Question about tire pressure vs. door stamp!

[doomcandy]

So my 2000 ranger 4x4 has a stamp on the door stating to set the tire psi to like 30 or so... my kelly tires are pretty aggressive and are rated for 80psi.

ive heard different answers from everyone as to where to set my tire pressure but I was wondering what all of you thought.

since Ive set them to about 60psi my bump steer isnt as bad.. but im worried about putting it down to 30 cause of weird wear.

 

[RangerSVT]

Follow the door tag ONLY for the original tires purchased with the truck. Since replacement tires might be a different load range (in your case), always follow the tire manufacturers recommended pressure, located on the sidewall of the tire...

SVT

 

[don4331]

RangerSVT:

I would say you are 1/2 right: Follow the door tag if you are using original tires (mfr/size/load range) and using your Ranger as a truck.

For replacement tires, it is still a good starting point. The information cast into the sidewall is the maximum load/pressure combination the tires can take.

I have 245/75R16s on my F-250. Ford doesn't even require me to run the LT245/75R16s on my F-250 at 80psi (max pressure on sidewall); door post say 55psi but that assumes I have a load on it. (well, at least too lazy to change pressure between loaded and unloaded.) But I weighed my truck, so know the axle weights and I found the inflation table for the tires I am using:

The inflation table for the LT265/75R16 Firestone Steeltex tire

Weight Pressure
1910 35
2100 40
2280 45
2470 50
2625 55
2790 60
3000 65
3105 70
3260 75
3415 80

65-74mph add 10psi
75-84mph add 10psi & decrease load 10%

With this information, I can make an informed decision on pressure to run. I run about 35 psi 90% of time because mostly it just goes to rink and back empty. But when I put the camper in the back and hook up the boat, it goes to 55psi front/70psi rear to match the loads.

You can probably use this as a starting point:

http://www.trucktires.com/bridgestone/us_eng/load/load_pdf/loadTables.pdf

Around pg. 98 (8 in the pdf) is the sizes we are concerned with.

Hope I helped you.

 

[RangerSVT]

While i agree with your statement, the reality is most people dont think about upping the air pressure when the carry a load or hook to a trailer. Most people dont even check pressure for most of a tires life. My current tires are load E rated at 80 psi, I'm running 65 front, 70 rear. My sport trac is 6k lbs daily, well over 10k when i hook to the trailer, which is frequently, for me...

SVT

 

[Captain Ledd]

Don4331's chart is the going to be the easier option. (Thanks for posting by the way, rep'd ya)

But if you REALLY want to dial it in, get a laser thermometer. Drive down the highway for a good 10 minutes or so. Get out, and quickly run it across the tread of the tires, inside, middle and outside. If it's warmer than the edges in the middle, pressure too high. cooler in the middle than the edges, pressure is to low. If it slopes from one side to the other you have an alignment issue. Rim width can have an effect on what pressure you need to run as well, a wider rim needs a bit more pressure. Tedious I know. All the temps should be even all the way across the tread.

 

[brokemechanic3000]

An easier way is to draw a line across the tread face with chalk and drive up the road a bit and back. worn in the middle = too high worn on the edge = to low worn evenly = just right.

 

[don4331]

RangerSVT:

I'm always a little nervous:

Is this an enthusiast site, where users check the oil, fluids, lights, tire pressure and leaks before starting the engine. Or do they just get behind the wheel and drive. As I do all the checks, and have the pump in garage, changing pressure isn't big deal.

Your Sport Trac weighs 10k with trailer! What are you pulling? Tongue weight should be 10-15% of trailer, so +4k = 40k lb trailer. I assume you mean truck + trailer = 10k so only 500lbs more on Sport Trac = 6,500lbs <Still healthy amount over mfr. gvwr> So, your pressures are safe, but probably harder on kidneys than necessary.

Captain Ledd:

Thx for the rep. I'm too old school for laser thermometer; I'll need to re-educate myself.

Brokemechanic3000:

We used liquid shoe polish on the tires at the drag strip to check wear. Driving through a puddle works too for a quick reference.

 

[cp2295]

Yeah I would run those at 40 or 45 psi. 60 is going to wear it unevenly due to overinflation. You're truck doesn't weigh as much as a truck requiring 10 ply tires so if you over inflate it will wear the center.

 

[cp2295]

If you put a heavy load in it you could run higher pressure if need be. I got 6 ply tires and run them at 35 they wear pretty evenly. It's a 99 4x4 super cab

 

[RangerSVT]

Truck's about 6k, trailer 2500, 10k+ with any given load. When I pulled SVT to STL last year I was just over 15k. When I pulled John's (railman's) truck this year I was just over 14k. My trailer can handle 10,400. Trailer tires support 3418 each. Quite a bit heavier than the average person would normally pull with a gen 1 sport trac, but I've got the balancing load down on the trailer, just enough tongue weight to prevent trailer sway, even with gusts of winds from big trucks. I really need a one ton for what I do, maybe even an MDT. I've been on the lookout for one, just havent found one i like in my price range yet...

SVT