Shaft flex is definitely a factor for distance. If you swing 95-105 you will need a stiff but if you swing 85-95 you will need a regular. Any higher than 107 I would suggest an Xstiff.

There is no industry standard rating for flex on a golf shaft.  One company's Stiff is another's Regular or X-stiff.  The same shaft with different tipping, length, or club head weight will affect the frequency of the club.  Soft stepping and/or hard stepping of the shaft can also be performed to tune in the playing characteristics.

There is also no correlative rule between swing speed and required flex/frequency of shaft to be played.  A high swing speed player who is smooth in transition (loading) may be perfectly comfortable with a "softer" flex shaft than a slower swinger who heavily loads the shaft.

Lastly, stiffness of the shaft's tip, butt section, etc. have a tremendous impact on how the shaft plays as well as the way it feels to the player.  Torque of the shaft will also affect the "feel."

The most important thing to do is to find a good professional who will fit you into the proper shaft/head combination to achieve the results you need.  Whether that be distance, dispersion/accuracy, spin, etc.

I hate to be this person, but that's a rather general statement.  While the flex is a definite factor in distance and control, the swing speed to stiffness relationship varies by manufacturer.  Additionally, the weight of the shaft must also be considered when matching swing speed to stiffness.

For instance, I use the UST Proforce V2 shaft in my woods and hybrids.  The specs for those shafts are as follows:

56 gram shaft:

Regular Flex   -   80-95 MPH

Stiff Flex           -   90-105 PMH 

66 gram shaft:

Regular Flex   -   83-98 MPH

Stiff Flex           -   93-108 PMH 

76 gram shaft:

Regular Flex   -   85-100 MPH

Stiff Flex           -   95-110 MPH

im a 5 handicapper who have been all over the place with my driver....trying different shafts, stiff and x stiff, my swing is 103-105 mph but just couldnt control any driver....was messing about on the range one day with some i-mix heads and shafts and tried an old ft-iz tour head with a senior flex project x (4.5),  yes senior flex...normally project x is the worst shaft you can give me but this combo is ridiculous good for my swing....i now hit most fairways and im soo confident every time ill step on the tee....always thought i would be hooking the living dayligts out of it but no....this is the one for me..its abomb, its straight and dont care if it says a flex on my shaft even though im 6.5 tall and only in my mid thirties.

.conclusion: i reckon if you have a smooth transition with an early release youll benefit from a lot softer flex as you'll struggle to load the shaft when its stiff (unfortunately it dosnt show on any monitor). my advise would be dont be afraid to try out a soft flex if you are struggling with hitting it straight...all above is just numbers.

I came on here for advice on purchasing a new driver/shaft.  I have been playing golf since I was ten and am only 5'5" tall. Over the years my worst club has been my driver. Dead nuts one shot huge slice the next. I was using a TM driver with a stiff shaft because I have a club head speed of 110 +.  I hated it. I have all the shots but couldn't get off the tee most holes. I then borrowed a g2  reg shaft from a buddy and Have been playing with it for 2 years. Hitting 75% of FIR.  But it's an older club and I want some new technology. I have titleist 910f 19.5, 906 15', for my woods. I want to grab a 910 or 913 in a 9.5 degree but still can't figure out what shaft will match up well with my small smooth swing?

Since my last post my setup has changed.  My two cents is that golf is a feel thing.  It is true that a shaft marked "stiff" may not feel stiff or one marked "A flex" may not be whippy.

I still have the same driver (TM Burner 2007 HT draw M flex) but shortened it to 44.5".    M flex is TM's a flex.  The best thing I ever did was go to a lofted draw driver and I can swing smoother with the a flex shaft. 

I replaced my TM 5 and 7 woods with a 910F 19*.     The shaft is Bassara A flex but I have it shortened to 41" and the Surefit setting is A3.  I actually get a much lower trajectory vs the 7 wood and hit it around 190 with a conservative swing (I'm capable of over 200 yards if I get into it).

My 910H 27* and my AP1 irons are all regular flex.

The SM4 52 and 60 are wedge flex (S200).

I've tried an Amp driver with an a flex shaft and I had the worst time trying to hit it.  It was also 46"

I have a rather heavy persimmon 10 wood with a steel TT Lite XL regular shaft (it has a midsize Golf Pride Tour Wrap to tame the swingweight) and I can knock it pretty stiff.  About 175 yards with a 28.5 degree fairway wood - I actually out hit my 910H 21* hybrid with it.

According to the guy at the Titleist fitting center there is no correlation between swing speed and shaft stiffness. It depends on how and when you load the shaft in the swing. You have to hit balls with different shafts and see what you stats are on ball speed, launch angle and spin rate and dispersion. Trial and error is the only way.  

I somewhat disagree. While those numbers are a good guideline, stiffness is based mostly on personal feel and your ability to control a shaft, ie. dispersion. It is true that if you go too stiff you may lose distance, but if you can control a regular flex then there is no reason to change. good luck!

I would say if you are happy with your ball flight and feel, don't change the shaft flex. Shaft flex does have an influence on distance and ball flight. If the shaft is TOO flexible, you would lose distance due to too high of a ball flight Sometimes with a stiff shaft vs regular you gain direction control but may lose yardage on distance (more noticeable on woods). You may notice hitting a high fade with too flexible of a shaft if you swing too fast. You can also hook it if too flexible or slice if too stiff. There are also some stiff shafts that actually feel close to a regular. One that comes to mind is a Proforce ATR (stiff with soft tip) - my dad gave me a X Speed driver and two Titleist 975F (16.5 and 20.5). They went dead straight but had a bit high of a ball flight and I could barely hit 220 with the driver (I got about 200 out of the 4 wood and 180 out of the 7 wood on a good hit but often ballooned). I gained 20 yards on my drives by going to a G2 with Grafalloy Pro Launch Blue (although it was a bit of a fade) and I got a lower ball flight by putting DG R300 on the fairways. My current driver and 5 wood are Burner with senior flex (because they are both shorter than stock, it may be closer to regular). From the 7W down to the 9 iron are regular flex and the wedges are S200. I hit everything straight with the trajectory I want. I can hit a stiff or X flex club. Don't really notice a difference in feel with the short irons but it becomes more prevalent as you go to the longer clubs.

If you are getting the distance and trajectory (shape of the ball flight in relation to the surface of the earth) that you want, you do not need to change anything. With regards to the flex of the shaft affecting distance the answer is yes, it is a factor, one of several, that add to your overall performance in executing your swing through the ball. But only one of several factors. 

Swing speed is an indicator of shaft stiffness requirements. But at one time, shaft whippiness was the rage. So everyone wanted what is now considered excessive flex in their shaft to gain distance. Now most pros are stiff to xtra stiff. And most pros look like athletes since Tiger arrived on the scene. These guys generate all the power they need and use the stiffer shaft for controlling that power and keeping the ball in the fairway, or at least trying to.

Hi David,

I agree with you. If you switched to a shaft with too much flex you would lose yardage for the reason you stated. If, however, as another poster wrote, if you are only getting a moderate amount of whip and can benefit from the additional spring, you will gain yardage.

I hit a shaft with regular flex, but the more I practice the more I see myself reaching for a stiffer shaft.

Thanks for writng,

David

I believe that the shaft has everything to do with distance. I was recently fitted for a driver and with a shaft fitted to my game i gained easily 15 -20 yards. I recommend that you go to a professional fitter and get fit for the correct shaft. It will improve your golf game majorly.  Best of luck.