How does a carbon faced driver get hotter with use?

[Jc0]

4 hours ago, Nixhex524 said:

Cracks would be easily identifiable by the player I would imagine. It's not hard to hear a difference or even notice an inconsistent ball flight.  Especially with how many balls these guys hit on a given day, I would find it the rarity that a crack is the issue that a tour pro would not notice. Super easy to test for at any time, too.   I get why people are arguing sides here but I think we need to stop pretending that the thinner, hotter face is not the issue with these failed tests.  It has to be the majority of the reason the heads fall out of conformity and are taken out of play.  

 

Also, with the access these guys have to technology these days, are we to believe that they don't notice consistently higher ball speed numbers on their quad or trackman during practice?  I know the idea is to protect the player, but are we to believe that they really don't notice something is off?  

 

These aren't falling by 3-5%, they're failing by like .1%. They're maybe getting a yard of extra distance, not some noticeable jump. 

[dubbelbogey]

Similar, recent thread over in the Club Tech forum. See the post I made there with a link about a study out of Penn State on how this effect is seen in baseball bats (with similar carbon-fiber layup construction): https://forums.golfwrx.com/topic/2052421-question-about-non-conforming-drivers/?do=findComment&comment=25854151

 

[Nixhex524]

39 minutes ago, grm24 said:

In a not subtle way you're accusing tour players of knowingly cheating. Peak WRX.

 

If a driver becomes non-conforming due to CT creep it doesn't magically gain 25 yards.

 

When Xanders driver in 2019 at the Open Championship was deemed non-conforming Chip Brewer of Callaway stated in an article then the difference of the legal CT low/high range (237-259) was around one yard. Others have posted elsewhere it's less than that. 

 

EDIT: IBT the inevitable lock.

 

Just posing a question.  We've seen players try and gain advantages, I was just wondering if there are any signs as to when a driver starts to show a little improvement due to face thinning that a player might notice.  

 

 

[grm24]

4 minutes ago, Nixhex524 said:

 

Just posing a question.  We've seen players try and gain advantages, I was just wondering if there are any signs as to when a driver starts to show a little improvement due to face thinning that a player might notice.  

 

 

Uh-huh

[Nixhex524]

32 minutes ago, dubbelbogey said:

Similar, recent thread over in the Club Tech forum. See the post I made there with a link about a study out of Penn State on how this effect is seen in baseball bats (with similar carbon-fiber layup construction): https://forums.golfwrx.com/topic/2052421-question-about-non-conforming-drivers/?do=findComment&comment=25854151

 

 

So if a baseball can gain 3-5 mph of BBS, are we assuming a driver with a hotter face isn't seeing that kind of improvement?  That would surely equate to more than a yard of performance, no?

[dubbelbogey]

2 minutes ago, Nixhex524 said:

 

So if a baseball can gain 3-5 mph of BBS, are we assuming a driver with a hotter face isn't seeing that kind of improvement?  That would surely equate to more than a yard of performance, no?

 

It really depends on by how much the driver face has exceeded the CT limit (or, by inference, how many balls have been hit since the limit threshold was passed.) Presumably, this effect continues to increase up to some point where the matrix breaks down completely and the effect diminishes or even reverses. 

 

We should probably make a conservative assumption that any driver on Tour found to be non-conforming does so by only a minute amount (i.e. it was caught "early"), so any performance gains seen in those particular drivers would likely be small.

 

For a club that does not get tested (e.g. that one that you or I might own and play), seems possible that it could go a good bit farther and possibly see a larger gain.

 

 

[Nixhex524]

2 minutes ago, dubbelbogey said:

 

It really depends on by how much the driver face has exceeded the CT limit (or, by inference, how many balls have been hit since the limit threshold was passed.) Presumably, this effect continues to increase up to some point where the matrix breaks down completely and the effect diminishes or even reverses. 

 

We should probably make a conservative assumption that any driver on Tour found to be non-conforming does so by only a minute amount (i.e. it was caught "early"), so any performance gains seen in those particular drivers would likely be small.

 

For a club that does not get tested (e.g. that one that you or I might own and play), seems possible that it could go a good bit farther and possibly see a larger gain.

 

 

 

Thanks, and yes that makes sense.  And kind of where I was going with this.  We are assuming these heads are tested on the regular when they may not be.  I thought that article earlier stated they were tested as it was a USGA event, whereas the PGA Tour isnt testing regularly,  and only 30 drivers where done?  Unless I read that wrong.  At some point they will get caught and pulled but I would imagine these heads are getting played past tolerances that are conforming with as many balls as these guys hit.  Some to minute improvements but some may be well past and into a more noticeable gain range.  I just don't think it should trigger anyone here that much to think a little bit past what we are being told if we have studies showing composite material can actually show a significant gain if gone unchecked before it starts to fall off.  I would venture a guess to say that if anyone noticed a loss of 5 yards or say 3 mph of ball speed, there would be questions and the head would be checked.

