I have some new 9R-22.5's going on soon and would like to run lower air pressure to soften the ride. The truck is a short wheelbase--123"---N600 with a pickup bed on the back and nothing in it. 90 PSI is too rough of a ride and not needed but how low can I go?

Can I take the air pressure down to, say 60 or so? Lower? Higher?

Any advice helpful on this. Thank you.

 

Try 60. That should still be plenty unloaded.

You will be at 66.66% of pressure, so figure the maximum load should be reduced at least 33.33%.

So, if the tire is rated for 1000 lbs, no more than 667 lbs at 60 PSI.

This is of course subject to inspection at that pressure with or without a load. If it looks too low, air it up. You do not want to roll the tire off the rim.

 

Thank you, 85e

 

I get nervous giving answers on questions like this because safety is at issue. In this instance there are references to fall back on. My references are, however, old and I would suggest consulting your tire dealer for current standards. Below, if it is clear enough to read, is a page from the 1981 Tire and Rim Association Annual that shows load capacity at various tire pressures for designated radial tire sizes. The lowest weight listed for a 9R22.5 is 2960 lbs with tire pressure at 60 psi. That's for each tire. An early edition of this book cites load capacity at pressures as low as 45 psi for a 9R22.5" tire. Stu

 

truckdog/Stu...That is amazing that you had that info and that is information I can do something with. I follow these books religiously for farm tires and never had a bad experience. Good advice. Thank you.

I'm going to start at 60 psi and drop lower depending on how things look and feel. I do think I can go to 45 or 50 psi but need to check it out.


Currently, on a 2000 lb hot rod I'm running 265-75-16 on the rear @ 14 psi and 205-75-15 on the front at 17 psi. The difference in ride quality adds shock absorbing qualities and the car rides great.

 

That's too low on those car tires. You may get away with it, but you ought to at least be in the mid 20s or more...... Especially for any long trips.

 

Maybe for low ply cheap tires but not for 8 (?) ply truck tires. They are so heavy and with such thick sidewalls I could use them as runflats. Remember, the car weighs under 2000 lbs with me in it and is a "salt flats" style with nothing above or beyond the rear axle. In fact, I could run less pressure in back. No long trips in a hot rod.

Same with the N600 in question. It's a 123" WB with an empty pick up box on the back and that's all it will ever be. As long as the tires don't roll off and I'm within safe margins, they are entirely adequate for a ride to a car show. I've been building this stuff for 50 years and am not a risk taker.

 

All that keeps 22.5 and 24.5 tires beaded is air. When pressure is too low they will dismount. So 60 psi is really kinda low. I run 95-100 in 11-22.5s on the dump truck of course it weights 13000 empty and 28500 loaded.

 

OK, here's what I came up with after pondering the comments here and thinking about it. I decided you guys are smarter than I am at this so I'm going to start at 80 psi and probably leave it at that. While I would like to go 60 psi to lighten the ride, it probably is too low unless I very slowly take it down. It will probably stay at 80 psi. Thank you for the insight.

 

I have been running my 9r22.5 at 75psi for the past 10 yrs. Truck weighs 9500lbs. I rarely load it.
I did try running 80psi in the rears and the ride was noticeably harsher.

Good luck and tell us what works for you.

 

Will do but it will take a month or more because I'm cleaning and painting the back end underneath right now. Thanks.