Tire pressure at 55 lbs?

[groundpounder]

Class C tire pressure at 55 lbs does this sound too low?
My 23 ft is 11250 fully loaded. Front axle is 3938 lbs, rear is 7312 lbs
The chart for my tire says the rear dual axle for 50 lbs is 7060 lbs and at 55 lbs is 7500 lbs.
I am in the middle, add some for good luck and I call it 55 lbs and ad 5 lbs for high speed.
Am I crazy for setting up the rear tires at 60lbs?
Front set to 60lbs too.
Door sticker for 12500 says 75 front, 65 rear

[Mac man]

Fords dealers go by door stickers others go by tire labels which is my choice! 80 psi is what I carry!

[Bob Denman]

Take a good look at what's on the sticker on your doorjam…
Mine said 75 front, and 80 rear...
So I went with 77, and 83!

[groundpounder]

Originally Posted by Mac man

Fords dealers go by door stickers others go by tire labels which is my choice! 80 psi is what I carry!

I use to do that too but change my mind to actually weigh the vehicle and then air it up according to Tire Manufactures specifications.

I have just 5,000 miles on this rig, no clue what pressures were used before. I just replaced the 2 outside dual that showed that it was over inflated.

Notice the mfg sticker is for max weigh and the same on the tire itself.

A properly inflated tire will improve ride, wear, breaking, impact survival and traction. Tires will also absorb some energy and not transfer it to the suspension. A rock hard tire is not good.

I did add a few pounds to be sure I was not under-inflated. Being over inflated is far better than under-inflated.

[The Gritz Carlton]

The tire manufacturers have no idea what you are going to do with this tire. The automotive industry does and this includes motorhomes. Do what works best for you but the numbers in the door jam (adjusted to final curb weight) are the correct numbers you should go by...period...assuming you are using the size tires they also recommend!

[Lt Keefer]

I weigh and then adjust the door jamb numbers to match my actual weight. I never go by what the tire says. That is max safe inflation for the tire.

[The Gritz Carlton]

You know what you're doing...this is proper procedure. Tire manufacturers simply rate the tire for proper running profile based on max load capacity.

[Long & Winding road]

55 sounds way to low to me.

I usually use what the vehicle manufature recommend at the door jam or in our case under/by the window in the drivers seat. Then adjust a little accordingly.

Mine shows 75 / 80 but I been runnig 73/73 lately. Last year I ran 77 / 77 then 75/75.

Since im not near max compass. most of the time I figured I would try the lighter 73/73 Tire pressure to smooth out the ride some.

Tell you the truth I dont think I can tell the difference between any of them.

Im thinking of trying 75 F and 70 R (since it rides rougher on our models with the front coil / rear leaf springs).

[gmtech16450yz]

If you guys have a tire pyrometer you can get a pretty good idea of inflation and alignment issues. An infrared gun will work also, just not as good. If you use an infrared gun, try to get the temps in the centers of the grooves. You want the temp closest to the core, not the tread itself.


For those of you with Ford Twin I Beam suspensions, ride height is very important since the camber will change quite a bit with height. If you check your tire temps and one of the inside or outside edges are way hotter, that means the camber is off. If both the inside or outside edges are hotter, that means the pressure is off. Hotter in the centers means you're running too much tire pressure. Hotter on the edges means not enough pressure.


If your front end is sagging, you'll end up with temps on the inside of the front tires reading hotter. Get the front end up higher with airbags or shims and you should be able to get even temps across the entire tire. (Assuming the alignment has already been done and maximum caster has been dialed in.)


Soooo, for the OP, if you check your tire temps IMMEDIATELY after running on the freeway for awhile and the temps are even across the tire, 55psi is ok. If both the inside and outside edges are hotter than the center, then 55psi is too low.


Just a thought. Tire temps tell a LOT about how the vehicle is working. Checking them properly and getting consistent readings is the secret. If you learn how to do it right, all of this guesswork on what tire pressures to run can be done a little more accurately.

[groundpounder]

The cold spec for my weight is between 50 & 55 so why would I over inflate to 65 or 75 per the vehicle label (noting the vehicle label is at 12,500) or 80 lbs on the tire.

Yes the tire heats up but everybody knows that and that is considered.

Fortunately tires don't fail easily even when we abuse them, but why abuse them? I got a lot invested in tires and want them to work properly and last.

I don't like to guess so I weighed my rig and looked up the right pressure.

By the way the spec for cold tire pressure is 68 F. One more spec hard to find is a bump for speed, add 5 lbs if running over 65 mph

[gmtech16450yz]

I'm not sure you got what I was trying to say. Did the rest of you guys get it?

