Run the tire pressure according to the scooter specs, not according to the max pressure on the tire sidewall. Seems like you need to back the pressures down even more. Be careful.
The reason i've been upping the PSI to 40 lately is that I had a weird experience last month where, after me and my girlfriend went to Ojai on the bike (about 80 miles from my place of residence in southern cal) I experienced the PSI being reduced from 34ish to like 20. I attributed this to the extra weight (we also had the top cases full of about 30 pounds) and the long haul, it's like 160 miles round trip.
But ever since then i've been checking the PSI every other day and it seems to be maintaining the pressure ever since then. I have no idea why that occurred but I am sure, having not noticed it till I drove with it after a few miles, that it caused some minor cracking of the side wall of the stock maxxis tires.
Anyway, I feel it's ridiculous to have tires that only last 5000-8000 miles so i'm getting the city grips ASAP because I have no doubt they should last 10,000-12,000 from what i've researched.
I know 5000 miles might seem like a lot to hobbyists but I am not using the bike for hobby and weekend play, I am using it as a primary form of transportation, which is why I have almost 5000 miles on it despite only owning it 4 months.