What is Golf Club Bounce? Technical Director Jeff Summitt Explains
Bounce angle is a term generally associated with wedges, but any golf club can have a bounce angle. Besides the golf shaft, bounce angle may be the next most misunderstood concept of a golf club design. Part of this lies in the definition. I have seen many places where the writer defines the bounce as:(Old definition) The measurement of the number of degrees from where the club rests on the ground and the club’s leading edge.While the definition above may have been true in the past, it is technically not correct anymore. Before I explain why, let us lead you gradually in this discussion by examining the anatomy of the sole.
First, there are four factors that go hand-in-hand in understanding this design parameter of a golf club; sole radius (if at all), sole width, leading edge height and contact point on the sole.If you look at a barrel of old irons, there will be two things you will notice about the sole of a golf club: they were very narrow and they were flat (or almost). Going through my collection of clubs, even game improvement irons as late as the end of the 1990s exhibited relatively narrow soles (0.75” wide or less) and very little radius compared to custom golf clubs offered today. Take one of these clubs and place it on a table with the shaft being perpendicular to the ground. A toe view of the club should look something like the following diagram.
Looking at the anatomy of the sole, there are a couple important terms to know. The outermost dimensions of the sole are the leading edge (positioned at the bottom of the face) and the trailing edge (positioned along the back edge of the head). The distance between the leading and trailing edges is the sole width. Note that the trailing edge of the sole may be tapered, so the sole width may vary along its’ length. Most manufacturers will reference the center point of the sole for this dimension. It is also important to realize that few irons are perfectly flat on the sole although it may look that way. In addition, head manufacturers will normally grind or radius the leading or trailing edge so that it is not a sharp point.
The next term to mention is the contact point or where the sole makes contact with the ground line when the hosel or shaft is perpendicular to the ground. In the diagram above, the contact point is in the center of the sole meaning that both the leading and trailing edges of the sole are parallel to the ground. If the sole were perfectly flat, then the contact point would be the entire sole width.
What happens when the contact point is not in the center of the sole? To start out the understanding of bounce let us use our example where the sole is perfectly flat, contact on the sole is not in the center and yet the hosel is perpendicular to the ground. In this case, there are only two possible positions that the sole can rest on; the leading and trailing edge of the sole.
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In the case where the contact point is on the leading edge, then the trailing edge with rest above the ground line. The sole angle relative to the ground line forms the bounce angle. In our example, a 0.75” wide sole has the trailing edge measuring 0.052” above the ground line, which creates a 4° sole angle pointed toward the ground. When this condition occurs, it is referred to as a negative bounce angle or also referred to as a “digger” sole. A digger sole does just that as it has a tendency to dig into the ground, which could be considered a negative design characteristic for any club designed to hit off of the ground.
Conversely, if the contact point is on the trailing edge, then the leading edge with rest above the ground line again forming a sole angle relative to the ground line. The bounce angle with a 0.75” wide sole with the leading edge measuring 0.052” above the ground line creates a 4° sole angle pointed upward from the ground. When this condition occurs, it is referred to as a positive bounce angle.
Why would a golf manufacturer design a golf club with bounce in the first place? It is important to understand at impact that the club may not return with the hosel perpendicular to the ball or that the golfer starts out with the club positioned as the manufacturer measures the loft of the club, but perhaps with a forward press. Whenever the ball is positioned on the ground, it may be necessary for the golfer to hit “down” on the ball in order to make solid contact and achieve getting the ball airborne and with increased back spin. For a further explanation why it is important to hit down on the ball, please reference the Angle of Attack article. To account for the downward angle of attack, manufacture’s needed to create some bounce into their designs in order to avoid the club from burying into the ground conditions.
Here is an example of the same flat-soled iron with a 4° bounce angle with the shaft parallel to the ground and next to it, the same club at impact with a 4° angle of attack. By creating the bounce leaving the leading edge above the ground at address, avoided the club from digging into the ground at impact. As the angle of attack matched the bounce angle, the contact point of the sole on the ground is in the center of the sole. If the angle of attack had been any less than 3°, then the trailing edge would have made contact with the ground, thus the ball would make contact on the face closer to the leading edge of the face. However, if the golfer struck the ball with an angle of attack greater than 5°, then the leading edge would have made contact with the ground first.