Yes, tires get hot. WHERE they get hot (across the width of the tread specifically, but the sidewall temps are meaningful also) will tell you a ton about what you need to know about your inflation levels and a lot about your alignment too.

There's a big factor that isn't totally taken into account when simply going off inflation charts or door stickers, that's the tire itself. Different tire designs, brands and even tire age will change what the ideal running pressures should be. Door stickers don't designate between M/S, A/S, L/T, Summer Truck or Highway tires. All of those would have different ideal pressures even in the exact same size and load range.

Using tire temps to adjust pressures and alignment is the definition of "Not guessing". It obviously takes more time and knowledge than simply going by vehicle weights though.

[The Gritz Carlton]

I got it but it's like fileting a fish with a chainsaw. There's enough checks and balances already with owning MH. Credit given...your method will work, no doubt, but it's not that significant enough to prove anything to me. I watch tire wear, check inflation before every startup and do visual inspections. Do you use the same temp gun in the shower to check water temps before stepping in (pun intended)?

[gmtech16450yz]

Wow. That analogy doesn't even make sense. It's nothing like filleting a fish with a chainsaw. If anything it's more like filleting a fish with a scalpel. Blindly going by the door sticker is actually as crude as filleting a fish with a chainsaw.

The OP asked a question about tire pressures he believes are correct, but that don't necessarily agree with the sticker recommendations. I suggested a way he can verify if his pressures are indeed correct. There are really only two accurate ways to know if your tire pressures are correct, either wait until the tires show wear (kinda dumb) or read tire temps.

Gritz you can fillet your fish however you want, it doesn't matter to me. For the OP, if you're worried that those pressures might be too low, either wait until the tires show wear, get a tire pyrometer or just run them and don't worry about it. The problem is, unlike getting in a shower without knowing the exact water temperature, running your tires with the wrong pressures can actually kill people.

[The Gritz Carlton]

Here we go again...I'm out of this thread. Y'all have fun!! Life is too short!!

[Bob Denman]

You're giving up too easy, for this to be a normal Friday...

[gmtech16450yz]

lol.

It's all good, I'm probably just a little sensitive on this forum because it seems like every time I post something technical (which is pretty much all I post), I get a bunch of people saying I'm crazy/dangerous/insane/or just plain wrong. haha.

I know I come up with off the wall or outside the box ideas that are often hard to accept. That's the story of my life. lol. That's also what's made me extremely successful throughout my entire career. People that know me or have worked with me realize that as crazy as something I'm saying sounds, they should probably listen because chances are they'll learn something valuable.

Yes, I fully realize checking tires with a pyrometer is beyond what 99.9% of the forum members here would want to do. Duh. It's like my thread about my wheel/tire/wheel well mods. Of course I know nobody on here would, or SHOULD try to do what I did. But sometimes just seeing something done helps motivate people to try their own level of mods or experiments. And there are ALWAYS lurkers that read and never post that may benefit from tidbits of info. And like I said, the OP in this thread himself was questioning his assumptions, and I gave him a "tool" to use if he wants to verify what he was thinking.

So we just all have to remember that even if something seems crazy, silly or unnecessary for YOU to do yourself, there might be somebody lurking that might say "Hey, that sounds like something I want to try" or "That sounds a little extreme, so maybe what I'm doing isn't so crazy". Those are the people I post for.

[Bob Denman]

I know how you feel...

My Endocrinologist keeps saying that he doesn't know why I'm still alive...

But since what I'm doing seems to be working for me: just keep on doing it!

So keep pushing against the barriers!

[The Gritz Carlton]

We still love you!!! See you at the campfire!!! It's all fun!!!

[Bob Denman]

[Long & Winding road]

Originally Posted by groundpounder

The cold spec for my weight is between 50 & 55 so why would I over inflate to 65 or 75 per the vehicle label (noting the vehicle label is at 12,500) or 80 lbs on the tire.

That does seem odd.... You would think it would be more like 60 - 65, Perhaps the manufature is taking other things into consideraton for these "over inflated" pressure? I dont know. Just a thought. For me I usually go with the door sticker (Under Window sticker for RV?) and adjust down or up 5 psi if your light or heavy. I might do when GM Tech said - check tire temps across the entire tread. That would be more accurate but not the norm so I might try it once.



add 5 lbs if running over 65 mph

I dont Think I ever heard of this? Perhaps thats why the manufactures shows more psi? That way if we go 100 mph we are good? LOL.

Wont your tires build up more pressure (From heat) on thier own at these speeds? Perhaps higher tire heat at 75 vs 65? So you might want to leave PSI alone since they will raise up a few PSI already? Just a thought.