Tire pressure for off road sand

[wyorancher]

You can also risk spining the tire on the rim. Tubeless tire probably only need re-balance. Tube type can tear out valve stem.

[TdogKing]

Originally Posted by TXiceman

Airing down on a heavily loaded tire will likely result in damzging the sidewalls. I would not take a chance on ruining an expensive tire.

Ken

A properly aired down tire especially driving on sand will not damage the sidewall. A under inflated tire driven at freeways speeds will ruin the sidewall.

[VanDiemen23]

Mr D, TXIceman - airing down for sand does not damage the sidewalls. If you are worried about spinning the tire on the rim, just take a silver sharpie and stripe the tire next to the valve stem - but it's never happened to me.

I've helped extract a guy that was buried 50% and he had more than 50 psi in his truck tires. Took em down to about 15, did a little digging in front, and it walked right out.

It's all about spreading the weight out over a larger area, to the point where the vehicle might have half the surface load of the same vehicle with fully aired tires.

Remember, you're not going to get any heat build up or centrifugal force (and it takes both to make the tire fail)

[wyorancher]

Originally Posted by VanDiemen23

Mr D, TXIceman - airing down for sand does not damage the sidewalls. If you are worried about spinning the tire on the rim, just take a silver sharpie and stripe the tire next to the valve stem - but it's never happened to me.

I've helped extract a guy that was buried 50% and he had more than 50 psi in his truck tires. Took em down to about 15, did a little digging in front, and it walked right out.

It's all about spreading the weight out over a larger area, to the point where the vehicle might have half the surface load of the same vehicle with fully aired tires.

Remember, you're not going to get any heat build up or centrifugal force (and it takes both to make the tire fail)

Guess I spent too much time around farm equipment. You can easily spin the tire on the rim with low pressure. At $1,000 a tire I'll call a tow truck.

[wyorancher]

I learned tire 101 the hard way plowing a field and tires spinning in loose soil. Dropped the air pressure, tire spun in the rim, tore off valve stem, dumped the calcium in the field, waited half a day for repair truck with new tube, calcium and costly repair. Not even mentioning the wasted day and tire repairman basically calling me an idiot because I lowered my air pressure. LOL

[BCooke]

But tractor tires were designed for non road use. So airing them down only gives you slipping tires.
Airing down, to a point, a road tire will give you some additional traction, just like 4wd, use it to get out of where you were heading.
A good example would be logging trucks, some have a airing system built in, for that little extra.

[TXiceman]

Originally Posted by VanDiemen23

Mr D, TXIceman - airing down for sand does not damage the sidewalls.

Tire manufacturers warn that truck, motorhome and even auto tires are subject to sidewall damage if run below the manufacturers ratings for a given weight load. The problem is excessive side wall flex while under load.

You may get by with airing down for a short time, but I would be worried about side wall damage if done for long.

Ken

[TdogKing]

I can't imagine why you need to do it for long periods of time in a Motorhome. I worked a career in Freeway Construction and seen/watched abuse of every kind of tire you can think of and never seen any sidewall damage that caused us to throw away a tire just from being low pressure..... But like all things in life...common sense goes further than a degree.

[VanDiemen23]

That's if you RUN the tire (in other words, down the highway) where you get enough sidewall flexing in a short period of time to heat the tire. the flexing (bending the wires in the sidewall plies back and forth) creates not only local heating that de-laminates the sidewall, but heats the bond to the tread cap, which isn't as strong, so you usually get a tread separation first - where the centrifugal forces conspire with the heat to pull the tire apart.

Going 10mph down 1/2 mile of beach isn't going to heat anything up.

In a sand situation weight is being carried by a much larger surface area, even the sidewalls themselves.

Now if you managed to get the sidewall so flat that it crimped the sidewall belts (bent the wire past the elastic limit) then that's a whole 'nother conversation.

[FDNYdave]

I deflate to 22 psi and would be willing to drop to 18-20 psi to get out of trouble,

[jackfish]

If you think you can't get there without reducing tire pressure then maybe you weren't meant to go there. Most attempts at this I've seen results in a stuck vehicle anyways.

[BCooke]

Remembered one of the systems.
A little company called Dana (Eaton) has one called Dana®Spicer®Tire Pressure Control

Looked them up and came up with:
http://www.eaton.com/ecm/idcplg?IdcS...ILE&dID=269991

Which lead to a statement they made, but it looks like that was made in or around 2001, so I do not know if it is still valid for today's tires.

