The 90psi is the pressure for the maximum load and for the HE in your size (10x16.5 10ply) the max pressure is 75psi. The 90psi HE is a 14ply 12x16.5.
Those are simply the max load numbers, rarely where you actually want to run the tires. You need to know the load you will be putting on them and then you can adjust the pressures based on the tire OEMs load charts. You can weigh the rear of the machine and front to be perfect. Set the rear pressure for the unloaded weight. The rear tires will never have more weight on then than when you have nothing on the front of the machine. The front tires you can set the same if you feel it will allow enough room for whatever weight you will lift and carry. Don't crank them up for the random heavy load you might have once and awhile, set them where you think you will normally operate. Remember that if you lift 1000lbs for example, that doesn't translate to exactly 1000lbs of extra weight on the front axle, it's actually higher depending on the distance the load is from the axle, it will remove weight from the rear and transfer it to the front. If you are just picking things up and not carrying then far you won't need terribly high pressures necessarily, but if you will be traveling a lot with a load you need the proper pressure to prevent excess heat/stress/wear. Overall though SSL tires are pretty tolerant to being run low. Not suggesting you should just saying it won't implode if you don't have the perfect pressure.
Too high of pressure will give you a crappy ride which is hard on you and the machine, there's less give to the tire when running into/over things which is hard on the hubs/bearings etc. Your traction will also suffer significantly and if you are doing a lot of work that requires traction you will get less done per hour and use more fuel to accomplish the same task. The latter isn't as obvious with a skid steer but on bigger equipment like tractors, there can be a significant difference. Overinflation in general can lead to irregular wear but it's unlikely to be that noticeable on an SSL tire.
Under inflation can also lead to irregular wear, but the main issue is the stress it puts on the casing leading to early failure. Again not common on SSL tires with their tough rigid casings.
What machine do you have? You should be able to run that tire anywhere from 35psi up to the max of 75psi if desired. In my experience the Titans are so stiff, they ride just as rough at 35psi as they do at 70psi. Your experience max vary. They're a very stiff tire which also means as mentioned, you won't notice they are low until they practically come off the bead. Even then they drive like a damn run flat and barely squat. You will notice a front a lot sooner than a rear obviously. On that note, a tire that "looks" low is not necessarily low,especially with radials. Radials are not common for SSLs, the Bibsteel and a couple others are all that exist. They are commonplace for everything else though. Radials are designed to squat much more. Bias tires carry the majority of the load through the center of the tire tread working to the outside. Like if you were to push a ball into the sand, the center would be the deepest. Radial tires carry a lot of the load at the sidewalls and more evenly across the tread. Almost like pushing a cube into the sand, much more even footprint sometimes with slightly higher loads near the sidewall. Due to their design, many radials when properly inflated on equipment, tend to appear to squat some. With Ag equipment the "squat" can be pretty large especially with IF/VF tires that are designed for very low pressure. The squat allows the tire to have a longer footprint for less compaction and better traction.
With any tire, you need to consult the manual for the machine and the manual for the specific tire you purchased. Aside from cars, inflate the tire based off the tire OEMs manual. The machine manual doesn't know what tires you have an can be outdated. With cars however, inflate to what the door says as things like handling and safety can be effected. Most car tires within a given size and load/speed range now run very similar pressures anyways.
), they lasted bout 700 hours of mixed used, clearing land, working on concrete/pavement, spreading gravel...
