Why We Judge A Fitting By Keep Rate, Not By The Best Swing Of The Day

A golfer came in last spring holding a printout from a big-box demo day, proud of a single 178 mile-an-hour ball speed off the launch monitor screen. It was real. It also told me almost nothing, because it was the best of maybe forty swings taken over an afternoon with no record of the other thirty-nine. A round of golf does not give you your best swing forty times. It gives you your ordinary swing, over and over, with the good one showing up on maybe one drive in eight.

This is the entire reason keep rate exists as a number on our spec cards. It is not exotic. It is the median ball speed across a fourteen-swing census, measured against the best strike in that same group, expressed as a percentage. A golfer keeping 96 percent of his peak is playing something close to one club. A golfer keeping 84 percent is playing two different golfers depending on which swing shows up, and no amount of fitting the peak will fix that.

Fourteen Swings, Not Three

The number of swings matters more than people expect. Three swings will occasionally agree with each other by accident and produce a keep rate that looks tidy and means nothing. By swing eight or nine a real pattern is usually visible, and by fourteen we have enough data that a single mishit does not distort the median the way it would in a smaller sample.

Face tape goes on for every swing, not just the ones that look interesting. That is deliberate. Golfers are notoriously bad at remembering their own misses accurately, and a fitter who only reviews the shots that felt wrong is quietly editing the dataset before it has even been recorded.

What Keep Rate Actually Predicts

Peak speed predicts one thing: what happens on the shot you already know you can hit, under conditions that let you hit it. Keep rate predicts something closer to a scorecard, because it describes the whole distribution rather than the top of it.

Two golfers can share an identical peak number and post entirely different rounds. The one with the tighter keep rate is the one whose bad days are still playable.

We have watched this play out on the bench dozens of times. A shaft profile change that moves the median 1.1 miles per hour and the worst strike in the group 5.9 miles per hour barely registers on a peak-speed leaderboard. It is, in our experience, the single biggest predictor of whether a fitting actually changes a scorecard.

Where Peak Speed Still Matters

None of this makes peak speed useless. It sets an upper bound — the physical ceiling of what a given head, shaft, and swing combination can produce — and a very low ceiling is worth knowing about. But a fitting that optimises the ceiling while ignoring the floor has optimised for a shot you produce roughly twice a round, and left the other twelve exactly where they were.

Reading Your Own Keep Rate Without Instruments

You do not need a launch monitor to get a rough sense of your own pattern. Hit fourteen balls with the same club on the range, note the distance of each one honestly, and look at the gap between your longest shot and the one sitting in the middle of the group once you sort them. A tight gap means your equipment is probably not the limiting factor. A wide gap is worth bringing to a sitting, because it usually has a specific, fixable cause.

Rough keep rate bands, from what we see across a season on this floor

Keep rate	What it usually means
Above 95%	Equipment is rarely the limiting factor; look at technique instead
88% to 95%	Typical of a competent amateur; length and shaft weight are the first levers
Below 88%	Real speed sitting on the table, almost always recoverable on the bench

The number we write on your card is specific to the build we settled on, and it is directly comparable the next time you come in. When a golfer returns three seasons later, that single figure tells us within minutes whether the club has stopped suiting him or whether something in his delivery has changed.