Spare tire pressure

Something is up? Lol.
This isn’t a murder mystery!

Depends what your trailer weighs.
Likely scenario, OE tires 65psi, hence the spare. Tires on trailer upgraded to heavier load rating when replaced.
The real question is do you need 80psi in your 80psi max tires or are they overinflated for the job they’re doing.
(With few exceptions, like the “.5s” , 17.5, 19.5, 22.5 tires, most all passenger vehicle and ST tires are fine to be used at the proper pressure even if rated higher. Side benefit, stronger, longer lasting tires)

If you say so yes. Clearly something is up. Are they the original tires? If not someone upgraded the tires on the ground or downgraded the spare.

The tires on the ground are likely Load Range E which has a max inflation pressure of 80 psi. The Spare is a Load Range D which has a max inflation pressure of 65 psi.

Somewhere along the line the tires on the ground have been upgraded from the OE tires but spare was not.

I would NOT inflate the spare to 80 psi if you ever have to use it.

I would check the sticker on the side of your trailer (usually on the left side,
front corner) and see what tires were OE and the pressure specified. If it specifies 80 psi I'd replace the spare with a Load Range E so if you DO have to use it, you won't be running on an under-rated tire.

I keep my two spare TT tires at their max rated pressure…ready to go.