 

That study is very interesting and I think can show us the possibilities of what can happen over time.  Thanks for posting!

[Socrates]

1 hour ago, Shallowface said:

I reviewed my earlier post.  

 

I admitted to not being aware of the ongoing process of driver testing on the Tour.  A process characterized by some major publications as "random" and "secretive."  Their words, not mine.

 

And I stated that the USGA has no authority over the PGA Tour.  Nothing false about that.

 

I'm not promoting anything.  But nice try.  You scored three hearts.  Well done. 

I also reviewed your post.  Seems you have an issue with the USGA and their role with the PGA Tour.

[cardoustie]

13 hours ago, Jc0 said:

 

Are you on a which hunt? All brands fail. The same thing happen to Xander at the British open like a year or two ago. 

 

All driver's get hotter over time until they fail. Carbon fiber has a bit more flexibility so the odds of it failing the test are probably higher because it's less prime to cracking. Where a metal faced driver would have already cracked a carbon fiber driver will continue to work. 

 

Also these are failing by like .001. It's not like they are getting 5-10 yards extra distance out of them. 

I am certainly not on a witch hunt, I’m trying to discuss equipment on a golf forum.  I thought I was asking an interesting question as I hadn’t seen a list by player or by brand.   I’m brand agnostic

[phizzy30]

7 hours ago, Jc0 said:

 

These aren't falling by 3-5%, they're failing by like .1%. They're maybe getting a yard of extra distance, not some noticeable jump. 

One of the commentators was talking about the Rory incident and said that there's only like a 4 yard difference between conforming and non-conforming.  

[RickyBubbs]

Here’s the real question: Why isn’t this thread locked? It’s already a dumpster fire. We have too many about these evil, nasty, non-confirming drivers and that sad fact that only because of Rory are people now understanding that when you bang two objects together s**t happens. 

[Josh H]

Trottie discusses

 

May be of interest and relevant here, discussion from Trottie starts at 10:40 in. 

[Stuart_G]

1 hour ago, Josh H said:

Trottie discusses

 

May be of interest and relevant here, discussion from Trottie starts at 10:40 in. 

 

Thanks all the same, but 10 seconds was all it took for me to realize there would be nothing of interest in it for me.  Listening to the random rantings of the uninformed is just not something I'm into - at least not sober :-)  But to each their own.

Edited May 25 by Stuart_G

[King_Slender]

21 hours ago, Socrates said:

Completely false.  Just because you have a theory, doesn't mean it is close to right. 

 

The pros actually get heads that are below the threshold of conformity.  They don't want anything to fail and heads are hand picked to make sure they are well below the CT levels.  The heads are not made any differently than a production head other than they are tested to make sure of their COR and CT numbers.  They check other parameter, but those are the key ones.  Every Tour player knows that eventually their head will crack or break or become illegal due to the high number of balls they hit and speed at which they generate.

 

Why don't a lot of pros play off the shelf golf balls? 

[Shallowface]

13 hours ago, Socrates said:

I also reviewed your post.  Seems you have an issue with the USGA and their role with the PGA Tour.

The only role they have is that which they are granted.  No different than you or I when we don't play stroke and distance for a lost ball or pick up a two footer.

 

The PGA Tour says they play by the rules of the USGA.  However, most people seem to believe there is some legally binding relationship there.  There isn't.  The Tour chooses to play by those rules.  If they wanted to, they could do something else.

 

That is why in my opinion there will ultimately be no rollback to the golf ball.  If the USGA proposed a significant rollback, I believe the PGA Tour would choose to ignore it because they like their product as it is.  The golfing public and the manufacturers would follow the PGA Tour because no recreational players want to hit it shorter and no manufacturer wants to make gear inferior to its current products.  The PGA of America seems to be opposed to it as well.

 

And if all that were to happen the USGA couldn't do a single thing about it.  And they know that. So they will do nothing and like it in an effort to keep the small scrap of relevance they still have. 

 

If you are so inclined read "In The Rough.  The Business Game of Golf" by David Hueber, who worked for the Tour, the NGF and ran the Hogan Company for a time.  Near the end of the book he wrote a chapter on this subject.  When I read it I thought I could have written it because it echoed much of what I believe on the subject of golf equipment and how the USGA has become, his word, a "eunuch" and how it got to that point.          

Edited May 25 by Shallowface

[Josh H]

1 hour ago, Stuart_G said:

 

Thanks all the same, but 10 seconds was all it took for me to realize there would be nothing of interest in it for me.  Listening to the random rantings of the uninformed is just not something I'm into - at least not sober :-)  But to each their own.

