Looks like a really nice bike, I apologize for replying so late.
They give you the best answer I can. The bicycle tires state to inflate to 40 PSI, It was a huffy cruiserback from Walmart and it had been sitting for probably 5 years at my house. If I'm truly honest, I haven't kept track of it. It's always been indoors but it was never ridden more than a mile in total. It's entire life so the original tires definitely have some age on them.
The package of slime tires that I purchased do appear to have been old too.
As promised though I took the advice and I actually didn't do 5 under. I ended up doing 15 under. I kept sitting on the tire and checking it until I saw a little bit of sag, I'm not having any trouble with it but the tire is relatively bouncy and there's a lot of bad roads out here where the asphalt just isn't flat and there's just little ripples quite constant just all over the place. These back roads are in a bad state of disrepair and so when I hit them I'm probably not going to lose traction, but it feels unnaturally bouncy considering there's no suspension.
I've been trying to keep the weight on the bike to an absolute minimum. I myself might be about 185 to 195 lb. The bike in total probably doesn't weigh no more than 70 lb. That's motor side saddle everything, I didn't really throw any special new stuff on there because at the moment money is tight. The whole reason I did this swap was so that I could start putting back money to repair my car while still having a job.
I could definitely see myself putting some nice rims and stuff on it in the future though.
The side saddle I've been carrying the bare minimum. I keep two headlight units on the bike. I keep a tail light unit that does turn signals and a backup tail light unit that just has a red light.
And inside the side saddle I carry a flashlight pocket knife. A. Bearman Derringer 22 handgun.
I keep my wallet in there as well along with because of the weather recently a beanie for my head. A spare pair of clear riding glasses for at night simply because my shift ends at 10:30 at night and I drive home in the 40° weather this way.
The bag does often include a mountain dew or sundrop bottle and I have a personal size Gatorade bottle that has been spray painted thoroughly and label very thoroughly as bike gas so that no one can mistaken it for a drink. I think in total the whole bag may weigh 20 pounds so I've been inflating the tire to roughly 25 in the cold night air. It probably sits around 30 during the day.
The problem here is that when I drive to work the weather is between 75 and 90. God bless that North Carolina weather and then at night the weather is between 40 and 60 so the tire pressure is definitely going to be different there and back. I'll include a photo . As far as the problem goes this week I haven't had anything pop but the tires are definitely sagging for me. It feels like if I was to have to take a really hard turn, they're just wouldn't be enough pressure to keep the tire where it needs to be