They state, " The tire manufacturers have approved operation at reduced pressures when limiting the vehicle speeds. Their industry group, The Tire and Rim Association (T&RA), has published guidelines which outline the tire sizes, loads and pressures to apply this technology."

[NFlcamper]

As a native Floridian and having driven on the beach since I was 16 (back in 1982) I have pulled MANY 4x4 trucks out of the sand - with a 2wd car! Airing down tires is the BEST traction for ANY vehicle on a sand surface! Tractors and ATVS excluded, because they are low pressure tires to begin with.

Weight on the tires dictates how low you can lower the pressure. Light weight vehicles with bigger tires can go MUCH lower than heavy trucks with narrow tires. My old jeep with 33" tires could be safely driven at 45 with 8 psi in the rear tires and 10 psi in front (front held engine weight). A 2wd F150 I had, could go 10 psi rear, but had to have at least 12 psi in the front with smaller tires. My previous truck, a GMC Z-71 with the factory size tires had a hard time in sugar sand with full pressure. Lower pressure to 15 psi all the way around and I could drive the same place in 2wd! I haven't had my new to me Dodge Cummins powered truck in the sand yet, so I don't know how low I can go, but I will start about 20 psi and go as low as I can.

Now, HOW TO: park on a level and hard surface, using an air gauge, lower the pressure EQUALLY (especially on dual rear tires) till they bulge on the side wall fairly well but DO NOT LOOK FLAT (dual rear tires should not touch each other). Tires that look flat are too low! The sidewall should not be less than 1/2 its original height EVER (unless you are an AVID OFF ROADER in an off road vehicle). 5/8 of the sidewall original height is a great starting point. Example - a fully inflated tire with a rim measured at 8 inches from the ground should never be lowered below a measured height of 4". A measurement of 5" is a great starting point to look if the sidewall is flexed too much (looks flat). You want it to look like it is low, so that traction is greatly increased over fully inflated.
DO the FRONT too! You want the tires to ROLL over the sand, NOT plow through and create rolling resistance. Too many people only lower the rear tires and forget the front. The front tires are just as important even if they are NOT drive wheels!

The tires lowered to this point should be safe to be driven on a paved surface at speeds lower than 45 to get them reinflated within 5-8 miles. DO NOT go farther as damage happens with distance and heat building with the flexing of the sidewall. A way to reinflate the tires as soon as you get off the beach is best. Small portable pumps will burn up trying to inflate to high pressures (especially 12v). An A/C powered pancake compressor will do the job. OR locate a place to reinflate BEFORE deflating tires.

Tips for driving on sand:
1. Do NOT turn steering wheel unless MOVING! The front tires become PLOWS in the sand and will get you stuck fast! Big wide turns work best!
2. Have the wheels straight before stopping on sand. Keep them straight to start out again. Be rolling about 5 mph or more to turn.
3. In sand, do not stop hard - slow in advance and roll to a stop. It keeps from having front tires dig into sand.
4. If you have trouble starting forward motion, try backing easily to pack a trail for the tires to get rolling on.
5. Spinning should be avoided. If you are not moving forward or back, you are moving DOWN! Moderate the throttle for momentum and not spinning! Give it as much throttle to keep moving, minor spinning is sometimes necessary but NOT excessive spinning. Axle bounce (hop) will break things and is caused by excessive spinning.
6. If you can move forward or back at all, you aren't comlpetly stuck. At either end, there will be a steep sand ramp. Dig that steep sand ramp into a long tapered ramp, drive that direction and dig the opposite end to get a longer run, back and forth, till you are free.
7. NEVER stop at the bottom of a gully. Gravity is a force to overcome and it can be used to get you rolling, if you stop on a high point. Stop with the direction you will be leaving slightly lower than the other.
8. Never park below the tide line - you won't be there when the tide comes in! I have seen it too many times!
9. Momentum can carry you through some soft spots. Most beaches have a posted speed limit of 10 or 15 mph. If you see a streach you have to go through, be going the limit before entering the soft spot. Like posted in another post in this thread, WALK the soft spot first to pick your line through it. CAREFUL about going too fast as you can bounce pretty hard on small hills or drop offs.

[joemcgin]

Thanks for the great tips! Done up here on Cape Cod for the season but will keep this all at hand for next summer.