Question

1.85K viewsSeptember 16, 2022

tomopheim 72 September 15, 2022 0 Comments

I understand that the bulge and roll on a driver produces a gear effect which helps to correct off center hits. Is there an industry standard or do different manufacturers have differences in bulge and roll? I have a Mizuno 10.5 degree loft and a Cleveland 10.5 degree loft and I find the Mizuno to be more forgiving. Both clubs have the same shaft so they are in essence equal except for what appears to be the amount of bulge and roll. The Mizuno looks to have more bulge and roll while the Cleveland looks to be more straight faced. The amount of bulge and roll does not appear to be something that is listed in club manufacturer’s specifications. Also, do you have a tool for measuring this?

Britt Lindsey Answered question September 16, 2022

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Answer 1 · 2022-09-16T13:50:51+00:00

There is no industry standard for bulge and roll. As drivers have become larger (460cc), the dimension has changed. In the old days on actual wood heads, we basically made most drivers with 10″ bulge and 10″ roll. We might go a little off of that, but not much. As heads got larger, that dimension just did not look good. Today, I think most 460cc Titanium drivers will have 12″ x 12″ or higher, which is less bulge and roll (even thought the number is higher). At least that is the design spec we use on our drivers. Does this make them less forgiving? It makes the gear effect aspect less, but the MOI on todays large drivers makes them many times more forgiving than the old, smaller driver heads. The less horizontal bulge simply means the ball may not curve as much on the off center hit, but with the increased MOI you get with the larger head, it generally will not start as far off line and will not curve as much. You have to have some curvature and gear effect does still occur. It’s just less than the old days due to the size of the drivers. Definitely don’t want a flat face. We used to have a flat face driver we used to demo for a students in our schools and when that driver was hit off center, the ball flight was interesting. A toe hit would generally create a shot that started straighter than a driver with horizontal bulge, but then move much farther off the target line. The driver with horizontal bulge, on a toe hit, starts right of the target line and tends to curve back a bit.

I don’t know what the measurements are on the two drivers you have so I can’t know what the difference and the effect may be. My guess is what your seeing has nothing to do with the bulge and roll. My guess is the bulge and roll measurements are similar. As far as a tool, we used to sell a series of gauges for measuring bulge and roll. They were mainly for use on wooden drivers. We do still have one four sided gauge with 7,9,11,13 degree sides. Its code is FRG7. We no longer carry the 8,10,12,14 or the others we used to have. If you wanted to order the FRG7, you would need to call in. We do not list it on our website.

Britt Lindsey