under pressure

stpete

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From what I understand, the high load rated tires are supposed to be inflated to near max pressure. At that pressure is where it has it's load rating. I suppose you could use the drive through water/chalk method, and that ?may? tell you how low you can go. But, it may not.
As I mentioned, I found that the truck literally jumps over bumps in the road when I inflate the tires to max (80psi in my case). If I go down to the 55 psi Ford recommends with whatever stock tires came on it, it multiplies the "truck steering". Meaning you have to work a lot harder to keep it going straight. I found with the truck unloaded the pressure it works best at is around 65. When I tow a heavy trailer, I up the rears to 75 or 80 and the fronts to 70. When I pull my open race car trailer that comes in at around 5K, no adjustments necessary. Don't even notice that thing behind me. But if I borrow the big enclosed trailer at 8.5K and significantly more tongue weight, the truck will get squirmy without upping the pressures.
 
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Racer47

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pass1over,

Your load range G 110psi max tires will not overheat, over-deflect or blowout by running them at 95psi because your truck is still at load range F weight which needs only 95psi.

Who do you think knows more about your truck, Ford? or the company that bolted a bed on? Take that coachworks label off and throw it away.

Back to tires. In practice there is little difference between a 95psi and 110psi truck tire from the same manufacturer. I believe the HDR/HSR tires are all wire, meaning no polyester or nylon in the construction (the sidewall will say what it is made of).

So to go from a 95psi tire to a 110psi tire, the most likely difference will be that the wires will be slightly closer together, which is capable of handling the higher air pressure. The alternative would be that the wire gauge could have been increased slightly with the same spacing. Either way, there is more metal in the higher psi tire, which makes it a stronger, stiffer tire capable of higher loads because it can handle higher pressures. Most, if not all, of the rubber components will be the same.

Just because the tire says 110psi max does not mean that’s what you inflate it to. It won’t hurt the tire to run it at 110psi but you will give up a slight bit of traction and a slight bit of ride quality due to the higher than necessary psi.

The tires on my Mustang right now say 51psi max. So should I run them at 51psi? Ford does not know what tires I put on the car, so maybe I should do what the tire says? This is incorrect logic because it’s based on incomplete information. The tire is Z speed rated, 149+ mph, and that high inflation pressure is meant to be used to carry the max tire load (which is way higher than the on car actual tire load) at sustained speeds of over 149mph. I don’t need or want 51psi. I run them at 30psi.

I know this is about truck tires and truck tires are very different but this example works. Your 110psi max is meant to carry the higher load which you correctly stated in the original post. But in practice you did not increase the actual tire load, you simply bought better, higher load capable tires. So run them at the pressure Ford says. Ford has 1000’s of engrs and dozens of PhD level vehicle dynamics engrs. They know way more than you think. It is certainly not “anybody’s guess” as someone said above.
 

Racer47

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As I mentioned, I found that the truck literally jumps over bumps in the road when I inflate the tires to max (80psi in my case). If I go down to the 55 psi Ford recommends with whatever stock tires came on it, it multiplies the "truck steering". Meaning you have to work a lot harder to keep it going straight. I found with the truck unloaded the pressure it works best at is around 65. When I tow a heavy trailer, I up the rears to 75 or 80 and the fronts to 70. When I pull my open race car trailer that comes in at around 5K, no adjustments necessary. Don't even notice that thing behind me. But if I borrow the big enclosed trailer at 8.5K and significantly more tongue weight, the truck will get squirmy without upping the pressures.

This is solid, real world experience and advice from someone who obviously has at least a fair amount of towing experience (and maybe a lot of towing experience).
 
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pass1over

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I don't think that the Ford engineers are dumb at all, i'm just trying to find some clarity in this fog of numbers that I'm in.

After all of this forum reading and talking to "professionals" about it, i'm going to run the 75/95. Was going to get an IR heat gun, keep it in the truck, and shoot the tires/hubs whenever we stop. I know i'll have to see what my truck runs at, but any ballpark as to what normal tire temps should be? Do I shoot the sidewall or the tread? or both?

So far, this forum has provided much better info than the other two truck specific forums. I knew you guys would come through ....
 

Racer47

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The only tire temp that really matters is the temp under the tread and just above the top steel belt. The IR gun will not really help much and may just add to your worrying. The tread surface temp can vary due to sun, road temp, road surface, etc. The internal tire temp is what measures how hard the tire is really being worked.

You will be fine. New tires. 1 step high load rating. Proper inflation 75/95. Nothing to worry about, really.
 

tjm73

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I think you are worrying too much about heat.
 

pass1over

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im worried about blowing a tire while i'm towing this big trailer. Just trying to get all the knowledge I can about this before I head out on this trip.

Like I said, this is the biggest enclosed trailer i've hauled to date. I had a 35ish foot flatbed with my big JD tractor, bush-hog, and box blade on it. Drove it about 300 miles no problem.

Sorry if it seems i'm worrying too much, just want to be as informed as possible. Who better to ask than people who have towed big stuff too?
 

tjm73

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Have you heard the term "analysis paralysis"? I think you are getting caught up in the details when you don't need to. I did this to myself not log ago in educating myself on weight ratings/capacities for my F150 and travel trailer.

Sometimes you gotta step back and accept that if you are following Ford's guidelines for their trucks, you will be ok. They have built in significant safety margins. They don't want customers to get hurt or be liable for them getting hurt.
 

pass1over

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I'm not that far in, but yes, I hear ya. I also don't feel that it's bad to get opinions of others and to be as prepared as possible.

I sit in front of a computer for most of the day and want stuff to talk about too, lol
 
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pass1over

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the trailer has been sitting for approx. 10 years untouched. The truck sat for about 8 years untouched.