Fair enough. I'd not personally consider trottie uninformed on the subject of TM drivers failing USGA testing, he worked for years as a tour fitter/club builder for TM prior to being based at the kingdom and provided some insight into their process, reserve driver selection etc.

 

But nothing scientifically specific as to how a carbon face gets hotter as they wear in. 

 

 

[Shallowface]

1 hour ago, King_Slender said:

 

Why don't a lot of pros play off the shelf golf balls? 

https://golf.com/news/secretive-nature-driver-testing-questions/?srsltid=AfmBOooYg7bLMzI7tKZNlfOojcgRXa23mn703MI6xoh3dSsXdclXmMTo

 

This article is about the recent driver controversy, but it makes the excellent point that for multiple reasons the Tour should want to avoid any appearance that the product it presents is any less than 100 percent in conformity with the rules by which it claims to abide.

 

Unless at some point it chooses to write its own rules, which it has every right to do.

Edited May 25 by Shallowface

[Red4282]

Asked my little friend chatgpt:

 

 

Titanium Driver Faces

 

 

You’re right: titanium driver faces can become slightly “hotter” over time — though it’s more accurate to say they lose structural stiffness from repeated high-speed impacts. This can cause a slight increase in the trampoline effect (CT or COR), though eventually it can become nonconforming or even crack. This is because titanium is a metal, and under repeated stress it can fatigue, thin, and subtly deform, increasing rebound.

 

 

Carbon Fiber Faces

 

 

Carbon fiber driver faces, like those used by TaylorMade (e.g., Stealth series), behave very differently:

 

• Carbon fiber is not metal — it’s a composite made of carbon strands embedded in resin.
• It does not deform plastically like metal, so it doesn’t stretch or thin under repeated impact in the same way.
• The resin matrix can degrade over time or under extreme conditions (heat, UV, moisture), but not in a way that typically makes it “hotter.” 

 

Bonus Insight

 

 

Most modern “carbon face” drivers (e.g., Stealth) still include titanium or aluminum reinforcement behind the carbon face. That structure may still have fatigue properties, but the carbon surface itself isn’t going to stretch like titanium.

 

If a carbon-faced driver suddenly fails a CT test, here are the most likely reasons:

 

 

 

 

✅ 1.

Face/Structure Deformation Behind the Carbon

 

 

Even though the outer face is carbon, the support structure behind it (frame or backing) is often made of titanium, aluminum, or another metal. Over time:

 

• Repeated high-speed impacts (especially with faster players or frequent use) can cause slight deformation of that metal frame.
• This leads to increased flexibility or trampoline effect — even though the carbon itself hasn’t changed.

 

 

Key point: It’s not the carbon getting “hotter,” it’s the structural backing flexing more than it did originally.

 

 

 

 

✅ 2.

Manufacturing Tolerances Close to the Limit

 

 

Most OEMs build drivers to push right up to the legal limit (CT = 239 µs ± test tolerance).

 

• A new club might be just inside the legal range, but repeated impacts can nudge it just over.
• Carbon-faced heads (like the TaylorMade Stealth series) are built very close to this line to optimize ball speed.

 

 

Over time, normal use can push the club just past the CT threshold, especially if it was already near the edge.

 

 

 

 

✅ 3.

Micro-Cracks or Bonding Degradation

 

 

Carbon fiber is extremely strong in tension but can be susceptible to:

 

• Micro-cracks in the resin matrix.
• Delamination or breakdown of the bond between layers or where the carbon face meets the frame.

 

 

These issues can increase flexibility or trampoline effect subtly, just enough to cause CT failure.

 

[Stuart_G]

 

7 minutes ago, Red4282 said:

Asked my little friend chatgpt:

 

Got to love all the inconsistencies and contradictions in those answers.

[Red4282]

3 minutes ago, Stuart_G said:

 

 

Got to love all the inconsistencies and contradictions in those answers.

Well to be fair, not everything I copy and pasted made it over. But from what it sounds like it doesnt take much to put it over the line, micro cracks in resin or flexing of framework. The carbon itself doesnt really flex (apparently)

[grm24]

2 hours ago, King_Slender said:

 

Why don't a lot of pros play off the shelf golf balls? 

Every ball tour pro's use are listed on the USGA/R&A conforming ball list. They aren't using non-conforming balls as you are implying. Keep on thinking tour players are cheating using non-conforming equipment. It's humorous.

[gvogel]

On 5/24/2025 at 8:52 AM, iNeedMoreGolf said:

The ball bites the face on every impact. Everyone knows this. Carbon face feels softer then steel face so its easier for ball to bite. Each bite makes face thinner and adds 15 yards duh. Problem solved.

That would explain why I play worse with cheap balls - they don't bite as much.

