I use my F-150 as a jack-of-all-trades vehicle. It alternates between being a Jeep, an F-350, and a daily driver Civic from day to day every week. But two days a week I use it on the beach up here to haul my boat out of the water. Launching on the sand sucks, and the F-150 really sucks at it. It'll start digging in almost instantly.

I'm gonna lower the tire pressure down from 65PSI (the max load for the Mickey Thompson 285/75R16 tires) in a last ditch hope, but what would be a safe PSI for both beach work and highway cruising?

Two different animals, by trying to satisfy both categories, neither will be happy. To get a good pressure on the road, it'll suck in the sand and vice versa. Usually for sand, I don't air down any further than 10psi...beyond that, I get a little worried of loosing a bead. For street use, just use what's on the sidewall. If you try to find a middle ground, you'll have sloppy handling on the street, even worse gas mileage and you'll still end up getting stuck in the sand.

Ben is correct. I ran my tires at 10psi on the street, handled like crap, but it was a big slow truck and i didn't care, the gas mileage was horrendous and the tires wore much faster....

Airing down will be a big help in getting the boat out. If your just making a trip back to the house, and its not a long drive, i would say its ok. Just keep in mind it will be handling different with the lower psi in the tires, when you get back to the house then air back up...

yeah if need be air em down to get the boat out easier, then stop at the nearest gas station and air em back up or at least when ya get home.

Look for one of those onboard air compressors.... then you can lower the pressure at the beach, and then air back up before you hit the pavement.

HazzardMadWolf said:

Look for one of those onboard air compressors.... then you can lower the pressure at the beach, and then air back up before you hit the pavement.

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If he goes with a York setup, those bad boys eat an easy 2.5mpg's...don't ask me why, but they do. The thing to do if he wants a portable air compressor is grab a 12/120V plug in style that you can get just about anywhere for under $40. Get an extension, plug in to your lighter or just jump it off the battery and you're good to go.

All the ones I've seen hook up to the battery, don't know how that would affect your mpg. They are expensive though.

HazzardMadWolf said:

All the ones I've seen hook up to the battery, don't know how that would affect your mpg. They are expensive though.

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York style runs off a belt...and is a common mod. The only electric air compressor I've seen made to be kept in a vehicle that runs off your battery is the Warn setup, that won't fit under your hood and starts out at $500. I've never seen an underhood electric air compressor.

An old truck I used to have, had a rear bumper fashioned out of a large metal pipe. I welded up some ends, installed some fittings, and had a very handy air tank.

I will not introduce myself in an opening-topic becaus I yust want to answer your question.
I have been busy with calculating tire-pressure with the same system that the car-and tire-manufacturers in Europe used up to 2000.
They are still using the same Equation but keep it extremely high nowadays.
learned myself Excell to make spreadsheets for it and translated a few from Dutch to English.
Here is a simple one for whenn you dont drive faster then 99miles/h.
Afterward you can play with the temperatures, to see how it influences the pressure.
Always take enaug reserve for misreadings, pressureloss in time, and when you want to take some extra load.
But your tires are probably oversised and can probably be used at a much lower pressure.
Yust calculate it.
Important for the needed presssure is the load the tire must carry and the speed you drive with.
http://cid-a526e0eee092e6dc.office.live.com/self.aspx/.Public/pressurecalculationwithtemp.xls
Then you could find that you can use a much lower pressure for on the road, wich would be less worse for in sand.
The gripp-percentage I myself introduced, and means that the real weight on the tire is percentage of the weight fyou calculate the pressure for.
Save would be to keep it as low as possible , but if you go to low , you experiënce discomfort by bouncing ( probably do already now but are used to it) . I placed the bouncing border , by reactions, on 85% for persons in the vehicle and 80% for no persons in it ( trailers,caravans).
You can navigate my complete public map of hotmail , where I have a E-mail adres with the same username as here, from the link mentioned above.
Greatings from Holland
Peter

try 40-45 psi might help a bit

Evan's f250 said:

try 40-45 psi might help a bit

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Not for the sand...and it would only help on the street and only if his tires are rated for that...some are rated for less air than that.

Yeah, you need to get down below 20psi on the sand. Maybe as low as 7-8 to get a nice large footprint in the sand so you don't dig down and sink. Also leave it in 4 hi and try to take off slowly. For street driving if you have the truck loaded go as high as your tires can take. Like everyone else said, try to get an on board compressor of some type. I have the york OBA setup in my bronco and love it, it fills a 5 gallon tank to 100+psi in seconds and if all of the rest of the stuff in the truck were rated for it it would easily go well over 200psi, but all of my stuff is rated at or around 100-125 so I try to keep it below that. Yeah, it's FTE, but there is some good info in here about it.

http://www.ford-trucks.com/forums/528076-full-york-oba-install.html

If you want to run the electric style compressor just wire it in in place of the york style compressor. Run your hot wire from the pressure switch to a solenoid/relay that will run 12v hot to the leads that come off of the compressor you buy. Wire it directly into the battery from here and ground it as close as possible with a short a wire as possible to the frame or some other substantial piece of metal (engine block, seat mounts, bolts of the body, etc, just make sure you clean it to bare metal before hand). Also, make sure you get a compressor that can handle that kind of load. Those cheapo ones might work, but I don't know. It will certainly help if you use a tank as well, but I don't know if those cheapo ones have enough power to fill a 5/10 gallon tank. I have the pressure switch on a 12v switch in the cab as well so I can turn it on/off manually in case of emergency or just so it's not running when I don't need it. Though I have air horns, so I usually keep it running most of the time. I have a pretty large leak at the moment that I haven't had time to fix, so it runs a lot when it's on.

For street use (I can't use the recommended psi for the vehicle, both trucks I own have larger rubber), get the truck weighted with whatever load you are carrying that day, draw a line across the tread of all four tires, drive a couple times around the block and see what paint has been worn off. If there is still some paint towards the shoulders of the tires, take out 5 psi at a time till all of the paint diasappears.

Thanks for the help everyone! I'm gonna definitely try to lower the PSI as much as I can tomorrow evening. However, I can't go too low. I can air up at home, but my home is about 10 miles from my beach sight and there are no compressors in between that I could use.

So one last question. Whats the lowest I could go, but still be able to drive those 10 miles home to refill?

I wouldn't go too far below 30 if you want to drive on the street, what's everyone else think?

Captain p4 said:

I wouldn't go too far below 30 if you want to drive on the street, what's everyone else think?

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Ehhh...I woulda said 20-25...but it'll be sloppy. It is only 10 miles...although loaded with a boat.

You probably overread my post here ( end of page 1, post #10) about calculating the lowest pressure yourselves. Because the tires are probably overrated you mayby may go verry low on the road , and so dont have to be afraid of damaging your tires on the way home. But first calculate it , I could be wrong about the overrating tires. If it is all abacadabra for you give me here the Gross axle weight ratings front and behind, and from the tires the maximum load and reference pressure ( xxxx LBS at 65psi) , and I will use it as an example here.
Greatings again from holland
Peter