JasonFJ are you not worried about putting a V-speed rated tire on your bike? V means less traction overall then a Z-rated. You may not be racing but it's still a motorcycle and you will still get less real life characteristics that every ST needs: wet traction, Braking distance, handling.
I'm not worried about it, as the speed rating has little to do with the tire's traction potential. V rated means the tire is designed to not come apart and to maintain shape at speeds up to 149 MPH .... which is probably faster than the top speed of the bike, and is quite a bit faster than I ever intend to travel on the street on two wheels. Z rated simply puts that speed limit in excess of 149 MPH. The official rule of thumb is that you shouldn't put a tire on your vehicle with a lower speed rating than what the manufacturer shipped it with, but in this case, I think I'd be splitting hairs.
Traction is rated as part of the Uniform Tire Quality Grade (aka, UTQG). The UTQG shows a tire's treadwear rating, traction rating, and resistance to heat. Unfortunately, the traction rating is only based on the tire's straight line wet coefficient of traction as the tire skids across a test surface. The traction test does not evaluate dry braking, dry cornering, wet cornering, or high speed hydroplaning resistance, so while it is useful information, it still has to be taken with a grain of salt. Even so, the Potenza is an all weather high performance tire that has been used with good results on Goldwings, Victory Vision, the VTX and other heavyweight tourers. It's rated at 460 treadwear, A traction, A heat resistance.
For comparison, these are other tires being used in dark side ST1300 applications:
Hankook Ventus V12 evo K110: 280, AA, A (Max Performance Summer)
Hankook Ventus Sport K104: 280, AA, A (Ultra High Performance Summer)
Michelin Pilot Sport A/S: 500, AA, A (Ultra High Performance All-Season)
Goodyear Triple Tred: 540, A, A (Passenger All-Season)
Falken Ziex ZE-512: 360, A, A (Performance All Season)
That all being said, I fully expect to burst into flames and/or be hit by lightning the moment I put the rim back on the bike, so it all probably doesn't matter much
