I have a dual axle trailer. The tag on the trailer says inflate front tires to 65psi and rear tires to 50psi (d load tires).

A few questions, is it normal to have different inflation for the different axles? If so why?

I have since switched over to E load tires that are rated to 80psi. What pressures should I be running now?

Thanks

The PSI should be the same unless they have different ratings or construction maybe?

I have E-rated and air them up to 80PSI cold, the way I understand it is under inflation is worse than over inflation.

When I was running D-rated tires I inflated them to 10% over the recommended PSI.

Hope this helps.

I've never heard of different tire pressures on a trailer. That sounds bizarre.

I run my E-rated tires at 75psi. Sidewall says 80psi max.

For best tire life and the most load carrying capacity, inflate to max recommended cold pressure on the tire.

Interesting a mfg sticker plate would have different tire pressures. Are they still in business? Can you call them?

Highest inflation is recommended for maximum weight carrying. If the tires are not heavily taxed, the higher inflation will lead to crowning - greater wear on the center tread than outer.
Age and elements usually take out a tire before tread wears out and under inflation is usually a bigger problem.
I would say 70-75 psi would be good as long as the load on your trailer is decently balanced and you are not close to the rated maximum weights.

My dual axle trailer does not say that but I have learned that if you want your tires to live you need to keep them at the maximum pressure stamped on the sidewall. 50 psi in my case.

Does the same hold true for truck tires?

I have a Chevy 2500HD, tires are LT24575R16. The tires says 80 PSI for max load. I'm towing around 6000lbs. I just had the tires replaced and the shop put 70 psi in them. If I recall I was running around 55 psi in the past.

Now this is going to get good! I'm going to sit on the sidelines and watch this conversation take a 180 deg turn from everyone saying to read the sidewall recommendation on a trailer tire but ignore it on a vehicle and only go by what the manufacturer of said vehicle recommends.

I think most people who run that truck (and I'm one of them) will often run 55 all the way around when not towing. I believe the door sticker calls for 55 front and 80 rear, but I never run 80 "unless" I'm towing.

Tire inflation and weight carrying ability follow a similar formula whether truck, trailer or car tires.

The vehicle manufacturer has specified a tire pressure on the door because that it the max tire pressure they have calculated needed to yield full load, usually retaining as much handling and mileage characteristics as possible.

IF a person runs their E truck tires at 80psi unloaded there is not enough weight to flatten the tire and create even tire wear. That is why 2500/3500 unloaded personal trucks will often air down to give both better tread wear and improved ride.

Trailer could be the same way depending on how much the boat/trailer combo weighs and how the load is distributed.
example chart - http://www.goodyearrvtires.com/pdfs/rv_inflation.pdf