Driving in sand....deflate tires or not?
 

I'm doing all my 4-wheeling on the beach sand at Carolina Beach (Fort Fisher/South end)d, where the sand is considered "sugar sand" by the locals, due to the soft sugar-like flow it has.

I am able to drive on the sand with my tires fully inflated, but I have also noticed that I have an overheating problem with the engine/transmission, which I have not been able to pin-point. I thought that after our first trip on the beach, in 4H, maybe it was driver error, but we has similar results when I recently went out in 4L. While it didn't get so hot that it stalled, I was watching the temp. gauge this time, and it started climbing up around 220F, when I decided to stop for awhile. Once off the sand and on the street, it seems to maintain 190F, which is what the T-stat is rated at (I believe).

I didn't deflate the tires (31x10.5 R15), since a neighbor said that he seldom deflated his, but wonder if maybe that was my mistake. I know that deflated tires will help with traction in the sand, and I wonder if it would also reduce the strain on the engine/tranny. I really wasn't running the engine hard, but did try to keep the RPMs up a bit, to have the mechanical fan running more efficiently.

What are your thoughts? I know that lots of you guys in this area driving on sand, and have lots more experience than I have. About 30 years ago, I drove a 1977 GMC Jimmy with 32" tires and a 350 V-8, but it was new, and had a auxiliary oil cooler installed....and honestly, I think I dropped the air in those tires, but that was up on Long Island, NY.

it's always a good idea to drop air pressure whenever possible off the pavement.

for your overheating, did you have the a/c on? this will overheat a slow moving jeep all day. also, maybe the clutch in your mechanical fan is a little on the weak side.

how's the coolant condition and level?

ah yes good ol' suga sand. We have tons of that here in jersey (even off the beach in the Pine Barrens). Requires a ton of throttle and it'll sink you down when you start losing speed. Airing down helps by giving your tires a nice fat footprint which will keep you on top of the sand better. The idea is you want to float so fat tires work great on sand. It's the exact opposite of what you want in snow lol. I would get your overheating problem nailed down before anything. It never really gets better and you don't want it to ruin a fun day.

As stated by others, airing down is your friend.

I have experienced the same thing as far as engine temps. 220 isn't necessarily all that bad. The efan doesn't kick on until 215. Driving on loose sand means you're always in the throttle and at low speeds generally means the torque converter is always slipping. This will lead to a spike in tranny temps and since the tranny fluid runs through the radiator, you are now exchanging that temp spike to the engine coolant making the entire cooling system less efficient.

There are other factors of course. Age/condition of coolant, water pump, t-stat, fan clutch, cap, and radiator all play into this.

What I did to solve/battle the temps on sand are the following:

efan on a switch
coolant flush and replacement
drive at higher speeds (allows torque converter to fully lock and also helps with airflow through radiator and around engine bay)

Just a note: I was on 33s with 3.55 gears when I did all of the above

if driving any distance in sand, always air down. 18 psi is good.
Match the driving surface, soft/deep sand requires soft tires. Airing down causes the tire to flatten front to back and become like a tank track.
Will reduce the load on transmission and engine and driveline by a great deal.

4-Low will certainly work better in the deep stuff when speeds are slow. The torque converter will remain engaged more in 4-low. When driving in 4-hi there is significant slip of torque converter.

This picture is what happens when driving 11 miles on the beach with an automatic transmission and full tires. The transmission overheats, vents its fluid which ignites on engine. There is no stopping that once started.

Hey, just planning a move to Wrightsville Bech and the Jeep Compass needs new tires. Will probably want some sand tires for the occasional, not serious, driving on sand. What would you recommend? Seen some on tire rack but sand tires were 160$ each.

Wow was that first picture from Summer of 2014 on the beach north of Corolla? I remember seeing that. As for driving in the sand deflating the tires makes a huge difference even if you are running larger tires. I have had my truck on the beaches of OBX on two vacations. The first year I had stock size tires and I deflated them to 25 psi and never had any problems getting anywhere I wanted to go in 4x4. The next time I went I had 35X12.50s and I figured since they were 2" wider than my stock tires that I wouldn't need to deflate them. I was WRONG, I got into a soft spot and almost buried it to the axles, I then deflated to 25 psi like I should have then I drove right out and never had anymore issues the rest of the trip. Keep in mind though that a 7,500 lb truck is going to be a little bit different than a 3,500 lb XJ.

I heartily disagree here.......airing down makes the tires effectively wider, which means more traction/friction surface that the engine has to overcome.

It actually increases the load on all of the above....not decrease.

Have you ever pushed a vehicle with a low or flat tire ? It is a lot harder than if the tire is properly aired up.....same thing when intentionally airing down.

I have to chime in on this. Whether I disagree or agree, this is how it works. I have many hours/days on the Oregon coast dunes etc and there is only one situation you want to run full pressure. If you have paddle tires. All other tires you drop the pressure and increase the foot print of the tire. It works best with radials since the sidewall will distort and allow the tread to remain unaffected and increase the length. Works with bias ply tires too, but not as well since the tread squirms as it goes from front of the foot print to the back. The idea with sand is to not disturb it, unless you have paddles. All those little grains act like ball bearings and the tire will start to dig holes if it is too hard. By dropping air, the tire is soft enough to conform to the profile of the sand and not disturb it. Whether or not this takes more horsepower is up for debate, but traction is better and is a much more enjoyable experience. Also you will be able to run at a lower engine rpm since you are not trying to climb out of a hole all the time. You can choose any speed from slow to fast.

On pavement that will apply, in sand it does not. There are other forces involved that override the resistance of a partially flattened tire. What I stated is true when deep sand is involved, airing down reduces "load on transmission and engine and driveline by a great deal."
Not only that, but if you run full pressure (33+ psi) than you may not even make it onto the beach from the access trails before you get stuck or overheat.
Land Rover drivers are notorious for thinking they do not have to air down and they always get stuck at the beach entry, all four wheels digging holes.

In sand it is not about rolling resistance, it is about floating on top of surface. If you don't float, you will not make it far.

Made a trip to the Outer Banks and the 4x4 Beach last fall, had all the gear to air down and up easily. One significant thing I noticed during the various beach runs to get sunrise/sunset pictures, I burned less fuel with the tires correctly aired down, as I was not using the skinny pedal and momentum to simply keep moving in the deeper sand. Air down and go green :icon_wink:

Here on Hatteras we have issues with those that do not know better or are too lazy to air down. The new motto is "Don't be a Clown, Air Down"