Thanks for the question. We were surprised as well with the Nike Viper series of irons, especially after their advertising talked about “moving the center of gravity closer to the center of the club”. Guess that tells us it was not in the center to begin with. Anyway, based on our measurements, the cg’s on all three models were slightly toward the heel. Not much, but they were not in the center of the face. Please understand, just because they are rated in the Player Classic category does not mean they are bad irons. It just means it would take a really good player to get any kind of benefit out of the iron, because they would not be considered very forgiving. The measurement(s) that hurt the rating on the Vapor Pro and Vapor Pro Combo was the C dimension (hosel centerline to horizontal location of the cg). Both were less that 1.2 inches, which is short. Shorter dimensions mean less stability on off center hits. The vertical cg’s were not as low as they could have or should have been, which also affected the rating. The Vapor Speed’s actual vertical cg was way high 1.010″, so even though it had a high MOI and a C dimension over 1.4″ (which is good), the actual vertical cg was aver 1″! When you consider the cg of a golf ball is .840, driving the cg of that iron below that of the ball might be a challenge. Good looking irons, but when you consider playability, you have to look beyond the appearance and consider the mass and dimensional characteristics and how they affect the playability of the design.
Britt Lindsey
With regards to the MOI, it is a factor, but when you combine a high MOI with a bad or high cg position, the high MOI does not override the bad cg location. Ralph explains in the book this condition. We have measured many irons that have high MOI, but very poor cg locations. Basically, if you have a model that has high MOI and low cg, the formula adds positive points to the score. If you have a high MOI and a high cg location, there are no bonus points added. The MPF is simply looking at the mass and dimensonal characteristics. You can not take a visual and assume it affects playability in a certain way. The horizontal cg, the vertical and the rearward cg are very key and if they are designed well into the design, and they are combined with a high MOI, you will have a higher playability rating. The difference in the MOI of the two models you mention is very small. Actually, all the measurements on these two models are very close. You should not base a decison on a models that only have a 37 point difference in the MPF rating. Ralph would tell you for most players, it would be difficult to tell the difference between 150 – 200 MPF points. MPF is more a measure of stability and forgiveness than sweet spot size, but I guess those are kind of saying the same thing. I would really encourage you to get the books and dive in. You seem to be like me, wanting to know the how’s and the why’s, which is exactly why Ralph published every aspect of how the MPF was created and how all the measurements and calculations are done. Simply too much information to try and put in this box. We will continue to put more and more of the graphics and information from the books on the site, so keep checking the index.
Britt Lindsey
Britt, Thanks so much for the info – the site keeps getting better. If you could expound on a few more items. So if I’m comparing the Titleist CB 714 to the Pro Combo Nike for example: I read in the learn section about COG, etc, but for instance – The Nike has a much higher MOI but a lot lower MPF. It seems the high MOI would help, but it doesn’t… How are the factors weighted in the overall MPF? Is C the most important, the MOI, adjusted VCOG…. Furthermore, if you compare these, even though the CB is a smaller more bladelike head, it’s more forgiving according to the MPF – in reading the MOI info, it seems that it’s a measurement of the SIZE of the sweetspot? If so, what is a significant difference in two MOI’s? Hope that’s all not too confusing. :) Thanks!!!!