In concrete mixing trailers, the ball makes a difference
As I said in another post, one-yard mixer trailers weigh about 7000 pounds when fully loaded. Cart-Away Concrete Systems even makes a mixing trailer that has a 10,000 pound GVW (the MixKing). The towing hitch, brake actuator, and towing ball must all be rated for that weight.
Unless they have been modified, manufacturers will put on actuators and couplers that, at the least, be rated at the GVW and often exceed it. That leaves the towing ball attached to your truck, and that’s what you bring to the party. It used to be that you had 1-7/8”, 2”, 2-5/16” balls with little definition between functions and availability. In the portable cement mixing trailer industry, the 2-5/16” wasn’t something we saw very much simply because the towing weight capacity wasn’t necessary. That left us with the two smaller sizes, and coupler manufacturers had to make one coupler that would fit both.
While I can’t say I ever had any type of accident with one of those 1-7/8″ styles, putting one on the smaller size ball never seemed to fit right and I was never comfortable doing it, especially on a concrete mixer. The diameter of towing balls for trailers has become more defined over the years, though. The 1-7/8” ball has, for the most part, gone away from heavy equipment towing and manufacturers of the one-yard cement mixer trailers have standardized with the 2” ball.
However, while the cement trailer manufacturers have begun building with one size diameter, the towing ball makers have different shaft lengths and sizes to fit different mounts. That’s where you need to know the specs of the mounting device and the cement mixer that you will be pulling. Your first concern should be the shank width. Make sure that the mounting shank that you have fits the diameter of the hole of your receiver mounting device or bumper mounting hole. If the shank is too small the ball may slide around in the hole and wear the steel.
In a severe case, the shank could snap. Just as important, actually more so, is the length of the shank. The shank must pass through the bumper or receiver hitch far enough so that when the lock washer is on and the nut tightened up there are threads past the end of the nut.
Many times I have turned away someone because they had removed the lock washer to get more thread or the threads didn’t show through the nut. It’s unsafe to hook any concrete mixer trailer to a ball like that.