Why Air Down?

[Dave]

Why air down? You will actually note an immediate increase in the vehicle's off-road capability and performance. With less air, the vehicle will have a larger contact patch to provide more grip which is especially helpful in mud, deep sand, or snow. It’s preferable to float on top of rather than sink into these substrates. You will also be able to crawl over larger objects with less effort.

That brings us to the next major benefit. Lowering PSI makes things a lot easier on the driveline, suspension parts, and the vehicle as a whole. With street PSI your ride quality will suffer offroad, but a softer tire will absorb impacts better and ensures a measure of “mechanical sympathy”. Smaller bumps, sharp stones, and debris will be absorbed before the suspension even gets a chance to do it’s job, and you’re less likely to receive a puncture.

Additionally, the larger contact patches are easier on the trail system, which helps us Tread Lightly! You’ll need an air compressor too so remember to air up once you head back out onto the pavement!

 

[Dean]

As I like to say, "Your tires are just as much a part of your suspension as your springs and shocks." Too much air for the terrain will contribute to shock fatigue and a harsh ride which will increase premature wear on suspension components. Too little air for the terrain or speed can increase premature tread wear, heat build-up in the sidewall, and possible delamination of tire layers - not to mention possible bead failure.

My rule of thumb is the "rule or thirds."

• Daily Driving = Street PSI @ Highway speed
• Trail Pressure = 2/3 street psi @ 2/3 highway speed max
• Technical Pressure = 1/3 street psi @ 1/3 highway speed max

Example using my jeep

• Daily Driving = 36 psi @ 60 mph
• Trail Pressure = 24 psi @ 40 mph max
• Tech Pressure = 12 psi @ 20 mph max

There are a lot of variable to consider when tweaking air pressure.

• Speed = lower pressure means slower speed. If you're hooning it down a gravel road at 50 you'll want more air than 2/3 rule of thumb, if you're going slower over more technical terrain you may need less (if your wheels and tires can handle it)
• Wheel size = larger sidewalls on smaller wheels (a 35" tire on a 15" rim) handle lower air pressure a lot better than big wheels with small sidewalls (like a 35" tire on a 20" wheel)
• Weight = more weight means more air pressure, so if you're out there with a bloated pig on wheels you may want to run a higher pressure than the above mentioned rule of thumb

As with most things, your preferences may be different than someone else's. There are tons of variables to consider and the ultimate check is the chalk test. Run a bead of sidewalk chalk on your tires and test/confirm you air pressure and adjust as needed.

• Even wear pattern = correct air pressure
• Chalk worn off the middle = over inflated (tire is riding on the crown of the tire tread)
• Chalk worn off the outside edges = under inflated (tire is riding on the shoulders of the tire tread)

 

[WashingtonTaco]

Thanks for posting those images, I saved them for future use.

 

[ArkansasDon]

Good information