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  #1  
Old 07-22-2001, 01:37 PM
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Question Tire Pressure of LT (light truck) tires?

C, D, or E load rated LT tires.....What tire pressures do you inflate to when....

1. normal everyday driving around town.

2. Off-roading

3. Fully loaded down or towing.

Any tire brand, what is your "method of operation" based on experience?
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  #2  
Old 07-25-2001, 12:25 AM
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Inflate the tires to the vehicals recomended air pressure for normal driving. when off roading lower the air pressure about 6-8 lbs.
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  #3  
Old 07-25-2001, 01:19 AM
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inflating your tires to the "vehicles recomended air pressure" is a good way to find your explorer on its top(so to speak). your tire dealer should be able to recomend the best ply rating and inflations for the types of driving you do on the tire of your choice. off roading in sand requires differant pressure than in muddy terains ... the tire manufacturers dealer can usually tell you how to get the best performance and life out of your tires.
good luck connor
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  #4  
Old 07-25-2001, 05:07 PM
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I've wondered about this, too. Recently BF Goodrich over the phone told me to inflate my LT265/75R16 D tires to what the door sticker on my 97 F150 says, which is 35psi. That's what the guy at the desk at Tires Plus said, too. The guy in back who mounted them, put 60psi (max 65 on sidewall) and said he wouldn't go below 50psi.

A few years ago BF Goodrich emailed me a few data points from a table of load weight vs. tire inlation for LT255/70R16 D tires. The upshot was 40psi was all it would take for four tires to support a truck with a 6000 GVW. I ran about 47 in them. Replaced 'em after 35,000 miles mostly cuz I wanted the next bigger size.

I am currently running about 43psi in my LT265/75R16 tires. I have been lowering the pressure until the entire tread (for the front tires) seems to make contact evenly with the road. They are mounted on stock 16x7 steel wheels. I didn't want to wear the tread off the middle. Empty, the rear tires still don't sit flat but I won't go any lower cuz I don't want to have to pump them up just to throw something in the back. I guess I'll just have to make sure I rotate them.

Karl Nyhus, Minneapolis, MN
1997 Pacific Green Ford F-150 SuperCab XL,
short box, 4.6L V8, 4x4, 3.08 axles, 5-speed manual tran,
LT265/75R16 load range D BF Goodrich All-Terrain T/A
(max 65 psi, currently running 43-50 psi cold)
VDO tachometer, Better Built toolbox,
Line-X spray-in liner, rust-proofed/undercoated,
argent styled steel wheels with "chrome" wheel skins
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  #5  
Old 07-25-2001, 09:07 PM
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a C load rated tire is 50 PSI max.
a D load rated tire is 65 PSI max
a E load rated tire is 80 PSI max

That max rating for a D or E would really only be used when you have a fully loaded down truck. If your truck was empty, what PSI would give you a good ride (street) without abnormal tire wear?
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  #6  
Old 07-25-2001, 11:14 PM
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I would inflate tires to something between what door jamb of vehicle specifies and the max inflation for that tire. I eyeball how it sits on flat concrete, whether I can slip a piece of paper under the edges, and notice that the sand on the street is sticking to the middle four inches or of the tire and not the outside inch on either side. Then I lower the pressure until the tire tread sits flat on the pavement. As long as you're still above what the door jamb says, you should be good.

Some people have recommended chalking the surface of the tires to help see how even an impression is left on the pavement.

Some tire manufacturers will tell you what load their tire can carry when inflated to a certain psi. I'm certain they all have this data, but it's been very hard for me to find it. BF Goodrich gave me some data points for a tire a couple years ago, but when I called them recently they would only say, "Use what's specified on the door jamb." Probably only going to be more difficult with the Firestone/Ford fiasco.