[King_Slender]

52 minutes ago, grm24 said:

Every ball tour pro's use are listed on the USGA/R&A conforming ball list. They aren't using non-conforming balls as you are implying. Keep on thinking tour players are cheating using non-conforming equipment. It's humorous.

 

Did I say they were non-conforming?

 

No.

 

But many of them aren't sold to the public. 

[grm24]

19 minutes ago, King_Slender said:

 

Did I say they were non-conforming?

 

No.

 

But many of them aren't sold to the public. 

Doesn't matter if they are sold to the public as long as they are legal by the ROG. Which they are. All matter of golf gear isn't sold to the public. It's nothing new. Your laughable complaints won't change anything. Enjoy your day. 

[gvogel]

3 hours ago, Shallowface said:

The only role they have is that which they are granted.  No different than you or I when we don't play stroke and distance for a lost ball or pick up a two footer.

 

The PGA Tour says they play by the rules of the USGA.  However, most people seem to believe there is some legally binding relationship there.  There isn't.  The Tour chooses to play by those rules.  If they wanted to, they could do something else.

 

That is why in my opinion there will ultimately be no rollback to the golf ball.  If the USGA proposed a significant rollback, I believe the PGA Tour would choose to ignore it because they like their product as it is.  The golfing public and the manufacturers would follow the PGA Tour because no recreational players want to hit it shorter and no manufacturer wants to make gear inferior to its current products.  The PGA of America seems to be opposed to it as well.

 

And if all that were to happen the USGA couldn't do a single thing about it.  And they know that. So they will do nothing and like it in an effort to keep the small scrap of relevance they still have. 

 

If you are so inclined read "In The Rough.  The Business Game of Golf" by David Hueber, who worked for the Tour, the NGF and ran the Hogan Company for a time.  Near the end of the book he wrote a chapter on this subject.  When I read it I thought I could have written it because it echoed much of what I believe on the subject of golf equipment and how the USGA has become, his word, a "eunuch" and how it got to that point.          

YEsterday Matti Schmid drove a 385 yard green.  There are more Matti Scmnids coming along.  The PGA Tour realizes that it is getting very difficult for their tournament sites to find more yardage to increase hole lengths.  They won't say so publicly because they know the importance of young strong players, like guys on this site, who want to drive the ball like Rory or Bryson, and who spend money on equipment and other means to do so.  But behind closed doors they realize the efforts to roll back equipment are important for the long term sustainability of the game.

 

Games need rules.  The USGA has been providing that framework for a long time.  We might disagree over some of their recent decisions, but the PGA Tour finds it convenient to play by USGA rules.  I don't see that changing in 2028.

[Socrates]

4 hours ago, King_Slender said:

 

Why don't a lot of pros play off the shelf golf balls? 

They are all playing a golf ball that at one point was off the shelf.  There are a few that are playing a ball from prior years, but every ball they are playing was tested and on a conforming list.  Now, some are harder to come by, but they are generally available if you look for them.  The Tour players have tons of data to look at and they might find that a Left Dash ProV1X from 2019 works better for them.  Most don't care and are just playing whatever the ball company is making that year and giving to them.  For the most part they make a decision based on what part of their game they value the most and deal with the other part of it.

 

[hammergolf]

13 hours ago, phizzy30 said:

One of the commentators was talking about the Rory incident and said that there's only like a 4 yard difference between conforming and non-conforming.  

It’s the “random” testing that I have an issue with. Somehow Rory, Scottie, Xander and other top players always get their driver tested. Either test everyone in the field or test nobody.

[Stuart_G]

4 hours ago, Red4282 said:

Well to be fair, not everything I copy and pasted made it over. But from what it sounds like it doesnt take much to put it over the line, micro cracks in resin or flexing of framework. The carbon itself doesnt really flex (apparently)

 

The individual carbon fibers don't have have plastic deformation or act elastically in any way.  And they only are strong in tension, not compression.  The individual fibers can fracture which effects strength  e.g.say 1 out of 100 fibers might fracture as it breaks in which might effect the total strength.  That not a real number, just an illustration. 

 

But that's not the same as saying the composite material can't undergo plastic deformation or flex.  It wont be isotropic like metals when it comes to deformation - but it can happen on some dimensions.   And they certainly can flex.  Shafts are a carbon fiber composite and they flex quite a bit.

Edited May 25 by Stuart_G

[Socrates]

2 hours ago, hammergolf said:

It’s the “random” testing that I have an issue with. Somehow Rory, Scottie, Xander and other top players always get their driver tested. Either test everyone in the field or test nobody.

I'm sure it is a matter of logistics and time.  It might be a matter of getting more units to test with so that they could increase the number of tests.  Or there is an agreement that tests are only done during a certain window of time and only a certain number of players are available in this window.  Lots going on Mon-Wed.

[farmer]

Somewhere, I have a Callaway C4.  Anyone who would like to try to make it fail is welcome to try.