Shaft flex and CPM

Wondering why shaft manufacturer do not use CPM as the indicator of the shaft flex rather than just L-ladies/R-regular/SR-stiff regular/Stiff or Xstiff. We all know that everytime we get our driver or irons fitted, the club fitter measures our club head speed and than tell us the CPM of the shaft that suits us. Thus it seems that the CPM of a shaft is the most accurate indicator.

Recently, I did a test on the accuracy of a branded high end shaft (costing more than $500.00 each)
the specs says that base on my club head speed of 85-90mph, I should choose a Regular which is equivalent toapproximately a CPM of around 235. So I borrowed from a shaft distributor, 1 regular and 1 Stiff regular and get it measured for CPM by a reputable club fitter . The result is as follows;

Regular one -- CPM 218
Stiff regular one-- CPM 219

Both CPM indicates the flex as ladies flex. So if I were to just bought the shaft thinking that the regular one is just right for me, I will not be getting the right results had I fit it to my driver.

So question is, how much can we trust the flex indicated on the shaft by the manufacturer? If a high end shaft can deviate so much from actual, those cheaper shaft will deviate even more.

Those experts out there could shed some light on this issue and correct me if I am wrong.

thanks.

I believe there is no standard even for CPM.
who's to say CPM of 220 is regular or stiff?

Also how is the CPM measured? What shaft length, clamp length, head weight, etc? e.g. most clubfitters who use a golfsmith/auditor system use a 5" clamp length. But I think the Fujikura analyzers have a 1 or 2" longer clamp length that would give a slightly higher cpm reading.

Also since you measured the CPM with a butt clamp, it does not really take into account the shaft construction/characteristics. The shaft designer can have different kick pt/flex profile designed; different graphite weave/wrap pattern so that the butt cpm might be soft, but the shaft might play "stiff" ???

My 2 rupiah worth.. take with a pinch of salt.
I leave all my clubfitting to the pros these days; your clubfitter should be able to advise you what shaft suits your game...

There are too many characteristics to worry about besides the cpm. That is why trackman is invented. If a shaft that is ladies flex gives the most distance, accuracy, best trajectory etc i'll use it.

The club fitter who did the measurement to determine the suitability of the shaft for me base on my swing data. So he certainly knows what he is doing. Of course the best is to buy the shaft from the club fitter and get him to recommend base on one's swing data right. But point is if one were to buy the shaft separately base on it's specs indicated by the manufacturer, I find the deviations too big in this case.

Then again, i wouldn't just spend 400 on a shaft based on specs. Get what i mean? If it is not suitable then what next? Sell for 300 or less? But you are right in that sense that the rating r or s etc doesnt really mean a thing

Shaft CPM was established by a group of clubfitters in the now defunct PCS (Professional Clubmakers Society). they basically matched the oscillation of the shaft at a given length on a load to represent the club head. the movement of the shaft on a clamped butt as they have established represent the flex of the shaft. this was used by PCS, PGA Tour and many other association as the standard in determining flex.

however there is no standard frequency machine that this associations recommend...be it Auditor, Mitchell or even the manufacturers. the length of the butt grip also varies but the default standard establish by the PCS stands at a 5 inch grip at the butt. that has not changed.

the other thing that has varying reading is torque reading. if you use a 3 pound load or a 7 pound load to establish the torque (sideway twist) of the shaft, they will give you a different reading. i have asked different manufacturers about this and they have all given me different answers on the load that they use.

let me try and explain what is the right flex based on the PCS theory of flex. if you take your driver and flex the shaft, you will notice that there is a natural tendency for the shaft to flex away and return to the original position of the shaft. every shaft flex will have a different tension and the degree of tension can be measured using CPM. What the PCS did was establish a standard CPM reading that represents the flex of a shaft in a consistent and measurable manner. for example if you have a 45 inch wood shaft (total length from head to grip) fitted with a 200 g load, 208 represents LL flex, 218 represents L flex, 228 cpm represents A flex, 238 represents R flex, 248 represents S flex, 258 represents XS flex and so on.

if there is any interest in how kickpoint works (shaft characteristic), i will be most happy to share this.

contrary to SS observation, there is a standard in flex. but it all depends on the manufacturer and their detailing to flex. if you fit a good aftermarket shaft for example, the CPM they state are usually 99% accurate when fitted on a 200g load and at 45 inch.

