Every now and then we come across a ridiculous video that is just fun to watch. The video above is a great example. The guys at H&S Performance decided it would be fun to hook a lifted Ford Super Duty powered by a 6.4 Power Stroke to play tug a truck with a Cummins powered school bus.

By the looks of it, the school bus is a Class 3 or 4. According to School Bus News, that means the bus can weigh anywhere from 10,000 to 16,000 pounds. Basically, the school bus weights twice what the Ford Super Duty does.

Looking at the setup, there is a 4 ton lifted truck on the left hooked to a 8 ton school bus on the right. The truck is four wheel drive, but only has a single wheel and probably has 3.73 gears. The school bus has dual rear tires and a gear ratio probably around 4.56 or 4.88.

Initially looking at it, the bus should win hands down. It weights so much more than the Super Duty. On the other hand, the Super Duty easily has more power than the stock Cummins powered school bus. The thing is, engine power is only a small percentage of tug a truck. The success of tug a truck is more a matter of how that power is used.

More Power!

Traction is a matter of friction. Friction can be determined by the normal force (in this case, weight on each tire) times the friction factor. If we assume the truck weighs 4 tons and the coefficient of friction is somewhere around 0.65 (off road tires not meant for maximum traction like a drag tires), the tires can handle roughly 5,200 lbs of force. The school bus on the other hand, is only sending power to the rear tires. So, the friction on the front actually opposes the force produced by the rear tires. Ignoring that, and assuming the bus has a 60/40 weight distribution biased to the front (bus isn’t loaded with people yet) and the a coefficient of friction around 0.8 (highway tires have more friction than off road tires), the bus’s tires can handle roughly 5120 lbs of force.

Maybe too much power.

5,200 is greater than 5120 but not by much. If you notice the Super Duty starts smoking the tires pretty quickly and then the bus starts to move backwards. As the tires heat up, the coefficient of friction increases, resulting in more force being able to be applied.

Either way, this video is fun to watch as the Super Duty just roasts the tires off pulling the bus. The icing on the cake, the Power Stroke blows a head gasket!