How much weight to significantly change MOI in a driver?

[teddyironboy]

I don't know very much about the subject. Can the MOI be changed much? Is it possible to add weight in a way to increase MOI without increasing spin too much? Could MOI be increased too much to where it passes the USGA limit?

 

Just thinking to build a driver with the accuracy maxed out, without losing too much distance. Like use an already high MOI driver (but not exactly game improvement - G425 max? Kind of loud for me though. PXG?), cut it down a few inches, add weight to get it back to a normal swingweight, and then more on top of that. And also use a shaft that's really light while also being really stiff to allow for more weight to be in the head for the same swingweight.

[Valtiel]

To a certain extent there will always be a trade off. The higher the MOI of a driver head, the less spin reduction you'll get from slightly high strikes and the greater possibility for increased dynamic loft at impact (this relates to CG location and its relationship to shaft deflection). Regarding the legal MOI limits, you would be pretty hard pressed to make your driver "illegal" this way. The G400 MAX, G425 MAX, and the PXG 8011 Gen2 XF are the closest to the legal limit, and you'd need to add a healthy amount of weight all the way back in the head to potentially bump up against or exceed the legal limit, because the clubs are naturally going to have a bit of a buffer to allow for weight related fitting adjustments before the club becomes illegal. I wouldn't worry about that. 

In terms of building the most forgiving setup, you're on track for the most part. High MOI head, shorter playing length (within reason based on your swing), and additional head weight back (again within reason) are all good moves for that type of build. Just as important though is how it feels and how you swing it, so don't be afraid to experiment with weight. Also consider that all the additional headweight you're likely to add will impact shaft feel and performance, so extra tipping should be considered depending on what type of shaft you want to use and what feel you prefer (looser vs tighter). 

[teddyironboy]

Thanks for the info!

 

I wonder if it is an equal give or take? Like adding weight to the front will decrease spin, but since it's overall more heavy, the MOI goes up too. Dreams of having a medium to low spin driver with minimal face twisting/gear effect. Although this kind of stuff genius engineers probably have already optimized better than someone like me could ever figure out haha.

Edited August 15, 2021 by teddyironboy

[Valtiel]

29 minutes ago, teddyironboy said:

Thanks for the info!

 

I wonder if it is an equal give or take? Like adding weight to the front will decrease spin, but since it's overall more heavy, the MOI goes up too. Dreams of having a medium to low spin driver with minimal face twisting/gear effect. Although this kind of stuff genius engineers probably have already optimized better than someone like me could ever figure out haha.

You're welcome! It sounds like you may be confusing a couple different versions of MOI though, or maybe have a misunderstanding of how head MOI works. Head MOI is measured in grams per centimeter squared and tells us how much the head will resist the twisting forces created by off center strikes. The more weight you move back and away from the face, the higher the MOI of the head. Therefore, the reason moving weight forward lowers spin is also because it lowers MOI, which lowers the head's resistance to twisting and therefore increases the effects of mishits. Mishits above the sweet spot that will naturally cut spin will now cut more, and this is what low spin heads that utilize low MOI (SLDR, M1/M3/M5 (forward weight positions) and many other older "low spin" driver models) count on for spin reduction. The drawback being obvious; all other mishits will be worse as a result of the lower MOI, including low strikes which will now spin up much more as well, ironically making a low MOI/low spin driver head extremely high spin for anyone with a low face miss. 

This is one of the reasons an objectively perfect driver doesn't and really can't exist, and only a few combinations of characteristics can be considered objectively better than another for a certain person. What that optimum set of characteristics is will depend on things like your path, AoA, dynamic/delivered loft, typical strike locations (good and bad), and subjective preferences in aesthetics, face angle, size/shape, and sound/feel. You can still find the perfect match without knowing all these things, but more info is better for this type of thing usually, especially when you fall in love with all the subjective stuff but need to figure out why the performance may be lacking. 