Just got done rebuilding the rear door's on the trailer as the original design was not the best and they rotted out. Trying to fix everything and be prepared for whatever happens with it.
 

Norm Peterson

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This isn't mustang related, so i'm not sure if it belongs here or in the Off Topic thread. My apologies if I chose wrong.

I figure you guys know about a lot more than just mustangs. I need some help with my truck.

2003 F550 Super Duty crew car dually, 225/70/19.5. Just recently put tires on it and am a little confused at to what pressures I should be running.


Their Conti HSR/HDR 19.5 on a dually setup. Pull a 3 horse GN with living quarters. Believe the sticker on it says 12k lbs.

OEM tires were General LMT400's

3640lb Single 95psi max
3415lb Dual 95psi max

Current Conti's are

3970lb Single 110psi max
3750lb Dual 110psi max

Sticker from Ford says to put it at

F - 75psi
R - 95psi

Sticker from Utility Bodywerks (who put the bed on) says

F - 75psi
R - 75psi

So, whom do I believe? Why would Utility Bodywerks spec 20psi less in the rears? It's a cab/chassis with a pickup bed on it. Since the Conti's on it can carry more, should I bump up the Ford spec by 10psi or so?
Listen to Racer47. Trust me on that.


I bet if you could look up the rated load (T&RA tables in a fairly expensive book) for your new Load Range G tires when inflated to 95 psi it'd match or be very close to matching the Load Range F rated load for the same tire size at the same 95 psi. It's the higher inflation pressure that buys the new tires their higher maximum rated load.

Kind of like 255/45-18 tires for a Mustang that can be either 103 XL or 99 SL that you'd still inflate to the same pressure in order to maintain the same load capacity. Just on a heavier-duty scale.


I have a copy of some of the T&RA Load vs Inflation tables, but not the one(s) needed for your truck. Sorry.


Norm
 
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skwerl

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The Ford engineers who place the tire inflation label on the truck have a lot of different people to answer to, none of which include the end user. Lawyers, EPA testers and accountants all have their say and none of them care how comfortable you are.

Listen to Racer47 and just use the max tire ratings and Ford engineer stickers as a guideline, then adjust as needed for your particular circumstances. Generally you will want higher pressure with higher loads, and lower pressure with lower loads. There is no single correct answer.

I'll admit I don't check tire pressures as much as I should. I will check them if I notice an issue or if I'm getting ready to haul a very heavy load. Otherwise they just get the parking lot glance once in a while if I think I notice the steering wheel pulling to one side while driving.
 

Racer47

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I bet if you could look up the rated load (T&RA tables in a fairly expensive book) for your new Load Range G tires when inflated to 95 psi it'd match or be very close to matching the Load Range F rated load for the same tire size at the same 95 psi. It's the higher inflation pressure that buys the new tires their higher maximum rated load.

The loads would be exactly the same. That's how the load tables work. I guess I was not clear on that. This exact same tire could be used on a load range D truck at 65 psi. Although it would be a bit of overkill because an actual load range D tire would be cheaper.

Here is the load table with the size in question at the very top.

otWTl1A.jpg
 

Racer47

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For those who have read my tire postings in both of the recent threads, it may seem like I'm being two-faced or hypocritical. On one hand I'm saying that you can easily mount and use tires outside of the T&RA guidelines. But in this thread, I'm saying to follow the recommendations.

The reason is these are two very different situations. Car tires are generally oversize and have plenty of capacity to spare. But when you move to real truck tires (not 33x12 mudders) the situation is very different. The loads are much higher, the tire pressures are much higher and the consequences for getting it wrong are much higher.

A load G 110psi tire is nothing to play games with. You are now firmly in the semi-truck tire area. Pass1over is correct in worrying about getting it right and that means the right tire, the right wheel and the right pressure.
 

pass1over

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the other thing to take into consideration, or at least I do, is that most of the time when hauling this trailer, my cargo is LIVE.

Yes, it would suck to have something happen and your race car or boat or whatever get damaged, but theoretically it can be fixed.

After my wife was done grieving over her killed horse, I would be next, haha

I really do appreciate all the information that has been provided. It's not something that keeps me up all night or that i'm constantly worried about by any means. I just wanted to get some information from real world experiences and/or informed individuals.

I do tend to over-prepare for most situations (gotta be the eagle scout in me lol), but it hasn't let me down yet!
 

Racer47

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I am in no way criticizing you for your concern. The people I worry about are the ones who have no idea what they are doing. Or they simply get complacent after hauling 20,000 lbs around for years and think its no big deal. I raced cars for a long time and saw some pretty sketchy stuff related to trucks, towing, tires, etc and this was from guys that should know better.
 

pass1over

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I am in no way criticizing you for your concern. The people I worry about are the ones who have no idea what they are doing. Or they simply get complacent after hauling 20,000 lbs around for years and think its no big deal. I raced cars for a long time and saw some pretty sketchy stuff related to trucks, towing, tires, etc and this was from guys that should know better.

Oh, I know your not. A few other's kind of have, so I was just stating again that this thread was just a quest for knowledge. These are my questions and these are my concerns ....

Complacency is the devil for sure.
 

Scrat

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where I work all of our box trucks came factory with tire rated load F at 95 psi max and that's where they were set from the dealer, even says it on the door sticker. Now we have changed some of the tires over the years to a brand that was load G rated at 110psi max but we still run the pressure at 95psi. And even with that tire when the truck is empty, 98% of the tire tread contacts the ground and when loaded, 100% of the tread touches with no over bulge of the sidewall and no excess heat. The only time time we ran a higher pressure than 95 was when we tried out a cheaper priced tire that was a load F tire with the same weight ratings as the oem tire but rated at 110 psi, so that tire we ran at 110.
 
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