An empty pickup is heavy in front and light in back. I get the front tires sitting flat and then inflate the rears the same, even if they do wear a little more in the middle cuz of the light weight. That's what rotating tires is for! I don't want to have to inflate them just to throw something in the back. On very heavy loads I will increase rear pressure, but without manufacturer data, I'm just guessing how high to go.

Personally I don't worry about smooth ride in my truck. It's a truck after all and the modern ones do very well for themselves already. You'll get better steering and handling and gas mileage by inflating your tires to spec or even higher. Don't under inflate just to get a soft ride.

Karl Nyhus, Minneapolis, MN
1997 Pacific Green Ford F-150 SuperCab XL,
short box, 4.6L V8, 4x4, 3.08 axles, 5-speed manual tran,
LT265/75R16 load range D BF Goodrich All-Terrain T/A
(max 65 psi, currently running 43-50 psi cold)
VDO tachometer, Better Built toolbox,
Line-X spray-in liner, rust-proofed/undercoated,
argent styled steel wheels with "chrome" wheel skins
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  #7  
Old 07-26-2001, 01:12 AM
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Exclamation Depends....

The door jamb tire pressure is for the tires specified on the same sticker. Usually a 255/70/16 or even a 235/70/16 "P" rated tire. Which is a Passenger tire! These tires are usually only 4 ply, so they give you that smooth ride. Once you go to an LT rated tire, all that door jamb stuff is out the window. Mine are "C" rated, and say 50 lbs max. That's the max pressure you should run if you have a full load. I think it's something like 2470 lbs per tire at that pressure, or 4940 per axle. D and E would be higher.

I run mine at 45 lbs all the way around for everyday running around. I carry one of those cheapo air pumps that go to 200 lbs and plug into the accessory socket if I carry a full load of 1000# (or more ) Not very often, but rotating the tires is the key to keeping everything even. Do it every 5k miles.

Once you move to LT rated tires, the number of plys increase, so your ride is going to be effected by this. If you run too low pressure, there will be more heat generated in the tire, which will kill it faster then any uneven wear would.......
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  #8  
Old 07-26-2001, 02:11 PM
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I agree that the door jamb psi spec is for the OEM tire. But it's a starting point. And, as I mentioned above, it was the advice given to me by BF Goodrich customer rep for the specific (not OEM) tire that I'm running now.

You don't say how you picked 45 as the value to run yours at.
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  #9  
Old 07-26-2001, 02:33 PM
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Smile Snarl

Just seemed to be a good balance from the Max pressure on the tire to how the tires actually handled. When lower, it feels too "musshy" while turning. The tire store had them at 48 lbs. I thought that was a bit high for everyday driving. It seemed a bit harsh on the ride too. At 45, it's not "musshy" and it isn't jarring either. Unloaded, the rears do seem to just ride on the center more compared to the fronts, but I plan to rotate every 5k anyway, so that should help even things out.

I don't expect the tires to last more then 40k anyway. I usually replace tires when the tread is just over 3/4 warn out anyway. I just don't like the loss of traction on wet pavement trying to run them to the wear marks......
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  #10  
Old 07-26-2001, 04:38 PM
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I have LT245/75-15 Goodyear Wrangler AP on my truck. That's what was on it when I bought it earlier this month. The door sticker is for this size and type tire. The pressures on the sticker say 42psi front and rear. I am running them at 40 right now and this seem good. I just got back from camping in Old Forge NY this weekend and with the camper and the bed loaded with gear the truck ran great. The camper it a 27' tent camper that weighs about 2500lbs loaded up. I am going to play with the pressures and see what happens.

DF
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  #11  
Old 07-26-2001, 04:58 PM
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Question DF4.6

What does the Max pressure on the sidewall of the tire say? I'd go with what the sticker says in your case. You have the specific tires listed on the sticker and it says 42. You may not think 2 lbs is a big deal, but you can tell the difference! Running a lower pressure will give you a smoother ride, but cornering and it's weight rating will be lower.
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Old 07-26-2001, 04:58 PM


 
 
 
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