Driving on beach and told to let air out of my tires so we didn’t get stuck. It’s like I sort of understand but I don’t really?
In: Physics
When you air down your tires, they sag out and distribute the load of your vehicle across a wider contact area on the sand.
By increasing the surface area of the tires, they become less likely to sink into the sand and become stuck, while also allowing more traction by increasing the amount of tire that’s in contact with the sand.
By lowering the pressure you flatten the tires out, giving you a larger contact patch, which spreads the weight out and helps prevent digging in.
The contact area between your tires and the ground is equal to the load on the tire divided by the pressure in the tire.
If you have high pressure the tire will load up a small area of sand and then cut into it, and will then have ineffective contact with the surrounding sand making it hard to get traction – the actual load will still be transferred to a small area of sand.
If you lower the pressure the contact area gets much larger, so your tires cut into the sand less to start with and if they do they have more effective contact for getting traction to get out.
This is a surface area thing.
Bigger tires would sink less.
Since you aren’t likely to replace your tires to go to the beach you can let some air out causing the part with contact to be slightly larger and increase surface area.
It’s easier if you think of it as a more extreme change.
Pretend your car tires are your feet at the beach.
Walk on your tip toes and see how far you sink down.
Now try it with a flat footed step. You will likely sink less
Same concept. Letting air out is sorta like walking flat footed but your weight didn’t change.
Ever watch a slow motion gif of a drag racer launching? The tires are very soft. They wrinkle and buckle. This makes much more of the tire contact the pavement. Bigger area of contact means more traction. The crazy levels of power those cars produce would overwhelm standard tires. With normal tires, most of that power would be wasted. The tires would just spin and smoke.
The same thing happens when offroaders deflate their tires. The tire gets softer, the contact patch gets bigger and more grip, more traction is achieved.
At its extreme, say with rock climbers, the tire actually wraps around smaller projections in the terrain. It’s like the difference between dragging a rock toward you with a flat palm or actually grabbing it to slide it towards yourself.
Latest Answers