I have a 1997 F 350 . 5.8 gas job . Work truck .
Primary use ( so I thought ) was too tow a 30 ft boat few times a year .boat weight 9000 lbs
At boat ramp rear wheels were spinning on algae WORN tires , NO DUEL WHEELS ..
Replaced 4 worn tires all around with heavy duty 6 ply mud tires, 265 -75- 16 . No more spinning at ramp. .
Now Use the truck local & highway . Seldom tow boat since its left at a marina
Mud tires on open road is extremely loud , annoying , hard ride . .
Considering changing front tires with regular tread keeping the two front as back up . . .
Driving truck into a tire shop other day with a flat tire from another vehicle ,
Repair guy looking at mud tires SAID LOUD ARENT THEY ? YEP . DRIVE MY CRAZY
He said his buddy had same tires on his truck , same issue

Saying he correct by lowering tire pressure from 60 psi too 30- 35 psi ? Hardly hears the tires now . ?????????
Never heard of this . COULD THIS BE SAFE ? EFFECT FUEL USE ,
I believe recommended PSI is around 60 psi on 16 inch rims . ?????? . .

 

Well don't go guessing inflation pressure based of wheel size. You need to check the sidewall of the tire for inflation. Also I do wonder why you put light duty tires on a F350? You said you installed 6ply tires which are not correct for an F350. Actually really surprised a tire shop would even mount and install them.

 

You can play with the tire pressure but I doubt it will make much difference those mud tires are loud... should have bought all terrain tires.

 

They are noisy because of the open tread pattern on the outside edges. All those little rubber ***** are smacking on the road surface. Lowering the air pressure likely won't do much of anything to help. Only make them squirrely on the road.

 

I don't have it handy but there are load inflation tables that tell you how much weight a given tire size will support at a wide range of pressures. I use that as a guide based on what I'm hauling. Keeps the ride acceptable, tread wear even, and the most traction without overheating the tire. Running 60psi empty sounds miserable to me. That's the pressure for hauling a bigger load, not run around town pressure. As for the hum, I'm not sure if pressure will help, might, might not. Do you rotate them often?

What tires do you have? E-rated?

 

No. Correct tire pressure has nothing to do tire size, tread pattern or tire load capacity, it is what produces the most even contact patch for the load in the vehicle at the current time.. or for most people that don't want to be airing tires up and down all the time how the vehicle is loaded and driven most often. If that means empty most of the time then you probably won't need more than 45psi in the tires... less in the rears.

 

If anything, raising the tire pressure is your answer. This will make the center of the tire bulge out and get the outside lugs up off the pavement. Lowering the air pressure is going to make it worse.

 

Probably the best thing to do, if you really hate the noise, is sell them before you wear the centers out from running excessive pressure, or cup them (maybe too late? That'll make them loud). Then go pick up some all terrains. No reason to run mud terrains for a simple boat ramp, imo.

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Little off topic here (not so much noise related), but it is pressure relevant. This expands on what Conanski is saying.

Factory tire size wasn't 265/75R16, more likely it was 235/85R16, so the door jamb sticker doesn't exactly apply. The 265/75R16 will support more weight at the same pressure as the stock tires, meaning you can run lower pressure with the larger volume tire for the same weight. I'm finally on here on my computer again, so here's an example of a load inflation table (see attached PDF). This is from Toyo but seems to be nearly universal for all tires, given the same type (P, LT, etc.), size, & load index. You can graph these tabulated values for a given tire size if you'd like, helps visualize the relationship, but it is just a linear relationship for Load vs. Pressure. Typically the slope of the Load vs. Pressure plot is the same (at least very close) for tires of different sizes: the line is simply shifted up (higher volume tire) or down (lower volume tire) depending on tire volume. I attached such a plot for a few tires sizes I was interested in (Excel file). There's some safety factors for a LT tire vs a P rated tire of the same size; the LT tire is de-rated 10%, but that's a minor detail, you should run LT tires regardless. The take away is that a given tire will support a specific weight at a specific pressure and retain even tread contact (if you have it on the correct rim width), giving optimal performance for traction & ride while safely supporting the weight up to the speed rating. Running over the pressure needed to support the load gives you a rough ride and will reduce traction (shorter contact patch & less compliant tread). Running under pressure for the weight supported can over heat the tire, cause wallowing, and reduce fuel economy. Like I said, 60 psi empty sounds terrible. Depending on the trucks weight I'll run anywhere from 30 psi (empty) to 70 psi (summer pavement, loaded heavy). There is no one correct tire pressure for all conditions/weights. Ford put the door jamb pressure there for running at GVWR and not blowing a tire from under inflation.

I would be surprised if this effected noise much, but it will effect the ride quite substantially. Either way, it's the easiest thing to adjust on the truck and see if you like the changes, short of the seat back position.

 

How do you plan on running 70 psi in those 6 ply tires? You put C rated tires on a truck that should have E rated tires. Your max inflation is 50 psi.

 

Back in the late 80's and early to mid 90's. I read an article,yep before computers......... about unloaded tire pressures and traction/contact patch. The take away was pull into a nice flat parking lot or driveway. Slowly come to a stop with the wheel straight. Check tire pressures by taking a match cover or a thin piece of non corrugated cardboard at the tire's edge of the parking surface. Once it's just able to slip in at the tires Edge you've got created the optimum contact Tire surface.

 

Good article you read. That is a simple and effective trick.