Hi Dave Pelletier

(tire choice DEFINITELY affects sway. A taller tire, one with a softer sidewall, one with less air pressure (or any combination of the three) WILL increase sway. Do yourself a favor and take two identical trucks, one with stock size load range E tires aired up to 80 psi and one with load range D tires aired up to 65psi and give them both a shove sidways on the back end. Note the results.)


1. 285X75R 16 are the same height of 235x75R 16, 285 or 235 = the width of the tire. 75 is the height. Therefore, the height of the tires are the same. 285's have wider foot print (its just physics) and safe per the manufacters load of over 3000 lbs per tire. This wider foot print distributes forces over a greater surface area.

2. With regard to tire pressure, 80 vs 65 psi. Mag trucks that can carry tons of stone have tire pressures of only 40 to 50 psi. Why, because the foot print of the tire can be feet across.

What does E and D mean, "E" tires are rated for 80 psi with 10 ply. "D" tires are rated for 65 psi with 8 ply. The alpha relates to tire pressure and the number of ply on the side wall. This (E) enable manufacturers to produce a narrower tire for a heavier load. This produce less fiction and a small engine can be used with higher fuel eff.

Its just physics, (duallies included) if your driving on a fiat road going around a curve. the physics that are encountered are the weight of the load and outside curve forces are compressing the spring directly over the axle. This compression is what we call sway (tilt). With single rear tires or duallies trucks install air bag to counter this force by stiffing up the spring and reduce sag. The air bag hinder the compression of the spring and thereby reducing the sway. The sway bar takes it a step further by transferring some these load forces to the opposite tire and spring. In the above, the tire are still sitting fiat on the ground and all tires have some compressions on the load side.

PS >There is no such thing as "no sway" all trucks have some sway< You should read my statement again. No where do I make that statment. I say the main cause of sway are the springs and is corrected with air bags, shocks, and sway bar.

>load range D tires aired up to 65psi and give them both a shove sidways on the back end. Note the results.< I have, about the same as a dually.

Bobster,

There seems to be some confusion here. I am well aware of all of the physics involved.

1) Your wrong about how the tires are measured. A typical metric tire breaks down as follows;

- 285R75 16LT means 285 mm tread width; an ASPECT ratio of 75 (meaning that the tire sidewall is 75% of the treadwidth), 16 - meaning 16" rim and LT standing for light truck. A 285 75R16 tire is taller than a 235 75R16 tire. In fact your 285 75 will have a sidewall height of 214mm and a 235 75 will have a sidewall height of 176mm.


2) Mag trucks don't run on load range D tires or take corners on the highway at 70mph. Apples to Oranges, this analogy means nothing.

3) You said (and I quote) "..4 years and no sway". so I'm unsure what I missed in your post.I reiterate: all trucks have sway.

4) Keep trying my pushing on the rear end experiment until you get different results! I've done it several times and logic simply dictates that you WILL NOT have as much lateral stability as a stiffer tire with more air pressure. I won't even comment on the dually. You can't change the physics by wishing it so.

What can I say? Load range E tires offer more stability and sway control than equivalent D rated tires when thier both aired up to maximum settings. DRW trucks have more stability and sway control than SRW trucks for the exact same reasons.

Dave

Try www.1010tires.com/tiretech.asp for a detailed description of metric tire sizing.


Dave

Hey I didn't want to start a fued! Thanks to all that replied. I will give some thought to all the good info you all gave. I am trying to get best set up without buying new truck. I have beefed up the front and rear end with extra leifs and added overload springs. Rancho shocks. Truck sits little higher (maybe an inch) front end is level and ride is not bad empty. Rides and handles great loaded I see the new fords have increased the pay load a lot over the old trucks and you dont loose pay load with crewcab or deisel any more. i may have to look at them. merry Christmas. Scotty.

Scotty,
No feud here. Just having a discussion . It sounds like you have a handle on the situation. Merry Christmas to you too.

Dave

Toyo makes a E rated 285/75/18 tire. I think it is rated for 3750 pounds. Also Discount tire claims Pathfinder has a similar tire. From another forum I was told Michilin (sp) has a 305/70/16 e rated.

The only one I can vouch for is the Toyo - it is their M55 series.

I meant to say the TOYO tire is 285/75/16(not 18)

Hey that sounds like what I was looking for! Who carries them?

Discount tire said they could order them. If you do a search on the net for TOYO tires and look for the M55 series you can read the specs. They also have a bunch of testimonials that indicate they are very sturdy tires.

The Pathfinder tires at Discount have always been good. Are the Toyos available in s M+S tread pattern?