On trucks & Off-roading

Airing down
It’s something that I always had heard about, but hadn’t ever really done on my truck: airing down the tires substantially while off-roading. The reasons for having not are simple, really. Airing down a lot means I’ll have to air up a lot at some point in the not-so-distant future, and an air hose is not usually readily available out in the boonies. Also, there’s the fact that really & truly, I’ve never been some sort of off-road master or anything. I have really just been off-roading so far as to say that I got my 4Runner dirty or whatnot.

But then we got a new truck, and we went all-out and got all the off-road goodies. And there’s a LOT more room for the dogs in the back, so going all out is more a possibility now; we explore a lot anymore, especially along the beaches & rivers. And lastly, I sort of solved the “airing back up” problem.

I had always heard that airing down the tires gets you much better traction, especially on sand. I know the mechanics of it: you extend the “contact patch” of the tire out, giving you a larger footprint for the same-sized vehicle. On sand, this allows you to “float” on the sand a bit better, without sinking in as much. How much? Well I wanted to find out, so yesterday I took the dogs out to the local dunes @ the bay, to experiment. I drove around in some areas I’m familiar with and knew I wouldn’t get full-on stuck to begin with. I felt how the truck responded, how it handled certain obstacles, and how it drove in the sand.

Then I aired the tires down. And what a difference it made. I was truly impressed I honestly was. I don’t have bead locks (which hold an unaired tire onto the rim when there’s little or no air pressure) so I didn’t want to get crazy with the amount of air I let out; I dropped from a streetable 36psi to 20psi – about 16psi difference. And I was instantly stunned at the difference it made.

Typically when aired up, as I take off in the sand the truck first digs down about 2-3 inches before really moving forward much. When they were at 20psi, it just went forward. I tested to see how much “float” I had, and drove at the same speed right next to my old “aired up” tracks. Just going down to 20psi shaved almost – if not a little more than – two inches off of the amount of sink I experienced in the sand. I was impressed.

Then I went to a sandy hill that I can’t climb from a slow start fully inflated. Usually what happens is the tires just start to dig and throw sand out the back, and the truck starts to buck and I go nowhere. With the tires aired down though, it didn’t even hesitate, not even a little. It just climbed right up.

Which makes sense. With such a long contact patch, to throw sand out from underneath means that a lot more sand needs to move, and the sand in front is waiting on the sand behind it, which is being held down firmly by the length of tire above it. The rim rides a little forward on the rubber footprint, so the digging force is applied there, but with a long tract behind that holding the ground underneath steady, physics dictates that it’s easier for the truck to go forward from that spot than it is for the ground underneath to try and cover that much area and move. It makes sense, I just didn’t think that a mere 16psi would accomplish that much.

It’s like night & day. Really. Aired down, there’s about nowhere I think I couldn’t go with this setup. It’s beautiful.

Now I just need somewhere to go!



4Runner sand performance question also answered
I had felt for some time that it seemed to me that the 4Runner would float a little better on the sand than the Tacoma. I think I know why now. The tires I put on the tacoma are a little stiffer and have a higher air pressure rating. So of course I oblige and fill them up more. On the truck, I run with 38psi up front and 36 out rear. On the 4Runner, I ran with 32psi up front and 28-30psi in the rear.

I think that the few psi difference explains why – in street trim – the 4Runner floated better on the sand.



The “Air Solution”
The Tacoma has a power outlet in the bed of the truck. Yeserday morning, I stopped by sears to check out small compressors. They had a handful there, so I picked one and ran. The one I got said it would fill a certain sized automobile tire from 0psi to 30psi in 1 minute 50 seconds. “great” I thought, “since I’m only going from 20 to 35 or so psi (average), it’ll probably be about the same for me with my bigger tires; 10 minutes or less, baby!”

Wrong. That compressor’s going back. It took – I kid you not – at LEAST 5 minutes a tire to go from 20psi to 36psi. I don’t mind waiting a few minutes to get back on the road, but f*ck man, I stood around waiting like 30 damned minutes! Ain’t happening like that again; I’m going to get a more powerful one from somewhere. That is just not cutting it.



Bottom line
If you’re going to go mess around off-road, take the air pressure out. It makes a world of difference, even if you’re not going all-the-way and running with just 8psi. Seriously, don’t get stuck – get the air out of the tires and just go.

I’ll try to get pictures up maybe and link to them. If I remember.