I'm trying to find out how to see if my brakes will lock up or my tires will continue to roll through the following scenario. I have a machine that weighs 42,000 lbs. I'm pulling a 110,00 lbs trailer with load (no brakes on the trailer). This is a rubber tired machine going down a 8 degree slope at 5 mph. I'm using a 0.7 coefficient of friction (rubber on good concrete) and rolling resistance of 15 lb/1000 lb. The weights on the axles of the machine are 31,500 lbs on the front axle and 10,500 lbs on the rear axle. I have 622,000 in-lb of braking in each axle. If I slam on the brakes, will the wheels lock up? What is the calculation I'm missing? I have found calulations on stopping distances and times if the wheels are locked up and the tires are slidding but I need to prove they will lock up. Sorry if this a bad question but I have been out of the engineering field for a while and have just started back into it so I'm trying to learn it over again.