Tire Pressure - What's Right for You

Feb. 01, 2002 By Rick Sieman
Off-Road Tech: Tire Pressure:
What Works, What Doesn't and Why
By Rick "Super Hunky" Siemen
I've seen a whole lot of questions on OFF-ROAD.COM about what kinds of tire pressures should be run for off-road use. Nobody seemed to have the right answer. Perhaps I can shed some light on the subject. Here are the facts: General Info
  • If you run a radial tire on your 4x4, the maximum pressure you can use is 32 p.s.i. cold. When the tire is running hot, it will rise up to 35 p.s.i.
  • If you run more than 35 p.s.i. in a radial tire, it will lose its radial characteristics, and will become much more vulnarable to flats, will lose traction, and become very skaty on hard packed roads. Also, it will lose most of its flotation ability on soft sand.
  • About the lowest pressure you can normally use for off-roading is ten p.s.i., but care must be taken not to push the vehicle, especially under hard side loads. At this pressure, flotation in deep sand is excellent. However, steering accuracy suffers badly and the front end will respond in a sluggish fashion. Even with power assist, the steering feels heavy, much like your pump belt is slipping
  • The lowest pressure I have ever run is 4 p.s.i., and that was at some sand drags at an event in Rosarito. The tire looks damn near flat at that pressure, but it works and you get incredible traction in soft sand or silt. For mud , it's great.
  • Naturally, you have to completely avoid rocks or any other sharp stuff at this low setting, but I made a dozen 1/8 th mile runs at this setting and my 35 inch BFG All Terrain tires stayed on the 15 X 7 rims
  • At low settings (10 p.s.i. or less), the stress on the carcass is incredible and prolonged usage will actually break down the metal wire on the inner lip and cause seperation of the tire layers in cheaper tires.
  • Radials are the only way to go for serious off-road use. I have never - REPEAT NEVER - seen a really good non-radial tire for off-road work.
     Size Does Matter!
Tire size is critical when it comes to running lower pressure. While you can get away with really low pressures in a 33 or 35 inch tire, the same pressures in a 29 inch tire is begging for a flat For all day running in soft sand (or mud) I would suggest the following guideline:
  • 31 inch tires ... 16 to 18 lbs
  • 33 inch tires ... 14 to 15 lbs
  • 35 inch tires ... 13 to 14 lbs
Anything smaller should not be on your truck in the first place. If you're running monster sized tires, like 44 inch Gumbo Mudders, there's no reason for you to air down in the first place. On rocky terrain, like the Mint 400, I always ran maximum pressure. On mixed terrain with a mixture of deep sand and some rocks, 28 p.s.i. cold was always our choice. For use on slippery hard-packed roads with a lot of turns, do not run low pressures. It makes for fuzzy steering accuracy and contributes to excessive body roll if you're pushing it. Keep it firm and control increases.
     Side Notes
  • All Terrain tires work better on sand than Mud Terrain patterns. The M/Ts tend to dig through the sand, rather than float.
  • Steering accuracy is better with the M/Ts in sand, but you'll spend more time spinning your wheels with the agressive tread than with the A/Ts.
  • On hard-packed dirt roads, the A/Ts hook up much better than the M/Ts, and you can actually hear them squeal when you're sliding on adobe surfaces.
  • Always run valve caps, especially if you run at high speeds. When you're on a dry lake bed doing 120 mph, the small spring on the valve core can lift and let air out. Not a good thing. Only run valve caps with rubber gaskets in them.
  • If you just want a super comfortable ride, say for chattery fire roads, try 22 to 24 p.s.i. and it'll smooth the ride out amazingly well.
Rick/Somewhere in Baja

Off-Road.com Newsletter
Join our Weekly Newsletter to get the latest off-road news, reviews, events, and alerts!