Driving iron MOI

[hurley999s]

I just picked up an Auditor MOI speedmatch and started off with a couple of my favorite feeling irons (between 2805-2815), and I haven’t got to my driving iron yet, but I have a question about where it should fall. Hear me out...

After going through some other MOI threads it seems like the irons should be at the low point of the slope with woods (hybrids if you play them) and wedges all some amount higher.

My driver right now is 2902, but I’m not set on that exactly yet. I’ll have to try some differences with lead tape and weights over the winter, but let’s say 2900+.

So in theory if irons are the low point of the curve, should the driving iron be treated like a hybrid and be higher than irons, but not as high as driver/3W? I know feel trumps everything, but let’s assume all else equal that seems reasonable.

My question is, if the driving iron should be treated as heavier than irons, what exactly is the purpose of using a graphite shaft in them (which is lighter than steel)?

I was looking for posts about how people handle MOI in driving irons and couldn’t come up with anything and I just had this thought and was curious.

Do people have success with it same as irons? Same as hybrid (is higher)?, lower than irons?

Howard, Stuart - anyone else with any thoughts?

[Valtiel]

Lighter graphite would typically be used to achieve longer lengths without getting too heavy. You often see pros that bag two long iron replacements; one with their set iron shaft and the other with a heavier weight graphite shaft (or lighter weight steel). So one iron is treated more like the set and the other more like a hybrid. I would treat it like a slope and start at the lower end since it is easier to add weight than it is to remove it. @Howard Jones can comment further, but i'd use that as a starting point while trying not to get too hung up on the numbers themselves. If it feels wrong then it IS wrong for you.

[hurley999s]

Great advice @Valtiel - I think I’ll get my UDIs on the Auditor this weekend and see where they are currently. As it is, my one I had loaded up with lead tape before I even got deep into researching MOi so I’m curious where that one comes out. I’ll report back.

[Valtiel]

Please do, I should get myself one of those Auditor MOI machines for the amount of "trying to make things feel consistent" tweaking I do.

[hurley999s]

I love it so far. I figured since I’m now in to MOI, I might as well take the time to learn how to do it myself so I can go that route in the future with new sets. I think only one club builder around me does it, and for the convenience it beats shipping clubs out to get built to spec.

[jll62]

Do it. Life became so much better after I got mine.

To the OP - I struggled trying to figure out where my UDI fit when I was rebuilding the P790 UDI. In the end, I just grabbed the number from my original UDI and used that as the target since I hit it well. I don't remember the exact number, but it was between my irons and my 3w.

[Howard_Jones]

Im using about 50 MOI points higher on my driver, and a slope from irons via hybrids and woods to the driver.

100 points is IMO "a lot", but what ever works......we are all different, and ive seen those using 150 MOI points or more, so its more about finding what works for you, so dont use the scale itself, then we can do the same mistakes as with the SW scale, tracing values we dont know the effect of.

 

I posted a series of charts who might be handy when we deal with MOI builds. Here is the link to them, but i got many more...2900 on a driver sounds like a longer club than 45"https://forums.golfwrx.com/discussion/comment/19239053/#Comment_19239053

[MountainGoat]

I've used hundreds of pieces of scientific test equipment over my lifetime, the the Auditor is one of the trickiest. I'm not 100% convinced that it's actually measuring MOI, but it's all we've got, so I accept it for what it is. As much as I love the concept of MOI-matching, my experience is that clubs matched with a high degree of precision with the Auditor don't necessarily perform better.

Take several readings in a row, and you'll see that the device produces a range of results. You have to pay attention to the slope of those results (which isn't linear), pick a strategy for choosing a number, and stick with that strategy. I tend to take three readings and accept the third. I always test with the grip off, because I get better repeatability that way. The device is also sensitive to ambient temperature. It really needs to be recalibrated every time you use it.

As to the present question, the issue isn't head type (woods vs irons), it's shaft type and weight. When it comes to MOI, graphite and steel simply do not match up. If your driving iron is has a graphite shaft, I'd be inclined to match it up with other graphite-shafted woods. If it's steel shafted, I'd match it to steel-shafted irons. Finally, I agree with Howard -- a value above 2900 is really high and sounds like it comes from a long driver with a very light shaft. Drivers are a breed unto themselves, and numerical assessments of performance relate poorly to other clubs.

 

[hurley999s]

Driver is 44.75” with a 70g shaft and I’ll weigh today, but headweight I usually like at ~203g.

Back to the UDI - incidentally I measured this AM and it’s 2862 so pretty much in between where my irons and driver are. It’s encouraging that this is with the lead tape I added even before looking into MOI. As Howard says, I was just tuning that club up and adding some lead tape until it felt good.

[Howard_Jones]

Here is a small chart who show a driver head weight as part of total MOI for play lengths above 45.50"

Here is one for the shafts contribution to MOI - Neutral Balance point

a 46.50" long club with a 70 gram shaft (uncut shaft weight) is 250 MOI points ,and a head of 207 grams is 2650 , the sum gives 2900 MOI points ex the grip. (if COG is 1 4/8 above ground)

If we drop to a 55 gram shaft, wee need about 211 grams head weight at 46.50 to get to 2897

 

 

 

[hurley999s]

Back to the driver - took off the head and weighed 202g (TM M4); shaft with grip and TM adapter tip = 132g; total weight = 334g and total assembled play length = 44.75”