I'm learning here, because I am thinking about this all wrong maybe. First, I was weary of airing down E tires so low thinking that any tire needs have at least ~25% of its max pressure or risks overheating (from extra friction), damaging the sidewall or falling apart (needing the air pressure to hold its shape and support the vehicle's weight). Guess I was wrong about these?
Second, I had sort of figured that air pressure wouldn't matter much to a puncture wound. If a rock is sharp enough and at the correct angle to cut the rubber, then it will. Whether the tire is softer or harder isn't going to matter much since it is still (literally) tons of weight pushing on the sharp edge.
Do I have this all wrong? Man, I'd love to see the Mythbusters test this one out.
Here's a far from scientific example, but relevant I think... If you blow up a balloon so it is full or nearly full and push a pin into it, it will quickly puncture it & pop. However, if you blow up a balloon only halfway, then push a pin into it, the balloon will deform around the pin quite a bit before it punctures and pops. It's similar with a tire... especially at any kind of speed on a rock filled trail. Less air in the tire will allow the tire to deform over a sharp rock, while a tire at max PSI won't deform, possibly leading to a puncture.
The 'hard bounce' you mention is another factor that is eliminated with an aired-down tire. What you don't see on the photo I posted, is an extreme drop-off on the driver's side (that was taken at the exit/entrance to Elephant Hill in the Needles Dist. of Canyonlands) A few hard bounces coming down that narrow rocky stretch potentially could have bounced me uncontrollably off the side to a likely demise or severe injury.
So rather than leave my tires aired up, resulting in a ride down that section like sliding down a staircase on your butt - a jarring, semi-controllable experience, I aired down my tires, eliminating any hard bounce/recoil from the rocks, so I "flowed" down that section like pouring water down a staircase instead.
Again, I apologize for my less-than-scientific examples here but they're a couple of decent analogies... The softer ride on aired down tires makes it easier on the kidneys (SunMan is right) the dental work and the vehicle & camper which aren't forced to absorb all of that recoil from the hard bounces. I never used to air down going over the Alpine Loop and it was like riding a horse, bouncing in the saddle all day. Now I air down and it is much more tolerable. Still a bouncy ride but kinda in slow-motion. Much easier on me, my passenger and vehicle. Same in the Maze District, Death Valley, etc. These 3 off-road areas are notoriously rough on tires, shocks, leaf-springs, coils etc. but airing down makes them more tolerable.
Peeling a tire off the rim is a concern, but as UglyScout mentioned, those happen primarily at high speeds while taking a sharp turn, like when out in sand dunes or in deep snow. It can happen anywhere I suppose, but primarily those are the type of places & conditions where peeling a tire off happens.
Give it a shot sometime and see what you think. Just make sure you have a way to air up, or that there is a gas station nearby with air, before driving too far on pavement back home.
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