Tire Pressure

[squeekyM]

I was curious what PSI some people would recommend running for highway driving. I am going to be driving about 4 hours roundtrip and just wanna check a few things before I head out, one of them the tire pressure. I believe the tires are currently @ 60PSI... I wanted to make sure that they were not either under or over inflated.

I have an '86 F250 SuperCab 4x4... I believe the truck weights approx 8900# I run a set of Dunlop Mud Rovers 285/75/16. I want to run a good PSI for mileage, what would you recommend? Thanks in advance.

 

[MIDNIGHT RIDER]

I run the MAX plus five to ten PSI, regardless of tire size or vehicle weight.

I just hate to see a squatty tire.

Everything around here recommends 80 PSI; so, I run 80 plus.

 

[TLBREWER]

It depends on if you're running D or E load tires. Eight ply tires, D rated, usually are 65 psi max, while ten plys, E rated, are 80 psi max. I usually run fronts at max due to weight (engine) and rears 5-10 psi under max so it doesn't bounce around so much (when empty). I too hate to see "squatty" looking tires, unless they're aired down for traction reasons.

I would assume the tires you specified are D rated. Maximum recommended pressure will yield the best fuel mileage due to less rolling resistance. Sometimes this sacrifices ride quality if that is a concern in these trucks.

Tom

 

[squeekyM]

Thanks for the info, that was exactly what I was looking for. I just changed the diff fluids, and drained and filled the trans with RedLine MT-90 in preperation for this little "trip".

One more thing.... how often are you supposed to change the ATF in the transfer case? Thanks again.

 

[Agnem]

A hard tire definitely lets you feel all the bumps. I like to run about 5 pounds under to soften it up a little.

 

[Mr_Roboto]

I was curious what PSI some people would recommend running for highway driving. I am going to be driving about 4 hours roundtrip and just wanna check a few things before I head out, one of them the tire pressure. I believe the tires are currently @ 60PSI... I wanted to make sure that they were not either under or over inflated.

I have an '86 F250 SuperCab 4x4... I believe the truck weights approx 8900# I run a set of Dunlop Mud Rovers 285/75/16. I want to run a good PSI for mileage, what would you recommend? Thanks in advance.

Unless you are carrying a lot of tools or equipment in the back of the truck, I suspect that you are overestimating your weight.

Here are the minimum inflation pressures for your tire, this is weight PER tire. To use this chart properly, you need to have the front and rear axles of your truck weighed seperately, then divide each weight by two. This will give you the proper minimum inflation for each axle. You should run 5 to 10 psi above the minimum inflation.

35 psi, 2130# 40 psi, 2340# 45 psi, 2540#

50 psi, 2755# 55 psi, 2925# 60 psi, 3110#

65 psi, 3305#

This document has the various tire sizes, along with worksheets to figure for different speed ranges etc. http://www.goodyear.com/truck/pdf/databook/loadInflation.pdf

 

[icanfixall]

Every tire made has the running pressures printed on the sidewalls of the tire. Its usually small print but its there. The "D" rated pressure is as atated along with the "E" rated tires. If you run too low of an inflation pressure heat will buildup and cause low mileage & tire loss. Thats what all those tire treads you see along the roads. Low pressures and overloaded trucks and trailers will heat up tires in a very short time. When I'm hauling horses accross country I touch every tire when I fuel up. That way I may be able to catch a low tire before it catches me out on the road.

 

[Mr_Roboto]

The pressures on the tires are only the max pressure for the max load. If you are running 80 psi all the way around on a 8000# truck you are way overinflated.

Same with flotation type tires, if you run a 33" D rated tire at full inflation you will have little traction and crash your truck into a phone pole when you try to stop fast. (Damn tire shop decided to fully inflate my tires to 44 psi when they rebalanced them. I ran them at 19 front, 17 rear. Totaled a perfectly good truck that way).

 

[Agnem]

Ultimately you can tell more about your tire presure from tire wear. I've seen tires too inflated that end up wearing in the middle only. I'd have to agree that inflating it to the rated maximum isn't the way to go on a truck that is never loaded.

 

[sle2115]

Ultimately you can tell more about your tire presure from tire wear. I've seen tires too inflated that end up wearing in the middle only. I'd have to agree that inflating it to the rated maximum isn't the way to go on a truck that is never loaded.

Well the statement was made about overestimating weight, but if his truck weighs 8900 lb, I would guess he is loaded. My standard cab only weighed 6300 with a long bed. I would say you could safely add 800 to 1000 pounds for a 4 door cab, making that weigh in about 7000 to 7300 lbs. but if it weighs 8900 lbs. (weight verified of course) he is running loaded I would guess. That's an additional 1600 lbs. plus. Now if he is just guessing at the weight, all bets are off!

 

[sle2115]

Unless you are carrying a lot of tools or equipment in the back of the truck, I suspect that you are overestimating your weight.

Same here, I would guess 7,000 or so empty.

 

[squeekyM]

I think the weight that I guessed was way off then. For some reason I thought I read somewhere that these trucks weighed almost 9000#. Aside from a few motorcycles from time to time, this truck is empty/unloaded. Sounds like it is closer to the 7000# mark. What would the inflation/PSI recommendation be? Thanks again.

 

[sle2115]

Ok then, I would look on the tire sidewall and see what the max is. I would then run 5 or so PSI under that and see how it rides. You can then adjust according to ride quality and tire wear, high wear in the center of the tire means overinflated, high wear on the sides means underinflated, both cases of course assuming all else is fine in the drivetrain/suspension.

 

[670x]

Grab your kids sidewalk chalk and make a thick line across the tread. Then drive the truck slowly forward about a half a block and see how it wears. You want enough pressure that it wears off evenly. So just add or subtract it till you find it.
I run 55psi on the front and 50 on the rear while empty. This has kept my soft swampers from wearing to fast and they ride great.

 

[icanfixall]

As posted above the rating printed on the sidewall is for a loaded tire-truck combination. I posted a comment to yours about a truck being 9000 lbs so that would be what the "D" or "E" sidewall states. An unloaded truck IS much differant as some have pointed out here. Just be cautious whatever pressure you try. It will change as you change how and on what surface you are driving on along with the load your carring. I guess there is no exact tire pressure to recommend for you but these postings will head you in the correct direction.