Luckily manufacturers have done away with flat soles as the margin for error is small. The modern iron looks more like the following diagram and as you can see has a sole radius from front to back with no well defined trailing and leading edges to reference. Sole radius accounts for variable angles of attack with minimal contact of the sole on the ground
Producing a radius on the sole, the clubs could conceivably make contact with the ground line at several different positions not possible with a flat sole. Examine the next diagram in regards to the sole radius and the contact point. With a flat soled club, contact made with the center of the sole touching created no bounce as the leading and trailing edges would be level with one another. Therefore on a radius soled club, 0° bounce occurs when the contact point is made in the center of the sole when the shaft is hosel is perpendicular to the ground. A positive bounce angle occurs when the leading edge is higher than the trailing edge. For this to occur with the shaft perpendicular to the ground, then the sole contact must be made rearward from the center of the sole. A negative sole angle occurs when the trailing edge is higher than the leading edge. Again, with the shaft perpendicular to the ground, the contact point on the must be forward of the center of the sole.
However, this is the very reason why the original definition does not apply anymore. For example, the contact point could be located in the very center of the sole. By the old definition, it was the angle created by the contact point and leading edge. When the sole was flat, this was true, but not with a radius sole. Look at the following diagram to see the reason why. As mentioned before, if the contact point is in the center of the sole on a club with a radius, then there is 0° bounce therefore this drawing doesn’t accurately depict what sole bounce really is.
(Correct definition) The measurement of the number of degrees between the clubs’s leading and trailing edges in relationship to the ground line when the club is in the square position and with the hosel perpendicular to the ground.
This leads us to the next part of the discussion to understand how bounce is made / measured on a club with a radius sole. In order to produce a radius, there first needs to be a circle. For example, let’s say the circle on the right has a diameter of 4” so the radius of the circle is half of that or 2”. The radius of the sole can only be as wide as the sole itself. Scaling to the diagram, the sole radius will be 1.25” (as indicated by the solid red line), which is extremely wide, but selected to better illustrate the basic idea.
Look at the two pie-shaped segments within the circle. At the base, each is one-half the width of the sole. Where they connect would be the contact point on the ground line which would be in the center of sole. Due to the radius of the arc, only one point along the circle can make contact with our ground line, therefore the outermost positions of the pie shaped pieces along the circumference of the circle will be higher than the ground line. These are labeled “leading edge” and “trailing edge”, which the red line depicting the “sole width” which is parallel to the ground line. Using our example with a 2” radius and a 1.25” wide sole width, the leading edge will be 0.1” above the ground line, yet the bounce is 0°.
A flat soled club with a 1.25” wide sole and 0° bounce, the leading and trailing edges would be on the ground. It is important to understand effect of sole width on the distance from the leading edge to the ground line. There is a faint dotted orange line above and parallel to the red line. If the sole width was 2”, then the leading trailing edges would be 0.268” above the ground. Contrarily, the shorter the sole width, the leading edge would not be as high given the same sole radius. The importance of this statement will come later.
Now that we have established the sole radius and sole width, the next thing is to select the degrees of bounce to create the leading edge height and contact point on the sole. To help understand this part, let’s take the two pie-shaped pieces and the solid red line out of the circle. In the diagram below it looks like we now have four tiny ships. The one on the furthest left is our original model from the diagram above. The second model is the same segment of the circle, but rotated 4° counterclockwise from the center of the circle so that leading edge is higher than the trailing edge. The dimension to the right of each segment is the dimension from the leading edge to the ground line. This would be considered positive bounce because the contact point is now located rearward of the center of the sole. Again, it is not the contact point that determines the bounce it is the difference between leading and trailing edges in relationship to the ground line.
The third model in the diagram shows when the segment of the circle is rotated 4° clockwise from the center of the circle so that trailing edge is higher than the leading edge. This creates a negative sole angle, but due to the radius, the leading edge is above the ground line (0.052”). The last model represents what happens more on a sand wedge where the bounce is much higher than typically the rest of the set (in this case 12°). The contact point is much closer to the trailing edge, which also raises the leading edge higher off of the ground. A situation where the leading edge is too high can lead to shots that can be bladed in certain situations.
As mentioned earlier, the narrower the sole, the less height the leading edge is above the ground line. By narrowing the sole from 1.25” to 0.781” (closer to a normal sole width), the leading edge lowers substantially with the same 2” sole radius. The model on the far right illustrates just how bounce itself does not tell the whole story. There is a term called effective bounce, which is the bounce measurement, along with the leading edge height and sole width. Even though the fourth model in the two diagrams have 12° bounce, the leading edge height is a little over 0.1” difference. While this may not seem that great, it can make a big difference in the playability from a tight lie versus a fluffy lie, with the former being better for tighter lies or firmer terrain.
In addition, sole radius plays a factor in how the leading edge can be up off of the ground. Let’s use the same 0.781” sole width as above, but increase the radius to 1.5” (remember the smaller the circle the more radius occurs). Incorporating a greater radius on the sole allows the leading edge to be higher off of the ground. Look at the difference between first two models in the two diagrams as both of these have 0° bounce. Where the difference really shows up is when the sole is rotated clockwise, the same as if the head was de-lofted due to a descending angle of attack, the leading edge is not as low to the ground and less likely to dig in. This is one of the reasons why normally you find more bounce on narrower soled clubs as often the sole has more radius than a wider sole model.
