Air Bag Question
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Air Bag Question
Newbie question - I have the Firestone Ride Rite air bags for our 2015 F250 PSD. Just installed the bags. Are you supposed to reduce the air pressure to 5psi when you disconnect at the campground and refill after connecting the trailer to head home? I also assume you never add pressure to the bags (above the 5psi min) until after connecting the trailer. Thanks for the advice.
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Thanks. Hat is helpful. I am trying to get a ballpark starting pressure point. We have a 37 foot TT weighing 10k when loaded. Hitch weight is 1000#. I read somewhere that 1 psi will lift 40 lbs. that translates to approx 25 psi in the bags. Does that sound right or way off?
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Joined: Jul 2006
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Once you figure out what your optimum pressure is while towing, you can air them up just before you hook up. It was easier for me to air them up before hooking up because my fill valve was located in the rear bumper by the license plate. I ran 75 psi with my 4000 lb pin weight fifth wheel.
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Post Fiend
Joined: Jan 2009
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From: Greenwood, SC
I don't have a real science to it, I tow 6 different trailers regularly so I have a little system.
I usually hook up with almost zero pressure in the bags. A heavy tongue will squat the truck and the bags will show 20psi (usually stops the springs juuuuust short of the overload leaf). So, I add another 20lbs to offset and I usually come out to the factory ride height, maybe just short of it at times. A lighter tongue will only add 10psi and then I would fill to 20-25 and see where it sits.
When cruising around empty, a F250 is a little softer than my current truck, I run at least 10psi to keep things nice. 86 gal of diesel, 5th wheel hitch, bumper hitch, tools, wood, etc add up to an easy 1000lbs of cargo just when I'm driving around town. Truck feels strange when I take everything out and I'm low on fuel.
I usually hook up with almost zero pressure in the bags. A heavy tongue will squat the truck and the bags will show 20psi (usually stops the springs juuuuust short of the overload leaf). So, I add another 20lbs to offset and I usually come out to the factory ride height, maybe just short of it at times. A lighter tongue will only add 10psi and then I would fill to 20-25 and see where it sits.
When cruising around empty, a F250 is a little softer than my current truck, I run at least 10psi to keep things nice. 86 gal of diesel, 5th wheel hitch, bumper hitch, tools, wood, etc add up to an easy 1000lbs of cargo just when I'm driving around town. Truck feels strange when I take everything out and I'm low on fuel.
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Cargo Master
Joined: Sep 2007
Posts: 2,470
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From: Chandler, AZ
Just make sure you don't deflate to 5psi BEFORE you remove load. If you do, the suspension will raises and pull a negative pressure (vacuum) in the bags. If you look at the construction of an air bag, they are designed to use positive pressure to hold themselves together. This is why a min of +5psi is recommended. Bags are pretty robust and will survive a vacuum but I wouldn't drive any distance that way.
Cargo Master
Joined: Sep 2007
Posts: 2,470
Likes: 535
From: Chandler, AZ
Thanks. Hat is helpful. I am trying to get a ballpark starting pressure point. We have a 37 foot TT weighing 10k when loaded. Hitch weight is 1000#. I read somewhere that 1 psi will lift 40 lbs. that translates to approx 25 psi in the bags. Does that sound right or way off?
The lift to pressure ratio is dependent on the bag diameter, vehicle weight and leaf spring rate. It's not a simple linear equation due to the leaf springs.
For a 5" bag (typical AL, FS kit) the area is 7.8 sq in. If you have 1 psi pushing on 7.8 sq inches, you get a lifting force of 7.8 lbs.
I run 7" bags, area is 11 sq in, so they take 40% less air pressure to lift the same weight.
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