I have a 140/70 r 17 on my 2021 SR, it is kinda close on the belt guard. I agree, if the road is slightly damp, the painted lines are a challenge. Ima do some figgerin an see how close I can get to the belt guard.
(2 refreshin beverages later)
What I measured is a 5 mm gap so max would be a 150, and that would leave NO room for flexing , a 55 is gonna throw your speedo off and possibly odo also , (mpg should remain the same

though ) the belt guard doesn't look that hard to trim but taking 15 mm off it would weaken it considerable, so compensation would hafta be made for that,
Seein as how the Zero is a fair weather bike (not waterproof) I think I will just stick with my slippery tire.
Oh, i did read something about traction control capability if you got a phone that talks to your bike, (my phone won't even talk to ME) or something like that , it should stop SOME of the white line problem on accel, but not in cornering.
now after thinkin a bit, the tire is kinda odd shaped, sidewall is wider at the chain guard than it is at the tread/contact point, maybe a different make of tire wouldn't have that shape and have a wider tread aspect (like a darkside)