Adjusting rating/slope for a tee box change

larrybud · March 4

The USGA has the following procedure when a temporary change of a tee box is made:

https://www.usga.org/content/usga/home-page/handicapping/roh/Content/rules/Appendix G Golf Course Course Rating Slope Rating.htm

But I don't understand why there is a separate chart for 18 hole course and 9 hole course, and when to use each.

Let's say the front 9 of a course is rated at 36.0/120 and a tee box on hole #5 is moved up 100 yards. Now let's say I'm playing only 9 holes (the front 9). Do I use the 18 hole chart, or the 9 hole chart to make the adjustment?

It doesn't make sense that there's a difference in the two charts. In this example, the 18 hole chart has a reduction of 0.5/1, and the 9 hole chart has a reduction of 0.5/2. The two charts also have different yardage ranges that they use. The 18 hole chart has no adjustment for < 100 yards, while the 9 hole chart goes down to 50 yards.

Why the difference? If a tee box is moved up 100 yards, it seems like the adjustment should be the same whether it's a 9 hole course or 18 hole course.

Edited March 4 by larrybud

Newby · March 4

Given that the major factor in CR is primarily length, a reduction in the CR for 1 hole in 18 should be proportionate to 1 hole in 9.

larrybud · March 4

Not following what you're saying or what your answer to the questions I posed are.

If I'm only playing 9 holes, should I use the 9 hole chart or the 18 hole chart?

DaveLeeNC · March 4

Look at this example. A course has a front 9 rated at 36/140 and the back 9 is rated the same. So a player goes out and shoots a 82. But some temporary tee changes on the front side creates a 5 point reduction in the slope. So that 82 (41/41 scores) gets a differential of 8.37 instead of 8.07 (which is what he would get with a slope of 140). I am ignoring roundoff to avoid that confusion. The difference here is 0.3.

Another player goes out and only plays (and posts) the front 9. He also shoots a 41. If we apply the same slope reduction as for the 18 hole case, his front 9 differential will be 4.18 instead of 4.03 and his posted differential for 18 holes will be only 0.15 higher because of the slope change instead of 0.3 as it the 18 hole case. Note that in the new procedure for 9 hole scores, the adjustment made to turn a 9 hole differential into an 18 hole differential is unaffected by the 9 hole score.

This occurs because the slope calculation is applied to a larger number in the 18 hole case vs. the 9 hole case, so that is accounted for in the procedure that was quoted.

dave

Edited March 4 by DaveLeeNC

Newby · March 5

13 hours ago, larrybud said:

Not following what you're saying or what your answer to the questions I posed are.

If I'm only playing 9 holes, should I use the 9 hole chart or the 18 hole chart?

9 hole for the 9 you are playing

davep043 · March 5

I'd just like to point everyone to some of the narrative in the rules which discuss temporary changes:

Quote

The Handicap Committee must notify the Authorized Association when temporary changes are being made to the golf course that may affect the Course Rating. The Authorized Association will determine whether scores made under such conditions are acceptable for handicap purposes, and whether the Course Rating and Slope Rating should be modified temporarily.

Where a temporary Course Rating and Slope Rating has been issued, this information must be made available to players prior to the commencement of their round.

For an 18-hole golf course:

If approved by the Authorized Association, the issuance of a temporary Course Rating and Slope Rating is determined by the Handicap Committee and/or the Authorized Association following the procedure set out below:

If your course has temporary changes, you should really work through the Committee to get a temporary re-rating done.

On 3/4/2024 at 10:22 AM, larrybud said:

It doesn't make sense that there's a difference in the two charts. In this example, the 18 hole chart has a reduction of 0.5/1, and the 9 hole chart has a reduction of 0.5/2. The two charts also have different yardage ranges that they use. The 18 hole chart has no adjustment for < 100 yards, while the 9 hole chart goes down to 50 yards.

Why the difference? If a tee box is moved up 100 yards, it seems like the adjustment should be the same whether it's a 9 hole course or 18 hole course.

The difference is in the way CR and Slope are calculated. For an 18-hole course, the CR is the SUM of the CR for the front and the CR for the back. The Slope is generally the AVERAGE of the front and back numbers. So if you make a change that changes the CR and Slope by 0.5/2 for that 9, the change to the 18-hole combination is 0.5/1.

larrybud · March 23

I do see how the ratings change is, well, KIND OF the same between the two charts. Not sure why there should be any discrepancy between them. e.g. there's no adjustment for 9 holes if a tee is moved up 160 yards (because it's beyond the limit of the chart) but if I move up on the same hole when playing 18 holes that is "allowed" by the chart.

It completely slipped my mind about the slope being averaged between front/back. I know better!