As you will know, drivers are about hitting the ball as far and as straight as possible and one of the major factors is how fast the club head is moving when it strikes the ball.
This in turn depends on how fast you deliver the club head to the ball and that in turn will depend in part on how aerodynamic the head is.
However with drivers you are moving a flat face through the air and as it accelerates into impact it also rotates. Not the ideal scenario for a moving a metal object at speed, which is why for the XR 16 driver Callaway went to have a chat with the boffins at Boeing.
Both parties gained in different ways from the liaison and what Callaway took away was learning how to manipulate air flow over an object to alter the amount of air friction.
Boeing had researched this for their planes and use dots along the front of the wings to break up the airflow to reduce drag and make their planes more fuel efficient.
Callaway had already done work in this area as was seen from the Speed Step Crown on the original Callaway XR driver. What their pow wow with Boeing gave them was an insight into the airflow over their head, which was almost the opposite to an aerodynamic wing because they need to keep the air flow attached to the head for longer before it disperses.
I saw wind tunnel images of the airflow and it looks like a giant Elvis quiff shaped wave rolling back over the toe side of the crown.
Using the raised Speed Step on the leading edge of the crown seems a bit counterintuitive to keep the airflow attached, but that is what it does.
So that is a long way of saying that Callaway has reshaped the Speed Step on the crown of the XR 16 driver, but at least you now know that a whole lot of thought and time has gone into it from the best brains from two of the top aerodynamic engineering companies around.
As you can see the Speed Step is a little shorter in length and also closer to the leader edge of the crown. The result is the XR 16 driver that has a 30% lower head drag and a 10% lower face drag than the original XR driver.
But this is not all, as one of the other tenets of driver design is that a bigger head is more forgiving, but slower through the air due to the extra mass. Ignoring this Callaway also made the XR 16 driver bigger front to back to move the Centre of Gravity (CG) lower and further back to make it more forgiving.
Not only is the head more aerodynamic, but it is also 5g to 15g lighter than its current competitor drivers, which makes it easier to move through the air. This is done through using lighter 8-1-1 Titanium that has more aluminium in it than before to reduce weight whilst maintaining strength.
The new material makes the head chassis is 2g lighter than before and works with the 9g lighter R-MOTO face. The R-MOTO ribs are also longer and enable the face to flex a little more at impact to increase the ball speed.
This 11g weight saving is then used to move the CG back in a deeper head, that is longer back to front than the previous XR head in order to make it more forgiving.
It does look a little stretched when you first put it down in the same way as other drivers of this style do, but you get used to it pretty quickly as the shape is not as extreme as other models.
The CG height is also lower and so that should help the launch of the driver, so with the weight saving and the more aerodynamic and more forgiving head, the key question is, does it go further?
Using the usual Callaway Optifit adjustable hosel I tested both heads with the shaft I had been fitted into by Callaway for the XR 16 which is the Fujikura Speeder 565 Evolution II.
Callaway has always been really good at creating drivers with good sound and feel and the XR 16 delivers here again with a responsive face and solid sound that gives the feeling you have nailed it again.
The deeper head was very forgiving and provided enough spin that I had to use the Optifit hosel to lower the loft of the 10.5 edge head down by 1° to get the optimum performance for me.
There is a choice of lofts from 9°, 10.5° and 12° each of which can be adjusted up or down 1° or up 2°. Therefore you may need to work with a fitter to get the right loft as if you need exactly 10° you will need to go up 1° from 9° as you can't get there by delofting the 10.5°.
There is also a draw setting that will close the face a little too, which could be useful as thankfully the XR 16 sits a little less closed than the previous XR and for this reason I can see it appealing to more single figure golfers than before.
The sole of the club looks very dramatic with the wavy lines, but I have it on good authority that these don't do anything for the club aerodynamically and are purely cosmetic.
They do however give the designers some wiggle room on the volume measurement and that helps with the larger footprint of the head.
On the face of it, the changes to the XR 16 don't visually look like much, but having seen behind the scenes the lengths that Callaway has gone to improve the XR 16, then I would have to say that it is a more complete driver than before.
The deeper head is just on the right side of being too stretched for most golfers' eyes and the slightly squarer position at address and flight performance makes this a driver that will suit more players across the handicap range.
It is medium to high spin depending on the set up and shaft, so if that is an issue then there is also a lower spinning Pro version.
Callaway XR Pro 16 Driver Review
In order to make it lower spinning, the Callaway XR Pro 16 driver has a more traditional shape with a taller face than the standard model to make it more compact.
It also sits squarer at address and if I was basing a decision purely on head style then I would probably go for the Pro version.
However it has to be based on more than that and my optimum performance came when I had a setting with about 2 degrees more loft than I did with the standard version. Tee it high and hit it in the middle on the up and there is not really much between them.
The smaller head sounds a little more muted and solid as you would expect, but if you stray from the centre the forgiveness is less with a resulting greater variance in performance.
This is really the trade off between the two models of lower spin and a squarer set up versus a larger head with more forgiveness. If you are a high spin player, or hit it out of the middle more often than not, then you probably have a choice depending on what your fitting numbers say.
For these players, the standard XR 16 could still be an option in the 9° head, as the set up means it can go further down the handicap range than before. Therefore, the XR Pro 16 may prove to be more of a niche play for those who want it, even though it is also an excellent choice.