DGman

Lots of interesting information posted above but as we are merely amateur players, why worry so much?

every club will feel different so as good players, lets just adjust ourselves to different characteristics of each club

DGman, thanks for the detailed explanation.
That's why I leave my clubfitting work to you and your team!

the objective of the discussion is whether it is better to have cpm or flex as indicator for types of shaft. It is not whether we should care or not care about it as some says.

As what DGman had said, there is no standard in measuring cpm as well. That would translate it back to the same problem again wouldn't it?

general golfing public would not understand cpm.

The swing speed / shaft flex matrix is a more 'simpler' guide

The R and S are more simple guides for general public (most have printed guides for which flex is suited according to swing speed) . if you see 235, 237, 239, 243, 246 cpm etc readings on the drivers, the public will be blur which one to choose. Its get more complicated when u start using cpm for 3 wood, 5 wood......

ppl already (including myself) dont understand the full effects of torque, kick point..throw in trimming the tip, shaft length, swing weight as customization ..... i know the theory but have not tested enough shaft to appreciate the difference.

R, S are simple to understand but every company has their own definition... so maybe for brand A a R flex will feels more like a S flex for brand B...

It is because the flex rating of different manufacturer is different, don't you think between the 2, cpm is the more accurate indicator?

like car owners there are some who wants to know the HP, torque, gear ratio, etc....then there are those who just want to 12 km per litre and those who want to drive a car from point a to point b.

whatever the case, you decide what you want to know and if you are those who buy based on feel, make sure you buy the demo driver.

for the golf specs enthusiast, CPM is a good indicator of flex but it will not tell you about torque or kickpoint.

DGman

I was also quite obsessed with CPM for a while, until i realized that it's most useful for narrowing down your choices, and not the single most important factor when choosing a shaft. Ultimately, you still have to try the shaft to see if you like it. There are other factors to consider besides what's already mentioned above, such as FEEL and weight (which affects swing weight obviously).

Some comments about your original post though.. i assume you're talking the Cobra Speed drivers? Coz that's the only one i know of that markets itself as matching a certain swing speed. If so, they come with Aldila/Cobra shafts, which are not exactly high end.

Even if i guessed wrongly, as long as the shaft comes stock with the driver (assuming no custom upgrades), it can be from a super high end company, but don't expect it to be even close to the original, especially if it's a Taylormade driver (hope i don't offend TM fans). For example the aldila voodoo or diamana blueboard that comes with titleist drivers.. severely watered-down versions. The only company i know of that consistently provides full versions of brand name shafts as a stock option is Adams.

Now if you're saying that you bought a high-end aftermarket shaft, and it says R with 218CPM, then there's something seriously wrong.

The test was done using 2 shafts from a high end shaft manufacturer and not stock shaft. Just the raw shaft was measured using standard length/head weight etc. As I mentioned in my original post
it was done by a reputable club fitter in Singapore. So he knows what he is testing on and for. You may be right that there is something seriously wrong with the shaft tested. But 2 shafts from the same manufacturer is quite shocking to me. In the Japanese market, those shaft are selling at US$400.00 each.

Out of curiosity, I intentionally choose this expensive product to test how precise they are in specs. High end products should have very low deviation from stated specs right?

My post was to share what I have found out from the test and not to claim which is right or wrong.

Ok i just re-read your original post, and realized that i misunderstood. Thought you meant that the specs of the driver were based on your swing speed, but actually you meant the specs of the shaft.

Well yeah, assuming the tests were all done properly, then i do agree that there's something wrong with the shafts. These are the kind of readings you expect to get from stock shafts, especially japanese specs, but not from expensive high end shafts.

First time i'm hearing of this about aftermarket shafts btw.. mind sharing what shafts they are?