How to know how much weight a Trailer/Truck can handle w/o damage

I currently work for a company that uses end dumps and side dumps to haul coal fines.
We drive heavy loads but not as heavy as the Coal Trucks that I am told are meant to be driven heavy.

After running multiple loads that put my gross at 105-107k lbs, I was told I was running WAY to heavy and that I would break the truck and trailer down very quickly.

I get paid percentage on the loads, so obviously I want to run as heavy as possible (105-107k lb gross makes me 150 a load, twice a day). They want me to load no more than 95-97k lbs.

So, question is this, how can someone find out how much a truck SHOULD haul.
Again, I am being told that although the truck will pull it, I will damage the truck and trailer in short order.

Where did they get this number from?
I have a hard time believing that 5 extra tons is going to break the truck down that much faster since we are are already running 7.5 tons over 80. But hey, what do I know? That's why I am asking here.

Is there somewhere I can look at the specs for the specific truck I have and get an idea of what is realistic to haul without putting undo stress on the engine?

If I called a company that sold this specific truck, would one of their sales rep be able to give me some details that might give me an idea of how much the truck should be pulling?

Thanks for the help

 

Overweight meaning, over 80k. I should of made that more clear.

Overweight for the door swingers that work for the megas.

 

The company is really small and I am being told I am WAY TOO HEAVY by one of the fellow drivers that also has the responsibility to watch whats going on and ask for volunteers for overtime. I wouldn't really call him a Driver Manager in the traditional sense of the word.

I was getting different answers from different people at the company, some of them fellow drivers and some of the higher ups. I am new and it's not like I knew all these things.To get a much more specific answer, I went straight to the owner and asked him how much he wanted us to load.

And I get it that it's cummulative. But I'm curious and I never take anyones opinion as truth without having
something to back it up. So while I have listened and made changes to my loads, I was still curious where they might of got an idea of how much I could load or if they are just pulling it out of their ###.

 

Never said I wouldn't, just curious as to where I might get some proof of that number or something there abouts.

Up until this I never ran for a company that was set up to haul heavy loads.