Orikoru
Tour Winner
Yeah, the 85mph was relative to driver swing speed, not 85 with the actual 8 iron. ?The slow 85mph swing was for driver, the 8 iron was actually at 65mph I think.
Technically it's nothing to do with compression at that swing speed (especially with irons) and more to do with spin. The ProV1 simply spins way more than the "softer" balls. Launches lower and spins more means less carry.
The only swing speed "rule" I would adhere to was if I had a driver swing speed in excess of 115mph that I would use a firmer ball. At that speed the softer balls don't transfer the energy as well as the firmer ball and will lose a bit of distance off the driver but also will not spin as well on iron shots. With that speed control is much more important than distance imho.
I always find that the softer lower spin Urethane balls like BRX, AVX and the old Project(a) were all at least 1/2 club longer off mid irons and I didn't really notice any difference off the driver (my swing speed is around or just over 100mph). The Honma TW-X I've used all year is definitely shorter off my mid irons than the BR-X/AVX I used in previous years, it took me a few rounds to notice and get used to it. It also stops faster on the greens than the AVX (1st version which was stupidly low spin).
You are also right to say there was not as much difference on the driver distances with those balls I listed. But I selected iron as that was relevant to what Jim said about being a club longer/shorter. Personally using Tour Response as I've mentioned, so I'm happy I'm getting good iron distance so I can hopefully be hitting 7 iron instead of 6 iron and so on. Every little helps. A few years ago I tried those Inesis Tour 900 balls and I really did notice them being a club shorter - the data on MGS backs that up as they have one of the highest spin ratings. Personally don't think I'd benefit from lots of spin around the greens, I'm more comfortable playing chip and runs with a PW or 8i anyway. Would rather take the distance.