Trailer suspension air pressure gauge.

Just get a t valve and add an air gauge. Get a full load, swing by a cat scale and verify your air gauge and legal scale weight. Done for less than $50

 

Our trailers are a mix of PSI gauges and calibrated weight boxes. In a large fleet where trailer swaps happen regularly, the gauges are not terribly useful since most have about a 2 PSI +/- variance at 34k (in our fleet of Great Danes... 34k may be 76 PSI, or it may be 80 PSI)

I guess it depends on precisely where the ride height is set at.

 

search trailer scale
https://search.yahoo.com/search?fr=chr-greentree_ie&ei=utf-8&ilc=12&type=926458&p=trailer+scale

 

Stexan has it dead on.

My tractor scales are accurate enough to know that I'm not over on my drives, but unless I scaled an earlier load and compared it to the trailer scales I don't trust the scales to know that I'm not over gross, which is often more important since I pull a spread axle and almost never have problems with axle weights. It does come in handy with weird loads that you can't tell where the center of the weight is.

However, part of our fleet stays with their trailers and so long as they make sure they are staying calibrated, can know how much they weigh and where that weight is without a scale. Very convenient when a load might take a few hours to set up properly and the nearest scale is 30 minutes away.

 

Had this on my Trailking lowboy,pretty accurate,once you calibrate it.

 

Like was stated above, T into a trailer airbag after the leveling valve and run to a gauge. If its your trailer, you'll figure out what pressure you need to be at to be legal. I've seen some guys with super b's get creative and run the airlines back up to the truck through a 2nd set of gladhands and mount the gauges in the window of their hedache racks so they can watch the gauges as they get loaded and not have to leave the cab.

 

Here's a question for you @NorthernMechanic
would it be possible to make an air gauge in a line that you can connect between your truck and trailer red gladhands? Would it show you the same as T-ing into an airbag on the trailer? If it is possible it might be something for people to carry around if they haul many different trailers to know if they are for sure under or are for sure need to scale it.

 

If you're talking to read suspension pressure then no. The red line will be charged to ~120psi at all times the brakes are released. The gauge would have to be connected somewhere in the line between the air bags and the trailer leveling valve.

 

Had one on my dash at Beelman. All company trucks did and most o/o's as well. Our trailers had a quick connect and the tractors had a air line equivalent to fifth wheel slide line to plumb it all. Very handy since we usually pulled the same trailers as well as had to load off our gauges as well.