point is not to obsess about the spin numbers from a launch monitor, but to learn to analyze the ball flight to see if it may be flying with too much spin or not. It is OK to hit the driver on a higher trajectory as long as the shape of the trajectory from start to finish is more boring, more penetrating, on more of a gradual and consistent angle up and down. It is also possible to see a flight that is NOT indicative of too much spin as much as a case of too high of a launch angle because the golfer could be playing with too much loft for his swing speed and/or angle of attack. When you see the ball climb and drop too steeply always be sure to check whether your launch angle is optimal rather than to assume you have a spin problem.

If your ball flight shape is decent, if your launch angle and ball speed numbers are decent for your clubhead speed and angle of attack but the launch monitor spin numbers are high, forget about the spin numbers and just go play golf.

Environmental conditions also will significantly affect the performance of the ball down range. We’ve all seen the ball climb when there is wind in our face and excessive spin will only cause the ball to rise higher faster and result in less distance. So the optimal numbers for launch and spin (we’ll assume that ball speed is a constant for what an individual’s swing produces) will change depending on if we have wind in our face, wind at our back or calm conditions. Note that wind in the face has a greater detrimental effect than the benefit of wind at our back. So if we would lose 20 yards off the tee with some wind in our face, that same velocity at our back will result in maybe half of that. And very high wind at our back will push the ball down, lower the spin as it flies thru the air and can result in less distance.

Additionally, the firmness of the fairways has a lot to do with total distance. When playing on hard and fast fairways, we want the lowest launch angle to achieve about the same carry distance that will result in the ball coming into contact with the turf at a shallow angle. This is called the “angle of descent” and is what we use to predict how much the ball-will run out after contacting the ground. Conversely, if we are playing on soft fairways that will not result in much roll, we are looking to maximize carry distance.

Part 4 – What is my optimum launch angle and spin rate for my clubhead speed and my angle of attack?

The ideal combination of launch angle and backspin on a driver changes for different combinations of clubhead speed AND angle of attack into the ball. Many golfers are well aware of their launch angle but make a BIG mistake when they pay no attention to their angle of attack.

The lower the golfer’s clubhead speed and the more downward their angle of attack, the higher the launch angle and the higher the amount of backspin must be to fully optimize the golfer’s driver distance. This is because a lower clubhead speed with de-lofted face from the downward angle of attack means a lower ball speed with lower launch to begin with – that combines to dictate the need for a higher launch angle with more spin to keep the ball in the air long enough to turn that ball speed into the most distance possible.

Conversely, the higher the clubhead speed and more upward the golfer’s angle of attack, the lower the launch angle and lower the spin must be to optimize the golfer’s driving distance. A higher clubhead speed generates a higher ball speed. The upward angle of attack enhances the launch angle to get the ball up. The higher ball speed keeps the in the air so less spin is needed to add to that to maximize distance.

Fredrik Tuxen, the inventor of the TrackMan™ launch monitor, has spent a lot of time researching this subject. From analyzing literally tens of thousands of shots hit by many different golfers using his TrackMan launch monitor, Fredrik has created a chart of information showing optimum driver launch parameters for TOTAL distance (carry + roll). Remember, TrackMan has created a separate chart for optimal launch numbers for CARRY distance only – not to be confused with this one following which takes optimum carry + roll into account for clubhead speeds from 75-120mph and angles of attack from -5° downward to +5° upward.

The information in these charts represents the very latest and most technically accurate answers for what the launch angle and spin should be for a wide range of clubhead speed and angles of attack. Remember, this information is for TOTAL DRIVING DISTANCE of carry + roll.

Golfers must understand the HUGE effect that the angle of attack has on the optimum amount of backspin with a driver. The more downward the golfer’s angle of attack, the HIGHER THE SPIN MUST BE to optimize the shot for maximum total distance. In other words, if you have a downward angle of attack, you do not want your spin to be less than 3,000 rpm or else you are going to sacrifice even more distance.

The most common swing problem that causes a downward angle of attack is an over-the-top move to start the downswing that results in an outside-in swing path. Plain and simple, if the golfer makes this swing error, there is NO clubhead, NO shaft and no golf club that will change the fact that he will generate more backspin. The golfer will have to use a higher loft driver and live with more backspin to optimize his driving and will be giving up a lot of potential distance for his swing speed.

****NOTE**** The situation does exist where a downward angle of attack DOES NOT result in a lower launch angle and the same is true for an upward angle of attack. The loft of the face at impact can be independently manipulated from angle of attack by the position of the wrists at impact. For the right handed golfer a broken down left wrist will add loft. If you see a downward angle of attack that results in a launch angle greater than the loft of the club, then this is what is occurring. If you see an upward angle of attack with a launch angle that is lower than the loft of the club, this indicates that the left wrist is bowed.

Part 5 – When is low spin good, and when is higher spin good?

Few golfers realize that low spin with the driver is only good if you have BOTH a high clubhead speed and a very upward angle of attack. TrackMan’s charts show optimal total distance launch measurements for 5mph increments of each clubhead speed from 75mph to 120mph for -5° downward, Level and +5° upward angles of attack into the ball. Please realize that a +5° upward angle of attack is VERY RARE. Few golfers get their angle of attack to be that much upward.

On the other hand, a downward angle of attack approaching -5° is not uncommon – especially among golfers who swing over the top with an outside in swing path, meaning most golfers who slice the ball.