Based on what you said in your initial post, I think your idea about adding weight forward might still he worth experimenting with despite the misunderstanding about MOI. Starting with an extremely forgiving driver head like the 400/425 MAX, decreasing the rear weight a bit and adding tons of weight forward can kill several birds with one stone. It lowers spin because it also brings the CG down as well as forward, but not so much that the head becomes too unforgiving. You could take a stock G400 MAX for example, shorten it to something like 44", and have 10g of hotmelt added to the front of the head and it still be well above average in terms of forgiveness. The sound would also be very muted because of the hot melt, which sounds like something you might enjoy if the stock PINGs are too loud, and you still have the swappable weight if you need to fine tune the head. The same goes for the 425 model of course!

[Stuart_G]

13 hours ago, teddyironboy said:

I don't know very much about the subject. Can the MOI be changed much? Is it possible to add weight in a way to increase MOI without increasing spin too much? Could MOI be increased too much to where it passes the USGA limit?

 

Just thinking to build a driver with the accuracy maxed out, without losing too much distance. Like use an already high MOI driver (but not exactly game improvement - G425 max? Kind of loud for me though. PXG?), cut it down a few inches, add weight to get it back to a normal swingweight, and then more on top of that. And also use a shaft that's really light while also being really stiff to allow for more weight to be in the head for the same swingweight.

 

It's really a moot question.  The shorter playing length (to maintain a reasonable swing weight when adding weight) is going to have WAY more of an effect on your swing, the face impact, and ball flight results than anything you could do to the MOI of the head.   The question of what that effect might be can only be answered by testing out the idea.

 

As far as reaching the USGA limit, with some of the highest MOI drivers, if you go short enough, it's possible but unlikely.

 

 

1 hour ago, Valtiel said:

Head MOI is measured in grams per centimeter squared

 

Sorry, just a little nit-pick.   It's "grams centimeter squared".   No 'per'.   (grams times squared centimeters, not grams divided by squared centimeters).

 

Edited August 15, 2021 by Stuart_G

[Valtiel]

5 minutes ago, Stuart_G said:

 

It's really a moot question.  The shorter playing length (to maintain a reasonable swing weight when adding weight) is going to have WAY more of an effect on your swing, the face impact, and ball flight results than anything you could do to the MOI of the head.   The question of what that effect might be can only be answered by testing out the idea.

 

As far as reaching the USGA limit, with some of the highest MOI drivers, if you go short enough, it's possible but unlikely.

 

 

 

Sorry, just a little nit-pick.   It's "grams centimeter squared".   No 'per'.   (grams times squared centimeters, not grams divided by squared centimeters).

 

Hah thanks. That's frustrating because I wrote it that way to begin with, then googled to make sure I had it right since i'm not familiar with the actual math and quoted the Golf.com article which uses the "for". 😅

[teddyironboy]

What if you had a driver with all the weight forward, but it was super heavy like 2000g? Just a hypothetical. Would the spin rate be low, but also resist face twisting because of the sheer amount of weight on the club?

[Stuart_G]

1 hour ago, teddyironboy said:

What if you had a driver with all the weight forward, but it was super heavy like 2000g? Just a hypothetical. Would the spin rate be low, but also resist face twisting because of the sheer amount of weight on the club?

 

Low spin heads are low spin because of low c.g. (not forward) and low MOI (resistance to twisting on off center hits).  Both result in an increase in gear effect which is what reduces the spin.    But gear effect is also determined by how far back the c.g. is.   If all the weight was moved forward, there would be no gear effect - just like there is no gear effect in irons.   So no spin reduction and it would no longer be a low spin head.

 

Also, doesn't really matter where the weight is, adding weight always increases the MOI - so that much weight would increase the MOI and reduce the twisting (about the horizontal axis) - which is another way in which it would theoretically prevent the head from reducing the spin.   How it might effect the twisting about the vertical axis (left/right gear effect spin) would depend on where the weight was with respect to heel/toe placement.

[teddyironboy]

Think I got it now. Thanks guys 😊