Tire pressure and air-bag pressure - How to find the sweet spots?

Stereo

Adventurer
I have a 2003 Toyota Tacoma 4x4 extended cab with a Northstar popup truck camper. I finally got around to locating a CAT scale to check my axle weights. Loaded, they are 2700 lb front, 2960 rear. (Taco owners with loaded FWC's, what is your total weight or your axle weights?)

The truck originally came with P265/70R16 tires. Based on previous forum readings, I chose to upgrade to an E-rated tire for more puncture-resistant side walls, due to the rocky roads we frequent. (They're called the Rocky Mountains for good reason!) Per the tire store's recommendations, I am currently running on Falken Wildpeak A/T 3W tires, size LT245/75R16. What is the best tire air pressure for average conditions? The tire store suggested I run on 40 lbs all around with the camper on, 35 when off. Another tire store suggested 45 front, 55 rear with the camper. I called Falken and they asked for the OEM passenger tire rating and then said to run at 48 all around. I looked up the load-rating chart for these tires which shows 1700 at 35 lbs, 1870 at 40 lbs, 2030 at 45 lbs, etc. The tire charts are per tire, not axle weight, right? So, dividing my rear axle weight by 2, I get 1480 per tire on the rear axle. Based on the mfg's chart, it would seem I would be well within the tire's load limit at 35 lbs per tire which would be much more comfortable on the rough roads we drive in the mountains after hours on the highways.

If 35 is right, how low can I safely air down for really rocky sections?

I would like the best tire wear at the most comfortable pressure within safe margins. I'd appreciate your advice, especially if you have a Taco/camper combo.

I'm also uncertain about my air bag pressure. Before I loaded the camper, I measured the distance from the ground to the top of frame on both sides. After adding the camper, I pumped up the air bags until I reached those measurements. It took about 63 lbs on the heavy side (frig furnace, sink, cabinets), 52 on the light side (propane, bench). But the camper tilts markedly down towards the front of the truck, I guess because Tacoma beds are generally pitched that way. Should I just lift 'till level? I would guess the camper would ride better on rocky roads at lower pressures.

Thank you for your advice.
 

LandCruiserPhil

Expedition Leader
I have a 2003 Toyota Tacoma 4x4 extended cab with a Northstar popup truck camper. I finally got around to locating a CAT scale to check my axle weights. Loaded, they are 2700 lb front, 2960 rear. (Taco owners with loaded FWC's, what is your total weight or your axle weights?)

The truck originally came with P265/70R16 tires. Based on previous forum readings, I chose to upgrade to an E-rated tire for more puncture-resistant side walls, due to the rocky roads we frequent. (They're called the Rocky Mountains for good reason!) Per the tire store's recommendations, I am currently running on Falken Wildpeak A/T 3W tires, size LT245/75R16. What is the best tire air pressure for average conditions? The tire store suggested I run on 40 lbs all around with the camper on, 35 when off. Another tire store suggested 45 front, 55 rear with the camper. I called Falken and they asked for the OEM passenger tire rating and then said to run at 48 all around. I looked up the load-rating chart for these tires which shows 1700 at 35 lbs, 1870 at 40 lbs, 2030 at 45 lbs, etc. The tire charts are per tire, not axle weight, right? So, dividing my rear axle weight by 2, I get 1480 per tire on the rear axle. Based on the mfg's chart, it would seem I would be well within the tire's load limit at 35 lbs per tire which would be much more comfortable on the rough roads we drive in the mountains after hours on the highways.

If 35 is right, how low can I safely air down for really rocky sections?

I would like the best tire wear at the most comfortable pressure within safe margins. I'd appreciate your advice, especially if you have a Taco/camper combo.

I'm also uncertain about my air bag pressure. Before I loaded the camper, I measured the distance from the ground to the top of frame on both sides. After adding the camper, I pumped up the air bags until I reached those measurements. It took about 63 lbs on the heavy side (frig furnace, sink, cabinets), 52 on the light side (propane, bench). But the camper tilts markedly down towards the front of the truck, I guess because Tacoma beds are generally pitched that way. Should I just lift 'till level? I would guess the camper would ride better on rocky roads at lower pressures.

Thank you for your advice.
Attached is more than you will ever want to know about street time pressure. It looks like you are very close to where you should be but take a look at PDF.

For airing down I developed this system https://www.expeditionportal.com/forum/threads/airing-down.212890/#post-2744197

Not sure the manufacture of your air bags but that seems like a lot of PSI. Have you reached out to the manufacture? Air lift was helpful to me.
 

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quickfarms

Adventurer
Lower the airbag pressure until the truck is level. Check the manufacturers mac pressure, if you are exceeding that you need to add a long ad a leaf or go with custom springs.

Tire pressure is an interesting game for a loaded truck which I would consider this. You need to factor in load capacity, tread contact for tire wear and handling.

What I do is inflate the tires to max. Use sidewalk chalk across the tread, drive about 100 yards and check the wear, then lower the pressure until you get full contact, all the chalk is worn off. This will get you maximum tread life but often the handling is not great and you may find that more pressure is better.
 
I’ve got Air-Lift bags on my Ranger with a Khaya (1200lbs +- loaded) and keep them at about 30lbs. I also have load Range E tires, I keep around 40lbs.

Your airbag pressure seems a bit high to me, my truck would feel like a pogo stick with that much air.
 

jonathon

Active member
Max cold pressure on those tires is 80 PSI and that is where they get their max load rating. Obvious your truck is pretty light even with the camper but you do have to take into consideration that pressure not only relates to load capacity and wear, but handling. The tires will probably support the weight just fine at 35 PSI but may not handle very well. I would start at Falken’s recommendation of 48 PSI and check with chalk. As quickfarms mentioned once you are at a pressure with even contact you may need to add more air to get desirable handling back. Off pavement is a little different and there really isn’t a do all tire pressure. I run 20 to 30 depending on terrain, my truck is at least 8000lbs when loaded for a day trip.
 

primussucks

New member
Carli has a pretty good write up on tire pressure.

 

CoyoteThistle

Adventurer
I've been playing with tire pressure and airbag psi's lately. Here's what I've found so far.

I'm at a similar weight but in a Nissan Frontier (I think my weight is more biased towards the rear than you, but don't know for sure). 235/85-16 E-rated tires. I found 65psi in back and 55 up front works good for highway. For non-4X4 dirt roads, 50 in back and 40 in front results in big improvements in ride quality over rough stuff. It's okay for highway but there is some noticeable squirm. Slowing through the curves is good, but an emergency maneuver could get a bit dicey. Tires are noticeably bulging out at the bottom at this pressure too. I've aired down to high 20's rear and low 20's front for technical stuff with no problems.

In regards to airbags, I've had three different leaf spring setups. 1) Overload leaf removed and single add a leaf. Had to run pressure at 65psi in the bags to maintain ride height. Rode terribly. 2.1) Stock leafs (with overload). Had to run pressure at 55psi in the bags to maintain ride height. Rode a bit better than above, still bad. 2.2) Stock leafs (with overload). Ran about 40psi, sagged in the rear (overload leaf mostly engaged at all times). Rode okay but definetly sagging in the back. 3) Old Man Emu Medium Duty leaf springs plus 1.5" lift block (rear sits 2.5" higher than front unloaded). 20psi in the airbags and the truck is level, overload leafs mostly engaged when sitting level. Ride is a 1,000 times improved versus other versions. I think to get a decent ride with airbags on our relatively light rigs, it's pretty important to get air bag pressure down pretty low.

Curious to hear other's experience.
 
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