Brake proportions?

2005 Sierra 3500 4x4 dually CAB CHASSIS...it's got a contractors dump on it.

I've done some searching and not really found the answer that I'm looking for, and thought I'd throw out a bone here...

Typical passenger vehicles use the front brakes as their primary (like 70%) of their braking, and 30% for the rear....

What's the ratio for a truck this size?

Please, help satisfy my curiosity!!

My guess was 50/50...:runaround:

Thanks!