A question that gets asked at almost every trail head. Also added to this question: I can't air down I don't have beadlocks, I can't air down too much because I don't have beadlocks. I'm told airing down my tires will damage them.
When it comes to off highway tire pressure, there are few disadvantages to reducing your tire pressure. how much is always the question. And making sure you have the ability to return the tire to street pressure when ready to go home - or adjust as the day changes (buy a portable compressor).
I have off-roaded a wide array of tires and tire sizes. The Jeep with flames is running 37 inch tires in this picture, but it has run all the way up to a 44 inch tire. The Grey Toyota Tacoma (pictured) is a stock TRDPro model I borrowed from Toyota for a trip to Moab for Easter Jeep Safari on factory tires - yes I aired those down too, 8PSI in the sand 12 PSI in the Moab rocks. and third is my current Jeep, which runs 40-inch tires for summer and generally 43-inch tires for winter. Pictures here on 40 inch tires at about 8 PSI . We won't get into brands here or beadlocks, just air pressure and what it can do for you off road.
Lets start with why:
Decreasing your tires pressure INCREASES the amount of tire touching the road surface and helps the tire conform around obstacles. A fully inflated tire will try to grab onto whatever the top of any pointy object you are trying to get over. A manufacturers recommended tire pressure for your vehicles takes into account a lot of different things and is balance for all the on road conditions it may encounter, keeps the best handling requirements, best fuel mileage and keeps the heat generated from road speeds to a minimum. No tire manufacturer will give you a recommended off-road tire pressure for your vehicle. And I'm going to be a little vague here too - for the same reason - there are far too many variables. but we can look at some typical situations and how you can visually check, your own rig, and get a pressure that will work for you.
The variables:
Vehicle weight
Tire size
Rim size and type
Where you are off roading.
Gravel roads:
We all run gravel roads, I air down my off road rigs the second I hit continual gravel. It simply takes the harshness out of every pot hole and wash board sections and helps with vehicle control. Even with todays new vehicle with all the tractrion control nannies built it. Stopping your truck or off road vehicle from chattering across gravel corners will help you maintain control and reduce the amount those traction control systems kick in. Yup even on my 2020 Sierra X31. Yes I pack a air compressor. On my truck I am in the mid 20PSI range on gravel roads 33 inch tire. If needed I can comfortably get to a gas station after a gravel trip to air back up, on my Jeep with a larger tire I would be in the 12-14 PSI range, but those large tires carry more weight and I only run them at 24 PSI on the street where my truck is 35psi on the street 40psi towing. always experiment in 2PSI increments. Visually check your tires as you do so, feel out the handling characteristics as you air down, as that will change as well.
Rough off-road trails:
Now we are getting serious. Beadlock wheels or no beadlock wheels. If your running a good quality tire that has good side walls (A key factor here) on a Jeep style vehicle I would be no more than mid teens for air pressure. I have comfortably run single digits on a good rim and tire combo (not beadlocked) and as low as 5 PSI on a good wheel in the sand with no beadlocks. Adding beadlocks adds confidence that you will not pull a tire off a rim - which can be challenging to get back on the rim without proper tools. My Jeep on 40 inch tires and beadlock rims I generally start around 8 PSI and for rock trails have gone down to 5PSI pretty regular depending on conditions. Again the variables, Tire quality (radial versus bias-ply), rim quality, vehicle weight, tire size etc all come into play. so there is no solid rule here. Take your time, every tire and vehicle is different, try different pressures, again carry some type of compressor to air your tires back up as conditions change. The chart below borrowed form the internet gives a pretty good example of tire tread patch on the ground based on tire pressure on a typical size tire. This is not a tried and true sample as every tire is different and tires are rated to hold "weight" based on class of tire and size. C,D,E ratings coincide with weight handling ability. a Radial tire will bulge out faster than an off-road dedicated Bias ply tire.
Snow:
Think like sand, soft moving surface, easy to dig holes, generally away from objects you can winch too. At left are my 43-inch tires, on beadlock wheels with a Coyote inner air bag beadlock at 2PSI which is a typical air pressure for me in deep snow but I have tried lower. They are also grooved and studded, everything I can do to make that tire size work, yes I rock fast trails like this but that huge footprint is what enables me to go as far as I do, but not as far as the guys on 46's, 54's, 58's etc haha!!!!
Recap:
There is no true have it all tire pressure no mater the tire, wheel, vehicle, conditions you are in you need to find what works for your rig, Experiment, could be you change tire pressure several times a day on a wheeling trip - I do. Altitude also changes tire pressure by about 1 PSI for every 1000 feet, check often you could start at 12 psi at the start - climb a long ways and check your tires and you could be 15-18 or more! Same goes for coming back down - you will lose that pressure - you will probably need to add some air to your tires, but there is virtually no negatives to adjusting your tire pressure, try different pressures, experiment a bit and enjoy your added traction for your off-road pleasure!
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