Having had an Air-Weigh on-board scale on my previous truck, it was always rather simple to know when I was overweight on any of my axles. This is not the case however with the current CNG truck that I am piloting right now or on my 2018 New Cascadia that is on its way. Though this may change on the New Cascadia with the addition of another on-board system, I have always made it a point to still know my approximate weight prior to leaving a shipper or receiver anyway.
Since the beginning of my career as a driver, I have used air pressure to help me gauge my tractors drive axle, whether a fifth wheel was adjustable or not, as this is usually where most of my overweight issues tend to occur. Having an airbag gauge is something I made sure all of my tractors had for this exact reason. I would wait until my first heavy load on each new truck, get the axle up as close to 34K as I could, then mark the needle on the airbag gauge after I got it on a CAT Scale (on level ground). This would let me know if I was over or not from then on, even before I was able to leave a shipper and scale.
The trailer tandems have always been less of a concern for me, as they have the ability to slide great amounts and are able to shift the weight this way. I am of course thinking of trying a similar technique on the trailer axels that I was told about, if I do not get another on-board system. As I was told, it would be as easy as taking a standard air gauge and adding push fittings on the inlet and outlet, then adding it inline on the airbag line for the trailer. It would require me to mark the needle at 34K in a similar fashion as the drive axle airbag gauge for my tractor and work on the similar way of letting me know if I was over axle weight. I will definitely be looking into this for my two trailers a little bit more!
Being that my company hauls a lot of water loads throughout CA and NV, using this method save us a lot of time having to get our loads re-worked at the two plants we frequent most. Although they usually require scale tickets to rework their loads, they have finally started to see after several of our "I'll be right back" instances, that our method on our trucks works for us, giving us special privilege of being reworked based on that instead. As a matter of fact, this telltale gauge on my dash saved me about 30 to 45 minutes of my day just yesterday, letting me know ahead of time about my drive axles being overloaded by a new loader at the water plant. Take the time to mark that gauge and you might find yourself saving some time and frustration too later on down the road! No matter what though remember, “When in doubt, scale it out!”