To find the optimal launch numbers from the TrackMan™ Total Distance chart for angles of attack in between +5° to -5°, you simply have to do a little math extrapolation.

If you take only a few minutes to study the optimum launch numbers for each clubhead speed and angle of attack, the important common sense points are. . . .

• Low spin is only good as clubhead speed increases and angle of attack is level to upward.

• Higher spin is absolutely necessary as clubhead speed decreases and angle of attack becomes downward

• Hitting the driver with less than 2500 rpm of backspin, which has so often been written in magazine articles as “the ideal driver spin rate” is ONLY good if you have a level to upward angle of attack with a clubhead speed approaching 100mph and higher.

• The higher the ball speed the more sensitive the flight will be to spin rate changes. At slower swing speeds, greater changes in spin rate are necessary to affect the flight of the ball.

Part 6 – If you do have a spin problem how do you correct it?

OK, let’s say the visual inspection of the ball flight and reliable spin numbers off the launch monitor both indicate the golfer hits the ball with more spin than is optimal for their swing speed and angle of attack. What can you do about it to get that ball flight to flatten out more and make your ball speed work more forward rather than more upward?

Swing Mistakes that Bring About Too Much Backspin for the Golfer’s Swing Speed

Unfortunately, when a golfer really does have a spin problem with the driver, 9 times out of 10 it is not because of the driver but because of the swing motion and how the head arrives at impact. In short, the equipment can only do a little bit to solve a spin problem with the driver. If the golfer has any of the following higher spin inducing swing mistakes, they most definitely are going to need to work on the swing to have the most effect on solving the spin problem.

• Over the Top, Outside In Swing Path Causing Downward Angle of Attack

• Early Release Causing Higher Dynamic Loft as the Clubhead Passes the Hands Before Impact – Same Effect can come from Ball Position Being too far Forward

• Weight Left on the Back Foot or Spine Tilted Back at Impact, which also Causes Higher Dynamic Loft at Impact

From an equipment standpoint, and speaking truthfully in the face of several myths, your options are somewhat limited for equipment changes that can make much of a difference on driver spin.

• A lower loft on the driver head most definitely is the NUMBER ONE place to look to reduce spin, flatten out the trajectory and lower the angle of descent of your drives. For a 100mph clubhead speed golfer, a 1° decrease in driver loft will typically drop the launch angle by 0.9° and lower the backspin by 260 rpm. As clubhead speed is lower, the launch angle change remains the same at 0.9° per degree of loft change, but the spin difference is lower per degree of loft change as clubhead speed drops. Conversely as clubhead speed is higher, the launch angle change is still constant at 0.9° per degree of loft change while the backspin change increases. However, the “double edge sword” with a loft change to reduce spin is that you never want to lower the loft so much that the launch angle is way below what is optimal for your clubhead speed and angle of attack. If you do that, you definitely can sacrifice distance. In the end, it is better to achieve the optimal launch angle for each golfer’s clubhead speed and angle of attack than to sacrifice the launch angle to achieve the optimal spin rate. Always remember to think about the fairway landing conditions. Dry, firm ground and shorter grass means you should lower the loft to give up some carry distance to gain more roll on the ground for more total distance. Moist ground and longer, lush turf means you pick the loft that generates the greatest carry distance since there will be no real contribution of roll under these fairway conditions.

• Changing to a shaft that is stiffer overall or which has a much stiffer tip section can also lower the launch angle and put a little less spin on the shot. However, such a shaft change has two big limitations involved. First, few golfers can hit the ball as well with a driver that has a shaft that is too stiff or too tip stiff for a golfer’s swing speed + transition, tempo, and release. If the golfer uses a much stiffer shaft to lower the spin, but the shaft now is too stiff for the golfer, that defeats the purpose of trying to hit the ball with a lower spin rate. Once again, it is better in the long run to play the proper shaft flex and bend profile for the golfer’s swing speed + transition, tempo, and release and live with the higher spin than it is to use a shaft that is too stiff for the golfer in an effort to lower the spin. Second, the shaft only works to change launch angle and spin for golfers who have a later to very late unhinging of the wrist-cock angle on the downswing. Therefore, if the golfer has an early to midway release, it is a total waste to try to use a different shaft flex or different shaft bend profile to affect a change in spin. For these golfers, changing loft is the most effective way to change launch angle and spin.

• A sure way to change spin is to intentionally hit the ball above or below the vertical position of the CG in the clubhead. Hitting the ball ½” above the CG will definitely lower the spin while hitting the ball just below the CG on the lower part of the face will increase the spin. This is because of a factor called “vertical gear effect” that occurs when the clubhead twists very slightly about a horizontal axis through the CG in response to the impact occurring either slightly above or slightly below the plane of the CG. If you need to lower spin, hitting the ball in the upper third of the face will do that for ALL golfers, regardless of how they swing the club.

• Modern ball design most definitely has created ball options that allow golfers to decrease or increase the amount of spin on the shot. Again though, these ball design differences are moderate and are most definitely predicated by the golfer’s clubhead speed. For example, controlled robot hit testing at 100mph clubhead speed shows a 400 rpm difference between a Titleist ProV1 and ProV1x. At slower speeds, the rpm difference will be less, and greater at higher swing speeds.

3JACK