A prime example of this (although it does not exist in any head that I am aware of) is if the radius was very small (0.625” radius) and the width was extremely narrow (0.5” wide). Even if the club had 30° bounce, the leading edge would only be 0.25” above the ground line! Below is a quick guide to factors and how they affect leading edge height:
|More radius (think of a smaller circle)||=||The higher the leading edge will be off from the ground|
|Wider sole with the same radius||=||The higher the leading edge will be off from the ground|
|Greater degree of bounce||=||The higher the leading edge will be off from the ground|
|Ascending angle of attack||=||The higher the leading edge will be off from the ground|
|Less radius (think of a larger circle)||=||The lower the leading edge will be off from the ground|
|Narrower sole with the same radius||=||The lower the leading edge will be off from the ground|
|Lesser degree of bounce||=||The lower the leading edge will be off from the ground|
|Descending angle of attack||=||The lower the leading edge will be off from the ground|
To better illustrate the effect of sole width and radius on the bounce angle, examine the following chart. The chart represents two different width soles (0.781” and 1.25”) and three different sole radii (flat, 3” and 1.5”). Note: the leading edge has not been ground off in these cases leaving a sharp distinctive point of reference. In addition, these are not necessarily recommendations or fitting examples, rather more for the purpose of explaining their relationships.
The most common sand wedge bounce is 12° on a medium width sole (0.781”). Looking at the Leading Edge Height from the Ground Line chart, we can see that the distance to the leading edge would be 0.163”. The same leading edge height occurs with the flat sole and the one with the 1.5” radius. Remember we said before that the club may not end up in the exact same position? Let’s say a golfer was to use each of the clubs and had a 5° angle of attack. When the club returns to impact, now the leading edge has been lowered by the golfer. The underlined values at the 7° bounce (12° bounce minus the 5° angle of attack) show the new leading edge height. The head with the greater radius has the leading edge height higher than the other two heads with the same sole width (0.096” vs. 0.110”).
|Leading Edge Height from the Ground Line|
You might have noticed that most wide sole cavity back wedges do not have the same amount of bounce as a narrower blade-style model. To have the same effective bounce, less measured bounce is needed and here is the reason why. Let’s say we have a 1.25” wide sole wedge with a 3” radius. This will effective make the leading edge 1.81” above the ground. The same golfer with the 5° angle of attack will now return the club at impact with a leading edge height of 0.102” or the equivalent of the narrower sole clubs with greater bounce.
In an extreme example of where there is a very wide sole (1.25”) and has a high sole radius (1.5”) the manufacturer may select a bounce for the sand wedge may appear low on paper, for example 4°. This still leaves the leading edge height 0.183” above the ground. Even if the golfer returned the club with a 5° angle of attack, then effectively it has a negative 1° bounce. But due to the high radius sole, the leading edge will still be approximately 0.125” above the ground.
You might even see long irons with negative bounce as part of their specifications. Once considered that the head was inaccurately manufactured if the bounce was negative is no longer true. Often times the #1, 2 and even 3-irons are used off of a tee. Thus any time the ball is off the ground, then an upward or ascending angle of attack occurs which will add both loft and bounce to the club at impact. Even if clubs with negative bounce are hit of the ground with a level swing, the modern sole radius will prevent the chance of a “fat” shot as the leading edge will be above the ground line.
Most manufacturers do not provide bounce specifications other than for the wedges, perhaps for good reason as it can be quite confusing to the customer. Even if they did, sole radius and sole width specifications will not be included. So it is really up to the manufacturer to understand these relationships when designing a particular model to make it playable.
Very few times you see the exact same head, but in different bounce option from a fitting situation. The only time multiple bounce options are available occurs with only a few name brand manufacturers who will sell enough to make it a worthwhile investment in tooling. The two leaders in the wedge category (Cleveland and Titleist) offer some high bounce and even low bounce options for the different conditions and the golfer’s angle of attack. Otherwise it will require a skilled clubmaker to grind the sole or alter the loft to customize the effective bounce.
By reading this article, hopefully you have gained a better understanding and comprehension of what exactly the bounce angles mean and how the manufacturers derive at their final product. Bounce can be more complicated than this when you factor in any maladjusted lie angle, if the face is opened or closed or if the sole was produced with multiple radii or intricate grinds or bevels on the sole. However, the basics regarding sole width, leading edge height and contact point on the sole still apply.