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A pre-trip inspection includes many items to be checked in order, to ensure your truck and trailer are safe, and legal to operate. One of the areas that could be time-consuming, is physically checking your tire pressure with a gauge. This process can be sped up with a flow-through valve cap, but still, it requires you to put the gauge on each individual tire. Of course, if you’re running wide-base single tires, it can reduce your time checking them, from 18 tires in a normal truck and tire combination, down to 10.
In my operation, I utilize a tire pressure monitoring system called Tire View by PSI. What I like about having this system, is that I can see all of my tire pressures, before I even exit the cab of my truck. Having a tire pressure monitoring system does not eliminate visually inspecting my tires for defects. It only eliminates checking the pressure of each tire with a gauge. The other nice thing about having a tire pressure monitoring system, is that it notifies you with a warning, anytime a tire drops below the predetermined pressure, which I have programmed into the unit. Another nice feature, is that it also monitors the tire temperature. By knowing the tire temperature, you can often detect a wheel end that is having a mechanical problem, such as a hot wheel bearing, or a dragging brake.
So, aside from doing your proper pre-trip, it’s also important to know that none of your axles are overweight. What I’ve incorporated into my truck is my own cheaply made scale. I simply used a threaded air valve, which is nothing more than a Schrader valve with pipe threads on one end, instead of a grommet. These valves are often used on household water tanks when you have your own well. I put a fitting into the line feeding the airbag of that axle, to indicate the pressure in the airbag of my suspension. I use a tire gauge to read the pressure in the airbag. Then, through a process of trial and error, and a little bit of math backed up by scale data, I can calculate what the maximum pressure in the airbag can be, in order for me not to exceed the weight limits that I’m allowed to transport.
There are still some problems with knowing your exact weight when you’re not on level ground. So, what I do when I’m parked on unlevel ground, is take my glove and set them on the ground at the rear axle of my trailer, and the steer axle of the tractor. Next, I pull forward, turn around, and park the truck in the same spot, but in the opposite direction. I then check the airbag pressures again, add the figures together, and divide them by two. By following this procedure, I have increased the accuracy by averaging the air pressure over both angles that the truck was parked on. Of course, this doesn’t help determine the steer axle weight if you have a spring ride suspension, because there's no way to check the pressure without an airbag. Steer axle weight becomes an educated guess.
Soon I’ll be getting my new truck, which will have an air ride steer axle - a liftable pusher axle in a 6x2 axle configuration. My new truck will also adjust the suspension automatically in low traction situations. One day, when I was sitting in the driver's seat and looking at my tire monitor, an idea came to mind. I thought to myself, “Why can't I use a sensor for a tire monitor to give me the airbag pressures on all of the axles of my truck and trailer, which also has a liftable axle?”. So, in preparation for the next few weeks, I programmed tire monitor sensors to put on the steer axle, the liftable pusher axle, and the drive axle of my new, and upcoming truck. This week, I have already begun using the tire pressure sensor on my trailer, and it’s working well.
The only downfall I can see so far, is that when there’s a change in the air pressure of the airbag in a rapid fashion, it sets off the rapid air loss buzzer in my tire monitor. You simply hit a button on the unit, and it shoots the warning off. In the picture, towards the middle of my unit, you can see that I have 3 wheel positions to the bottom of the screen, which are going to be the steer axle, pusher axle, and drive axle. Then, to the top of the screen, is my trailer suspension. The way my Hendrickson Opti-Max suspension works is, as long as the pressure in the airbags is below 85 pounds, it can run with a lifted axle. If the pressure goes above 85 pounds, the lead axle automatically deploys to share the load. This system is great for reducing tire wear and increasing fuel mileage. Right now, I’m happy with how I’m using my tire pressure monitoring system to monitor my axle weight, as well as tires, and I’m eager to get my new truck, which will also have a liftable axle.
I’ll keep you posted in future articles on how all this works out on my new truck. Until then, drive safe and be profitable.
*UPDATE:
Recently, my blog was about using a tire pressure monitoring system (TPMS) for more than just monitoring my tires. I had already been using a digital tire gauge on a tank valve connected to the airbag of my suspension to give me a figure, which would let me know if I was overweight. I call this system a “go or no go” gauge, because I’m not paid by the weight of my load. Even if I was paid by weight, the shippers would either make me use their scale, or a certified scale. This system simply lets me know what the air pressure is in the airbag of my suspension, which allows me to calculate when I’m over the legal weights allowed.
This is where the TPMS came in. As I figured, putting a TPMS sensor on top of my tank valve, which was attached to my suspension airbag, would allow me the luxury of seeing the pressure reading from the comfort of my driver seat. This seemed like a good plan, and initially, I was super happy with the results. When I put the sensors on, I opened up the parameters, so that they wouldn’t set off low-pressure alarms, as this was a suspension pressure - not a tire. The one feature that the Tire View by PSI TPM has, that could not be overridden, is rapid air loss. Rapid air loss is a sudden change in air pressure.
So, here’s the problem. Going down the road and crossing a bridge, or turning on a curbside type entrance, or many other activities, can cause there to be rapid changes in your air suspension chambers. This causes the system to set off an annoying alarm, which is easily shut off by hitting a button on the unit. Nevertheless, it’s still annoying.
The second issue I’ve encountered using my TPMS sensors for my suspension airbag pressures, is that they only update approximately every five minutes - unless there’s a rapid air loss. As you can imagine, I don't want to wait five minutes for the sensor to indicate the change in pressure on my dashboard display. So, at this point, I’ve been talking to the fine people at PSI, to see if there’s a way we can alter the TPMS monitor, in order to use it for more than just monitoring tires. At this time, there is no solution.
Although the purpose of the TPMS is not made for my intended use, I’ll keep looking into it to see if it works out for me. In the meantime, I’ll keep you posted if I find anything useful. I’ll be using a tire gauge to figure out my suspension pressure until these issues are resolved.